Energy conservation
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This article is about decreasing energy consumption. For the law of conservation of energy in physics, see
Conservation of energy.
Energy conservation is the practice of decreasing the quantity of energy used. It may be achieved through efficient energy use, in which case energy use is decreased while achieving a similar outcome, or by reduced consumption of energy services. Energy conservation may result in increase of financial capital, environmental value, national security, personal security, and human comfort. Individuals and organizations that are direct consumers of energy may want to conserve energy in order to reduce energy costs and promote economic security. Industrial and commercial users may want to increase efficiency and thus maximize profit.
Introduction
Electrical energy conservation is an important element of energy policy. Energy conservation reduces the energy consumption and energy demand per capita, and thus offsets the growth in energy supply needed to keep up with population growth. 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 most preferred methods of energy production.
By reducing emissions, energy conservation is an important part of lessening climate change. Energy conservation facilitates the replacement of non-renewable resources with renewable energy. Energy conservation is often the most economical solution to energy shortages, and is a more environmentally benign alternative to increased energy production.
[edit] By country
[edit] United States
The United States is currently the largest single consumer of energy. The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial.[1]
U.S. Energy Flow Trends - 2002. Note that the breakdown of useful and waste energy in each sector (yellow vs. grey) is estimated arbitrarily and is not based on data.
Energy usage in transportation and residential sectors (about half of U.S. energy consumption) is largely controlled by individual domestic consumers. Commercial and industrial energy expenditures are determined by businesses entities and other facility managers. National energy policy has a significant effect on energy usage across all four sectors.
[edit] Transportation
The transportation includes all vehicles used for personal or freight transportation. Of the energy used in this sector, approximately 65% is consumed by gasoline-powered vehicles, primarily personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%.[2]
The two oil supply crisis 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 which originated in the late 1970s, along with the transition to front wheel drive. 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. The gas-guzzler tax ended the reign of large cubic-inched engines from the musclecar era.
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, but in 2003 only 3.5% of workers were telecommuters. Ironically, hundreds of thousands of American and European workers have been replaced by workers in Asia who telecommute from thousands of miles away.
Fuel economy-maximizing behaviors also help reduce fuel consumption. Among the most effective are moderate (as opposed to aggressive) driving, driving at lower speeds, using cruise control, and turning off a vehicle's engine at stops rather than idling. A vehicle's gas mileage decreases rapidly highway speeds, normally above 55 miles per hour (though the exact number varies by vehicle). This is because aerodynamic forces are proportionally related to the square of an object's speed (when the speed is doubled, drag quadruples). According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph (8.0 km/h) you drive over 60 mph (97 km/h) is similar to paying an additional $0.30 per gallon for gas [3] The exact speed at which a vehicle achieves it's highest efficiency varies based on the vehicle's drag coefficient, frontal area, surrounding air speed, and the efficiency and gearing of a vehicle's drive train and transmission.
[edit] 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 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". Beyond these minimum standards, the Environmental Protection Agency awards the Energy Star designation to appliances that exceed industry efficiency averages by an EPA-specified percentage.
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 1,500 sq ft (140 m2) in 1970 to 2,300 sq ft (210 m2) 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 furnace efficiency gets higher, there is limited room for improvement--efficiencies above 85% are now common. However, improving the building envelope through better or more insulation, advanced windows, etc., can allow larger improvements. The passive house approach produces superinsulated buildings that approach zero net energy consumption. Improving the building envelope can also be cheaper than replacing a furnace or air conditioner.
Even lower cost improvements include weatherization, which is frequently subsidized by utilities or state/federal tax credits, as are programmable thermostats. Consumers have also been urged to adopt a wider indoor temperature range (e.g. 65 °F (18 °C) in the winter, 80 °F (27 °C) in the summer).
One underutilized, but potentially very powerful means to reduce household energy consumption is to provide real-time feedback to homeowners so they can effectively alter their energy using behavior. Recently, low cost energy feedback displays, such as The Energy Detective or wattson [1], have become available. A study of a similar device deployed in 500 Ontario homes by Hydro One [2] showed an average 6.5% drop in total electricity use when compared with a similarly sized control group.
