10 Ways to Go Green and Save Green
1.Save energy to save money.
Purchase State of the World 2010:
Transforming Cultures to learn more
about the shift from consumerism
to sustainabilitySet your thermostat a few degrees lower in the winter and a few degrees higher in the summer to save on heating and cooling costs.
Install compact fluorescent light bulbs (CFLs) when your older incandescent bulbs burn out.
Unplug appliances when you're not using them. Or, use a "smart" power strip that senses when appliances are off and cuts "phantom" or "vampire" energy use.
Wash clothes in cold water whenever possible. As much as 85 percent of the energy used to machine-wash clothes goes to heating the water.
Use a drying rack or clothesline to save the energy otherwise used during machine drying.
2.Save water to save money.
Take shorter showers to reduce water use. This will lower your water and heating bills too.
Install a low-flow showerhead. They don't cost much, and the water and energy savings can quickly pay back your investment.
Make sure you have a faucet aerator on each faucet. These inexpensive appliances conserve heat and water, while keeping water pressure high.
Plant drought-tolerant native plants in your garden. Many plants need minimal watering. Find out which occur naturally in your area.
3.Less gas = more money (and better health!).
Purchase State of the World 2009:
Into a Warming World to learn more
about overcomig global climate changeWalk or bike to work. This saves on gas and parking costs while improving your cardiovascular health and reducing your risk of obesity.
Consider telecommuting if you live far from your work. Or move closer. Even if this means paying more rent, it could save you money in the long term.
Lobby your local government to increase spending on sidewalks and bike lanes. With little cost, these improvements can pay huge dividends in bettering your health and reducing traffic.
4.Eat smart.
If you eat meat, add one meatless meal a week. Meat costs a lot at the store-and it's even more expensive when you consider the related environmental and health costs.
Buy locally raised, humane, and organic meat, eggs, and dairy whenever you can. Purchasing from local farmers keeps money in the local economy.
Watch videos about why local food and sustainable seafood are so great.
Whatever your diet, eat low on the food chain [pdf]. This is especially true for seafood.
5.Skip the bottled water.
Use a water filter to purify tap water instead of buying bottled water. Not only is bottled water expensive, but it generates large amounts of container waste.
Bring a reusable water bottle, preferably aluminum rather than plastic, with you when traveling or at work.
Check out this short article for the latest on bottled water trends.
6.Think before you buy.
Learn more with Worldwatch's
Low Carbon Energy ReportGo online to find new or gently used secondhand products. Whether you've just moved or are looking to redecorate, consider a service like craigslist or FreeSharing to track down furniture, appliances, and other items cheaply or for free.
Check out garage sales, thrift stores, and consignment shops for clothing and other everyday items.
When making purchases, make sure you know what's "Good Stuff" and what isn't.
Watch a video about what happens when you buy things. Your purchases have a real impact, for better or worse.
7.Borrow instead of buying.
Borrow from libraries instead of buying personal books and movies. This saves money, not to mention the ink and paper that goes into printing new books.
Share power tools and other appliances. Get to know your neighbors while cutting down on the number of things cluttering your closet or garage.
8.Buy smart.
Great for classrooms:
Climate Change
Reference GuideBuy in bulk. Purchasing food from bulk bins can save money and packaging.
Wear clothes that don't need to be dry-cleaned. This saves money and cuts down on toxic chemical use.
Invest in high-quality, long-lasting products. You might pay more now, but you'll be happy when you don't have to replace items as frequently (and this means less waste!).
9.Keep electronics out of the trash.
Keep your cell phones, computers, and other electronics as long as possible.
Donate or recycle them responsibly when the time comes. E-waste contains mercury and other toxics and is a growing environmental problem.
Recycle your cell phone.
Ask your local government to set up an electronics recycling and hazardous waste collection event.
10.Make your own cleaning supplies.
Join the Million Car Carbon Campaign by purchasing your Earth-Aid kit today.
The big secret: you can make very effective, non-toxic cleaning products whenever you need them. All you need are a few simple ingredients like baking soda, vinegar, lemon, and soap.
Making your own cleaning products saves money, time, and packaging-not to mention your indoor air quality.
Sunday, August 7, 2011
Successful Zero Energy House
Successful Zero Energy House
To maximize efficiency, the same concept is applied to a home. The building shell, the windows, the HVAC, the hot water, the electrical are designed and constructed to optimize performance.
Here's a look at the components:
1. Design and Orientation: Roof overhangs, window size and placement, and overall home shape have a major impact. Consider the direction of prevailing winds and how to manage solar gain. If you will be using solar collectors, ensure that a portion of the roof faces true south. The placement of porches, garages, trees, and nearby buildings also have an effect.
2. Insulate and Seal the Building Envelope: Most of a home's energy is spent heating and cooling the interior. Minimizing heating and cooling requirements is the most important step in building a ZEH.
a. High R-Value Insulation: For a zero energy home, use high R-value insulation that provides a continuous, unbroken layer around the building envelope. Remember to insulate under the slab as well. Use a high-insulation, tightly-sealed roof system, such as Quad-Deck or closed cell spray foam. Seal all holes, cracks, and penetrations through the floor, walls, and ceiling to unconditioned spaces.
b. Concrete Thermal Mass: Build exterior walls and floors with concrete. Concrete will moderate temperature swings, and can even dampen seasonal fluctuations by "spreading" the constant ground temperature from the footings throughout the home.
c. Airtight Construction: ICFs will ensure airtight walls. Ensure that all windows and doors are tight and meet the required air-leakage standards. The roof and/or ceiling needs special attention, as do the kitchen and bathrooms, to make sure they have adequate ventilation but still maintain energy efficiency.
d. Windows and Doors: Use triple glazed windows and well insulated or double external doors. The passive gain of incoming solar heat through the windows will cover close to 40% of the heat losses, if all guidelines are followed. Skylights can decrease artificial lighting requirements, but use a high-quality, double glazed product.
3. Increase Heating and Cooling Efficiency: The heating and cooling systems need to be carefully matched to the high-efficiency building envelope. Standard-sized equipment will "short-cycle," turning on and off so frequently that it will negate any energy savings. Buying properly sized equipment will ensure maximum efficiency. Another benefit: smaller equipment will cost less.
a. Buy as high-efficiency equipment as affordable.
b. Take Advantage of Earth Temperature: Install a geothermal pump or/and a ground-air heat exchanger where space and cost conditions permit.
c. Radiant Floor Heating: Radiant floor heating (e.g. with Quad-Deck) provides warmth in a pattern that mimics the body, improving comfort. It heats evenly without drafts and uses far less energy than conventional systems. It also reduces noise and allows room by room zoning.
d. Optimize Ducting: Design the supply and return ducts appropriately and seal tightly using approved tapes or mastic. Run ducting in conditioned space only.
e. Alternate Cooling Methods: Where appropriate, consider alternative cooling systems such as ventilation only or evaporative coolers.
4. Decrease Other Energy Requirements: Decrease energy needs as much as possible throughout the home.
a. Install efficient lighting: Use compact fluorescent bulbs where possible, and consider installing permanent fluorescent fixtures throughout the home.
b. Install efficient appliances: Use the most energy efficient models available. Focus especially on the refrigerator, dishwasher, and laundry appliances, as they use the most energy. Look for the Energy Star label to help make decisions.
c. Tankless Water Heaters: Use tankless water heaters, especially if the home will not be constantly occupied. Low-flow fixtures in showers and faucets will also decrease hot water demands.
d. Turn off lights, computers, and appliances when not in use: The homeowner has the most significant impact on the actual performance of the ZEH. Programmable thermostats and photo-sensitive outdoor light fixtures will do some of this automatically. Simple things such as turning off lights when leaving a room or closing doors when performing even quick tasks outdoors can eliminate "wasted" energy.
5. Install Energy Generation Equipment such as solar panels
Remember the concept of "system engineering." Often, low-efficiency components can be compensated for in other areas. For instance a house with many doors may require significant improvement in other components, while a well designed, moderately-sized house may find standard doors sufficient
To maximize efficiency, the same concept is applied to a home. The building shell, the windows, the HVAC, the hot water, the electrical are designed and constructed to optimize performance.
Here's a look at the components:
1. Design and Orientation: Roof overhangs, window size and placement, and overall home shape have a major impact. Consider the direction of prevailing winds and how to manage solar gain. If you will be using solar collectors, ensure that a portion of the roof faces true south. The placement of porches, garages, trees, and nearby buildings also have an effect.
2. Insulate and Seal the Building Envelope: Most of a home's energy is spent heating and cooling the interior. Minimizing heating and cooling requirements is the most important step in building a ZEH.
a. High R-Value Insulation: For a zero energy home, use high R-value insulation that provides a continuous, unbroken layer around the building envelope. Remember to insulate under the slab as well. Use a high-insulation, tightly-sealed roof system, such as Quad-Deck or closed cell spray foam. Seal all holes, cracks, and penetrations through the floor, walls, and ceiling to unconditioned spaces.
b. Concrete Thermal Mass: Build exterior walls and floors with concrete. Concrete will moderate temperature swings, and can even dampen seasonal fluctuations by "spreading" the constant ground temperature from the footings throughout the home.
c. Airtight Construction: ICFs will ensure airtight walls. Ensure that all windows and doors are tight and meet the required air-leakage standards. The roof and/or ceiling needs special attention, as do the kitchen and bathrooms, to make sure they have adequate ventilation but still maintain energy efficiency.
d. Windows and Doors: Use triple glazed windows and well insulated or double external doors. The passive gain of incoming solar heat through the windows will cover close to 40% of the heat losses, if all guidelines are followed. Skylights can decrease artificial lighting requirements, but use a high-quality, double glazed product.
3. Increase Heating and Cooling Efficiency: The heating and cooling systems need to be carefully matched to the high-efficiency building envelope. Standard-sized equipment will "short-cycle," turning on and off so frequently that it will negate any energy savings. Buying properly sized equipment will ensure maximum efficiency. Another benefit: smaller equipment will cost less.
a. Buy as high-efficiency equipment as affordable.
b. Take Advantage of Earth Temperature: Install a geothermal pump or/and a ground-air heat exchanger where space and cost conditions permit.
c. Radiant Floor Heating: Radiant floor heating (e.g. with Quad-Deck) provides warmth in a pattern that mimics the body, improving comfort. It heats evenly without drafts and uses far less energy than conventional systems. It also reduces noise and allows room by room zoning.
d. Optimize Ducting: Design the supply and return ducts appropriately and seal tightly using approved tapes or mastic. Run ducting in conditioned space only.
e. Alternate Cooling Methods: Where appropriate, consider alternative cooling systems such as ventilation only or evaporative coolers.
4. Decrease Other Energy Requirements: Decrease energy needs as much as possible throughout the home.
a. Install efficient lighting: Use compact fluorescent bulbs where possible, and consider installing permanent fluorescent fixtures throughout the home.
b. Install efficient appliances: Use the most energy efficient models available. Focus especially on the refrigerator, dishwasher, and laundry appliances, as they use the most energy. Look for the Energy Star label to help make decisions.
c. Tankless Water Heaters: Use tankless water heaters, especially if the home will not be constantly occupied. Low-flow fixtures in showers and faucets will also decrease hot water demands.
d. Turn off lights, computers, and appliances when not in use: The homeowner has the most significant impact on the actual performance of the ZEH. Programmable thermostats and photo-sensitive outdoor light fixtures will do some of this automatically. Simple things such as turning off lights when leaving a room or closing doors when performing even quick tasks outdoors can eliminate "wasted" energy.
5. Install Energy Generation Equipment such as solar panels
Remember the concept of "system engineering." Often, low-efficiency components can be compensated for in other areas. For instance a house with many doors may require significant improvement in other components, while a well designed, moderately-sized house may find standard doors sufficient
GREEN BUILDING Zero energy
GREEN BUILDING Zero energy
Imagine buildings as elegant and efficient as a flower. Imagine a building that is informed by its eco-region's characteristics and that
generates all of its own energy with renewable resources
captures and treats all of its water, and
operates efficiently, and for maximum beauty
Produces its own vegetable on its green roof
THIS IS NOT AN IMAGINATION ANYMORE
Green Building refers to design and construction practices that significantly reduce or eliminate the negative impact of buildings on the environment and occupants. Potential positive effects of green building practices include sustainable use of energy, materials, and water, along with lower resource and waste disposal costs, as well as increased comfort and well-being for occupants. Buildings designed in an environmentally conscious manner represent an important opportunity to accrue environmental benefits for generations.
1. Use energy-efficient lights. Compact fluorescent bulbs use 66% less energy and last 5000 hours, ten times longer than a regular (incandescent) bulb. Which means they save you a lot of money? Cold cathode lights use the same energy as compact fluorescents but last an incredible 25,000 hours and can be used outside. They're currently only available to replace regular 20-25 watt bulbs and need to be ordered online (energyfederation.org, goodmart.com). If every US household replaced just one light bulb with a compact fluorescent or cold cathode bulb, it would prevent enough pollution to equal removing one million cars from the road. 1
2. Change your heating and cooling settings. Reduce your water heater temperature to between 115 and 120QF. Lower your thermostat to 68 degrees in the winter and turn it down at night. Raise it to no
more than 78 degrees in the summer. Almost half the energy used in a home goes to heating and cooling. 2
3. Plug the gaps in your home that allow heat to escape. This could save up to 10% on utility bills. Install weather-stripping around exterior doors and along thresholds. If the gap at the bottom of a door is high, install a door sweep. Use expanding foam to seal around pipes that enter your house from the outside. Check the joints and insulation on the ducts of your heating/ventilation/air conditioning system. Fix any leaks with mastic sealant. Make sure your water heater is wrapped in an insulation jacket, particularly if the unit is in an unheated part of the house. And definitely keep fireplace dampers closed when not in use!
4. Recycle, Yes, this oldie is still a goodie. Make sure you have separate bins or boxes for recyclables to make it super easy for everyone. 35% of the waste in landfills is recyclable paper and paperboard. Only 22% of glass waste is recycled. About 40% of aluminum is recycled And recycle your food, too! Start a compost bin (or a worm bin!) for all vegetable and garden waste. 10% of the waste in landfills is food.3
5. Use no-VOC and low-VOC primers, paints, sealants, and carpets. Volatile Organic Compounds can irritate eyes and throat, cause headaches and fatigue, damage major organs, and cause cancer. AFM Safecoat is one company that makes only no and low-VOC products. They do cost a little bit more, but it’s worth it for your health.
* we'll throw in an extra tip for free! where you live has a huge impact on the ENVIRONMENT BECAUSE IT AFFECTS HOW MUCH YOU DRIVE. NOT MUCH YOU CAN DO ABOUT THIS IF YOU ALREADY OWN A HOME. BUT IT IS DEFINITELY AN OPTION FOR YOU TO SAVE A LOT OF MONEY WHILE RESPECTING THE ENVIRONMENT AND FUTURE GENERATIONS OF PEOPLE BY
CHOOSING A CAR THAT GETS GOOD GAS MILEAGE AND MINIMIZING YOUR TIME DRIVING.
hybrid cars definitely get the best mileage out there --with the toyota PRIUS AND honda Civic getting over 50mpg and the honda insight 65. but THERE ARE MANY REGULAR CARS THAT GET OVER 40 AS WELL. AND WHILE SUVs STILL CANNOT COMPARE FOR MILEAGE OR SAFETY, THE HYBRID VERSIONS ARE MUCH LESS WASTEFUL THAN REGULAR SUVS. THE MOST EFFICIENT HYBRID SUV, THE FORD ESCAPE, ACTUALLY GETS OVER 30MPG.
AND WHATEVER CAR YOU DRIVE, YOU CAN MAKE A HUGE DIFFERENCE BY PLANNING YOUR TRAVELING SO YOU TAKE CARE OF ALL YOUR ERRANDS IN ONE RUN RATHER THAN MANY. THIS WILL SAVE YOU TIME AS WELL, GIVING YOU MORE SPACE IN YOUR LIFE FOR THE THINGS YOU ENJOY. THE HUDSON VALLEY IS NOT GREAT FOR PUBLIC TRANSPORTATION, BUT MUCH OF IT IS HEAVEN FOR CYCLISTS. TAKING SMALL TRIPS BY BIKE WILL HELP SAVE YOUR BODY WHILE SAVING THE EARTH!
