Alternative Energy

views updated May 11 2018

ALTERNATIVE ENERGY

The very notion that some sources of energy make up alternative energy demonstrates the way people impute normative values to technologies. For decades, proponents of alternative energy have done more than advocate particular technologies: They maintain that their proposed technologies are socially and morally better. These social and moral claims show that advocates regard alternative energy technologies as different in profound ways from existing conventional energy technologies.


Social Contexts

Alternative energy must be understood against a background of conventional energy. Conventional energy is not conventional just because it is in wide use. It is conventional in that it underlies the functioning and embodies the values of the conventional society. Thus coal, oil, and natural gas are conventional both because they dominate energy production in industrialized countries and, even more, because they make possible a high-consumption society and require large-scale industrial systems to extract, convert, and distribute the energy.

Advocates of alternative energy seek more than simply technological replacements for fossil fuels. They seek technological systems that will reinforce and embody alternative values, such as avoiding the exploitation of nonrenewable resources and people, favoring smaller scale production, and, most importantly, living in a manner more in concert with natural systems, in the early twenty-first century often termed living sustainably.

This normative orientation sets alternative energy advocates apart from people who simply advocate new technologies but have no interest in an alternative society. For example, consider the case of nuclear power. From World War II on, many scientists and others advocated the use of nuclear power plants to replace fossil fuels. They sought a new technology, one that was not then in widespread use. However their purpose was to reinforce, maintain, and enhance the existing social and economic system, with all the values that went with it, including a reliance on large-scale resource extraction and production. They simply thought that nuclear technology would do the job better, more cheaply, and for a longer period of time than fossil fuels. Since the 1990s, proponents of nuclear energy have also argued that it will meet what has become another more or less conventional goal, reduction in carbon emissions.

The alternative label does not necessarily apply to all people and groups who advocate renewable energy technologies, such as solar, wind, and biomass. Since the 1950s, many of those advocating such technologies have simply seen them as ways to preserve the social status quo and its values. For such advocates, photovoltaic panels (often called solar cells) are just another way of producing electricity, and biomass-derived alcohol is just another way of producing liquid fuels for internal combustion automobiles. In contrast, for others photovoltaic panels offer the means to live off the grid.

Alternative energy advocates thus make up a subset of advocates for particular energy technologies. These are advocates who seek not only different technologies but also to promote different social values to go along with them.


The Ethical Dimension

The driving ethical concern that motivates most alternative energy advocates is a particular type of environmental ethics. These people feel that the relationship of industrial society to nature is fundamentally flawed. They come out of the more radical wing of the environmental movement and the broader alternative (or appropriate or intermediate) technology movements. To understand this alternative it is therefore necessary to consider the conventional societal attitudes toward nature.

For an industrial society, nature offers a set of resources to be exploited. Material consumption and the use of natural resources that go with it are good things, ethically desirable, as well as pragmatically important. Even so, people committed to this industrial ethos recognize that resource exploitation causes certain problems. From the late 1960s onward, conventional political groups accepted the need to curb pollution from industrial production, and governments around the world passed numerous environmental laws and established new agencies to carry them out. The oil embargo of 1973 and the resulting shortages and price increases demonstrated clearly the financial and security risks of U.S. dependence on imported oil. But for conventional society, and most political elites, environmental pollution and security risks were no more than manageable problems to be solved. They did not cast doubt on the basic normative commitments to exploiting nature and maximizing material growth.

Alternative energy advocates, however, see the society-nature relationship quite differently. They believe that human beings must understand themselves as parts of ecosystems and that, therefore, human well-being depends on the health of those ecosystems. They want societal values to be more consonant with the way that ecosystems work and to regard ecosystems as things of inherent value, not just resources to be exploited. For these advocates it is not enough to put scrubbers on the smokestacks of coal-fired power plants or to reduce the emissions coming out of automobile exhausts. They seek instead a society that puts much less emphasis on high levels of material consumption, epitomized by the use of individual automobiles. Such a society would be organized very differently, with different values guiding both individual behavior and social and political institutions. These normative commitments lead them to advocate different energy technologies, ones that use renewable resources that could provide the foundation for a different type of society. However these commitments also lead them to make fine distinctions among these technologies, rejecting some, and to carry on vigorous debates about the merits of particular technologies and energy sources.