Standby power used by consumer electronics and appliances while they are turned off accounts for an estimated 5 to 10% of household electricity consumption, adding an estimated $3 billion to annual energy costs in the USA. "In the average home, 75% of the electricity used to power home electronics is consumed while the products are turned off." [3]
[edit] Home energy consumption averages
- Home heating systems, 30.7%
- Water heating, 13.5%
- Home cooling systems, 11.5%
- Lighting, 10.3%
- Refrigerators and freezers, 8.2%
- Home electronics, 7.2%
- Clothing and dish washers, 5.6% (includes clothes dryers, does not include hot water)
- Cooking, 4.7%
- Computers, 0.9%
- Other, 4.1% (includes small electrics, heating elements, motors, pool and hot tub heaters, outdoor grills, and natural gas outdoor lighting)
- Non end-user energy expenditure, 3.3%[4]
Energy usage in some homes may vary widely from these averages. For example, milder regions such as the southern U.S. and Pacific coast of the USA need far less energy for space conditioning than New York City or Chicago. On the other hand, air conditioning energy use can be quite high in hot-arid regions (Southwest) and hot-humid zones (Southeast) In milder climates such as San Diego, lighting energy may easily consume up to 40% of total energy. Certain appliances such as a waterbed, hot tub, or pre-1990 refrigerator use significant amounts of electricity. However, recent trends in home entertainment equipment can make a large difference in household energy use. For instance a 50" LCD television (average on-time= 6 hours a day) may draw 300 Watts less than a similarly sized plasma system. 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, Air and Water Source Heat Pump systems are the more energy efficient, environmentally clean, and cost-effective space conditioning and domestic hot water systems available (Environmental Protection Agency), and can achieve reductions in energy consumptions of up to 69%.
[edit] Best building practices
Current best practices in building design, construction and retrofitting result in homes that are profoundly more energy conserving than average new homes. This includes insulation and energy-efficient windows and lighting [5]. See Passive house, Superinsulation, Self-sufficient homes, Zero energy building, Earthship, 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.
[edit] 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.[6] 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. As a result, fluorescent lighting (about four times as efficient as incandescent) is the standard for most commercial space, although it may produce certain adverse health effects.[7][8][9][10] Potential health concerns can be mitigated by using newer fixtures with electronic ballasts rather than older magenetic ballasts. As most buildings have consistent hours of operation, programmed thermostats and lighting controls are common. However, too many companies believe that merely having a computer controlled Building automation system guarantees energy efficiency. As an example one large company in Northern California boasted that it was confident its state of the art system had optimized space heating. A more careful analysis by Lumina Technologies showed the system had been given programming instructions to maintain constant 24 hour temperatures in the entire building complex. This instruction caused the injection of nighttime heat into vacant buildings when the daytime summer temperatures would often exceed 90 °F (32 °C). This mis-programming was costing the company over $130,000 per year in wasted energy (Lumina Technologies, 1997). Many corporations and governments also require the Energy Star rating for any new equipment purchased for their buildings.
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.
Recent advances include use of occupancy sensors to turn off lights when spaces are unoccupied, and photosensors to dim or turn off electric lighting when natural light is available. In air conditioning systems, overall equipment efficiencies have increased as energy codes and consumer information have begun to emphasise year round performance rather than just efficiency ratings at maximum output. Controllers that automatically vary the speeds of fans, pumps, and compressors have radically improved part-load performance of those devices. For space or water heating, electric heat pumps consume roughly half the energy required by electric resistance heaters. Natural gas heating efficiencies have improved through use of condensing furnaces and boilers, in which the water vapor in the flue gas is cooled to liquid form before it is discharged, allowing the heat of condensation to be used. In buildings where high levels of outside air are required, heat exchangers can capture heat from the exhaust air to preheat incoming supply air.
[edit] 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.
Another example for efficiency improvements is the use of products made of High temperature insulation wool (HTIW) which enables predominantly industrial users to operate thermal treatment plants at temperatures between 800 and 1400°C. In these high-temperature applications, the consumption of primary energy and the associated CO2 emissions can be reduced by up to 50% compared with old fashioned industrial installations. The application of products made of High temperature insulation Wool is becoming increasingly important against the background of the currently dramatic rising cost of energy.
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.[11]) In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.
To conserve energy, some industries have begun using solar panels to heat their water.[citation needed]
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 overseas.