6. Great insulation is the most cost-effective energy saver there is. No use getting fancy with things like solar panels if your home leaks energy! Try to get your attic insulation value up to R-50 and your walls up to R-30. Blowing in cellulose (made of recycled newspaper) is the best for insulating a closed wall. If you are doing a big renovation or are able to open up the wall you have two options. If you have limited space and need to keep the wall the same size, then isonene is more environmentally-friendly than other foams and gets twice the insulation value of cellulose when not sprayed in? If you spray it in it only gets the same as cellulose which is a better product because it is recycled. Which is why cellulose is also the best option if you can increase the wall size to get the insulation value you wants using cellulose rather than foam? Atlas Roofing also offers polyisocyanurate board, that is a good insulator and that is made with no ozone-depleting chemicals. You should replace older windows with Energy Star windows (go for three panes if you scan) with a low-E coating. Pella Designer Series windows are currently the most energy-efficient windows that are widely available. Inefficient windows and doors cost Americans $40 billion each year in higher utility costs and waste as much energy as the US gets from the Alaska Pipelines.4
7. When you replace old appliances and water heaters, be sure to select models with the Energy Star symbol. They use 10-50% less energy than standard appliances, the change would be like planting 1.7 million new acres of trees. 5
8. Install Energy Star ceiling fans. Casablanca is a brand that offers a wide variety of quality fans. This will cut costs by circulating heat in the winter and cooling air in the summer.
9. Install solar panels – and leave out the batteries! Solar panels can help you avoid the massive environmental and social ills of coal, nuclear, natural gas, and big dam projects. New York State and other states will foot half the bill, and New York allows you to “Net Meter”. That means you stay connected to the electrical grid and any time you produce more electricity than you use, it gets sent into the grid for someone else to use and your meter runs backward – so you are part of helping provide clean energy to your neighbors. Then when you need more than your panels produce, you just draw from the grid like normal. This allows you to not use batteries, which are not so good for the environment, add a lot to the cost, and can only store so much energy before any extra is just lost.
10. Install geothermal heating and cooling. A geothermal system uses the earth’s constant underground temperature to cool and heat your home, as well as provide all of your domestic hot water. It uses about 50% less energy to heat your home and about 25% less to cool it.
11. Replace your toilets with “dual flushers”. 40% of the water used in a home goes right down the toilet. A dual-flush toilet lets you choose whether you need a big or a little flush. This simple choice saves at least 6,000 gallons of water per year for a family of four. They cost a little more, but not much. Low-flow shower and sink fixtures (with restrictors) will save additional water, much of it hot water, which saves money! (You can also use tankless water heater). 6
12. Buy green power or offset you carbon emissions. In New York State and other states you can choose who supplies your electricity and there are many companies that use renewable sources, such as solar, wind, and hydro power. It is very easy and reliable to switch. Just call your local utility or visit their website. If you are served by Central Hudson, sadly, none of the options is very green. But do not let that stop you! You can offset the electricity you use in your building or the emissions from your car or any flights you take by going on line and paying for the creation of an equivalent amount of clean energy. Two popular and reliable websites are nativeenergy.org and carbonfund.org.
13. When you need to replace the roof, consider a metal roof. They are long lasting, often made of recycled material, help to deflect heat in the summer, and are recyclable. Asphalt shingles are short-lived, made of oil, are rarely recycled, and give off toxic VOCs which can be drawn into the house. If you have to go asphalt, make sure you go with the 50-year asphalt shingles with recycled content. Regardless, never drink water coming off asphalt.
14. If you are re-siding your house, do not use vinyl (PVC) siding. Dioxins are a byproduct of PVC. They also happen to be the most toxic substance on the planet known to cause cancer, neurological damage, birth defects, and more. In the US, PVC is manufactured predominantly near low-income communities in Texas and Louisiana. Due to illegal dumping, mishandling, and burning, dioxins are now found all around the world – they are even detectable in our bodies. Dioxin exposure of the average American poses a risk of cancer of greater than 1 in 1,000. PVC is not biodegradable and less than 1% can be recycled. Powerful information about PVC and its alternatives can be found at www.healthybuilding.net/pvc/index.html
15. Whenever you do renovation work, be sure to buy FSC certified wood. The Forest Stewardship Council provides independent audits that assure the wood you buy was not stolen from protected lands or lands of indigenous people without their consent. The FSC label also means wood was not taken from fragile ecosystems, that it was harvested sustainably, and that local communities benefit from the process. Sadly, all too often wood without the FSC symbol was clear cut, or stolen from protected or sensitive lands, or from lands of indigenous people, and more.
16. Utilize rainwater for non-drinking purposes.
Imagine buildings as elegant and efficient as a flower. Imagine a building that is informed by its eco-region's characteristics and that
generates all of its own energy with renewable resources
captures and treats all of its water, and
operates efficiently, and for maximum beauty
Produces its own vegetable on its green roof
THIS IS NOT AN IMAGINATION ANYMORE
Green Building refers to design and construction practices that significantly reduce or eliminate the negative impact of buildings on the environment and occupants. Potential positive effects of green building practices include sustainable use of energy, materials, and water, along with lower resource and waste disposal costs, as well as increased comfort and well-being for occupants. Buildings designed in an environmentally conscious manner represent an important opportunity to accrue environmental benefits for generations.
1. Use energy-efficient lights. Compact fluorescent bulbs use 66% less energy and last 5000 hours, ten times longer than a regular (incandescent) bulb. Which means they save you a lot of money? Cold cathode lights use the same energy as compact fluorescents but last an incredible 25,000 hours and can be used outside. They're currently only available to replace regular 20-25 watt bulbs and need to be ordered online (energyfederation.org, goodmart.com). If every US household replaced just one light bulb with a compact fluorescent or cold cathode bulb, it would prevent enough pollution to equal removing one million cars from the road. 1
2. Change your heating and cooling settings. Reduce your water heater temperature to between 115 and 120QF. Lower your thermostat to 68 degrees in the winter and turn it down at night. Raise it to no
more than 78 degrees in the summer. Almost half the energy used in a home goes to heating and cooling. 2
3. Plug the gaps in your home that allow heat to escape. This could save up to 10% on utility bills. Install weather-stripping around exterior doors and along thresholds. If the gap at the bottom of a door is high, install a door sweep. Use expanding foam to seal around pipes that enter your house from the outside. Check the joints and insulation on the ducts of your heating/ventilation/air conditioning system. Fix any leaks with mastic sealant. Make sure your water heater is wrapped in an insulation jacket, particularly if the unit is in an unheated part of the house. And definitely keep fireplace dampers closed when not in use!
4. Recycle, Yes, this oldie is still a goodie. Make sure you have separate bins or boxes for recyclables to make it super easy for everyone. 35% of the waste in landfills is recyclable paper and paperboard. Only 22% of glass waste is recycled. About 40% of aluminum is recycled And recycle your food, too! Start a compost bin (or a worm bin!) for all vegetable and garden waste. 10% of the waste in landfills is food.3
5. Use no-VOC and low-VOC primers, paints, sealants, and carpets. Volatile Organic Compounds can irritate eyes and throat, cause headaches and fatigue, damage major organs, and cause cancer. AFM Safecoat is one company that makes only no and low-VOC products. They do cost a little bit more, but it’s worth it for your health.
* we'll throw in an extra tip for free! where you live has a huge impact on the ENVIRONMENT BECAUSE IT AFFECTS HOW MUCH YOU DRIVE. NOT MUCH YOU CAN DO ABOUT THIS IF YOU ALREADY OWN A HOME. BUT IT IS DEFINITELY AN OPTION FOR YOU TO SAVE A LOT OF MONEY WHILE RESPECTING THE ENVIRONMENT AND FUTURE GENERATIONS OF PEOPLE BY
CHOOSING A CAR THAT GETS GOOD GAS MILEAGE AND MINIMIZING YOUR TIME DRIVING.
hybrid cars definitely get the best mileage out there --with the toyota PRIUS AND honda Civic getting over 50mpg and the honda insight 65. but THERE ARE MANY REGULAR CARS THAT GET OVER 40 AS WELL. AND WHILE SUVs STILL CANNOT COMPARE FOR MILEAGE OR SAFETY, THE HYBRID VERSIONS ARE MUCH LESS WASTEFUL THAN REGULAR SUVS. THE MOST EFFICIENT HYBRID SUV, THE FORD ESCAPE, ACTUALLY GETS OVER 30MPG.
AND WHATEVER CAR YOU DRIVE, YOU CAN MAKE A HUGE DIFFERENCE BY PLANNING YOUR TRAVELING SO YOU TAKE CARE OF ALL YOUR ERRANDS IN ONE RUN RATHER THAN MANY. THIS WILL SAVE YOU TIME AS WELL, GIVING YOU MORE SPACE IN YOUR LIFE FOR THE THINGS YOU ENJOY. THE HUDSON VALLEY IS NOT GREAT FOR PUBLIC TRANSPORTATION, BUT MUCH OF IT IS HEAVEN FOR CYCLISTS. TAKING SMALL TRIPS BY BIKE WILL HELP SAVE YOUR BODY WHILE SAVING THE EARTH!
6. Great insulation is the most cost-effective energy saver there is. No use getting fancy with things like solar panels if your home leaks energy! Try to get your attic insulation value up to R-50 and your walls up to R-30. Blowing in cellulose (made of recycled newspaper) is the best for insulating a closed wall. If you are doing a big renovation or are able to open up the wall you have two options. If you have limited space and need to keep the wall the same size, then isonene is more environmentally-friendly than other foams and gets twice the insulation value of cellulose when not sprayed in? If you spray it in it only gets the same as cellulose which is a better product because it is recycled. Which is why cellulose is also the best option if you can increase the wall size to get the insulation value you wants using cellulose rather than foam? Atlas Roofing also offers polyisocyanurate board, that is a good insulator and that is made with no ozone-depleting chemicals. You should replace older windows with Energy Star windows (go for three panes if you scan) with a low-E coating. Pella Designer Series windows are currently the most energy-efficient windows that are widely available. Inefficient windows and doors cost Americans $40 billion each year in higher utility costs and waste as much energy as the US gets from the Alaska Pipelines.4
7. When you replace old appliances and water heaters, be sure to select models with the Energy Star symbol. They use 10-50% less energy than standard appliances, the change would be like planting 1.7 million new acres of trees. 5
8. Install Energy Star ceiling fans. Casablanca is a brand that offers a wide variety of quality fans. This will cut costs by circulating heat in the winter and cooling air in the summer.
9. Install solar panels – and leave out the batteries! Solar panels can help you avoid the massive environmental and social ills of coal, nuclear, natural gas, and big dam projects. New York State and other states will foot half the bill, and New York allows you to “Net Meter”. That means you stay connected to the electrical grid and any time you produce more electricity than you use, it gets sent into the grid for someone else to use and your meter runs backward – so you are part of helping provide clean energy to your neighbors. Then when you need more than your panels produce, you just draw from the grid like normal. This allows you to not use batteries, which are not so good for the environment, add a lot to the cost, and can only store so much energy before any extra is just lost.
10. Install geothermal heating and cooling. A geothermal system uses the earth’s constant underground temperature to cool and heat your home, as well as provide all of your domestic hot water. It uses about 50% less energy to heat your home and about 25% less to cool it.
11. Replace your toilets with “dual flushers”. 40% of the water used in a home goes right down the toilet. A dual-flush toilet lets you choose whether you need a big or a little flush. This simple choice saves at least 6,000 gallons of water per year for a family of four. They cost a little more, but not much. Low-flow shower and sink fixtures (with restrictors) will save additional water, much of it hot water, which saves money! (You can also use tankless water heater). 6
12. Buy green power or offset you carbon emissions. In New York State and other states you can choose who supplies your electricity and there are many companies that use renewable sources, such as solar, wind, and hydro power. It is very easy and reliable to switch. Just call your local utility or visit their website. If you are served by Central Hudson, sadly, none of the options is very green. But do not let that stop you! You can offset the electricity you use in your building or the emissions from your car or any flights you take by going on line and paying for the creation of an equivalent amount of clean energy. Two popular and reliable websites are nativeenergy.org and carbonfund.org.
13. When you need to replace the roof, consider a metal roof. They are long lasting, often made of recycled material, help to deflect heat in the summer, and are recyclable. Asphalt shingles are short-lived, made of oil, are rarely recycled, and give off toxic VOCs which can be drawn into the house. If you have to go asphalt, make sure you go with the 50-year asphalt shingles with recycled content. Regardless, never drink water coming off asphalt.
14. If you are re-siding your house, do not use vinyl (PVC) siding. Dioxins are a byproduct of PVC. They also happen to be the most toxic substance on the planet known to cause cancer, neurological damage, birth defects, and more. In the US, PVC is manufactured predominantly near low-income communities in Texas and Louisiana. Due to illegal dumping, mishandling, and burning, dioxins are now found all around the world – they are even detectable in our bodies. Dioxin exposure of the average American poses a risk of cancer of greater than 1 in 1,000. PVC is not biodegradable and less than 1% can be recycled. Powerful information about PVC and its alternatives can be found at www.healthybuilding.net/pvc/index.html
15. Whenever you do renovation work, be sure to buy FSC certified wood. The Forest Stewardship Council provides independent audits that assure the wood you buy was not stolen from protected lands or lands of indigenous people without their consent. The FSC label also means wood was not taken from fragile ecosystems, that it was harvested sustainably, and that local communities benefit from the process. Sadly, all too often wood without the FSC symbol was clear cut, or stolen from protected or sensitive lands, or from lands of indigenous people, and more.
16. Utilize rainwater for non-drinking purposes.
Strategies for Reining In Energy Costs
Strategies for Reining In Energy Costs
With gasoline surging toward $5 a gallon -- and oil flirting with $150 a barrel -- small businesses are scrambling to figure out how to keep their costs in check this summer.
Experts say small companies should start actively pursuing ways to lower their energy bills now, since rising energy prices aren't likely to abate anytime soon.
But with so many energy-saving strategies out there -- and not all equally cost-effective -- how do owners find the most appropriate strategies for their companies? Here are some tips:
Target the big culprits. It's tempting to take a patchwork approach to saving on energy. But for many time- and cash-strapped entrepreneurs, it's more practical to concentrate on the biggest energy sappers first. That's where they'll see the most bang for the buck.
Restaurants, for instance, might focus on installing highly efficient refrigeration systems and lighting, since those tend to be their biggest energy costs, says Virginia Lacy, a consultant for the Rocky Mountain Institute, a Snowmass, Colo., nonprofit that promotes energy conservation. Laundromats should consider buying an energy-efficient water heater. Consultants frequently on the road might switch to a vehicle with better gas mileage -- or cut the number of in-person meetings altogether.
For Susan Velie, owner of Cherry Hill Florists in Port Angeles, Wash., the big issue was driving. Her shop used to make deliveries twice a day, but she recently cut back to just one and raised her delivery rates to remote areas. She uses online mapping sites, like MapQuest.com, to plan efficient delivery routes and is considering buying Global Positioning System equipment for her fleet.
"We don't want our drivers circling the block 10 times to find a particular address," Ms. Velie says.
Her challenge is to adopt cost-saving strategies without alienating customers, who also are struggling with rising expenses. Ms. Velie has refrained from raising prices too much since flowers are a discretionary expense.
Sherwood Design Engineers altered its travel practices. The San Francisco civil-engineering firm began using Web conferencing last year, instead of having employees travel between its San Francisco and New York offices. The firm spends about $5,000 annually on equipment and service charges. But it saves about $48,000 annually in travel costs, says Bry Sarte, the firm's founder and chief executive.
Take small steps. Once the large energy zappers are taken care of, focus on small adjustments that could yield big savings as well.
