1、Energy Usage and Conservation Within the Household,Darryl Birtwistle Energy, Society, and Climate October 7, 2002,Facts,The energy consumed within the US increased exponentially from about 1850-1975. Projections indicated US would be using energy at a rate of 160 Qbtu/yr by 2000 (Q= 1015). By 1996,
2、we only used energy at a rate of 93.8 Qbtu/yr. Buildings and appliances now use about 38% of the total energy consumed in the nation. (industry: 36%, transportation: 26%),Energy Uses and Sources,Space Heating,Uses largest amount of energy in US households (20%). Natural gas is the predominant source
3、 used. Household heating is a very inefficient process as hot air leaks out roof, through cracks in walls and windows, through doors, and out the basement.,Furnaces, Stoves, and Fireplaces,Most use natural gas Furnaces are 60-90% effective. (50% for older units) Alternatives are electric resistance
4、heating and the use of electrically powered heat pumps.,Electric resistance heating is 100% efficient, however, costs more to operate. Electrically powered heat pumps can be used in places where temperatures are not too low. May also act as air-conditioner.,Fireplaces,Are inefficient unless used to
5、heat small part of house while thermostat is down. Efficiency of 40-65%. Open fireplaces have negative efficiency: they remove more heat from the house than they provide. Heat enters fireplace then goes out the flue.,Efficient Fireplaces,Some fireplaces are constructed with connective passages aroun
6、d back of firebox so air is air is drawn close to it, heated, then sent back into the room. This type of fireplace is more efficient.,Firewood provides energy at rate of 12 to 30 mil. Btu per cord. Cord = 128ft3 stack Higher density wood has more heat per cord. All wood is about 8600Btu/lb.,Solar He
7、at,Heat can be gained through direct light through south-facing windows. Light not reflected back out converts into heat. Conversion efficiency from light to heat is usually around 6090% Transmission of sunlight through glass and insulation factors need to be taken into account.,Effective Design,Sta
8、ndards for Home Heating,Space Heating and Conservation,Most important factor for conservation is thermostat settings. Normal settings have dropped from 72 to 65-68 degrees as comfortable living temp. Settings should be turned to around 55 at night, then brought back up before needed. The many critic
9、s of this idea are falsely informed. Buildings should be properly insulated.,Insulation,With perfect thermal insulation and no leakage of air, no energy source would be needed to keep a constant temperature. However, this is not possible. Well designed houses have been built that require no separate
10、 heating system. They are heated by existing internal sources such as lights and stoves. Insulation is important in controlling heat loss.,Insulation - Building Materials,Air Infiltration,Accounts for a complete change of air in a house about once per hour. Also accounts for 1/3 of heat loss. Air ex
11、change occurs around doors, windows, leaky siding, and other cracks. Fireplaces chimneys and furnace vents also account for loss of warm air.,Heat Loss,Air infiltration,Leakage can be reduced to about 10% by caulking, weather stripping, the addition of automatic flue dampers, and closure of fireplac
12、e and openings and chimneys. Must keep dangerous gases such as carbon monoxide and radon in mind when completely sealing a house.,Air to Air Heat Exchanger,Gets rid of harmful gases without heat loss. Heat is transferred from warm to cold air by conduction through a thin barrier. Brings incoming air
13、 up to temperature as well as gives it moisture.,Water Heaters,About 10-20% energy consumed in house. Usually gas or electricity heats a 30-50 gal. Tank of water to temp range of 120-140 F Gas heaters loose heat through flue. Pipes carrying water take away heat. Steady expenditure of energy is requi
14、red to maintain the water temperature.,Ways to Conserve,Reduction of the amount of hot water used. Lowering heaters thermostat to 120 deg reduces energy consumed and still provides hot enough water. Insulation can be added to the tank and pipes. Electric igniters eliminate energy wasted by pilot lig
15、ht. Flue damper can be installed.,Air Conditioning,About 60% (57 million) of US households now have air conditioners. 75% of new homes have central air conditioners. Takes output of 7 large power plants to provide energy for US air conditioning. Air conditioners should be turned down when not needed
16、, doors and windows should also remain shut to prevent loss of cool air.,Air Conditioning,Central air conditioners are rated by there seasonal energy efficient ratio (SEER). Typical SEER ratings have increased from 6 or 8 some years ago to 8.5 or 9.5 recently. Cost of energy to operate air condition
17、ers is enough to motivate people attention to good house design and insulation.,Appliances,Main energy consumers Refrigerators Clothes dryers Air conditioners Many appliances thought to waist energy such as electric carving knives and toothbrushes really use a negligible amount of energy.,Appliances
18、 - Energy Consumption Chart,Water Heater: 6,000 A/C: 4,300 Refrigerator: 1,300 Washer: 1,080 Dryer: 1,060 Lighting: 844,Appliances Energy Leakage,Appliances drain energy even when they are off in order to maintain settings, display clocks, and keep remote control alert. TVs drain energy to keep tube
19、s warm. 12-volt power transformers for many appliances drain energy when off. Typical house drains continuously about 50w of electric power when all switches are turned off. This leaked electricity costs about $3 billion per year nation wide.,Energy Guide,Must be posted on all new appliances. List e
20、nergy usage and cost for appliance for one year. Allows consumer to compare increased cost of energy conservative appliance to savings in energy usage.,Refrigerators,Companies began to minimize insulation to provide more space. Made refrigerators less energy conservative. 1972: 1700kWh/yr were used
21、($130),1997: 690kWh/yr ($50) is the standard. Projected 2001 standard is 535kWh/yr, down 30% from 1997.,Clothes Dryers,Consume about 15% of household electric energy. Energy can be conserved by hanging clothes outside. Air from electric dryer can be vented back into the house to conserve heat.,Light
22、ing,20% of electric energy is used for lighting. Standard light levels in public schools have increased from 20 lumens/sq ft. to 60 (suggested level for reading). Many office buildings have lighting levels of 80 to 100 lumens/sq ft, including corridors and stairways. Many office buildings have singl
23、e switches that turn on whole floors at once.,Lighting (light choice),Fluorescent light produces about five times more lumens per watt than incandescent lighting. 15 w fluorescent bulb = 75 w incandescent bulb Some people complain about quality of light of fluorescent bulb, this is being fixed Fluor
24、escent lamps last about 10,000 hours, ten times longer than conventional light bulbs. Lower energy usage and longer lifespan account for greater price of fluorescent light bulbs.,Lighting Chart,Lighting - Conservation,Choose efficient light fixtures. Use effective lighting design. Use switches allow
25、ing lights to be individual controlled, allow for dimming. Corridors and stairways should use less light. Users should remember to turn off lights or use automatic controllers to turn them off.,The Energy-Conservative House,Study done on 1200 sq ft California house to determine energy conservation i
26、n relationship to cost. Largest effect was for space heating which went from 120 mil Btu/yr to 35 mil Btu/yr, for an expenditure of $1600. (2/3 reduction) Total energy used was also decreased from 235 to 100 mil Btu with an investment of $2700,National Affect,If the conservation steps taken in this
27、experimental house were used across the nation, the 36 QBtu used nationally per year for buildings and appliances could be reduced to 15 Qbtu/yr, with a cost of about 150 billion dollars. Demonstrates the potential for energy conservation in homes and buildings.,Recycling,Recycling is important in reducing garbage but also in conserving energy. Takes only 1/3 amount of energy to form a beverage can from recycled aluminum as it does from virgin aluminum. Less energy to just reuse and existing container. Takes also 1/3 less energy to form steel products from scrap than from ore,The End,