Alternative Energy Options

Against this background, it is thus possible to consider at least three proposed alternative energies: solar, hydro, and wind.


SOLAR ENERGY. Numerous technologies use sunlight directly to produce either heat or electricity. During the 1970s, ecologically oriented alternative energy advocates pushed for certain of these technologies and opposed others. In general, the more high-tech and large-scale the technology, the less such advocates liked them. They favored solar panels that use sunlight to heat air or water. Such panels consist of little more than a black metal plate, which absorbs sunlight, encased in a box with a glass cover. Air or water flows over or through the plate, heating it up, and then enters the building to supply heat or hot water.

The principles of such technologies are not complicated, although it is not easy to make panels that last a long time and function well. The fact that they are easy to understand, small, and seemingly unrelated to large industrial systems and produce no pollution in their operation appeals to the ecological ethic of alternative energy advocates.

At the other extreme are proposals for solar power satellites (SPS). The idea is to launch a satellite into a stationary earth orbit and to attach to it many acres of photovoltaic panels, semiconductor solar cells that convert sunlight directly into electricity. The satellite could produce electricity almost twenty-four hours per day and beam it back to a receiving station on earth. This is the ultimate high-tech solar technology. Alternative energy advocates are hostile to the SPS system because it both requires and supports the conventional industrial system. As a system that could produce large quantities of electricity around the clock, SPS could substitute in a straightforward way for conventional power plants, making it just another conventional technology, albeit a solar, nonpolluting one. Due mostly to cost considerations, no one has yet put such a satellite into orbit.

HYDROPOWER. Controversies over hydropower again demonstrate conflicts over values. Many environmental groups opposed the hydropower dams the federal government sponsored in the 1950s and 1960s. While their operation produced no emissions, as would a coal plant, the dams flooded large areas and dramatically changed the ecosystems in which they were located. Besides the scientifically measurable damage they did, for many environmental advocates the dams represented a problematic relationship, of dominance and exploitation, to nature.

Therefore alternative energy advocates in the 1970s talked favorably about hydropower only when referring to low-head hydro (very small dams) or what was called run-of-the-river hydro. This latter technology consists of power-generating turbines that are put directly into rivers, without any dam at all. These technologies have the virtue of being smaller in size, more modest in environmental disruption, and less like large-scale industrial production.


Assessing Values

In the 1970s advocates of alternative energy did so in the hopes of moving toward a different society. They sought energy-producing technologies that were smaller in scale and simpler to understand, promoted local self-reliance instead of global dependence, and embraced an ecocentric environmental ethic. They thought that such technologies would provide the means to live in a society that was not only environmentally more sustainable but also more socially harmonious and cooperative, with less domination, hierarchy, and inequality. The ecocentric environmental ethic was particularly important to this view. Advocates thought that human domination of nature got reproduced in the domination of people. The energy crisis of the 1970s raised public awareness of the importance of energy to every social and economic function. For this reason, alternative energy advocates regarded changes in energy technologies as central to realizing their social vision. A final argument often made for alternative energy is that it supported projects in the developing world.

Were they correct? For the most part, no. The alternative energy advocate's vision of a new society based on a new energy source embraces the notion of technological determinism: Build the right technology, and one can get the desired society. Numerous studies show that this theory is false. Society does not simply evolve from technological choices. Many different societies can come out of similar technological choices.

