Renewable energy (Encyclopedia of Environmental Issues, Revised Edition)
The environmental movement and the oil crises of the 1970’s led to interest in the development of energy sources that would offer alternatives to the use of fossil fuels. Fossil fuels are limited resources, and the burning of fossil fuels to generate energy creates emissions of carbon dioxide, toxic chemicals, and air pollutants that harm the environment and human health. Because renewable, or clean, energy systems use natural, local sources that are inexhaustible and such systems have fewer negative impacts on human life and the environment, governments have provided increasing support for the development of renewable energy technologies.
(The entire section is 98 words.)
Biomass (Encyclopedia of Environmental Issues, Revised Edition)
The oldest renewable energy source is biomass, which is organic animal and plant material and waste. Biomass resources include grass crops, trees, and agricultural, municipal, and forestry wastes. Since the discovery of fire, humans have burned biomass to release its chemical energy as heat. For example, wood has been burned to cook food and to provide heat. Biomass energy has also been used to make steam and electricity. Biomass oils can be chemically converted into liquid fuels or biodiesel, a transportation fuel. