Energy conservation

Energy conservation is reducing the amount of energy used for different purposes. This may result in an increase of financial capital, environmental value, national and personal security, and human comfort.

Individuals and organizations that consume energy may conserve energy to reduce costs and promote economic, political and environmental sustainability.  Industrial and commercial users may want to increase efficiency and thus maximize profit.

On a larger scale, energy conservation is an energy policy.  In general, energy conservation  reduces the energy consumption and energy demand per capita.  This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports.  The reduced energy demand can provide more flexibility in choosing the methods of energy production.

By reducing emissions, energy conservation helps to prevent climate change.  Energy conservation makes it easier to replace non-renewable resources with renewable energy.  Energy conservation is often the most economical solution to energy shortages.

Energy efficiency trends in the United States
The U.S. is the largest consumer of energy, although at current levels of growth, China may become the leading energy consumer. The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial.US Dept. of Energy, " Annual Energy Report" (July 2006), Energy Flow diagram

Energy usage in the transportation and residential sectors (about half of U.S. energy consumption) is largely controlled by individual domestic consumers.  Commercial and industrial energy usage are controlled by businesses.  National energy policy has a significant effect on energy usage across all four sectors.

Transportation sector
The transportation sector includes all vehicles used for personal or freight transportation. Of the energy used in this sector, about 65% is used by gasoline-powered vehicles, mostly personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%.US Dept. of Energy, "Annual Energy Outlook" (February 2006), Table A2

The oil supply crises of the 1970s spurred the creation, in 1975, of the federal Corporate Average Fuel Economy (CAFE) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets.  The next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight. These gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" CAFE standard.

In addition to the CAFE program, the U.S. government has tried to encourage better vehicle efficiency through tax policy.  Since 2002, taxpayers have been eligible for income tax credits for gas/electric hybrid vehicles. A "gas-guzzler" tax has been assessed on manufacturers since 1978 for cars with exceptionally poor fuel economy.  While this tax remains in effect, it currently generates very little revenue as overall fuel economy has improved.

Another focus in gasoline conservation is reducing the number of miles driven. An estimated 40% of American automobile use is associated with daily commuting. Many urban areas offer subsidized public transportation to reduce commuting traffic, and encourage carpooling by providing designated high-occupancy vehicle lanes and lower tolls for cars with multiple riders. In recent years telecommuting has also become a viable alternative to commuting for some jobs. 

A vehicle's gas mileage normally decreases rapidly at speeds above 55 miles per hour.  A car or truck moving at 55 miles an hour can get about 15 percent better fuel economy than the same car going 65 mph. According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph you drive over 60 mph is similar to paying an additional $1.20 per gallon for gas (at $3.10 per gallon).

Residential sector
The residential sector refers to all private residences, including single-family homes, apartments, manufactured homes and dormitories.  Energy use in this sector varies significantly across the country, due to regional climate differences and different regulation.  On average, about half of the energy used in the U.S. homes is expended on space conditioning (i.e. heating and cooling).

The efficiency of furnaces and air conditioners has increased steadily since the energy crises of the 1970s. The 1987 National Appliance Energy Conservation Act authorized the Department of Energy to set minimum efficiency standards for space conditioning equipment and other appliances each year, based on what is "technologically feasible and economically justified".

Despite technological improvements, many American lifestyle changes have put higher demands on heating and cooling resources.  The average size of homes built in the United States has increased significantly, from 1500 ft² in 1970 to 2300 ft² in 2005.  The single-person household has become more common, as has central air conditioning: 23% of households had central air conditioning in 1978, that figure rose to 55% by 2001.

As a cheaper alternative to the purchase of a new furnace or air conditioner, most public utilities encourage smaller changes the consumer can make.  Consumers have also been asked to adopt a wider indoor temperature range (e.g. 65 °F in the winter, 80 °F in the summer).