[edit] United Kingdom
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Energy conservation in the United Kingdom has been receiving increased attention over recent years. Key factors behind this are the Government's commitment to reducing carbon emissions, the projected 'energy gap' in UK electricity generation, and the increasing reliance on imports to meet national energy needs. Domestic housing and road transport are currently the two biggest problem areas.
The UK Government has jointly funded the Energy Saving Trust to promote energy conservation at a consumer, business and community level since 1993.
[edit] Jevons paradox
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Main article: Jevons paradox
Standard economic theory suggests that technological improvements that increase energy efficiency will tend to increase, rather than reduce energy use. This was first observed by William Stanley Jevons in 1865 and is called the Jevons Paradox. In The Coal Question, Jevons argued that, "It is a confusion of ideas to suppose that economical use of fuel is equivalent to diminished consumption. The very contrary is the truth."
The Jevons paradox was later revisited by the economists Daniel Khazzoom and Leonard Brookes in a series of papers about energy conservation. In 1992, the US economist Harry Saunders dubbed this hypothesis the Khazzoom-Brookes Postulate, and showed that it was true under a wide range of assumptions.[12] Increased energy efficiency tends to increase energy consumption by two means. Firstly, increased energy efficiency makes the use of energy relatively cheaper, thus encouraging increased use. Secondly, increased energy efficiency leads to increased economic growth, which pulls up energy use in the whole economy.
This does not imply that increased fuel efficiency is worthless. Increased fuel efficiency enables greater production and a higher quality of life. For example, a more efficient steam engine allowed the cheaper transport of goods and people that contributed to the Industrial Revolution. However, energy conservation cannot be achieved through increased efficiency alone. In order for efficiency gains to improve energy conservation, the ecological economists Mathias Wackernagel and William Rees suggest that cost savings from efficiency gains be "taxed away or otherwise removed from further economic circulation. Preferably they should be captured for reinvestment in natural capital rehabilitation."[13]
[edit] Issues with energy conservation
Critics and advocates of some forms of energy conservation make the following arguments:
- It may be difficult for home owners or small business to justify investment in some energy saving measures. Often the available money has higher priorities, and in many cases the time and cost investment is not worthwhile.
- Condensing boilers are much more efficient than older types. Energy savings are achieved by extracting more heat, venting less heat externally. However the increased complexity results in more frequent breakdowns and much higher total servicing costs, and whether the end result is a gain is debated.
- Refrigeration is also a major factor of energy consumption, electronic Energy saving modules (ESM) can be added to some existing HVAC and refrigeration systems at little cost to conserve electricity.
- Some retailers argue that bright lighting stimulates purchasing. Health studies have demonstrated that headache, stress, blood pressure, fatigue and worker error all generally increase with the common over-illumination present in many workplace and retail settings (Davis, 2001), (Bain, 1997). It has been shown that natural daylighting increases productivity levels of workers, while reducing energy consumption.[14] Consumers are also motivated by a number of factors, and corporate stewardship may provide an incentive for shoppers to visit stores who conserve energy. Some believe lower overhead costs may allow retailers to lower prices, stimulating consumption, however few business managers seem to agree with this view.
- The use 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. [15]
- Electric motors consume more than 60% of all electrical energy generated and are responsible for the loss of 10 to 20% of all electricity converted into mechanical energy. [16] No doubt, electricity consumption and associated loss by electric motors will continually grow; particularly, as the transportation sector moves to vehicles with electric drivetrains. Migrating or retrofitting any applied base of electric motors (and electric generators) with energy efficient electric motor and generator technology and systems, such as the brushless wound rotor doubly fed electric motor or generator, can dramatically reduce energy consumption and resulting emissions of carbon dioxide (CO2) and sulphur dioxide (SO2) to the atmosphere. As a bonus, the technology can have a payback period of less than a year depending on use factors.
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Wind has been used by humankind as a natural source of energy for tens of thousands of years. The use of wind energy dates back to the dawn of civilisation when sailing vessels were powered by the wind. The first simple sailboats were set afloat in Egypt about 5,000 years ago. Around the year 700 AD, in what is Afghanistan today, the first wind machines rotating around a vertical axis were employed to grind grain. The famous fixed-tower windmills with sails provided irrigation for many parts of the Mediterranean island of Crete. Wind-driven gristmills were one of the greatest technical challenges of the Middle Ages. In the 14th century, the Dutch improved on the design that had spread throughout the Middle East and continued to use it for its primary purpose of grinding grain.