Turn off equipment and lights when not in use and make sure there is adequate building insulation. Energy-efficient light bulbs often cost several dollars more than standard light bulbs, yet they can pay for themselves in three years or less.
Other relatively affordable steps include installing programmable thermostats and motion sensors, which help control room temperature and lighting over the course of a day. These often cost less than a few hundred dollars each.
A so-called building recommissioning, or a professional building tuneup, can help a business save up to 10% on energy costs, says Ms. Lacy of the Rocky Mountain Institute. This might mean cleaning out and checking for leaks in a heating and air-conditioning system to ensure maximum efficiency. "It helps restore the optimal performance of your equipment," she adds, so you don't have to necessarily buy new equipment.
Get an energy audit. For many businesses the problem is figuring out what energy-saving strategies will reap the fastest returns.
Installing solar panels on the roof, for instance, can make dramatic reductions in a business's energy purchases but they take more than a decade to pay for themselves in many parts of the U.S. Many businesses want to see returns on investment in less than seven years.
So-called energy auditors can help a business determine which projects may garner the fastest returns. An auditor will thoroughly analyze a business's energy usage by poring over energy bills and inspecting its equipment and building environment. The auditor will then recommend steps that a business can take, and sometimes even suggest specific replacement equipment.
Auditors also can help companies qualify for state and federal tax rebates and other available incentives. In addition, they can help businesses find the best utility rate plans based on their usage patterns.
Many local utility companies offer free energy audits to their small-business customers. If not, the power company can refer you to a reliable auditor. Find out about energy audit programs in a given state and other incentives at dsireusa.org.
Consult the power company. Many utilities can help businesses find utility rate plans that best fit their usage patterns. For instance, a business that uses the bulk of its energy at night might qualify for an off-peak rate plan, with lower rates on energy during its busy hours.
Some utilities offer fixed-rate plans or prepayment plans that can help control rising energy costs by letting companies lock in their rates. No-interest loans and other incentives are often offered through utilities for businesses that make upgrades that improve their energy efficiency.
With gasoline surging toward $5 a gallon -- and oil flirting with $150 a barrel -- small businesses are scrambling to figure out how to keep their costs in check this summer.
Experts say small companies should start actively pursuing ways to lower their energy bills now, since rising energy prices aren't likely to abate anytime soon.
But with so many energy-saving strategies out there -- and not all equally cost-effective -- how do owners find the most appropriate strategies for their companies? Here are some tips:
Target the big culprits. It's tempting to take a patchwork approach to saving on energy. But for many time- and cash-strapped entrepreneurs, it's more practical to concentrate on the biggest energy sappers first. That's where they'll see the most bang for the buck.
Restaurants, for instance, might focus on installing highly efficient refrigeration systems and lighting, since those tend to be their biggest energy costs, says Virginia Lacy, a consultant for the Rocky Mountain Institute, a Snowmass, Colo., nonprofit that promotes energy conservation. Laundromats should consider buying an energy-efficient water heater. Consultants frequently on the road might switch to a vehicle with better gas mileage -- or cut the number of in-person meetings altogether.
For Susan Velie, owner of Cherry Hill Florists in Port Angeles, Wash., the big issue was driving. Her shop used to make deliveries twice a day, but she recently cut back to just one and raised her delivery rates to remote areas. She uses online mapping sites, like MapQuest.com, to plan efficient delivery routes and is considering buying Global Positioning System equipment for her fleet.
"We don't want our drivers circling the block 10 times to find a particular address," Ms. Velie says.
Her challenge is to adopt cost-saving strategies without alienating customers, who also are struggling with rising expenses. Ms. Velie has refrained from raising prices too much since flowers are a discretionary expense.
Sherwood Design Engineers altered its travel practices. The San Francisco civil-engineering firm began using Web conferencing last year, instead of having employees travel between its San Francisco and New York offices. The firm spends about $5,000 annually on equipment and service charges. But it saves about $48,000 annually in travel costs, says Bry Sarte, the firm's founder and chief executive.
Take small steps. Once the large energy zappers are taken care of, focus on small adjustments that could yield big savings as well.
Turn off equipment and lights when not in use and make sure there is adequate building insulation. Energy-efficient light bulbs often cost several dollars more than standard light bulbs, yet they can pay for themselves in three years or less.
Other relatively affordable steps include installing programmable thermostats and motion sensors, which help control room temperature and lighting over the course of a day. These often cost less than a few hundred dollars each.
A so-called building recommissioning, or a professional building tuneup, can help a business save up to 10% on energy costs, says Ms. Lacy of the Rocky Mountain Institute. This might mean cleaning out and checking for leaks in a heating and air-conditioning system to ensure maximum efficiency. "It helps restore the optimal performance of your equipment," she adds, so you don't have to necessarily buy new equipment.
Get an energy audit. For many businesses the problem is figuring out what energy-saving strategies will reap the fastest returns.
Installing solar panels on the roof, for instance, can make dramatic reductions in a business's energy purchases but they take more than a decade to pay for themselves in many parts of the U.S. Many businesses want to see returns on investment in less than seven years.
So-called energy auditors can help a business determine which projects may garner the fastest returns. An auditor will thoroughly analyze a business's energy usage by poring over energy bills and inspecting its equipment and building environment. The auditor will then recommend steps that a business can take, and sometimes even suggest specific replacement equipment.
Auditors also can help companies qualify for state and federal tax rebates and other available incentives. In addition, they can help businesses find the best utility rate plans based on their usage patterns.
Many local utility companies offer free energy audits to their small-business customers. If not, the power company can refer you to a reliable auditor. Find out about energy audit programs in a given state and other incentives at dsireusa.org.
Consult the power company. Many utilities can help businesses find utility rate plans that best fit their usage patterns. For instance, a business that uses the bulk of its energy at night might qualify for an off-peak rate plan, with lower rates on energy during its busy hours.
Some utilities offer fixed-rate plans or prepayment plans that can help control rising energy costs by letting companies lock in their rates. No-interest loans and other incentives are often offered through utilities for businesses that make upgrades that improve their energy efficiency.
How Power Grids Work
How Power Grids Work
by Marshall Brain
Inside This Article
1.
Introduction to How Power Grids Work
2.
The Power Plant
3.
The Power Plant: Alternating Current
4.
The Power Plant: Three-phase Power
5.
Transmission Substation
6.
The Distribution Grid
7.
Distribution Bus
8.
Regulator Bank
9.
Taps
10.
At the House
11.
Safety Devices: Fuses
12.
Safety Devices: Circuit Breakers
13.
Lots More Information
14.
See all Energy Production articles
Electrical power is a little bit like the air you breathe: You don't really think about it until it is missing. Power is just "there," meeting your every need, constantly. It is only during a power failure, when you walk into a dark room and instinctively hit the useless light switch, that you realize how important power is in your daily life. You use it for heating, cooling, cooking, refrigeration, light, sound, computation, entertainment... Without it, life can get somewhat cumbersome.
Power travels from the power plant to your house through an amazing system called the power distribution grid.
Power grid distribution lines can be above or under ground. See more power grid pictures.
The grid is quite public -- if you live in a suburban or rural area, chances are it is right out in the open for all to see. It is so public, in fact, that you probably don't even notice it anymore. Your brain likely ignores all of the power lines because it has seen them so often. In this article, we will look at all of the equipment that brings electrical power to your home. The next time you look at the power grid, you will be able to really see it and understand what is going on!
The Power Plant
Electrical power starts at the power plant. In almost all cases, the power plant consists of a spinning electrical generator. Something has to spin that generator -- it might be a water wheel in a hydroelectric dam, a large diesel engine or a gas turbine. But in most cases, the thing spinning the generator is a steam turbine. The steam might be created by burning coal, oil or natural gas. Or the steam may come from a nuclear reactor like this one at the Shearon Harris nuclear power plant near Raleigh, North Carolina:
No matter what it is that spins the generator, commercial electrical generators of any size generate what is called 3-phase AC power. To understand 3-phase AC power, it is helpful to understand single-phase power first.
Photo courtesy U.S. Department of Energy
A breakdown of the major power plants in
the United States, by type
The Power Plant: Alternating Current
Single-phase power is what you have in your house. You generally talk about household electrical service as single-phase, 120-volt AC service. If you use an oscilloscope and look at the power found at a normal wall-plate outlet in your house, what you will find is that the power at the wall plate looks like a sine wave, and that wave oscillates between -170 volts and 170 volts (the peaks are indeed at 170 volts; it is the effective (rms) voltage that is 120 volts). The rate of oscillation for the sine wave is 60 cycles per second. Oscillating power like this is generally referred to as AC, or alternating current. The alternative to AC is DC, or direct current. Batteries produce DC: A steady stream of electrons flows in one direction only, from the negative to the positive terminal of the battery.
AC has at least three advantages over DC in a power distribution grid:
1. Large electrical generators happen to generate AC naturally, so conversion to DC would involve an extra step.
2. Transformers must have alternating current to operate, and we will see that the power distribution grid depends on transformers.
3. It is easy to convert AC to DC but expensive to convert DC to AC, so if you were going to pick one or the other AC would be the better choice.
The Power Plant: Three-phase Power
The power plant produces three different phases of AC power simultaneously, and the three phases are offset 120 degrees from each other. There are four wires coming out of every power plant: the three phases plus a neutral or ground common to all three. If you were to look at the three phases on a graph, they would look like this relative to ground:
There is nothing magical about three-phase power. It is simply three single phases synchronized and offset by 120 degrees.
Why three phases? Why not one or two or four? In 1-phase and 2-phase power, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point.
And what about this "ground," as mentioned above? The power company essentially uses the earth as one of the wires in the power system. The earth is a pretty good conductor and it is huge, so it makes a good return path for electrons. (Car manufacturers do something similar; they use the metal body of the car as one of the wires in the car's electrical system and attach the negative pole of the battery to the car's body.) "Ground" in the power distribution grid is literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks, groundwater, etc., of the earth.
Transmission Substation
The three-phase power leaves the generator and enters a transmission substation at the power plant. This substation uses large transformers to convert the generator's voltage (which is at the thousands of volts level) up to extremely high voltages for long-distance transmission on the transmission grid.
A typical substation at a power plant
You can see at the back several three-wire towers leaving the substation. Typical voltages for long distance transmission are in the range of 155,000 to 765,000 volts in order to reduce line losses. A typical maximum transmission distance is about 300 miles (483 km). High-voltage transmission lines are quite obvious when you see them. They are normally made of huge steel towers like this:
All power towers like this have three wires for the three phases. Many towers, like the ones shown above, have extra wires running along the tops of the towers. These are ground wires and are there primarily in an attempt to attract lightning.
The Distribution Grid
For power to be useful in a home or business, it comes off the transmission grid and is stepped-down to the distribution grid. This may happen in several phases. The place where the conversion from "transmission" to "distribution" occurs is in a power substation. A power substation typically does two or three things:
It has transformers that step transmission voltages (in the tens or hundreds of thousands of volts range) down to distribution voltages (typically less than 10,000 volts).
It has a "bus" that can split the distribution power off in multiple directions.
It often has circuit breakers and switches so that the substation can be disconnected from the transmission grid or separate distribution lines can be disconnected from the substation when necessary.
A typical small substation
The box in the foreground is a large transformer. To its left (and out of the frame but shown in the next shot) are the incoming power from the transmission grid and a set of switches for the incoming power. Toward the right is a distribution bus plus three voltage regulators.
The transmission lines entering the substation and passing through the switch tower
The switch tower and the main transformer
Now the distribution bus comes into the picture
Distribution Bus
The power goes from the transformer to the distribution bus:
In this case, the bus distributes power to two separate sets of distribution lines at two different voltages. The smaller transformers attached to the bus are stepping the power down to standard line voltage (usually 7,200 volts) for one set of lines, while power leaves in the other direction at the higher voltage of the main transformer. The power leaves this substation in two sets of three wires, each headed down the road in a different direction:
The wires between these two poles are "guy wires" for support. They carry no current.
The next time you are driving down the road, you can look at the power lines in a completely different light. In the typical scene pictured on the right, the three wires at the top of the poles are the three wires for the 3-phase power. The fourth wire lower on the poles is the ground wire. In some cases there will be additional wires, typically phone or cable TV lines riding on the same poles.
As mentioned above, this particular substation produces two different voltages. The wires at the higher voltage need to be stepped down again, which will often happen at another substation or in small transformers somewhere down the line. For example, you will often see a large green box (perhaps 6 feet/1.8 meters on a side) near the entrance to a subdivision. It is performing the step-down function for the subdivision.
Regulator Bank
You will also find regulator banks located along the line, either underground or in the air. They regulate the voltage on the line to prevent undervoltage and overvoltage conditions.
A typical regulator bank
Up toward the top are three switches that allow this regulator bank to be disconnected for maintenance when necessary:
At this point, we have typical line voltage at something like 7,200 volts running through the neighborhood on three wires (with a fourth ground wire lower on the pole):
Taps
A house needs only one of the three phases, so typically you will see three wires running down a main road, and taps for one or two of the phases running off on side streets. Pictured below is a 3-phase to 2-phase tap, with the two phases running off to the right:
Here is a 2-phase to 1-phase tap, with the single phase running out to the right:
At the House
And finally we are down to the wire that brings power to your house! Past a typical house runs a set of poles with one phase of power (at 7,200 volts) and a ground wire (although sometimes there will be two or three phases on the pole, depending on where the house is located in the distribution grid). At each house, there is a transformer drum attached to the pole, like this:
In many suburban neighborhoods, the distribution lines are underground and there are green transformer boxes at every house or two. Here is some detail on what is going on at the pole:
The transformer's job is to reduce the 7,200 volts down to the 240 volts that makes up normal household electrical service. Let's look at this pole one more time, from the bottom, to see what is going on:
There are two things to notice in this picture:
There is a bare wire running down the pole.
This is a grounding wire. Every utility pole on the planet has one. If you ever watch the power company install a new pole, you will see that the end of that bare wire is stapled in a coil to the base of the pole and therefore is in direct contact with the earth, running 6 to 10 feet (1.8 to 3 m) underground. It is a good, solid ground connection. If you examine a pole carefully, you will see that the ground wire running between poles (and often the guy wires) are attached to this direct connection to ground.
There are two wires running out of the transformer and three wires running to the house.
The two from the transformer are insulated, and the third one is bare. The bare wire is the ground wire. The two insulated wires each carry 120 volts, but they are 180 degrees out of phase so the difference between them is 240 volts. This arrangement allows a homeowner to use both 120-volt and 240-volt appliances. The transformer is wired in this sort of configuration:
The 240 volts enters your house through a typical watt-hour meter like this one:
The meter lets the power company charge you for putting up all of these wires.
Safety Devices: Fuses
Fuses and circuit breakers are safety devices. Let's say that you did not have fuses or circuit breakers in your house and something "went wrong." What could possibly go wrong? Here are some examples:
A fan motor burns out a bearing, seizes, overheats and melts, causing a direct connection between power and ground.
A wire comes loose in a lamp and directly connects power to ground.
A mouse chews through the insulation in a wire and directly connects power to ground.
Someone accidentally vacuums up a lamp wire with the vacuum cleaner, cutting it in the process and directly connecting power to ground.
A person is hanging a picture in the living room and the nail used for said picture happens to puncture a power line in the wall, directly connecting power to ground.
When a 120-volt power line connects directly to ground, its goal in life is to pump as much electricity as possible through the connection. Either the device or the wire in the wall will burst into flames in such a situation. (The wire in the wall will get hot like the element in an electric oven gets hot, which is to say very hot!). A fuse is a simple device designed to overheat and burn out extremely rapidly in such a situation. In a fuse, a thin piece of foil or wire quickly vaporizes when an overload of current runs through it. This kills the power to the wire immediately, protecting it from overheating. Fuses must be replaced each time they burn out. A circuit breaker uses the heat from an overload to trip a switch, and circuit breakers are therefore resettable.
The power then enters the home through a typical circuit breaker panel like the one above.
