Energy-efficient buildings and appliances

Before the 1970s, buildings and appliances were designed largely without thought to efficient energy usage or their environmental impact. Then came a growing awareness that the burning of fossil fuels for energy releases gases that pollute the environment, causes acid rain, and contributes to global warming. Environmental and health concerns and energy costs led to the increased development of renewable, or "clean energy," resources: solar, wind, hydro, geothermal, and biomass. Movements toward "green buildings," energy management systems (EMS’s), and intelligent control systems developed.

Background

The concept of energy efficiency is regarded as the simplest way to reduce environmental impact on any scale. Together with renewable energy it is one of the main platforms of the sustainability goal espoused by the environmental movement. For most citizens and businesses, buildings and appliances are among the largest everyday consumers of energy. By making these necessary things more energy efficient, money can be saved and lower the amount of carbon pollution.

In 1990, the energy used in American buildings for heating, cooling, lighting, and operating appliances amounted to roughly 36 percent of US energy use and cost nearly $200 billion. About two-thirds of this amount was fuel energy, including the fuel energy lost in generating and delivering electricity. Electricity is considered worth the extra cost because it is quiet, convenient, and available in small units. According to the International Energy Agency (IEA), global energy use remained at a similar level in the first decades of the twenty-first century. However, with continuing improvements in space conditioning, appliances, and the controls for both, building and appliance energy use can potentially be cut by half or even three-quarters.

Insulation

"Space conditioning" is the warming and cooling of rooms and buildings. Ways to make it more efficient include improving insulation, siting, heat storage, heaters, and coolers. Structures gain and lose heat in three ways: air movement, conduction, and radiation. Insulating a building requires isolating it from these processes. The most important consideration is reducing a building’s air flow, and walls and ceilings are the primary reducers. The space-conditioning load of a structure may be construed as the number of "air changes" per hour. The next level of consideration is heat conduction through walls, windows, ceilings, and floors. Heat conduction can be slowed by constructing a building with thicker walls or by using insulating materials that conduct heat more slowly. A material’s insulating ability is measured by its resistance to conduction, called its R value. A major innovation during the 1970s was the practice of framing houses with 5-by-15-centimeter (2-by-6-inch) studs instead of the standard two-by-fours. That design allowed insulation to be 50 percent thicker.

Windows are a major heat conductor. One window can conduct as much heat as an entire wall. During the 1980s in the United States, the amount of heat lost through windows was estimated to have equaled half the energy that was obtained from Alaskan oil fields. Double-paned and even triple-paned windows (with air space between the panes) to reduce this loss became more common. To reduce conduction further, the air between panes can be partially evacuated, or the space can be filled with a less conductive gas, such as xenon. Finally, windows can also have coatings that reflect infrared (heat) radiation, thereby keeping summer heat out and holding heat inside during winter.

Beginning in the 1970s, Canadian researchers worked to develop "superinsulated" houses: structures so well insulated that they hardly required furnaces, even in the severe winter climates characteristic of much of Canada. The costs were an additional two thousand to seven thousand dollars in construction and an ongoing expense of running an air exchanger. In the winter, the exchanger warms incoming fresh air with the heat from air being exhausted; in the summer it cools incoming air. However, these designs are not without problems. Because such a building is so well sealed, without the air exchanger one could smell yesterday’s cooking (as well as more noxious lingering odors).

Siting

The importance of the siting of a structure—that is, the direction it "faces," including where windows and doors are placed and where there are solid walls—has been known since ancient times. In the developed nations of the twentieth century, as energy sources became widely and cheaply available, designers and architects often ignored this aspect of building design. For example, they often did not consider the importance of catching sunlight on south-facing sides, protection from the cold on the north side, planting of hardwood trees (which can supply summer shade and then drop their leaves to allow more sunlight to pass through in winter), and overhangs to shade against the high summer sun. These design elements alone can reduce the need for heating and cooling energy significantly.

