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= 10^15).

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%)

Energy Uses and Sources

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.

Furnaces, Stoves, and Fireplaces

Most use natural gasFurnaces 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.

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.

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 stackHigher density wood

has more heat per cord.

All wood is about 8600Btu/lb.

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 60–90%Transmission of sunlight through glass and

insulation factors need to be taken into account.

Effective Design

Standards 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 critics 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 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 exchange 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 fireplace 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 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 FGas heaters loose heat through flue.Pipes carrying water take away heat.Steady expenditure of energy is required to

maintain the water temperature.

Ways to Conserve

Reduction of the amount of hot water used.Lowering heater’s 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.

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.

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.

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 - Energy Consumption Chart

Water Heater: 6,000A/C: 4,300Refrigerator: 1,300Washer: 1,080Dryer: 1,060Lighting: 844

Appliances – Energy Leakage

Appliances drain energy even when they are off in order to maintain settings, display clocks, and keep remote control alert.

TV’s 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.

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.

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.

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.

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.

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.

Lighting Chart

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.

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

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.

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