However one should not entirely discount the advocates' ideas about energy. Technological choices do have profound effects on society, which in turn affects future technological choices. Moreover those choices are often not easy to change. If a society invests trillions of dollars in an energy system, as the industrial countries have done, they are reluctant to make rapid changes, a phenomenon historians call path dependence or technological momentum. So energy choices are heavily value-laden, long-term choices. It is difficult, however, to know just how those choices will interact with complex societies.

The case of wind energy illustrates this. Alternative energy advocates embraced wind energy in the 1970s, believing that wind turbines could produce electricity on a small scale and enable homes or communities to be less dependent on central-station power plants and the massive electrical grid that distributes the electricity. Those advocates were critical of federal research programs on wind turbines because such programs sought to build large wind turbines that the utility industry could use instead of smaller, off-the-grid turbines. These large turbines eventually achieved economies of scale that reduced the price of wind-generated electricity toward price-competitiveness. In the early-twenty-first century the wind industry is growing rapidly, with ever-larger turbines coming online as part of the large-scale electric utility industry. This technology is certainly cleaner than coal-fired power plants, but other than that, it bears no resemblance to the social vision held by alternative energy advocates of the mid-1970s.

The history of wind energy emphasizes another point about normative values and energy. Alternative energy advocates in the 1970s thought that society was in deep crisis and that its core values were debatable. The signs seemed to be everywhere. The economy was in a long decline during the 1970s after dramatic growth and prosperity in the 1950s and 1960s. Along with economic stagnation came social problems such as rising crime rates and declines in urban fiscal health, symbolized by the fiscal crisis in New York City. The oil embargo, along with the end of the Vietnam War and other problems abroad, seemed to indicate a loss of international influence for the United States. Faced with these realities, alternative energy advocates thought they were in a position to push for a society based on radically different values.

But they clearly miscalculated. In particular, the value of economic efficiency, an important ethical norm for conventional society, one that valorizes markets, has been an important, though not the only, driver of energy technology. In the early-twenty-first century virtually all advocates of renewable energy seek ways in which such technologies can succeed in competitive markets. Alternative energy advocates of the 1970s pushed a social vision that was greatly divergent from existing society. They never produced a narrative compelling enough to lead to widespread acceptance of their normative values and consequently to their technological system. Their values rather than their technologies kept them marginalized.


FRANK N. LAIRD

SEE ALSO Alternative Technology;Automobiles;Environmental Ethics;Sierra Club.

BIBLIOGRAPHY

Laird, Frank N. (2001). Solar Energy, Technology Policy, and Institutional Values. New York: Cambridge University Press. Studies federal government policy for renewable energy from 1945–1981, with an emphasis on the ways in which values drove policy debates.

Laird, Frank N. (2003). "Constructing the Future by Advocating Energy Technologies." Technology and Culture 44
(1): 27–49. Examines the values that alternative energy advocates used in their works from World War II through the energy crisis, with a heavy emphasis on the 1970s.

Renewable Energy

views updated May 23 2018

Renewable Energy


Renewable energy is energy that is regenerative or, for all practical purposes, virtually inexhaustible. It includes solar energy, wind energy, hydropower, biomass (derived from plants), geothermal energy (heat from the earth), and ocean energy. Renewable energy resources can supply energy for heating and cooling buildings, electricity generation, heat for industrial processes, and fuels for transportation. The increased use of renewable energy could reduce the burning of fossil fuels (coal, petroleum, and natural gas), eliminating associated air-pollution and carbon dioxide emissions, and contributing to national energy independence and economic and political security.


Historical and Current Use

Before the 1900s, the world as a whole used wood (including wood converted to charcoal) for heat in homes and industry, vegetation for feeding draft animals, water mills for grinding grain and milling lumber, and wind for marine transportation and grain milling and water pumping. By the 1920s, however, coal and petroleum had largely replaced these energy sources in industrialized countries, although wood for home heating and hydroelectric power generation remained in wide use. At the end of the twentieth century, nearly 90 percent of commercial energy supply was from fossil fuels.