The energy crises of 1973 and 1979 reminded builders of the drawbacks of old, energy-intensive approaches to building design and led to renewed consideration of natural heat flow. The awareness that oil is a limited resource also gave credence to a more radical siting idea known as terratecture: A structure can be made more energy-efficient by locating it partially underground. Terratecture is particularly efficient when used to shield a north-facing wall. Insulation and thermal inertia reduce heating and cooling loads, while windows facing south and opening into courtyards allow as much window space as conventional structures. For a slight increase in construction costs, terratectural houses have significant energy advantages, allow more vegetation, and require less maintenance. They are quite different from conventional houses, however, and have not been widely adapted.

Heating and Cooling

During the mid-1700s, the British colonies in North America faced an energy crisis: a declining amount of firewood. Traditional large fireplaces sent most heat up the chimney. Benjamin Franklin studied more efficient fireplaces in Europe, and he invented a metal stove that radiated more of the fire’s heat into the room. The Franklin stove (1742) provided more heat by increasing "end-use efficiency" rather than by increasing energy use. Two hundred years later, the energy crises of the late twentieth century led to the application of burner advances that had been developed or proposed earlier. Studies of flame dynamics and catalysts led to more complete fuel combustion, and better radiators captured more heat from the burner.

Hot climates and commercial buildings that produce excess heat require air-conditioning. Air-conditioning is based on heat pumping, which cools the hot internal air by moving the heat elsewhere. Most heat pumps compress a gas on the hot side and allow it to decompress on the cold side.

Electronic controls have helped reduce energy waste in space conditioning. For instance, in winter, computerized thermostats can maintain lower temperatures while people are not in a building and then automatically change the settings to a higher, more comfortable level at times when people are scheduled to return. For gas appliances, the replacement of pilot lights with electric igniters has helped reduce unnecessary fuel use. (Electric igniters are even more important for intermittently used burners, such as those used in stoves.)

Another way of decreasing energy input is storing heat or cold from different times of the day, or even different seasons of the year. Thick stone on walls and floors, such as those made of adobe bricks in the Southwest, have been used for centuries in desert climates; they remain relatively cool during the afternoon heat and then slowly give off the day’s heat during cold nights. Higher-technology variants of storage use less material per unit of heat. Office complexes that are designed to store cool air can use smaller air-conditioners and cheaper, off-peak power.

Lighting and Motors

Until the mid-nineteenth century, people rose at dawn and retired at sundown because there was no form of artificial lighting that could provide sufficient light for most work or leisure activities after dark. Improved oil lamps and then incandescent electric lights (first widely marketed by Thomas Edison in 1879) started a revolution that eventually consumed roughly a quarter of US electricity directly and, in addition, contributed to building cooling loads.

Incandescent lights use resistance heating to make a wire filament glow, so they generate significant heat in addition to light. Fluorescent lights, with a glow of current flowing through gases under partial vacuum, are more efficient and last longer. Fluorescent lighting was invented in 1867 by Antoine-Edmond Becquerel but not widely marketed until the 1940s. In the 1980s, compact fluorescent lightbulbs (CFLs) for small lamps were developed, followed by light-emitting diode (LED) technology. These low-energy forms of lighting have begun to supplant incandescent lighting, especially in new building projects, as they offer considerable cost savings and last much longer than incandescents. Moreover, controllers can improve efficiency by switching off lights when people are gone; they can also be programmed to reduce lighting when sunlight is available.

Electric motors range from tiny shaver motors to power drives for elevators and large air conditioners. A number of methods have been developed to make motors more efficient. The use of additional motor windings (costing more copper wire) has always been an option. Electronic controls that match power used to the actual load rather than based on a constant high load were developed after the 1970s energy crises. Amorphous metals (produced by rapid cooling from the molten state) have been developed to allow electromagnets in motors to switch off faster, reducing drag; they also make more efficient transformers for fluorescent lights.