Safety Devices: Circuit Breakers
Inside the circuit breaker panel (right) you can see the two primary wires from the transformer entering the main circuit breaker at the top. The main breaker lets you cut power to the entire panel when necessary. Within this overall setup, all of the wires for the different outlets and lights in the house each have a separate circuit breaker or fuse:
If the circuit breaker is on, then power flows through the wire in the wall and makes its way eventually to its final destination, the outlet.
What an unbelievable story! It took all of that equipment to get power from the power plant to the light in your bedroom.
The next time you drive down the road and look at the power lines, or the next time you flip on a light, you'll hopefully have a much better understanding of what is going on. The power distribution grid is truly an incredible system.
4. Heat
Heat
Heat may be defined as energy in transit from a high temperature object to a lower temperature object. An object does not possess "heat"; the appropriate term for the microscopic energy in an object is internal energy. The internal energy may be increased by transferring energy to the object from a higher temperature (hotter) object - this is properly called heating.
Mechanical equivalent of heat
Heat and Work Example
This example of the interchangeability of heat and work as agents for adding energy to a system can help to dispel some misconceptions about heat. I found the idea in a little article by Mark Zemansky entitled "The Use and Misuse of the Word 'Heat' in Physics Teaching". One key idea from this example is that if you are presented with a high temperature gas, you cannot tell whether it reached that high temperature by being heated, or by having work done on it, or a combination of the two.
To describe the energy that a high temperature object has, it is not a correct use of the word heat to say that the object "possesses heat" - it is better to say that it possesses internal energy as a result of its molecular motion. The word heat is better reserved to describe the process of transfer of energy from a high temperature object to a lower temperature one. Surely you can take an object at low internal energy and raise it to higher internal energy by heating it. But you can also increase its internal energy by doing work on it, and since the internal energy of a high temperature object resides in random motion of the molecules, you can't tell which mechanism was used to give it that energy.
In warning teachers and students alike about the pitfalls of misusing the word "heat", Mark Zemansky advises reflecting on the jingle:
"Teaching thermal physics
Is as easy as a song:
You think you make it simpler
When you make it slightly wrong.
Zemanzky's plea
Don't refer to the "heat in a body", or say "this object has twice as much heat as that body". He also objects to the use of the vague term "thermal energy" and to the use of the word "heat" as a verb, because they feed the misconceptions, but it is hard to avoid those terms. He would counsel the introduction and use of the concept of internal energy as quickly as possible.
Zemansky points to the First Law of Thermodynamics as a clarifying relationship. The First Law identifies both heat and work as methods of energy transfer which can bring about a change in the internal energy of a system. After that, neither the words work or heat have any usefulness in describing the final state of the sytem - we can speak only of the internal energy of the system.
Mechanical Equivalent of Heat
Heat flow and work are both ways of transferring energy. As illustrated in the heat and work example, the temperature of a gas can be raised either by heating it, by doing work on it, or a combination of the two.
In a classic experiment in 1843, James Joule showed the energy equivalence of heating and doing work by using the change in potential energy of falling masses to stir an insulated container of water with paddles. Careful measurements showed the increase in the temperature of the water to be proportional to the mechanical energy used to stir the water. At that time calories were the accepted unit of heat and joules became the accepted unit of mechanical energy. Their relationship is
First law of thermodynamics
Heat is Transfer of Thermal Energy
When you heat an object, you are transferring thermal energy to it from an another object that is at a higher temperature. Heat is the amount of thermal energy that is transferred between the two objects due to a temperature difference. Heat transfer between objects is done by conduction, convection and radiation. The standard unit of heat measurement is the calorie.
Questions you may have include:
What is heat?
How does heat get from one object to another?
What is the measure of heat?
Heat is energy in transit
Heating an object is when you are transferring thermal energy to the object from to another object that is at a higher temperature. Heat is often defined as energy in transit or the the flow of energy. Thermal energy is the energy itself.
Thermal energy is the amount of internal kinetic energy and potential energy of an object. It is also simply called internal energy. Temperature is a measure of the average kinetic energy of the particles in an object.
An object feels warm or hot if its temperature is higher than your skin. To say something is hot means its temperature is relatively high.
Cooling an object is when you are transferring thermal energy from the object from an another object that is at a lower temperature. You could say you are removing thermal energy from your object.
An object feels cool or cold if its temperature is lower than your skin. To say something is cold means its temperature is relatively low.
Whether heating or cooling, the end result is that the two objects become the same temperature after a period of time. This is called thermal equilibrium.
Heat transfer
Thermal energy is transferred from an object of high temperature to one of lower temperature by conduction, convention and radiation. This process is usually called heat transfer or heat flow, although it is the thermal energy that is really being transferred. Heat is the amount transferred.
(See Heat Transfer for more information on that subject.)
Conduction
Conduction is when materials are in physical contact and kinetic energy is transferred through collisions of their particles, according to the Kinetic Theory of Matter.
(See Kinetic Theory of Matter for more information on that subject.)
Convection
Convection is the movement of thermal energy from one area to another in a liquid or gas.
Radiation
Radiation is when warm or hot matter emits electromagnetic radiation--especially infrared--that is then absorbed by an object at a distance. The absorption heats the second object.
Units of heat
The amount of heat or thermal energy transferred from one object to another can be measured in joules, which is the unit of energy. But more often, you see heat measured in calories. A calorie (cal) is the amount of heat required to raise the temperature of 1 gram of of water by 1° C.
The relationship between joules and calories is: 1 cal = 4.186 J.
A kilocalorie (kcal) equals 1000 calories. Transferring 1 kcal of heat to 1 kilogram of water will increase its temperature 1° C. A kilocalorie is also called a Calorie (with a capital "C") by those dealing with food and diets. When you hear that some food has 200 Cal, that means it has the potential of transferring 200 kilocalories of heat energy to the body.
In the United States, some use the BTU (British Thermal Unit) as a unit of heat transfer. A BTU is defined as the quantity of energy necessary to raise the temperature of 1 lb. of water 1° Fahrenheit. Often the BTU is used to indicate the heat capacity of a home furnace.
In conclusion
Heat is the amount of thermal energy that is transferred between the two objects due to a temperature difference. Heat transfer between objects is done by conduction, convection and radiation. The standard unit of heat measurement is the calorie.
WHAT IS HEAT
The Universe is made up of matter and energy. Matter is made up of atoms and molecules (groupings of atoms) and energy causes the atoms and molecules to always be in motion - either bumping into each other or vibrating back and forth. The motion of atoms and molecules creates a form of energy called heat or thermal energy which is present in all matter. Even in the coldest voids of space, matter still has a very small but still measurable amount of heat energy.
Energy can take on many forms and can change from one form to another. Many different types of energy can be converted into heat energy. Light, electrical, mechanical, chemical, nuclear, sound and thermal energy itself can each cause a substance to heat up by increasing the speed of its molecules. So, put energy into a system and it heats up, take energy away and it cools. For example, when we are cold, we can jump up and down to get warmer.
Here are just a few examples of various types of energy being converted into thermal energy (heat).
(1) Mechanical energy is converted into thermal energy whenever you bounce a ball. Each time the ball hits the ground, some of the energy of the ball's motion is converted into heating up the ball, causing it to slow down at each bounce. To see a demonstration of how this happens click here
A thermal infrared image of a ball before (left) and after (right) being bounced.
(2) Thermal energy can be transfered to other objects causing them to heat up. When you heat up a pan of water, the heat from the stove causes the molecules in the pan to vibrate faster causing the pan to heat up. The heat from the pan causes water molecules to move faster and heat up. So, when you heat something up, you are just making its molecules move faster.
(3) Electrical energy is converted into thermal energy when you use objects such as heating pads, electrical stove elements, toasters, hair dryers, or light bulbs.
A thermal infrared image of a hair dryer and a flourescent light bulb.
(4) Chemical energy from the foods we eat is converted into heating our bodies.
(5) Light from the sun is converted to heat as the sun's rays warm the earth's surface.
(6) Energy from friction creates heat. For example when you rub your hands, sharpen a pencil, make a skid mark with your bike, or use the brakes on your car, friction generates heat.
A thermal infrared image of a pencil after being sharpened (left) and of hot brakes in a car (right). Notice the hot tip of the pencil.
4. Buildings
Energy use in commercial buildings (from EIA)
Commercial buildings include a wide variety of building types—offices, hospitals, schools, police stations, places of worship, warehouses, hotels, barber shops, libraries, shopping malls—and that’s just the beginning of the list. These different commercial activities all have unique energy needs but, as a whole, commercial buildings use more than half their energy for heating and lighting.
How Energy is Used in Commercial Buildings
TYPES OF ENERGY USED IN COMMERCIAL BUILDINGS
Electricity and natural gas are the most common energy sources used in commercial buildings. Commercial buildings also use another source that you don’t usually find used in residential buildings—district energy. When there are many buildings close together, like on a college campus or in a big city, it is sometimes more efficient to have a central heating and cooling plant that distributes steam, hot water, or chilled water to all of the different buildings. A district system can reduce equipment and maintenance costs, as well as save energy.
ENERGY USE BY TYPE OF BUILDING
Retail and service buildings use the most total energy of all the commercial building types. This isn’t too surprising when you think of all the stores and service businesses in most towns. Offices use a large share of energy, too. Education buildings, like your school, use 13 percent of all total energy, which is even more than all hospitals and other medical buildings combined! Lodging buildings (like hotels or dormitories) use 8 percent of all energy. Warehouses and food service (like restaurants) each use 7 percent. Public assembly buildings, which can be anything from libraries to sports arenas, use 6 percent; food sales buildings (like grocery stores and convenience stores) use 4 percent. All other types of buildings, like places of worship, fire stations, police stations, and laboratories, account for the remaining 10 percent of commercial building energy.
The Energy Efficient Commercial Buildings Deduction
EPAct 2005’s new incentive for lighting and building efficiency
The Energy Policy Act of 2005 created the Energy Efficient Commercial Buildings Deduction, which allows building owners to deduct the entire cost of a lighting or building upgrade in the year the equipment is placed in service, subject to a cap. This website, developed by the Lighting Systems Division of the National Electrical Manufacturers Association (NEMA) in cooperation with the Commercial Building Tax Deduction Coalition, provides education about the lighting aspects of the Deduction and resources to help with its implementation. It was created as the first of a series of lighting education initiatives by the lighting industry addressing lighting quality and efficiency.
More than one-third of the energy consumed in the United States is used in buildings.
EETD addresses building energy efficiency issues, including
· building technologies,
· the indoor environment,
· building codes and standards, and
· end-use energy efficiency issues,
through multidisciplinary research and analysis.
The Building Technologies Department works closely with the building industry to develop, test and deploy advanced technologies, integrated systems and new tools for design and operations that reduce energy bills while improving the comfort, health and safety of building occupants. Research and development efforts focus on windows and daylighting, lighting systems, building simulation tools, commercial building systems, demand response and high-tech buildings.
Indoor Environment Department researchers working in the buildings area focus on infiltration and mechanical ventilation systems, and on human health and productivity in buildings, with an emphasis on indoor chemistry and exposure and on air flow and air quality modeling.
Analysts working in the Energy Analysis Department gather and interpret information to examine the feasibility of different approaches to designing energy-efficient appliance standards and building codes in the U.S., and have worked with developing nations to create programs, codes and standards to reduce greenhouse gas emissions and encourage efficiency.
This website is a portal to more than fifty current and recent projects in commercial buildings. We have organized these projects into two broad areas:
· Technologies & Systems
Windows/Facades
Integrated Façade-Daylighting
•
•
•
•
Dynamic Window System Performance
•
•
•
Daylighting Quality
•
•
•
Lighting
Advanced Lighting Controls
•
•
•
•
HVAC/CHP
Low Energy Cooling Systems
•
•
•
Thermal Distribution Systems
•
•
Distributed Energy Site Simulation
•
•
•
Demand Response
Demand Response Automation
•
•
Ventilation/IAQ
Reducing Ventilation Energy with Air Cleaning
•
•
•
Establishing Control of Building Ventilation
•
•
•
Ventilation Performance of UFAD
•
•
IAQ, Health, and Productivity
•
•
Plug and Process Equipment
ENERGY STAR® Office Equipment
•
•
Power Control User Interfaces
•
•
· Tools & Process
Modeling and Simulation
Interoperability and Virtual Building Models
•
•
•
•
•
•
•
•
Life Cycle Building Information Models
•
•
•
•
•
•
•
•
EnergyPlus Development and Deployment
•
•
•
•
•
Building Controls Virtual Test Bed
•
•
•
Daylighting Modeling
•
•
•
•
Commissioning/Performance Monitoring
Costs and Benefits of Commissioning
•
•
•
Commissioning Persistence
•
•
Commissioning Tools and Guides
•
•
•
•
•
Functional Test Analysis Tool for AHUs
•
•
•
Monitoring Based Retro-Commissioning
•
•
•
Performance Metrics Tracking
•
•
•
•
•
•
•
Energy Information Systems
•
•
•
•
Automated Diagnostics and Prognostics
•
•
•
•
Performance Monitoring Specification
•
•
•
•
Benchmarking
Benchmarking
•
•
Design Assistance and Assessment
Design Assistance for Federal Buildings
•
•
•
Public Sector Procurement
•
•
Sustainable Design for Federal Buildings
•
•
•
Energy Use in Federal LEED Buildings
•
•
IPMVP
Last Revised: December 2006
Source: Energy Information Administration, 2003 Commercial Buildings Energy Consumption Survey.
I know I have sent you numerous emails with articles about efficiency, I hope it is helpful. It is not in any organized fashion.
If I can be of any additional help, let me know.
Jay Draiman, Energy analyst
by Marshall Brain
Inside This Article
1.
Introduction to How Power Grids Work
2.
The Power Plant
3.
The Power Plant: Alternating Current
4.
The Power Plant: Three-phase Power
5.
Transmission Substation
6.
The Distribution Grid
7.
Distribution Bus
8.
Regulator Bank
9.
Taps
10.
At the House
11.
Safety Devices: Fuses
12.
Safety Devices: Circuit Breakers
13.
Lots More Information
14.
See all Energy Production articles
Electrical power is a little bit like the air you breathe: You don't really think about it until it is missing. Power is just "there," meeting your every need, constantly. It is only during a power failure, when you walk into a dark room and instinctively hit the useless light switch, that you realize how important power is in your daily life. You use it for heating, cooling, cooking, refrigeration, light, sound, computation, entertainment... Without it, life can get somewhat cumbersome.
Power travels from the power plant to your house through an amazing system called the power distribution grid.
Power grid distribution lines can be above or under ground. See more power grid pictures.
The grid is quite public -- if you live in a suburban or rural area, chances are it is right out in the open for all to see. It is so public, in fact, that you probably don't even notice it anymore. Your brain likely ignores all of the power lines because it has seen them so often. In this article, we will look at all of the equipment that brings electrical power to your home. The next time you look at the power grid, you will be able to really see it and understand what is going on!
The Power Plant
Electrical power starts at the power plant. In almost all cases, the power plant consists of a spinning electrical generator. Something has to spin that generator -- it might be a water wheel in a hydroelectric dam, a large diesel engine or a gas turbine. But in most cases, the thing spinning the generator is a steam turbine. The steam might be created by burning coal, oil or natural gas. Or the steam may come from a nuclear reactor like this one at the Shearon Harris nuclear power plant near Raleigh, North Carolina:
No matter what it is that spins the generator, commercial electrical generators of any size generate what is called 3-phase AC power. To understand 3-phase AC power, it is helpful to understand single-phase power first.
Photo courtesy U.S. Department of Energy
A breakdown of the major power plants in
the United States, by type
The Power Plant: Alternating Current
Single-phase power is what you have in your house. You generally talk about household electrical service as single-phase, 120-volt AC service. If you use an oscilloscope and look at the power found at a normal wall-plate outlet in your house, what you will find is that the power at the wall plate looks like a sine wave, and that wave oscillates between -170 volts and 170 volts (the peaks are indeed at 170 volts; it is the effective (rms) voltage that is 120 volts). The rate of oscillation for the sine wave is 60 cycles per second. Oscillating power like this is generally referred to as AC, or alternating current. The alternative to AC is DC, or direct current. Batteries produce DC: A steady stream of electrons flows in one direction only, from the negative to the positive terminal of the battery.