Renewable energy, however, makes important contributions to world energy supplies. Hydroelectric power is a major source of electrical energy in many countries, including Brazil, Canada, China, Egypt, Norway, and Russia. In developing countries many people do not have access to or cannot afford electricity or petroleum fuels and use biomass for their primary energy needs. For example, most rural people in Africa use wood, scrub, grass, and even animal dung for cooking fuel. Small-scale renewable energy technologies are often the only practical means of supplying electricity in rural areas of these countries. The table indicates the relative consumption of energy sources in the United States.

Major Types of Renewable Energy Sources

Biomass. Biomass includes wood, agricultural crops and residues, municipal refuse, wood and paper products, manufacturing process waste, and human and livestock manure. It can be used to heat homes and buildings, produce electricity, and as a source of vehicle fuel. Wood and paper manufacturers and sugar mills use biomass residues for process heat and electricity production. There are power plants that burn wood, agricultural residues, and household trash to produce electricity. Biogas (composed of methane, carbon dioxide, and other gases) produced by decomposing biomass in anaerobic conditions is captured from landfills, municipal sewage treatment plants, and livestock waste management operations. This gas can be used for heat or to generate electricity.

Ethanol is used as a transportation fuel in the United States, Brazil, and a few other countries. Nearly all the fuel ethanol in the United States is made from corn, although it can also be produced from other sources, including wastepaper. There is a small but growing consumption of "biodiesel" made from grain oils and animal fats.

Geothermal systems. Geothermal energy (heat from the earth) created deep beneath the earth's surface is tapped to produce electricity in twenty-two countries, some of which include the United States, Iceland, Italy, Kenya, and the Philippines. Geothermal hot springs can also heat buildings, greenhouses, fish farms, and bathing pools.

Hydropower. Hydropower, produced from flowing water passing through hydroelectric turbines , is the leading renewable energy source, contributing to approximately 9 percent of the electricity generated in the United States. Most hydropower is produced at large dams, although there are many small systems operating around the world, such as the small hydropower plant in Namche Bazar, Nepal, which provides power for the tourist and market town near Mt. Everest. The production of hydroelectricity from year to year varies with precipitation.

Ocean energy. The world's oceans are a vast and practically untapped source of energy. There are a few operating wave and tidal power plants around the world, and several experimental ocean thermal energy conversion (OTEC) plants have also been built. A small wave power plant in Norway captures water from waves in a dam and lets the water out through a turbine. A 240-megawatt tidal power facility on the Rance River in France produces electricity as tidal flows move back and forth through turbines located at the mouth of the river. In Hawaii, a small OTEC plan was built which uses the temperature of warm surface water to evaporate cold seawater in a vacuum to produce steam that turns a turbine and generator.

Solar energy systems. The simplest uses of solar energy are for drying crops, and heating buildings and water. Solar-heated homes and solar water heaters can be found in nearly every country around the world. Crops can be simply laid in the sun to dry, or more sophisticated collectors can be used to heat air to dry food stored on drying racks. Solar water heaters use collectors to heat water that is stored in a tank for later use. Homes can be heated by using a masonry floor to absorb sunshine coming through windows, or by using solar collectors to heat a large tank of water than can be distributed for heating at night.

Concentrated sunlight can be used to produce high-temperature heat and electricity. Nine concentrating solar parabolic trough power plants, with a combined generation capacity of 354 megawatts, are located in the Mojave Desert in California. (A megawatt is 1 million watts, or 1,000 kilowatts.) The U.S. Department of Energy built and tested a ten-megawatt solar thermal central receiver power plant near Barstow, California, which operated successfully for about seven years. Another type of concentrating solar thermal power system is a parabolic dish. Systems with a capacity of up to twenty-five kilowatts have been developed.