Most improvements to appliance efficiency involve some combination of better motors and better space conditioning. The electrical loads from refrigerators—among the largest in most homes in industrialized nations—dropped by half in average energy demand in the United States between 1972 and 1992. More efficient motors and better insulation were responsible for the improvement. New technologies in the twenty-first century continued this trend of greater energy efficiency in appliances including refrigerators, dishwashers, and laundry machines.

The Energy Star Program

In 1992, the US Environmental Protection Agency (EPA) established Energy Star, a voluntary labeling program that identifies products meeting strict standards of energy efficiency. The program set the standard for commercial buildings, homes, heating and cooling devices, major appliances, and other products. The Energy Star concept eventually expanded to other countries, including members of the European Union, Japan, Taiwan, Canada, China, Australia, South Africa, and New Zealand.

In 1992, the first Energy Star labeled product line included personal computers and monitors. In 1995, the label was expanded to include residential heating and cooling products, including central air conditioners, furnaces, programmable thermostats, and air-source heat pumps. Energy Star for buildings and qualified new homes was also launched. In 1996, the US Department of Energy (DOE) became a partner in the program, and the label expanded to include insulation and appliances, such as dishwashers, refrigerators, and room air conditioners. By 2016, Americans had purchased more than two billion products that qualified for the Energy Star rating, and there were more than 1.6 million Energy Star qualified homes and more than 25,000 qualified other buildings nationwide.

By 2016, energy cost savings to consumers, businesses, and organizations under the Energy Star program totaled approximately $362 billion since 1992. The average house can produce twice the greenhouse-gas emissions as the average car. The amount of energy saved helped prevent greenhouse-gas emissions equal to about 2.5 billion tons. By 2016, Energy Star had partnerships with more than 18,000 public and private sector organizations, and had labels on more than seventy product categories, including thousands of models for home and office use.

Compared to conventional products, those approved by Energy Star are more energy-efficient, save on costs, and feature the latest technology. By using less energy, they help reduce the negative impact on the environment.

In the average home, heating and cooling are the largest energy expenditures, accounting for about one-half of the total energy bill. Energy Star compliant heating and cooling equipment can cut yearly energy bills by 30 percent. A qualified furnace, when properly sized and installed, along with sealed ducts and a programmable thermostat, uses about 15 percent less energy than a standard model and saves up to 20 percent on heating bills. An Energy Star room air conditioner use at least 10 percent less energy than conventional models, and they often include timers for better temperature control. To keep heating, ventilating, and air-conditioning (HVAC) systems running efficiently, Energy Star recommends changing air filters regularly, installing a programmable thermostat, and sealing heating and cooling ducts.

The second largest energy expenditure is water heating, which costs the typical household four hundred to six hundred dollars per year. A new Energy Star water heater can cut water heating bills by half.

Energy Star refrigerators use 20 percent less energy than other models, thus cutting energy bills by potentially hundreds of dollars over its lifetime. They also have precise temperature controls and advanced food compartments to keep food fresher for a longer time. Because they use much less water than conventional models, Energy Star dishwashers help ease the demand on the country’s water supplies. Energy Star also recommends running the dishwasher with a full load and that the air-dry option be used instead of the heat-dry.

Using the most innovative technology, Energy Star clothes washers cut energy and water consumption by more than 40 percent, compared to conventional models. Most do not have a central agitator and use a reduced amount of hot water in the wash cycle. Instead of rubbing laundry against an agitator in a full tub, front-load washers tumble laundry through a small amount of water. Modern top loaders flip or spin clothes through a reduced stream of water. Sophisticated motors spin clothes two to three times faster during the spin cycle to extract more water, thus requiring less time in the dryer.

Lighting accounts for 20 percent of the electric bill in the average US home, and 7 percent of all energy consumed in the United States is used in lighting for homes and businesses. An Energy Star qualified compact fluorescent light bulb (CFL) uses 75 percent less energy and lasts ten times longer than an incandescent bulb. It pays for itself in six months, and the savings are about thirty dollars over its lifetime.