AC has at least three advantages over DC in a power distribution grid:
1. Large electrical generators happen to generate AC naturally, so conversion to DC would involve an extra step.
2. Transformers must have alternating current to operate, and we will see that the power distribution grid depends on transformers.
3. It is easy to convert AC to DC but expensive to convert DC to AC, so if you were going to pick one or the other AC would be the better choice.
The Power Plant: Three-phase Power
The power plant produces three different phases of AC power simultaneously, and the three phases are offset 120 degrees from each other. There are four wires coming out of every power plant: the three phases plus a neutral or ground common to all three. If you were to look at the three phases on a graph, they would look like this relative to ground:
There is nothing magical about three-phase power. It is simply three single phases synchronized and offset by 120 degrees.
Why three phases? Why not one or two or four? In 1-phase and 2-phase power, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point.
And what about this "ground," as mentioned above? The power company essentially uses the earth as one of the wires in the power system. The earth is a pretty good conductor and it is huge, so it makes a good return path for electrons. (Car manufacturers do something similar; they use the metal body of the car as one of the wires in the car's electrical system and attach the negative pole of the battery to the car's body.) "Ground" in the power distribution grid is literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks, groundwater, etc., of the earth.
Transmission Substation
The three-phase power leaves the generator and enters a transmission substation at the power plant. This substation uses large transformers to convert the generator's voltage (which is at the thousands of volts level) up to extremely high voltages for long-distance transmission on the transmission grid.
A typical substation at a power plant
You can see at the back several three-wire towers leaving the substation. Typical voltages for long distance transmission are in the range of 155,000 to 765,000 volts in order to reduce line losses. A typical maximum transmission distance is about 300 miles (483 km). High-voltage transmission lines are quite obvious when you see them. They are normally made of huge steel towers like this:
All power towers like this have three wires for the three phases. Many towers, like the ones shown above, have extra wires running along the tops of the towers. These are ground wires and are there primarily in an attempt to attract lightning.
The Distribution Grid
For power to be useful in a home or business, it comes off the transmission grid and is stepped-down to the distribution grid. This may happen in several phases. The place where the conversion from "transmission" to "distribution" occurs is in a power substation. A power substation typically does two or three things:
It has transformers that step transmission voltages (in the tens or hundreds of thousands of volts range) down to distribution voltages (typically less than 10,000 volts).
It has a "bus" that can split the distribution power off in multiple directions.
It often has circuit breakers and switches so that the substation can be disconnected from the transmission grid or separate distribution lines can be disconnected from the substation when necessary.
A typical small substation
The box in the foreground is a large transformer. To its left (and out of the frame but shown in the next shot) are the incoming power from the transmission grid and a set of switches for the incoming power. Toward the right is a distribution bus plus three voltage regulators.
The transmission lines entering the substation and passing through the switch tower
The switch tower and the main transformer
Now the distribution bus comes into the picture
Distribution Bus
The power goes from the transformer to the distribution bus:
In this case, the bus distributes power to two separate sets of distribution lines at two different voltages. The smaller transformers attached to the bus are stepping the power down to standard line voltage (usually 7,200 volts) for one set of lines, while power leaves in the other direction at the higher voltage of the main transformer. The power leaves this substation in two sets of three wires, each headed down the road in a different direction:
The wires between these two poles are "guy wires" for support. They carry no current.
The next time you are driving down the road, you can look at the power lines in a completely different light. In the typical scene pictured on the right, the three wires at the top of the poles are the three wires for the 3-phase power. The fourth wire lower on the poles is the ground wire. In some cases there will be additional wires, typically phone or cable TV lines riding on the same poles.
As mentioned above, this particular substation produces two different voltages. The wires at the higher voltage need to be stepped down again, which will often happen at another substation or in small transformers somewhere down the line. For example, you will often see a large green box (perhaps 6 feet/1.8 meters on a side) near the entrance to a subdivision. It is performing the step-down function for the subdivision.
Regulator Bank
You will also find regulator banks located along the line, either underground or in the air. They regulate the voltage on the line to prevent undervoltage and overvoltage conditions.
A typical regulator bank
Up toward the top are three switches that allow this regulator bank to be disconnected for maintenance when necessary:
At this point, we have typical line voltage at something like 7,200 volts running through the neighborhood on three wires (with a fourth ground wire lower on the pole):
Taps
A house needs only one of the three phases, so typically you will see three wires running down a main road, and taps for one or two of the phases running off on side streets. Pictured below is a 3-phase to 2-phase tap, with the two phases running off to the right:
Here is a 2-phase to 1-phase tap, with the single phase running out to the right:
At the House
And finally we are down to the wire that brings power to your house! Past a typical house runs a set of poles with one phase of power (at 7,200 volts) and a ground wire (although sometimes there will be two or three phases on the pole, depending on where the house is located in the distribution grid). At each house, there is a transformer drum attached to the pole, like this:
In many suburban neighborhoods, the distribution lines are underground and there are green transformer boxes at every house or two. Here is some detail on what is going on at the pole:
The transformer's job is to reduce the 7,200 volts down to the 240 volts that makes up normal household electrical service. Let's look at this pole one more time, from the bottom, to see what is going on:
There are two things to notice in this picture:
There is a bare wire running down the pole.
This is a grounding wire. Every utility pole on the planet has one. If you ever watch the power company install a new pole, you will see that the end of that bare wire is stapled in a coil to the base of the pole and therefore is in direct contact with the earth, running 6 to 10 feet (1.8 to 3 m) underground. It is a good, solid ground connection. If you examine a pole carefully, you will see that the ground wire running between poles (and often the guy wires) are attached to this direct connection to ground.
There are two wires running out of the transformer and three wires running to the house.
The two from the transformer are insulated, and the third one is bare. The bare wire is the ground wire. The two insulated wires each carry 120 volts, but they are 180 degrees out of phase so the difference between them is 240 volts. This arrangement allows a homeowner to use both 120-volt and 240-volt appliances. The transformer is wired in this sort of configuration:
The 240 volts enters your house through a typical watt-hour meter like this one:
The meter lets the power company charge you for putting up all of these wires.
Safety Devices: Fuses
Fuses and circuit breakers are safety devices. Let's say that you did not have fuses or circuit breakers in your house and something "went wrong." What could possibly go wrong? Here are some examples:
A fan motor burns out a bearing, seizes, overheats and melts, causing a direct connection between power and ground.
A wire comes loose in a lamp and directly connects power to ground.
A mouse chews through the insulation in a wire and directly connects power to ground.
Someone accidentally vacuums up a lamp wire with the vacuum cleaner, cutting it in the process and directly connecting power to ground.
A person is hanging a picture in the living room and the nail used for said picture happens to puncture a power line in the wall, directly connecting power to ground.
When a 120-volt power line connects directly to ground, its goal in life is to pump as much electricity as possible through the connection. Either the device or the wire in the wall will burst into flames in such a situation. (The wire in the wall will get hot like the element in an electric oven gets hot, which is to say very hot!). A fuse is a simple device designed to overheat and burn out extremely rapidly in such a situation. In a fuse, a thin piece of foil or wire quickly vaporizes when an overload of current runs through it. This kills the power to the wire immediately, protecting it from overheating. Fuses must be replaced each time they burn out. A circuit breaker uses the heat from an overload to trip a switch, and circuit breakers are therefore resettable.
The power then enters the home through a typical circuit breaker panel like the one above.
Safety Devices: Circuit Breakers
Inside the circuit breaker panel (right) you can see the two primary wires from the transformer entering the main circuit breaker at the top. The main breaker lets you cut power to the entire panel when necessary. Within this overall setup, all of the wires for the different outlets and lights in the house each have a separate circuit breaker or fuse:
If the circuit breaker is on, then power flows through the wire in the wall and makes its way eventually to its final destination, the outlet.
What an unbelievable story! It took all of that equipment to get power from the power plant to the light in your bedroom.
The next time you drive down the road and look at the power lines, or the next time you flip on a light, you'll hopefully have a much better understanding of what is going on. The power distribution grid is truly an incredible system.
4. Heat
Heat
Heat may be defined as energy in transit from a high temperature object to a lower temperature object. An object does not possess "heat"; the appropriate term for the microscopic energy in an object is internal energy. The internal energy may be increased by transferring energy to the object from a higher temperature (hotter) object - this is properly called heating.
Mechanical equivalent of heat
Heat and Work Example
This example of the interchangeability of heat and work as agents for adding energy to a system can help to dispel some misconceptions about heat. I found the idea in a little article by Mark Zemansky entitled "The Use and Misuse of the Word 'Heat' in Physics Teaching". One key idea from this example is that if you are presented with a high temperature gas, you cannot tell whether it reached that high temperature by being heated, or by having work done on it, or a combination of the two.
To describe the energy that a high temperature object has, it is not a correct use of the word heat to say that the object "possesses heat" - it is better to say that it possesses internal energy as a result of its molecular motion. The word heat is better reserved to describe the process of transfer of energy from a high temperature object to a lower temperature one. Surely you can take an object at low internal energy and raise it to higher internal energy by heating it. But you can also increase its internal energy by doing work on it, and since the internal energy of a high temperature object resides in random motion of the molecules, you can't tell which mechanism was used to give it that energy.
In warning teachers and students alike about the pitfalls of misusing the word "heat", Mark Zemansky advises reflecting on the jingle:
"Teaching thermal physics
Is as easy as a song:
You think you make it simpler
When you make it slightly wrong.
Zemanzky's plea
Don't refer to the "heat in a body", or say "this object has twice as much heat as that body". He also objects to the use of the vague term "thermal energy" and to the use of the word "heat" as a verb, because they feed the misconceptions, but it is hard to avoid those terms. He would counsel the introduction and use of the concept of internal energy as quickly as possible.
Zemansky points to the First Law of Thermodynamics as a clarifying relationship. The First Law identifies both heat and work as methods of energy transfer which can bring about a change in the internal energy of a system. After that, neither the words work or heat have any usefulness in describing the final state of the sytem - we can speak only of the internal energy of the system.
Mechanical Equivalent of Heat
Heat flow and work are both ways of transferring energy. As illustrated in the heat and work example, the temperature of a gas can be raised either by heating it, by doing work on it, or a combination of the two.
In a classic experiment in 1843, James Joule showed the energy equivalence of heating and doing work by using the change in potential energy of falling masses to stir an insulated container of water with paddles. Careful measurements showed the increase in the temperature of the water to be proportional to the mechanical energy used to stir the water. At that time calories were the accepted unit of heat and joules became the accepted unit of mechanical energy. Their relationship is
First law of thermodynamics
Heat is Transfer of Thermal Energy
When you heat an object, you are transferring thermal energy to it from an another object that is at a higher temperature. Heat is the amount of thermal energy that is transferred between the two objects due to a temperature difference. Heat transfer between objects is done by conduction, convection and radiation. The standard unit of heat measurement is the calorie.
Questions you may have include:
What is heat?
How does heat get from one object to another?
What is the measure of heat?
Heat is energy in transit
Heating an object is when you are transferring thermal energy to the object from to another object that is at a higher temperature. Heat is often defined as energy in transit or the the flow of energy. Thermal energy is the energy itself.
Thermal energy is the amount of internal kinetic energy and potential energy of an object. It is also simply called internal energy. Temperature is a measure of the average kinetic energy of the particles in an object.
An object feels warm or hot if its temperature is higher than your skin. To say something is hot means its temperature is relatively high.
Cooling an object is when you are transferring thermal energy from the object from an another object that is at a lower temperature. You could say you are removing thermal energy from your object.
An object feels cool or cold if its temperature is lower than your skin. To say something is cold means its temperature is relatively low.
Whether heating or cooling, the end result is that the two objects become the same temperature after a period of time. This is called thermal equilibrium.
Heat transfer
Thermal energy is transferred from an object of high temperature to one of lower temperature by conduction, convention and radiation. This process is usually called heat transfer or heat flow, although it is the thermal energy that is really being transferred. Heat is the amount transferred.
(See Heat Transfer for more information on that subject.)
Conduction
Conduction is when materials are in physical contact and kinetic energy is transferred through collisions of their particles, according to the Kinetic Theory of Matter.
(See Kinetic Theory of Matter for more information on that subject.)
Convection
Convection is the movement of thermal energy from one area to another in a liquid or gas.
Radiation
Radiation is when warm or hot matter emits electromagnetic radiation--especially infrared--that is then absorbed by an object at a distance. The absorption heats the second object.
Units of heat
The amount of heat or thermal energy transferred from one object to another can be measured in joules, which is the unit of energy. But more often, you see heat measured in calories. A calorie (cal) is the amount of heat required to raise the temperature of 1 gram of of water by 1° C.
The relationship between joules and calories is: 1 cal = 4.186 J.
A kilocalorie (kcal) equals 1000 calories. Transferring 1 kcal of heat to 1 kilogram of water will increase its temperature 1° C. A kilocalorie is also called a Calorie (with a capital "C") by those dealing with food and diets. When you hear that some food has 200 Cal, that means it has the potential of transferring 200 kilocalories of heat energy to the body.
In the United States, some use the BTU (British Thermal Unit) as a unit of heat transfer. A BTU is defined as the quantity of energy necessary to raise the temperature of 1 lb. of water 1° Fahrenheit. Often the BTU is used to indicate the heat capacity of a home furnace.
In conclusion
Heat is the amount of thermal energy that is transferred between the two objects due to a temperature difference. Heat transfer between objects is done by conduction, convection and radiation. The standard unit of heat measurement is the calorie.
WHAT IS HEAT
The Universe is made up of matter and energy. Matter is made up of atoms and molecules (groupings of atoms) and energy causes the atoms and molecules to always be in motion - either bumping into each other or vibrating back and forth. The motion of atoms and molecules creates a form of energy called heat or thermal energy which is present in all matter. Even in the coldest voids of space, matter still has a very small but still measurable amount of heat energy.
Energy can take on many forms and can change from one form to another. Many different types of energy can be converted into heat energy. Light, electrical, mechanical, chemical, nuclear, sound and thermal energy itself can each cause a substance to heat up by increasing the speed of its molecules. So, put energy into a system and it heats up, take energy away and it cools. For example, when we are cold, we can jump up and down to get warmer.
Here are just a few examples of various types of energy being converted into thermal energy (heat).
(1) Mechanical energy is converted into thermal energy whenever you bounce a ball. Each time the ball hits the ground, some of the energy of the ball's motion is converted into heating up the ball, causing it to slow down at each bounce. To see a demonstration of how this happens click here
A thermal infrared image of a ball before (left) and after (right) being bounced.
(2) Thermal energy can be transfered to other objects causing them to heat up. When you heat up a pan of water, the heat from the stove causes the molecules in the pan to vibrate faster causing the pan to heat up. The heat from the pan causes water molecules to move faster and heat up. So, when you heat something up, you are just making its molecules move faster.
(3) Electrical energy is converted into thermal energy when you use objects such as heating pads, electrical stove elements, toasters, hair dryers, or light bulbs.
A thermal infrared image of a hair dryer and a flourescent light bulb.
(4) Chemical energy from the foods we eat is converted into heating our bodies.
(5) Light from the sun is converted to heat as the sun's rays warm the earth's surface.
(6) Energy from friction creates heat. For example when you rub your hands, sharpen a pencil, make a skid mark with your bike, or use the brakes on your car, friction generates heat.
A thermal infrared image of a pencil after being sharpened (left) and of hot brakes in a car (right). Notice the hot tip of the pencil.
4. Buildings
Energy use in commercial buildings (from EIA)
Commercial buildings include a wide variety of building types—offices, hospitals, schools, police stations, places of worship, warehouses, hotels, barber shops, libraries, shopping malls—and that’s just the beginning of the list. These different commercial activities all have unique energy needs but, as a whole, commercial buildings use more than half their energy for heating and lighting.