Photovoltaic (PV) systems are based on solar electric cells, which convert sunlight directly to electricity. They can be used to power hand calculators or in large systems on buildings. Many PV systems are installed in remote areas where power lines are expensive or unfeasible, although the number of systems connected to electricity transmission systems is increasing, and range in size from 1 to several kilowatts on houses, to systems over one hundred kilowatts on large buildings. PV systems are very suitable for use in developing countries where people have no electricity from electric power lines.

Wind energy systems. Water-pumping and grain-milling windmills have evolved into electric power turbines. There are now tens of thousands of wind turbines operating around the world. They range in size from tiny turbines on the back of sailboats to very large units that can produce as much as

U.S. ENERGY CONSUMPTION AND ELECTRICITY GENERATION, 1999
energy source(quads*) (%total)(bill. kwh**) (%total)
*a quad is quadrillion british thermal units (btus), and is the equivalent of about 180 million barrels of crude oil.
**bill. kwh = a billion kilowatt-hours; one kilowatt-hour (kwh) is the equivalent of running a 100-watt lightbulb for 10 hours.
note: values are rounded.
source: Energy Information Administration, U.S. Department of Energy.
total96853,641 
coal/coal coke22231,89152
petroleum38391163
natural gas222354615
nuclear8867419
renewables (total)7.27.541912
hydro3.53.63399.4
biomass/biofuels3.23.3581.6
geothermal0.40.4170.46
solar0.070.070.850.02
wind0.050.054.50.12

2 to 3 megawatts of electricity, with 100-foot (30-meter) blades. They can be installed on land and in shallow water in coastal areas.


The Future for Renewable Energy

Renewable energy has many advantages that will help to maintain and expand its place in world energy supply:

  • Renewable energy resources are enormoushundreds of times beyond the needs of world energy consumption in 2000.
  • Advances in technologies are reducing manufacturing costs and increasing system efficiencies, thereby reducing the cost of energy from renewable resources.
  • Negative environmental and health impacts of renewable energy use are much fewer than those of fossil fuels and nuclear power.
  • Many renewable energy technologies can produce energy at the point of use, allowing homeowners, businesses, and industry to produce their own power.
  • There is strong support for renewable energy from people around the world.
  • Many governments have programs that support renewable energy use to limit the emission of greenhouse gases and thereby reduce the threat of global warming.

As fossil fuels such as oil and natural gas become scarce, they will become more expensive. Some experts believe that demand for oil will exceed production capability within the next twenty years.

Using energy conservatively and efficiently, no matter how it is produced or where it comes from, is the most economical way to consume energy. Simply turning off lights and computers when they are not in use can save an individual household or business money and reduce the environmental impact associated with producing electricity.

Bibliography

U.S. Energy Information Administration. (2001). Annual Energy Review 2000. Washington, D.C.: U.S. Department of Energy.

U.S. Energy Information Administration. (2001). International Energy Annual 1999. Washington, D.C.: U.S. Department of Energy.

U.S. Energy Information Administration. (2001). Renewable Energy Annual 2000, with Data for 1999. Washington, D.C.: U.S. Department of Energy.


internet resource

Renewable Energy World. London: James & James Science Publishers. Available from http://www.jxj.com.

U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. Available from http://www.eren.doe.gov.

Paul Philip Hesse

Energy, Renewable

views updated May 21 2018

ENERGY, RENEWABLE

ENERGY, RENEWABLE. Wood, wind, water, and sun power have been used for cooking, heating, milling, and other tasks for millennia. During the Industrial Revolution of the eighteenth and early nineteenth centuries, these forms of renewable energy were replaced by fossil fuels such as coal and petroleum. At various times throughout the nineteenth and twentieth centuries, people believed that fossil fuel reserves would be exhausted and focused their attentions on sources of renewable energy. This led to experiments with solar steam for industry and solid wood, methanol gas, or liquid biofuels for engines. Attention has refocused on renewable energy sources since the 1960s and 1970s, not only because of concern over fossil fuel depletion, but also because of apprehension over acid rain and global warming from the accumulation of carbon dioxide in the atmosphere.