Home energy consumption averages:US Dept. of Energy, "Buildings Energy Data Book " (August 2005), sec. 1.2.3

 space conditioning (includes both heating and air conditioning) 44%
 water heating, 13%
 lighting, 12%
 refrigeration, 8%
 home electronics, 6%
 laundry appliances, 5%
 kitchen appliances, 4%
 other uses, 8%

Energy usage in some homes may vary widely from these averages. In most residences no single appliance dominates, and any conservation efforts must be directed to numerous areas in order to achieve substantial energy savings.  However, ground source heat pump systems are the more energy efficient, environmentally clean, and cost-effective space conditioning systems available (Environmental Protection Agency). They can achieve reductions in energy consumptions of up to 70%.

Best building practices

Current best practices in building design and construction result in homes that are much more energy conserving than average new homes.  See Passive house, Superinsulation, Self-sufficient homes, Zero energy building, Earthship, Straw-bale construction, MIT Design Advisor, Energy Conservation Code for Indian Commercial Buildings.

Smart ways to construct homes such that minimal resources are used to cooling and heating the house in summer and winter respectively can significantly reduce energy costs!

Commercial sector
The commercial sector consists of retail stores, offices (business and government), restaurants, schools and other workplaces.  Energy in this sector has the same basic end uses as the residential sector, in slightly different proportions. Space conditioning is again the single biggest consumption area, but it represents only about 30% of the energy use of commercial buildings.  Lighting, at 25%, plays a much larger role than it does in the residential sector.US Dept. of Energy, "Buildings Energy Data Book " (August 2005), sec. 1.3.3  Lighting is also generally the most wasteful component of commercial use.  A number of case studies indicate that more efficient lighting and elimination of over-illumination can reduce lighting energy by approximately fifty percent in many commercial buildings.

Commercial buildings can greatly increase energy efficiency by thoughtful design, with today's building stock being very poor examples of the potential of systematic (not expensive) energy efficient design (Steffy, 1997).  Commercial buildings often have professional management, allowing centralized control and coordination of energy conservation efforts.

Solar heat loading through standard window designs usually leads to high demand for air conditioning in summer months.  An example of building design overcoming this excessive heat loading is the Dakin Building in Brisbane, California, where fenestration was designed to achieve an angle with respect to sun incidence to allow maximum reflection of solar heat; this design also assisted in reducing interior over-illumination to enhance worker efficiency and comfort.

Industrial sector
The industrial sector represents all production and processing of goods, including manufacturing, construction, farming, water management and mining.  Increasing costs have forced energy-intensive industries to make substantial efficiency improvements in the past 30 years.  For example, the energy used to produce steel and paper products has been cut 40% in that time frame, while petroleum/aluminum refining and cement production have reduced their usage by about 25%.  These reductions are largely the result of recycling waste material and the use of cogeneration equipment for electricity and heating.

The energy required for delivery and treatment of fresh water often constitutes a significant percentage of a region's electricity and natural gas usage (an estimated 20% of California's total energy use is water-related.California Energy Commission, "California's Water-Energy Relationship " (November 2005), p.8)  In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.

Unlike the other sectors, total energy use in the industrial sector has declined in the last decade.  While this is partly due to conservation efforts, it's also a reflection of the growing trend for U.S. companies to move manufacturing operations offshore.

The usage of telecommuting by major corporations is a significant opportunity to conserve energy, as many Americans now work in service jobs that enable them to work from home instead of commuting to work each day.

Related pages
 Energy efficiency
 Light pollution
 List of renewable energy topics
 Sleep mode

References


 Bain, A.,  “The Hindenburg Disaster: A Compelling Theory of Probable Cause and Effect,” Procs. NatL Hydr. Assn. 8th Ann. Hydrogen Meeting, Alexandria, Va., March 11-13, pp 125–128 (1997)
 Gary Steffy, Architectural Lighting Design,  John Wiley and Sons (2001) 
 Lumina Technologies, Analysis of energy consumption in a San Francisco Bay Area research office complex, for (confidential) owner, Santa Rosa, Ca. May 17, 1996
 GSA paves way for IT-based buildings  

Other websites
Resources for homes
 Conserving energy with plants 
 Energy Savings Tips for Your Home 
 Energy conservation tips for apartments
 Energy Saving Resources for the Home 

Government and international websites
 U.S. Energy Information Administration
 Buildings Energy Data Book  - commercial/residential building consumption patterns
UNEP- Energy Branch. 
IEA Energy Conservation in Buildings and Community Systems Programme.


Category:Engineering