How Energy is Used in Commercial Buildings
TYPES OF ENERGY USED IN COMMERCIAL BUILDINGS
Electricity and natural gas are the most common energy sources used in commercial buildings. Commercial buildings also use another source that you don’t usually find used in residential buildings—district energy. When there are many buildings close together, like on a college campus or in a big city, it is sometimes more efficient to have a central heating and cooling plant that distributes steam, hot water, or chilled water to all of the different buildings. A district system can reduce equipment and maintenance costs, as well as save energy.
ENERGY USE BY TYPE OF BUILDING
Retail and service buildings use the most total energy of all the commercial building types. This isn’t too surprising when you think of all the stores and service businesses in most towns. Offices use a large share of energy, too. Education buildings, like your school, use 13 percent of all total energy, which is even more than all hospitals and other medical buildings combined! Lodging buildings (like hotels or dormitories) use 8 percent of all energy. Warehouses and food service (like restaurants) each use 7 percent. Public assembly buildings, which can be anything from libraries to sports arenas, use 6 percent; food sales buildings (like grocery stores and convenience stores) use 4 percent. All other types of buildings, like places of worship, fire stations, police stations, and laboratories, account for the remaining 10 percent of commercial building energy.
The Energy Efficient Commercial Buildings Deduction
EPAct 2005’s new incentive for lighting and building efficiency
The Energy Policy Act of 2005 created the Energy Efficient Commercial Buildings Deduction, which allows building owners to deduct the entire cost of a lighting or building upgrade in the year the equipment is placed in service, subject to a cap. This website, developed by the Lighting Systems Division of the National Electrical Manufacturers Association (NEMA) in cooperation with the Commercial Building Tax Deduction Coalition, provides education about the lighting aspects of the Deduction and resources to help with its implementation. It was created as the first of a series of lighting education initiatives by the lighting industry addressing lighting quality and efficiency.
More than one-third of the energy consumed in the United States is used in buildings.
EETD addresses building energy efficiency issues, including
· building technologies,
· the indoor environment,
· building codes and standards, and
· end-use energy efficiency issues,
through multidisciplinary research and analysis.
The Building Technologies Department works closely with the building industry to develop, test and deploy advanced technologies, integrated systems and new tools for design and operations that reduce energy bills while improving the comfort, health and safety of building occupants. Research and development efforts focus on windows and daylighting, lighting systems, building simulation tools, commercial building systems, demand response and high-tech buildings.
Indoor Environment Department researchers working in the buildings area focus on infiltration and mechanical ventilation systems, and on human health and productivity in buildings, with an emphasis on indoor chemistry and exposure and on air flow and air quality modeling.
Analysts working in the Energy Analysis Department gather and interpret information to examine the feasibility of different approaches to designing energy-efficient appliance standards and building codes in the U.S., and have worked with developing nations to create programs, codes and standards to reduce greenhouse gas emissions and encourage efficiency.
This website is a portal to more than fifty current and recent projects in commercial buildings. We have organized these projects into two broad areas:
· Technologies & Systems
Windows/Facades
Integrated Façade-Daylighting
•
•
•
•
Dynamic Window System Performance
•
•
•
Daylighting Quality
•
•
•
Lighting
Advanced Lighting Controls
•
•
•
•
HVAC/CHP
Low Energy Cooling Systems
•
•
•
Thermal Distribution Systems
•
•
Distributed Energy Site Simulation
•
•
•
Demand Response
Demand Response Automation
•
•
Ventilation/IAQ
Reducing Ventilation Energy with Air Cleaning
•
•
•
Establishing Control of Building Ventilation
•
•
•
Ventilation Performance of UFAD
•
•
IAQ, Health, and Productivity
•
•
Plug and Process Equipment
ENERGY STAR® Office Equipment
•
•
Power Control User Interfaces
•
•
· Tools & Process
Modeling and Simulation
Interoperability and Virtual Building Models
•
•
•
•
•
•
•
•
Life Cycle Building Information Models
•
•
•
•
•
•
•
•
EnergyPlus Development and Deployment
•
•
•
•
•
Building Controls Virtual Test Bed
•
•
•
Daylighting Modeling
•
•
•
•
Commissioning/Performance Monitoring
Costs and Benefits of Commissioning
•
•
•
Commissioning Persistence
•
•
Commissioning Tools and Guides
•
•
•
•
•
Functional Test Analysis Tool for AHUs
•
•
•
Monitoring Based Retro-Commissioning
•
•
•
Performance Metrics Tracking
•
•
•
•
•
•
•
Energy Information Systems
•
•
•
•
Automated Diagnostics and Prognostics
•
•
•
•
Performance Monitoring Specification
•
•
•
•
Benchmarking
Benchmarking
•
•
Design Assistance and Assessment
Design Assistance for Federal Buildings
•
•
•
Public Sector Procurement
•
•
Sustainable Design for Federal Buildings
•
•
•
Energy Use in Federal LEED Buildings
•
•
IPMVP
Last Revised: December 2006
Source: Energy Information Administration, 2003 Commercial Buildings Energy Consumption Survey.
I know I have sent you numerous emails with articles about efficiency, I hope it is helpful. It is not in any organized fashion.
If I can be of any additional help, let me know.
Jay Draiman, Energy analyst
Electricity Basics
Electricity Basics
Electricity starts with electrons. If you have read How Atoms Work, you know that every atom contains one or more electrons. You also know that electrons have a negative charge.
Simplest model of an atom
In many materials, the electrons are tightly bound to the atoms. Wood, glass, plastic, ceramic, air, cotton ... These are all examples of materials in which electrons stick with their atoms. Because the electrons don't move, these materials cannot conduct electricity very well, if at all. These materials are electrical insulators.
But most metals have electrons that can detach from their atoms and move around. These are called free electrons. Gold, silver, copper, aluminum, iron, etc., all have free electrons. The loose electrons make it easy for electricity to flow through these materials, so they are known as electrical conductors. They conduct electricity. The moving electrons transmit electrical energy from one point to another.
Electricity needs a conductor in order to move. There also has to be something to make the electricity flow from one point to another through the conductor. One way to get electricity flowing is to use a generator.
Generators
A generator uses a magnet to get electrons moving.
There is a definite link between electricity and magnetism. If you allow electrons to move through a wire, they will create a magnetic field around the wire. (See How Electric Motors Work and How Electromagnets Work for details.) Similarly, if you move a magnet near a wire, the magnetic field will cause electrons in the wire to move.
A generator is a simple device that moves a magnet near a wire to create a steady flow of electrons.
One simple way to think about a generator is to imagine it acting like a pump pushing water along. Instead of pushing water, however, a generator uses a magnet to push electrons along. This is a slight over-simplification, but it is nonetheless a very useful analogy.
There are two things that a water pump can do with water:
A water pump moves a certain number of water molecules.
A water pump applies a certain amount of pressure to the water molecules.
In the same way, the magnet in a generator can:
push a certain number of electrons along
apply a certain amount of "pressure" to the electrons
In an electrical circuit, the number of electrons that are moving is called the amperage or the current, and it is measured in amps. The "pressure" pushing the electrons along is called the voltage and is measured in volts. So you might hear someone say, "If you spin this generator at 1,000 rpm, it can produce 1 amp at 6 volts." One amp is the number of electrons moving (1 amp physically means that 6.24 x 1018 electrons move through a wire every second), and the voltage is the amount of pressure behind those electrons.
Electrical Circuits
Whether you are using a battery, a fuel cell or a solar cell to produce electricity, there are three things that are always the same:
The source of electricity will have two terminals: a positive terminal and a negative terminal.
The source of electricity (whether it is a generator, battery, etc.) will want to push electrons out of its negative terminal at a certain voltage. For example, a AA battery typically wants to push electrons out at 1.5 volts.
The electrons will need to flow from the negative terminal to the positive terminal through a copper wire or some other conductor. When there is a path that goes from the negative to the positive terminal, you have a circuit, and electrons can flow through the wire.
You can attach a load of any type (a light bulb, a motor, a TV, etc.) in the middle of the circuit. The source of electricity will power the load, and the load will do its thing (create light, spin a shaft, generate moving pictures, etc.).
Electrical circuits can get quite complex. But at the simplest level, you always have the source of electricity (a battery, etc.), a load (a light bulb, motor, etc.), and two wires to carry electricity between the battery and the load. Electrons move from the source, through the load and back to the source.
Moving electrons have energy. As the electrons move from one point to another, they can do work. In an incandescent light bulb, for example, the energy of the electrons is used to create heat, and the heat in turn creates light. In an electric motor, the energy in the electrons creates a magnetic field, and this field can interact with other magnets (through magnetic attraction and repulsion) to create motion. Each electrical appliance harnesses the energy of electrons in some way to create a useful side effect.
What About Lightning?
Photo courtesy NASA
If air is an insulator, then how can a bolt of lighting flash from a cloud to the ground through non-conducting material? In the case of lightning, there is so much electrical energy stored up between the cloud and the ground that, eventually, the energy is able to rip the electrons off the atoms in the air. Once this ripping process starts, the air becomes a plasma (a separate state of matter where there are lots of free electrons created by heat or high voltage -- see How Plasma Cutters Work to learn about this state). Once it turns to plasma, the air can easily conduct electricity with the free electrons, and the bolt of lightning shoots to the ground through the plasma conductor.
This same process allows a spark to flow between the conductors of a spark plug or a stun gun, and also carries electricity from one end to the other of a fluorescent tube.
Voltage, Current and Resistance
If you live in the United States, the power outlets in the wall of your house or apartment are delivering 120 volts.
Imagine that you plug a space heater into a wall outlet. You measure the amount of current flowing from the wall outlet to the heater, and it is 10 amps. That means that it is a 1,200-watt heater.
Volts * Amps = Watts
... so 120 volts * 10 amps = 1,200 watts.
This is the same for any electrical appliance. If you plug in a toaster and it draws 5 amps, it is a 600-watt toaster. If you plug in a light and it draws half an amp, it is a 60-watt light bulb.
Let's say that you turn on the space heater, you go outside and you look at the power meter. The purpose of the power meter is to measure the amount of electricity flowing into your house so that the power company can bill you for it. Let's assume that nothing else in the house is on, so the meter is measuring only the electricity used by the space heater.
Your space heater is using 1,200 watts. That is 1.2 kilowatts -- a kilowatt is 1,000 watts. If you leave the space heater on for one hour, you will use 1.2 kilowatt-hours of power. If your power company charges you 10 cents per kilowatt-hour, then the power company will charge you 12 cents for every hour that you leave your space heater on.
1.2 kilowatts * 1 hour = 1.2 kilowatt-hours
1.2 kilowatt-hours * 10 cents per kilowatt-hour = 12 cents
Similarly, if you have a 100-watt light and you leave it on for 10 hours, the light will consume 1 kilowatt-hour (100 watts * 10 hours = 1 kilowatt-hour).
If you have a 20,000-watt heat pump and you leave it on for five hours every day, you will consume 100 kilowatt-hours per day (20 kilowatts * 5 hours = 100 kilowatt-hours), or 10 dollars of power per day if a kilowatt-hour costs a dime. If you do that for a month, your heat pump costs you (30 * $10) $300 per month. That is why your electric bills can get so high when the temperature is very cold -- the heat pump runs a lot.
The three most basic units in electricity are voltage (V), current (I) and resistance (r). As discussed previously, voltage is measured in volts, and current is measured in amps. Resistance is measured in ohms.
We can extend the water analogy a bit further to understand resistance. The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size.
There is a basic equation in electrical engineering that states how the three terms relate. It says that the current is equal to the voltage divided by the resistance.
I = V/r
Let's say you have a tank of pressurized water connected to a hose that you are using to water the garden. What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow.
Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose. This is like decreasing the resistance in an electrical system, which increases the current flow.
When you look at a normal incandescent light bulb, you can physically see this water analogy in action. The filament of a light bulb is an extremely thin wire. This thin wire resists the flow of electrons. You can calculate the resistance of the wire with the resistance equation.
Let's say you have a 120-watt light bulb plugged into a wall socket. The voltage is 120 volts, and a 120-watt bulb has 1 amp flowing through it. You can calculate the resistance of the filament by rearranging the equation: r=V/I. So the resistance is 120 ohms. If it is a 60-watt bulb, the resistance is 240 ohms.
Direct Current vs. Alternating Current
Batteries, fuel cells and solar cells all produce something called direct current (DC). The positive and negative terminals of a battery are always, respectively, positive and negative. Current always flows in the same direction between those two terminals.
The power that comes from a power plant, on the other hand, is called alternating current (AC). The direction of the current reverses, or alternates, 60 times per second (in the U.S.) or 50 times per second (in Europe, for example). The power that is available at a wall socket in the United States is 120-volt, 60-cycle AC power.
The big advantage that alternating current provides for the power grid is the fact that it is relatively easy to change the voltage of the power, using a device called a transformer. By using very high voltages for transmitting power long distances, power companies can save a lot of money. Here's how that works.
Let's say that you have a power plant that can produce 1 million watts of power. One way to transmit that power would be to send 1 million amps at 1 volt. Another way to transmit it would be to send 1 amp at 1 million volts. Sending 1 amp requires only a thin wire, and not much of the power is lost to heat during transmission. Sending 1 million amps would require a huge wire.
So power companies convert alternating current to very high voltages for transmission (e.g. 1 million volts), then drop it back down to lower voltages for distribution (e.g. 1,000 volts), and finally down to 120 volts inside the house for safety. It is a lot harder to kill someone with 120 volts than with 1 million volts (and most electrical deaths are prevented altogether today using GFCI outlets).
See How Power Distribution Grids Work for details.
Electrical Ground
When the subject of electricity comes up, you will often hear about electrical grounding, or just ground. For example, an electrical generator will say, "Be sure to attach to an earth ground before using," or an appliance might warn, "Do not use without an appropriate ground."
It turns out that the power company uses the earth as one of the wires in the power system. The earth is a pretty good conductor, and it is huge, so it makes a good return path for electrons. "Ground" in the power-distribution grid is literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks, groundwater, etc., of the earth.
The power-distribution system connects into the ground many times. For example, in this photo you can see that one of the wires is labeled as a ground wire:
In the photo below, the bare wire coming down the side of the pole connects the aerial ground wire directly to ground:
Every utility pole on the planet has a bare wire like this. If you ever watch the power company install a new pole, you will see that the end of that bare wire is stapled in a coil to the base of the pole. That coil is in direct contact with the earth once the pole is installed, and is buried 6 to 10 feet (1.8 to 3 m) underground. It is a good, solid ground connection. If you examine a pole carefully, you will see that the ground wire running between poles (and often the guy wires) are attached to this direct connection to ground.
Similarly, near the power meter in your house or apartment there is a 6-foot (2-meter) long copper rod driven into the ground. The ground plugs and all the neutral plugs of every outlet in your house connect to this rod. (See "How Power Distribution Grids Work" for details.)
Electricity starts with electrons. If you have read How Atoms Work, you know that every atom contains one or more electrons. You also know that electrons have a negative charge.
Simplest model of an atom
In many materials, the electrons are tightly bound to the atoms. Wood, glass, plastic, ceramic, air, cotton ... These are all examples of materials in which electrons stick with their atoms. Because the electrons don't move, these materials cannot conduct electricity very well, if at all. These materials are electrical insulators.
But most metals have electrons that can detach from their atoms and move around. These are called free electrons. Gold, silver, copper, aluminum, iron, etc., all have free electrons. The loose electrons make it easy for electricity to flow through these materials, so they are known as electrical conductors. They conduct electricity. The moving electrons transmit electrical energy from one point to another.
Electricity needs a conductor in order to move. There also has to be something to make the electricity flow from one point to another through the conductor. One way to get electricity flowing is to use a generator.
Generators
A generator uses a magnet to get electrons moving.
There is a definite link between electricity and magnetism. If you allow electrons to move through a wire, they will create a magnetic field around the wire. (See How Electric Motors Work and How Electromagnets Work for details.) Similarly, if you move a magnet near a wire, the magnetic field will cause electrons in the wire to move.
A generator is a simple device that moves a magnet near a wire to create a steady flow of electrons.
One simple way to think about a generator is to imagine it acting like a pump pushing water along. Instead of pushing water, however, a generator uses a magnet to push electrons along. This is a slight over-simplification, but it is nonetheless a very useful analogy.
There are two things that a water pump can do with water:
A water pump moves a certain number of water molecules.
A water pump applies a certain amount of pressure to the water molecules.
In the same way, the magnet in a generator can:
push a certain number of electrons along
apply a certain amount of "pressure" to the electrons
In an electrical circuit, the number of electrons that are moving is called the amperage or the current, and it is measured in amps. The "pressure" pushing the electrons along is called the voltage and is measured in volts. So you might hear someone say, "If you spin this generator at 1,000 rpm, it can produce 1 amp at 6 volts." One amp is the number of electrons moving (1 amp physically means that 6.24 x 1018 electrons move through a wire every second), and the voltage is the amount of pressure behind those electrons.
Electrical Circuits
Whether you are using a battery, a fuel cell or a solar cell to produce electricity, there are three things that are always the same:
The source of electricity will have two terminals: a positive terminal and a negative terminal.
The source of electricity (whether it is a generator, battery, etc.) will want to push electrons out of its negative terminal at a certain voltage. For example, a AA battery typically wants to push electrons out at 1.5 volts.
The electrons will need to flow from the negative terminal to the positive terminal through a copper wire or some other conductor. When there is a path that goes from the negative to the positive terminal, you have a circuit, and electrons can flow through the wire.
You can attach a load of any type (a light bulb, a motor, a TV, etc.) in the middle of the circuit. The source of electricity will power the load, and the load will do its thing (create light, spin a shaft, generate moving pictures, etc.).
Electrical circuits can get quite complex. But at the simplest level, you always have the source of electricity (a battery, etc.), a load (a light bulb, motor, etc.), and two wires to carry electricity between the battery and the load. Electrons move from the source, through the load and back to the source.
Moving electrons have energy. As the electrons move from one point to another, they can do work. In an incandescent light bulb, for example, the energy of the electrons is used to create heat, and the heat in turn creates light. In an electric motor, the energy in the electrons creates a magnetic field, and this field can interact with other magnets (through magnetic attraction and repulsion) to create motion. Each electrical appliance harnesses the energy of electrons in some way to create a useful side effect.
What About Lightning?
Photo courtesy NASA
If air is an insulator, then how can a bolt of lighting flash from a cloud to the ground through non-conducting material? In the case of lightning, there is so much electrical energy stored up between the cloud and the ground that, eventually, the energy is able to rip the electrons off the atoms in the air. Once this ripping process starts, the air becomes a plasma (a separate state of matter where there are lots of free electrons created by heat or high voltage -- see How Plasma Cutters Work to learn about this state). Once it turns to plasma, the air can easily conduct electricity with the free electrons, and the bolt of lightning shoots to the ground through the plasma conductor.
This same process allows a spark to flow between the conductors of a spark plug or a stun gun, and also carries electricity from one end to the other of a fluorescent tube.
Voltage, Current and Resistance
If you live in the United States, the power outlets in the wall of your house or apartment are delivering 120 volts.
Imagine that you plug a space heater into a wall outlet. You measure the amount of current flowing from the wall outlet to the heater, and it is 10 amps. That means that it is a 1,200-watt heater.
Volts * Amps = Watts
... so 120 volts * 10 amps = 1,200 watts.
This is the same for any electrical appliance. If you plug in a toaster and it draws 5 amps, it is a 600-watt toaster. If you plug in a light and it draws half an amp, it is a 60-watt light bulb.
Let's say that you turn on the space heater, you go outside and you look at the power meter. The purpose of the power meter is to measure the amount of electricity flowing into your house so that the power company can bill you for it. Let's assume that nothing else in the house is on, so the meter is measuring only the electricity used by the space heater.
Your space heater is using 1,200 watts. That is 1.2 kilowatts -- a kilowatt is 1,000 watts. If you leave the space heater on for one hour, you will use 1.2 kilowatt-hours of power. If your power company charges you 10 cents per kilowatt-hour, then the power company will charge you 12 cents for every hour that you leave your space heater on.
1.2 kilowatts * 1 hour = 1.2 kilowatt-hours
1.2 kilowatt-hours * 10 cents per kilowatt-hour = 12 cents
Similarly, if you have a 100-watt light and you leave it on for 10 hours, the light will consume 1 kilowatt-hour (100 watts * 10 hours = 1 kilowatt-hour).
If you have a 20,000-watt heat pump and you leave it on for five hours every day, you will consume 100 kilowatt-hours per day (20 kilowatts * 5 hours = 100 kilowatt-hours), or 10 dollars of power per day if a kilowatt-hour costs a dime. If you do that for a month, your heat pump costs you (30 * $10) $300 per month. That is why your electric bills can get so high when the temperature is very cold -- the heat pump runs a lot.
The three most basic units in electricity are voltage (V), current (I) and resistance (r). As discussed previously, voltage is measured in volts, and current is measured in amps. Resistance is measured in ohms.
We can extend the water analogy a bit further to understand resistance. The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size.
There is a basic equation in electrical engineering that states how the three terms relate. It says that the current is equal to the voltage divided by the resistance.
I = V/r
Let's say you have a tank of pressurized water connected to a hose that you are using to water the garden. What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow.
Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose. This is like decreasing the resistance in an electrical system, which increases the current flow.
When you look at a normal incandescent light bulb, you can physically see this water analogy in action. The filament of a light bulb is an extremely thin wire. This thin wire resists the flow of electrons. You can calculate the resistance of the wire with the resistance equation.
Let's say you have a 120-watt light bulb plugged into a wall socket. The voltage is 120 volts, and a 120-watt bulb has 1 amp flowing through it. You can calculate the resistance of the filament by rearranging the equation: r=V/I. So the resistance is 120 ohms. If it is a 60-watt bulb, the resistance is 240 ohms.
Direct Current vs. Alternating Current
Batteries, fuel cells and solar cells all produce something called direct current (DC). The positive and negative terminals of a battery are always, respectively, positive and negative. Current always flows in the same direction between those two terminals.
The power that comes from a power plant, on the other hand, is called alternating current (AC). The direction of the current reverses, or alternates, 60 times per second (in the U.S.) or 50 times per second (in Europe, for example). The power that is available at a wall socket in the United States is 120-volt, 60-cycle AC power.
The big advantage that alternating current provides for the power grid is the fact that it is relatively easy to change the voltage of the power, using a device called a transformer. By using very high voltages for transmitting power long distances, power companies can save a lot of money. Here's how that works.
Let's say that you have a power plant that can produce 1 million watts of power. One way to transmit that power would be to send 1 million amps at 1 volt. Another way to transmit it would be to send 1 amp at 1 million volts. Sending 1 amp requires only a thin wire, and not much of the power is lost to heat during transmission. Sending 1 million amps would require a huge wire.
So power companies convert alternating current to very high voltages for transmission (e.g. 1 million volts), then drop it back down to lower voltages for distribution (e.g. 1,000 volts), and finally down to 120 volts inside the house for safety. It is a lot harder to kill someone with 120 volts than with 1 million volts (and most electrical deaths are prevented altogether today using GFCI outlets).
See How Power Distribution Grids Work for details.
Electrical Ground
When the subject of electricity comes up, you will often hear about electrical grounding, or just ground. For example, an electrical generator will say, "Be sure to attach to an earth ground before using," or an appliance might warn, "Do not use without an appropriate ground."
It turns out that the power company uses the earth as one of the wires in the power system. The earth is a pretty good conductor, and it is huge, so it makes a good return path for electrons. "Ground" in the power-distribution grid is literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks, groundwater, etc., of the earth.
The power-distribution system connects into the ground many times. For example, in this photo you can see that one of the wires is labeled as a ground wire:
In the photo below, the bare wire coming down the side of the pole connects the aerial ground wire directly to ground:
Every utility pole on the planet has a bare wire like this. If you ever watch the power company install a new pole, you will see that the end of that bare wire is stapled in a coil to the base of the pole. That coil is in direct contact with the earth once the pole is installed, and is buried 6 to 10 feet (1.8 to 3 m) underground. It is a good, solid ground connection. If you examine a pole carefully, you will see that the ground wire running between poles (and often the guy wires) are attached to this direct connection to ground.
Similarly, near the power meter in your house or apartment there is a 6-foot (2-meter) long copper rod driven into the ground. The ground plugs and all the neutral plugs of every outlet in your house connect to this rod. (See "How Power Distribution Grids Work" for details.)
Electricity
A SECONDARY SOURCE
Electricity is the flow of electrical power or charge. It is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or non-renewable.
Electricity is a basic part of nature and it is one of our most widely used forms of energy. Many cities and towns were built alongside waterfalls (a primary source of mechanical energy) that turned water wheels to perform work. Before electricity generation began over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. Beginning with Benjamin Franklin's experiment with a kite one stormy night in Philadelphia, the principles of electricity gradually became understood. Thomas Edison helped change everyone's life -- he perfected his invention -- the electric light bulb. Prior to 1879, direct current (DC) electricity had been used in arc lights for outdoor lighting. In the late-1800s, Nikola Tesla pioneered the generation, transmission, and use of alternating current (AC) electricity, which can be transmitted over much greater distances than direct current. Tesla's inventions used electricity to bring indoor lighting to our homes and to power industrial machines.
Despite its great importance in our daily lives, most of us rarely stop to think what life would be like without electricity. Yet like air and water, we tend to take electricity for granted. Everyday, we use electricity to do many jobs for us -- from lighting and heating/cooling our homes, to powering our televisions and computers. Electricity is a controllable and convenient form of energy used in the applications of heat, light and power.
THE SCIENCE OF ELECTRICITY developed by the National Energy Education Development Project
In order to understand how electric charge moves from one atom to another, we need to know something about atoms. Everything in the universe is made of atoms—every star, every tree, every animal. The human body is made of atoms. Air and water are, too. Atoms are the building blocks of the universe. Atoms are so small that millions of them would fit on the head of a pin.
Atoms are made of even smaller particles. The center of an atom is called the nucleus. It is made of particles called protons and neutrons. The protons and neutrons are very small, but electrons are much, much smaller. Electrons spin around the nucleus in shells a great distance from the nucleus. If the nucleus were the size of a tennis ball, the atom would be the size of the Empire State Building. Atoms are mostly empty space.
If you could see an atom, it would look a little like a tiny center of balls surrounded by giant invisible bubbles (or shells). The electrons would be on the surface of the bubbles, constantly spinning and moving to stay as far away from each other as possible. Electrons are held in their shells by an electrical force.
The protons and electrons of an atom are attracted to each other. They both carry an electrical charge. An electrical charge is a force within the particle. Protons have a positive charge (+) and electrons have a negative charge (-). The positive charge of the protons is equal to the negative charge of the electrons. Opposite charges attract each other. When an atom is in balance, it has an equal number of protons and electrons. The neutrons carry no charge and their number can vary.
The number of protons in an atom determines the kind of atom, or element, it is. An element is a substance in which all of the atoms are identical (the Periodic Table shows all the known elements). Every atom of hydrogen, for example, has one proton and one electron, with no neutrons. Every atom of carbon has six protons, six electrons, and six neutrons. The number of protons determines which element it is.
Electrons usually remain a constant distance from the nucleus in precise shells. The shell closest to the nucleus can hold two electrons. The next shell can hold up to eight. The outer shells cans hold even more. Some atoms with many protons can have as many as seven shells with electrons in them.
The electrons in the shells closest to the nucleus have a strong force of attraction to the protons. Sometimes, the electrons in the outermost shells do not. These electrons can be pushed out of their orbits. Applying a force can make them move from one atom to another. These moving electrons are electricity.
STATIC ELECTRICITY
Electricity has been moving in the world forever. Lightning is a form of electricity. It is electrons moving from one cloud to another or jumping from a cloud to the ground. Have you ever felt a shock when you touched an object after walking across a carpet? A stream of electrons jumped to you from that object. This is called static electricity.
Have you ever made your hair stand straight up by rubbing a balloon on it? If so, you rubbed some electrons off the balloon. The electrons moved into your hair from the balloon. They tried to get far away from each other by moving to the ends of your hair.
They pushed against each other and made your hair move—they repelled each other. Just as opposite charges attract each other, like charges repel each other.
MAGNETS AND ELECTRICITY
The spinning of the electrons around the nucleus of an atom creates a tiny magnetic field. Most objects are not magnetic because the atoms are arranged so that the electrons spin in different, random directions, and cancel out each other.
Magnets are different; the molecules in magnets are arranged so that the electrons spin in the same direction. This arrangement of atoms creates two poles in a magnet, a North-seeking pole and a South-seeking pole.
Bar Magnet
A magnet is labeled with North (N) and South (S) poles. The magnetic force in a magnet flows from the North pole to the South pole. This creates a magnetic field around a magnet.
Have you ever held two magnets close to each other? They don’t act like most objects. If you try to push the South poles together, they repel each other. Two North poles also repel each other.
Turn one magnet around and the North (N) and the South (S) poles are attracted to each other. The magnets come together with a strong force. Just like protons and electrons, opposites attract.
These special properties of magnets can be used to make electricity. Moving magnetic fields can pull and push electrons. Some metals, like copper have electrons that are loosely held. They can be pushed from their shells by moving magnets. Magnets and wire are used together in electric generators.
BATTERIES PRODUCE ELECTRICITY
A battery produces electricity using two different metals in a chemical solution. A chemical reaction between the metals and the chemicals frees more electrons in one metal than in the other. One end of the battery is attached to one of the metals; the other end is attached to the other metal. The end that frees more electrons develops a positive charge and the other end develops a negative charge. If a wire is attached from one end of the battery to the other, electrons flow through the wire to balance the electrical charge. A load is a device that does work or performs a job. If a load––such as a lightbulb––is placed along the wire, the electricity can do work as it flows through the wire. In the picture above, electrons flow from the negative end of the battery through the wire to the lightbulb. The electricity flows through the wire in the lightbulb and back to the battery.
ELECTRICITY TRAVELS IN CIRCUITS
Electricity travels in closed loops, or circuits (from the word circle). It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a light switch, we close a circuit. The electricity flows from the electric wire through the light and back into the wire. When we flip the switch off, we open the circuit. No electricity flows to the light. When we turn a light switch on, electricity flows through a tiny wire in the bulb. The wire gets very hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path through the bulb is gone. When we turn on the TV, electricity flows through wires inside the set, producing pictures and sound. Sometimes electricity runs motors—in washers or mixers. Electricity does a lot of work for us. We use it many times each day.
HOW ELECTRICITY IS GENERATED
A generator is a device that converts mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. In 1831, Faraday discovered that when a magnet is moved inside a coil of wire, electrical current flows in the wire.
A typical generator at a power plant uses an electromagnet—a magnet produced by electricity—not a traditional magnet. The generator has a series of insulated coils of wire that form a stationary cylinder. This cylinder surrounds a rotary electromagnetic shaft. When the electromagnetic shaft rotates, it induces a small electric current in each section of the wire coil. Each section of the wire becomes a small, separate electric conductor. The small currents of individual sections are added together to form one large current. This current is the electric power that is transmitted from the power company to the consumer.
An electric utility power station uses either a turbine, engine, water wheel, or other similar machine to drive an electric generator or a device that converts mechanical or chemical energy to generate electricity. Steam turbines, internal-combustion engines, gas combustion turbines, water turbines, and wind turbines are the most common methods to generate electricity. Most power plants are about 35 percent efficient. That means that for every 100 units of energy that go into a plant, only 35 units are converted to usable electrical energy.
Most of the electricity in the United States is produced in steam turbines. A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. Steam turbines have a series of blades mounted on a shaft against which steam is forced, thus rotating the shaft connected to the generator. In a fossil-fueled steam turbine, the fuel is burned in a furnace to heat water in a boiler to produce steam.
