Energy Usage and Conservation Within the Household

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Energy Usage and Conservation Within the Household

• Darryl Birtwistle
• Energy, Society, and Climate
• October 7, 2002

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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, 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)

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Energy Uses and Sources
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Space Heating

• Uses largest amount of energy in US households
  (20).
• Natural gas is the predominant source 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.

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Furnaces, Stoves, and Fireplaces

• Most use natural gas
• Furnaces are 60-90 effective. (50 for older
  units)
• Alternatives are electric resistance 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.

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Fireplaces

• Are inefficient unless used to 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.

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Efficient Fireplaces

• Some fireplaces are constructed with connective
  passages around 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.

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Solar Heat

• 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.

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Effective Design
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Standards for Home Heating
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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 critics of this idea are falsely
  informed.
• Buildings should be properly insulated.

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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 heating system.
• They are heated by existing internal sources such
  as lights and stoves.
• Insulation is important in controlling heat loss.

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Insulation - Building Materials
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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 exchange occurs around doors, windows, leaky
  siding, and other cracks.
• Fireplaces chimneys and furnace vents also
  account for loss of warm air.

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Heat Loss
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Air infiltration

• Leakage can be reduced to about 10 by caulking,
  weather stripping, the addition of automatic flue
  dampers, and closure of fireplace and openings
  and chimneys.
• Must keep dangerous gases such as carbon monoxide
  and radon in mind when completely sealing a
  house.

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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 up to temperature as well as
  gives it moisture.

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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 required to
  maintain the water temperature.

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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 light.
• Flue damper can be installed.

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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, doors and windows should also remain shut
  to prevent loss of cool air.

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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 conditioners is
  enough to motivate people attention to good house
  design and insulation.

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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.

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Appliances - Energy Consumption Chart
Water Heater 6,000 A/C 4,300 Refrigerator
1,300 Washer 1,080 Dryer 1,060 Lighting 844
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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 tubes 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.

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Energy Guide

• Must be posted on all new appliances.
• List energy usage and cost for appliance for one
  year.
• Allows consumer to compare increased cost of
  energy conservative appliance to savings in
  energy usage.

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Refrigerators

• Companies began to minimize insulation to provide
  more space.
• Made refrigerators less energy conservative.
• 1972 1700kWh/yr were used (130)

• 1997 690kWh/yr (50) is the standard.
• Projected 2001 standard is 535kWh/yr, down 30
  from 1997.

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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.

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Lighting

• 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 single switches that
  turn on whole floors at once.

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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
• Fluorescent 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.

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Lighting Chart
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Lighting - Conservation

• Choose efficient light fixtures.
• Use effective lighting design.
• Use switches allowing 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.

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The Energy-Conservative House

• Study done on 1200 sq ft California house to
  determine energy conservation in 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

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National Affect

• If the conservation steps taken in this
  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.

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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

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The End