The Green Building Movement

After the rise of environmental consciousness in the 1960s, and the 1973 and 1979 oil shortages, concerned groups around the world began to look for ways to conserve energy and preserve natural resources. One of the most important applications for this cultural shift was the transformation of human dwellings and workplaces, resulting in the green building movement. Starting with heat from the sun, architects incorporated active photovoltaic systems and passive designs that cleverly positioned windows, walls, and rooftops to capture and retain heat. Another factor was an increased attention to heat exchange as affected by materials and construction techniques. Building materials were also reexamined in terms of toxicity; pollution and energy consumption in factory processing; durability; interaction with soil, bedrock, water; and other factors.

Contemporary green building looks at all of these issues and more, because a narrow approach could actually do more harm than good. A building sealed too tightly, for example, could have excellent heat retention, but might not have enough internal air circulation. Recycled materials might lower resource consumption, but could actually be more toxic. Therefore cross-disciplinary collaboration is necessary in order to achieve effective green building design. In the United States, the Office of the Federal Environmental Executive (OFEE) recognizes the complexity of green building, and organizes the effort around two primary goals: limiting the consumption of basic resources such as materials, water, and energy and protecting the environment and people’s health.

One of the most important elements in a green building or green design is its use of green energy. Although some governments have established precise technical definitions of green energy for purposes of incentive programs, the term is generally associated with environmentalism; conveys the idea of safe, nonpolluting energy; and often means renewable energy. Although not all consumers are able to construct a new green building, many achieve these goals by transforming existing structures. A key element in both new and existing buildings is the use of Energy Star compliant appliances.

Renewable Energy Sources

The energy crises of the 1970s and environmental concerns led to interest in alternative, renewable energy resources. Renewable energy is "clean" energy from a source that is inexhaustible and easily replenished. Nonrenewable energy comes from sources not easily replaced, such as fossil fuels. Renewable energy does not pollute air or require waste cleanups like nonrenewable energy generation. One controversial aspect is the designation of nuclear energy, which is technically renewable but also creates potentially harmful radioactive waste.

Solar panels, or modules, are one of the most promising sources of inexpensive and environmentally safe energy. Although earlier efforts to harness solar energy utilized steam from solar-heated water, modern solar panels are photovoltaic: they produce electricity from sunlight. The photovoltaic effect was discovered in the eighteenth century and studied by Albert Einstein in the 1920s. After the widespread adoption of silicon for circuitry in the twentieth century, photovoltaic cells became less expensive to produce and more efficient in power output. The most common forms of silicon used for the cells are crystalline, which became available in the 1950’s, and amorphous silicon, which is more frequently used now.

Typically, the cells are joined together in panels, which may also be connected together in an array. The units are produced in a great variety of forms. In home applications, they may be placed on rooftops, or in independent structures at some distance from the dwelling. Some units are also designed so that they are able to move over time to capture the most sunlight, like the solar arrays on the International Space Station. For homes and other buildings, they may also be disguised visually as shingles or other kinds of roofing material, so that they are more seamlessly integrated with the design. The most desirable locations are unshaded or thinly-shaded areas. On roof installations in the Northern Hemisphere, southern exposures are preferred.

Solar panels may be connected to a grid or self-contained, depending on their function. Owners may earn credit by giving energy to the grid during times when their consumption is lower than their own unit’s production. The energy may also be stored in batteries. Solar power is a key element in the zero energy building concept. A zero energy building is defined as one which creates more energy than it uses. Combined with other elements such as energy-saving building design and the use of Energy Star qualified appliances, the building’s photovoltaic system, which contributes to the grid, earns energy credit equal to or in excess of its consumption.

Wind was an energy resource as early as the fourth century BCE, when the Egyptians used wind to move sailboats. Windmills appeared as early as 500 CE in Persia. In 1890, in Denmark, Poul La Cour built the first wind turbine, a large windmill capable of generating electricity. From 1956 to 1957, also in Denmark, Johannes Juul developed the Gedser wind turbine, which was the world’s first alternating current (AC) wind turbine. Typically, large wind plants are connected to the local electric utility transmission network. Energy Star recommends small wind electric systems as a highly effective home-based system, which could lower electricity bills by 50 to 90 percent. The world’s largest producers of wind power, as of 2016, were the United States, China (which had by far the largest installed capacity, but less actual generation), Germany, India, and Spain.