Coal, petroleum (oil), and natural gas are burned in large furnaces to heat water to make steam that in turn pushes on the blades of a turbine. Did you know that coal is the largest single primary source of energy used to generate electricity in the United States? In 2006, nearly half (49%) of the country's 4.1 trillion kilowatthours of electricity used coal as its source of energy.
Natural gas, in addition to being burned to heat water for steam, can also be burned to produce hot combustion gases that pass directly through a turbine, spinning the blades of the turbine to generate electricity. Gas turbines are commonly used when electricity utility usage is in high demand. In 2006, 20% of the nation's electricity was fueled by natural gas.
Petroleum can also be used to make steam to turn a turbine. Residual fuel oil, a product refined from crude oil, is often the petroleum product used in electric plants that use petroleum to make steam. Petroleum was used to generate about two percent (2%) of all electricity generated in U.S. electricity plants in 2006.
Nuclear power is a method in which steam is produced by heating water through a process called nuclear fission. In a nuclear power plant, a reactor contains a core of nuclear fuel, primarily enriched uranium. When atoms of uranium fuel are hit by neutrons they fission (split), releasing heat and more neutrons. Under controlled conditions, these other neutrons can strike more uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place, forming a chain reaction releasing heat. The heat is used to turn water into steam, that, in turn, spins a turbine that generates electricity. Nuclear power was used to generate 19% of all the country's electricity in 2006.
Hydropower, the source for almost 7% of U.S. electricity generation in 2006, is a process in which flowing water is used to spin a turbine connected to a generator. There are two basic types of hydroelectric systems that produce electricity. In the first system, flowing water accumulates in reservoirs created by the use of dams. The water falls through a pipe called a penstock and applies pressure against the turbine blades to drive the generator to produce electricity. In the second system, called run-of-river, the force of the river current (rather than falling water) applies pressure to the turbine blades to produce electricity.
Geothermal power comes from heat energy buried beneath the surface of the earth. In some areas of the country, enough heat rises close to the surface of the earth to heat underground water into steam, which can be tapped for use at steam-turbine plants. This energy source generated less than 1% of the electricity in the country in 2006.
Solar power is derived from the energy of the sun. However, the sun's energy is not available full-time and it is widely scattered. The processes used to produce electricity using the sun's energy have historically been more expensive than using conventional fossil fuels. Photovoltaic conversion generates electric power directly from the light of the sun in a photovoltaic (solar) cell. Solar-thermal electric generators use the radiant energy from the sun to produce steam to drive turbines. In 2006, less than 1% of the nation's electricity was based on solar power.
Wind power is derived from the conversion of the energy contained in wind into electricity. Wind power, less than 1% of the nation's electricity in 2006, is a rapidly growing source of electricity. A wind turbine is similar to a typical wind mill.
Biomass includes wood, municipal solid waste (garbage), and agricultural waste, such as corn cobs and wheat straw. These are some other energy sources for producing electricity. These sources replace fossil fuels in the boiler. The combustion of wood and waste creates steam that is typically used in conventional steam-electric plants. Biomass accounts for about 1% of the electricity generated in the United States.
THE TRANSFORMER - MOVING ELECTRICITY
To solve the problem of sending electricity over long distances, William Stanley developed a device called a transformer. The transformer allowed electricity to be efficiently transmitted over long distances. This made it possible to supply electricity to homes and businesses located far from the electric generating plant.
The electricity produced by a generator travels along cables to a transformer, which changes electricity from low voltage to high voltage. Electricity can be moved long distances more efficiently using high voltage. Transmission lines are used to carry the electricity to a substation. Substations have transformers that change the high voltage electricity into lower voltage electricity. From the substation, distribution lines carry the electricity to homes, offices and factories, which require low voltage electricity.
MEASURING ELECTRICITY
Electricity is measured in units of power called watts. It was named to honor James Watt, the inventor of the steam engine. One watt is a very small amount of power. It would require nearly 750 watts to equal one horsepower. A kilowatt represents 1,000 watts. A kilowatthour (kWh) is equal to the energy of 1,000 watts working for one hour. The amount of electricity a power plant generates or a customer uses over a period of time is measured in kilowatthours (kWh). Kilowatthours are determined by multiplying the number of kW's required by the number of hours of use. For example, if you use a 40-watt light bulb 5 hours a day, you have used 200 watthours, or 0.2 kilowatthours, of electrical energy. See our Energy Calculator section to learn more about converting units.
Electricity is the flow of electrical power or charge. It is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or non-renewable.
Electricity is a basic part of nature and it is one of our most widely used forms of energy. Many cities and towns were built alongside waterfalls (a primary source of mechanical energy) that turned water wheels to perform work. Before electricity generation began over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. Beginning with Benjamin Franklin's experiment with a kite one stormy night in Philadelphia, the principles of electricity gradually became understood. Thomas Edison helped change everyone's life -- he perfected his invention -- the electric light bulb. Prior to 1879, direct current (DC) electricity had been used in arc lights for outdoor lighting. In the late-1800s, Nikola Tesla pioneered the generation, transmission, and use of alternating current (AC) electricity, which can be transmitted over much greater distances than direct current. Tesla's inventions used electricity to bring indoor lighting to our homes and to power industrial machines.
Despite its great importance in our daily lives, most of us rarely stop to think what life would be like without electricity. Yet like air and water, we tend to take electricity for granted. Everyday, we use electricity to do many jobs for us -- from lighting and heating/cooling our homes, to powering our televisions and computers. Electricity is a controllable and convenient form of energy used in the applications of heat, light and power.
THE SCIENCE OF ELECTRICITY developed by the National Energy Education Development Project
In order to understand how electric charge moves from one atom to another, we need to know something about atoms. Everything in the universe is made of atoms—every star, every tree, every animal. The human body is made of atoms. Air and water are, too. Atoms are the building blocks of the universe. Atoms are so small that millions of them would fit on the head of a pin.
Atoms are made of even smaller particles. The center of an atom is called the nucleus. It is made of particles called protons and neutrons. The protons and neutrons are very small, but electrons are much, much smaller. Electrons spin around the nucleus in shells a great distance from the nucleus. If the nucleus were the size of a tennis ball, the atom would be the size of the Empire State Building. Atoms are mostly empty space.
If you could see an atom, it would look a little like a tiny center of balls surrounded by giant invisible bubbles (or shells). The electrons would be on the surface of the bubbles, constantly spinning and moving to stay as far away from each other as possible. Electrons are held in their shells by an electrical force.
The protons and electrons of an atom are attracted to each other. They both carry an electrical charge. An electrical charge is a force within the particle. Protons have a positive charge (+) and electrons have a negative charge (-). The positive charge of the protons is equal to the negative charge of the electrons. Opposite charges attract each other. When an atom is in balance, it has an equal number of protons and electrons. The neutrons carry no charge and their number can vary.
The number of protons in an atom determines the kind of atom, or element, it is. An element is a substance in which all of the atoms are identical (the Periodic Table shows all the known elements). Every atom of hydrogen, for example, has one proton and one electron, with no neutrons. Every atom of carbon has six protons, six electrons, and six neutrons. The number of protons determines which element it is.
Electrons usually remain a constant distance from the nucleus in precise shells. The shell closest to the nucleus can hold two electrons. The next shell can hold up to eight. The outer shells cans hold even more. Some atoms with many protons can have as many as seven shells with electrons in them.
The electrons in the shells closest to the nucleus have a strong force of attraction to the protons. Sometimes, the electrons in the outermost shells do not. These electrons can be pushed out of their orbits. Applying a force can make them move from one atom to another. These moving electrons are electricity.
STATIC ELECTRICITY
Electricity has been moving in the world forever. Lightning is a form of electricity. It is electrons moving from one cloud to another or jumping from a cloud to the ground. Have you ever felt a shock when you touched an object after walking across a carpet? A stream of electrons jumped to you from that object. This is called static electricity.
Have you ever made your hair stand straight up by rubbing a balloon on it? If so, you rubbed some electrons off the balloon. The electrons moved into your hair from the balloon. They tried to get far away from each other by moving to the ends of your hair.
They pushed against each other and made your hair move—they repelled each other. Just as opposite charges attract each other, like charges repel each other.
MAGNETS AND ELECTRICITY
The spinning of the electrons around the nucleus of an atom creates a tiny magnetic field. Most objects are not magnetic because the atoms are arranged so that the electrons spin in different, random directions, and cancel out each other.
Magnets are different; the molecules in magnets are arranged so that the electrons spin in the same direction. This arrangement of atoms creates two poles in a magnet, a North-seeking pole and a South-seeking pole.
Bar Magnet
A magnet is labeled with North (N) and South (S) poles. The magnetic force in a magnet flows from the North pole to the South pole. This creates a magnetic field around a magnet.
Have you ever held two magnets close to each other? They don’t act like most objects. If you try to push the South poles together, they repel each other. Two North poles also repel each other.
Turn one magnet around and the North (N) and the South (S) poles are attracted to each other. The magnets come together with a strong force. Just like protons and electrons, opposites attract.
These special properties of magnets can be used to make electricity. Moving magnetic fields can pull and push electrons. Some metals, like copper have electrons that are loosely held. They can be pushed from their shells by moving magnets. Magnets and wire are used together in electric generators.
BATTERIES PRODUCE ELECTRICITY
A battery produces electricity using two different metals in a chemical solution. A chemical reaction between the metals and the chemicals frees more electrons in one metal than in the other. One end of the battery is attached to one of the metals; the other end is attached to the other metal. The end that frees more electrons develops a positive charge and the other end develops a negative charge. If a wire is attached from one end of the battery to the other, electrons flow through the wire to balance the electrical charge. A load is a device that does work or performs a job. If a load––such as a lightbulb––is placed along the wire, the electricity can do work as it flows through the wire. In the picture above, electrons flow from the negative end of the battery through the wire to the lightbulb. The electricity flows through the wire in the lightbulb and back to the battery.
ELECTRICITY TRAVELS IN CIRCUITS
Electricity travels in closed loops, or circuits (from the word circle). It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a light switch, we close a circuit. The electricity flows from the electric wire through the light and back into the wire. When we flip the switch off, we open the circuit. No electricity flows to the light. When we turn a light switch on, electricity flows through a tiny wire in the bulb. The wire gets very hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path through the bulb is gone. When we turn on the TV, electricity flows through wires inside the set, producing pictures and sound. Sometimes electricity runs motors—in washers or mixers. Electricity does a lot of work for us. We use it many times each day.
HOW ELECTRICITY IS GENERATED
A generator is a device that converts mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. In 1831, Faraday discovered that when a magnet is moved inside a coil of wire, electrical current flows in the wire.
A typical generator at a power plant uses an electromagnet—a magnet produced by electricity—not a traditional magnet. The generator has a series of insulated coils of wire that form a stationary cylinder. This cylinder surrounds a rotary electromagnetic shaft. When the electromagnetic shaft rotates, it induces a small electric current in each section of the wire coil. Each section of the wire becomes a small, separate electric conductor. The small currents of individual sections are added together to form one large current. This current is the electric power that is transmitted from the power company to the consumer.
An electric utility power station uses either a turbine, engine, water wheel, or other similar machine to drive an electric generator or a device that converts mechanical or chemical energy to generate electricity. Steam turbines, internal-combustion engines, gas combustion turbines, water turbines, and wind turbines are the most common methods to generate electricity. Most power plants are about 35 percent efficient. That means that for every 100 units of energy that go into a plant, only 35 units are converted to usable electrical energy.
Most of the electricity in the United States is produced in steam turbines. A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. Steam turbines have a series of blades mounted on a shaft against which steam is forced, thus rotating the shaft connected to the generator. In a fossil-fueled steam turbine, the fuel is burned in a furnace to heat water in a boiler to produce steam.
Coal, petroleum (oil), and natural gas are burned in large furnaces to heat water to make steam that in turn pushes on the blades of a turbine. Did you know that coal is the largest single primary source of energy used to generate electricity in the United States? In 2006, nearly half (49%) of the country's 4.1 trillion kilowatthours of electricity used coal as its source of energy.
Natural gas, in addition to being burned to heat water for steam, can also be burned to produce hot combustion gases that pass directly through a turbine, spinning the blades of the turbine to generate electricity. Gas turbines are commonly used when electricity utility usage is in high demand. In 2006, 20% of the nation's electricity was fueled by natural gas.
Petroleum can also be used to make steam to turn a turbine. Residual fuel oil, a product refined from crude oil, is often the petroleum product used in electric plants that use petroleum to make steam. Petroleum was used to generate about two percent (2%) of all electricity generated in U.S. electricity plants in 2006.
Nuclear power is a method in which steam is produced by heating water through a process called nuclear fission. In a nuclear power plant, a reactor contains a core of nuclear fuel, primarily enriched uranium. When atoms of uranium fuel are hit by neutrons they fission (split), releasing heat and more neutrons. Under controlled conditions, these other neutrons can strike more uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place, forming a chain reaction releasing heat. The heat is used to turn water into steam, that, in turn, spins a turbine that generates electricity. Nuclear power was used to generate 19% of all the country's electricity in 2006.
Hydropower, the source for almost 7% of U.S. electricity generation in 2006, is a process in which flowing water is used to spin a turbine connected to a generator. There are two basic types of hydroelectric systems that produce electricity. In the first system, flowing water accumulates in reservoirs created by the use of dams. The water falls through a pipe called a penstock and applies pressure against the turbine blades to drive the generator to produce electricity. In the second system, called run-of-river, the force of the river current (rather than falling water) applies pressure to the turbine blades to produce electricity.
Geothermal power comes from heat energy buried beneath the surface of the earth. In some areas of the country, enough heat rises close to the surface of the earth to heat underground water into steam, which can be tapped for use at steam-turbine plants. This energy source generated less than 1% of the electricity in the country in 2006.
Solar power is derived from the energy of the sun. However, the sun's energy is not available full-time and it is widely scattered. The processes used to produce electricity using the sun's energy have historically been more expensive than using conventional fossil fuels. Photovoltaic conversion generates electric power directly from the light of the sun in a photovoltaic (solar) cell. Solar-thermal electric generators use the radiant energy from the sun to produce steam to drive turbines. In 2006, less than 1% of the nation's electricity was based on solar power.
Wind power is derived from the conversion of the energy contained in wind into electricity. Wind power, less than 1% of the nation's electricity in 2006, is a rapidly growing source of electricity. A wind turbine is similar to a typical wind mill.
Biomass includes wood, municipal solid waste (garbage), and agricultural waste, such as corn cobs and wheat straw. These are some other energy sources for producing electricity. These sources replace fossil fuels in the boiler. The combustion of wood and waste creates steam that is typically used in conventional steam-electric plants. Biomass accounts for about 1% of the electricity generated in the United States.
THE TRANSFORMER - MOVING ELECTRICITY
To solve the problem of sending electricity over long distances, William Stanley developed a device called a transformer. The transformer allowed electricity to be efficiently transmitted over long distances. This made it possible to supply electricity to homes and businesses located far from the electric generating plant.
The electricity produced by a generator travels along cables to a transformer, which changes electricity from low voltage to high voltage. Electricity can be moved long distances more efficiently using high voltage. Transmission lines are used to carry the electricity to a substation. Substations have transformers that change the high voltage electricity into lower voltage electricity. From the substation, distribution lines carry the electricity to homes, offices and factories, which require low voltage electricity.
MEASURING ELECTRICITY
Electricity is measured in units of power called watts. It was named to honor James Watt, the inventor of the steam engine. One watt is a very small amount of power. It would require nearly 750 watts to equal one horsepower. A kilowatt represents 1,000 watts. A kilowatthour (kWh) is equal to the energy of 1,000 watts working for one hour. The amount of electricity a power plant generates or a customer uses over a period of time is measured in kilowatthours (kWh). Kilowatthours are determined by multiplying the number of kW's required by the number of hours of use. For example, if you use a 40-watt light bulb 5 hours a day, you have used 200 watthours, or 0.2 kilowatthours, of electrical energy. See our Energy Calculator section to learn more about converting units.
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