Acid rain is clearly the result of the use of fossil fuels, and most authoritative climatologists also believe that these fuels are contributing to global warming. Many scientists and environmentalists have, therefore, urged a global switch to renewable energy, which derives from the sun or from processes set in motion by the sun. These energy forms include direct use of solar power along with windmills, hydroelectric dams, ocean thermal energy systems, and biomass (solid wood, methane gas, or liquid fuels). Renewable energy thus differs not only from fossil energy sources such as petroleum, gas, and coal, but also from nuclear energy, which usually involves dividing uranium atoms.

In the early 1990s, one-fifth of worldwide energy use was renewable, with by far the largest portion of this coming from fuel wood and biomass. Hydroelectric dams made up most of the rest. More than half the world's population relied on wood for cooking and heating, and although wood is generally considered to be renewable, excessive reliance has long been recognized as a cause of deforestation. Forests disappear faster than they can be renewed by natural processes. Energy "crops" —for example, fast-growing acacia or eucalyptus trees planted for fuel wood in the Third World—and more efficient wood stoves may be useful to poor, wood-reliant nations.

Solar energy is a term for many techniques and systems. The sun's energy can be trapped under glass in a greenhouse or within solar panels that heat water. It can also be concentrated in a trough or parabolic collector. In arid climates a small version of a concentrator is sometimes used to substitute for wood. Although economical, it is unreliable, hard to transport, and difficult to operate. Larger concentrators can produce steam economically for industry or for electric utilities in some climates. Another form of solar energy comes from photovoltaic cells mounted on panels. These panels are economical for all kinds of remote power needs, from cheap hand calculators to mountaintop navigational beacons to orbiting satellites. Costs have dropped dramatically since the mid-1970s, from hundreds of thousands of dollars to several thousands per installed kilowatt, and are expected to drop to under a thousand dollars early in the twenty-first century. At some point they may become competitive with nuclear and fossil energy.

Water power has been well known since its use in the Egyptian and classical Greek civilizations, and at the outset of the Industrial Revolution, it was widely used in Europe and the Americas to grind grain and run looms and in other small-scale industrial processes. Today water power is by far the cheapest of all fossil, nuclear, and renewable forms of energy for producing electricity, but the ecological disruptions caused by hydroelectric dams have caused many environmental controversies. Ocean energy takes advantage of the movement of water in tides or waves or of the temperature difference between sun-heated surface water and cold deep water. A few tidal energy projects have been built, but this form of energy production is expensive and remains largely experimental. Like tidal energy, geothermal energy is produced by continuous natural processes not directly related to solar cycles. Geo-thermal energy takes advantage of hot water trapped deep inside the earth to produce electricity or heat for homes and industry.

Wind power has been used for grinding grain, pumping water, and powering sawmills since the Middle Ages, and thousands of windmills once dotted coastal areas of northern Europe. Water-pumping windmills were a fixture in the American Midwest well into the twentieth century. Windmills are returning in a high-tech form in places like Altamont Pass in California, where they produce electricity. They are widely used for pumping water in the Third World.

Biomass energy involves a wide range of low and high technologies, from wood burning to use of manure, sea kelp, and farm crops to make gas and liquid biofuels. Brazil leads the world in use of pure ethyl alcohol derived from sugarcane as a replacement for petroleum. A common fuel in the United States is corn-derived ethyl alcohol, which is used as a low-pollution octane booster in a 10-percent blend with gasoline called "gasohol." Another form of renewable energy used in the rural Third World is the gas-producing biogas digester. Human and animal wastes are mixed with straw and water in an airless underground tank made of brick or cement. Methane gas is siphoned from the tank to a cooking stove. Meanwhile, the tank gets hot enough to kill disease-causing bacteria, which is an important sanitary improvement in many countries. Over the past few decades, 5 million biogas tanks have been built in China and half a million in India.