Centuries before electricity was harnessed, hydropower was a significant source of energy, largely in the form of water wheels, in which water moved wooden paddles attached to mechanical devices for grinding grains, pumping, and other functions. While displaced in industrialized regions, these mechanical forms of renewable energy technology are still used in rural areas. Typically, modern hydropower comes from large power plants attached to dams and connected to the grid. In the United States, for example, hydropower contributes roughly 45 percent of the electricity from renewable sources and 6 percent of the nation’s total electricity. Other countries—especially Norway, Switzerland, and Canada—derive a much higher portion of their electricity from hydropower. A less common use of hydropower to generate electricity is provided by micro hydro water turbines, which may be used when a home or other building is next to or over a stream or river. These may be self-contained, or used in conjunction with other systems, including renewable systems such as solar arrays.

The American Recovery and Reinvestment Act of 2009 (ARRA) provided measures benefiting renewable energy and tax incentives for energy efficiency. It includes a Treasury Department grant program for renewable energy developers and a manufacturing tax credit. The Act also allows individual taxpayers a federal tax credit of 30 percent of the cost of residential alternative energy equipment, such as geothermal heat pumps, wind turbines, and solar hot-water heaters. There are also tax credits for homeowners to make energy efficient improvements such as adding insulation, energy-efficient heating and air-conditioning systems, and energy efficient exterior windows.

Emerging Technology

Energy Star appliances have become commonplace. An emerging technology is the "smart appliance," which promises even greater energy efficiency and lower energy costs. Smart appliances can have a computer chip or "smart meter" which communicates with a central system, such as the local electrical grid. They can sense when the system is overloaded, such as during peak hours. The appliance can be programmed to turn off partially or to wait for convenient times when the system is less stressed. For instance, a refrigerator can delay running its automatic defrost cycle until the local grid signals that it is an off-peak time. Smart appliances can shut off their own power when they sense an electrical surge. They can be part of smart homes or buildings, where all electrical appliances or devices are connected to a computer system and function automatically or operate by remote control.

There are numerous benefits of smart appliances, which are considered part of the "Internet of Things." They reduce electrical demand upon grids during peak hours and help avoid huge power failures, such as the large-scale blackouts in the western United States in 1996 and in the Northeast in 2003. With the rise in electric vehicles, including plug-in models, decreasing peak energy demand nationally becomes even more important. Under a real-time pricing structure, consumers would receive price signals from the grid, indicating higher prices during peak hours and lower prices when demand is less. Consumers would see cost savings by managing their energy usage. Because utility companies have to build more generating plants to meet the huge stress on the system during peak hours, less demand would mean fewer plants and carbon emissions. Estimations indicate that this technology could eliminate the need to build thirty coal-fired power plants over twenty years.

Companies including General Electric have tested "energy management-enabled appliances" such as washers and dryers, microwaves, ranges, and dishwashers. These smart appliances are able to time themselves to operate during off-peak periods. Consumers can override the program if they want to use the appliance during peak hours.

The ARRA of 2009 provided billions of dollars to modernize the aging US electrical grid and create a "smart grid," a high-tech electricity distribution and transmission system. A digital communications system and networking technology would be applied to the existing grid. Wireless devices, controls, smart meters, and sensors would be installed along the whole grid, thus providing more services for consumers and giving utilities more control of power production and delivery. More renewable energy sources would be able to come online. The result would be improved electricity efficiency and reliability. A standardized system with a common language understood by all smart appliances when communicating with their grids is in development. A hacker could break into the system, however, so security issues are critically important. In 2009, US commerce secretary Gary Locke and US energy secretary Steven Chu announced the first set of technical standards for the interoperability and security of the "smart grid."

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