Renewable energy resources are cleaner and far more abundant than fossil resources, but they tend to be dispersed and more expensive to collect. Many of them, such as wind and solar energy, are intermittent in nature, making energy storage or distributed production systems necessary. Therefore, the direct cost of renewable energy is generally higher than the direct cost of fossil fuels. At the same time, fossil fuels have significant indirect or external costs, such as pollution, acid rain, and global warming. How to account for these external costs and assign the savings to renewable energy is a matter of continued policy debate. Another policy issue is research and development support. Conventional forms of energy, such as fossil fuels and nuclear power, receive more financial support from the federal government than does renewable energy. U.S. government policy toward renewable energy has been a roller coaster of support and neglect. By the end of President Jimmy Carter's administration in 1981, federal contributions to research in solar photovoltaics, solar thermal energy, solar buildings, biofuels, and wind energy research had soared to almost $500 million, but by 1990 the figure was only $65 million. A global transition to renewable energy will have to include developing nations, where energy use in proportion to the world total grew from 20 percent in 1970 to 3l percent in 1990.

BIBLIOGRAPHY

Berinstein, Paula. Alternative Energy: Facts, Statistics, and Issues. Westport, Conn.: Oryx Press, 2001.

Blackburn, John O. The Renewable Energy Alternative: How the United States and the World Can Prosper Without Nuclear Energy or Coal. Durham, N.C.: Duke University Press, 1987.

Butti, Ken, and John Perlin. A Golden Thread: 2,500 Years of Solar Architecture and Technology. New York: Van Nostrand Reinhold, 1980.

Flavin, Christopher. Beyond the Petroleum Age: Designing a Solar Economy. Washington, D.C.: Worldwatch Institute, 1990.

Kovarik, Bill. Fuel Alcohol: Energy and Environment in a Hungry World. London: International Institute for Environment and Development, 1982.

Sørensen, Bent. Renewable Energy: Its Physics, Engineering, Use, Environmental Impact, Economy and Planning Aspects. San Diego, Calif.: Academic Press, 2000.

BillKovarik/h. s.

See alsoAcid Rain ; Air Pollution ; Conservation ; Energy Policy ; Energy Research and Development Administration ; Global Warming ; Hydroelectric Power ; Nuclear Power ; Water Pollution ; andvol. 9:Address on Energy Crisis .

renewable energy

views updated Jun 11 2018

renewable energy (alternative energy) Energy from a source that can be replenished or that replenishes itself, and is more environmentally safe than traditional energy forms such as coal, gas, or nuclear energy. Solar energy harnesses the rays of the Sun. Tidal power stations use the gravitational force of the Sun and Moon on the ocean. Wave power harnesses the natural movement of the sea. The power of rivers and lakes can be tapped by damming the flow and using turbines to generate hydroelectricity. Wind power schemes have existed for centuries in the form of windmills. Another, less well-known, renewable source is the geothermal energy produced in the Earth's crust.

renewable resource

views updated May 08 2018

renewable resource Resource produced as part of the functioning of natural systems at rates comparable with its rate of consumption, e.g. food production by photosynthesis. Limits to renewable resources are determined by flow rate and such resources can provide a sustained yield. Compare NONRENEWABLE RESOURCE.

renewable resource

views updated May 14 2018

renewable resource A resource produced as part of the functioning of natural systems at rates comparable with its rate of consumption (e.g. food production by photosynthesis). Limits to renewable resources are determined by flow rate and such resources can provide a sustained yield. Compare finite resource.

renewable resource

views updated Jun 11 2018

renewable resource A resource produced as part of the functioning of natural systems at rates comparable with its rate of consumption, e.g. food production by photosynthesis. Limits to renewable resources are determined by flow rate and such resources can provide a sustained yield. Compare FINITE RESOURCE.

alternative energy

views updated May 29 2018

alternative energy See renewable energy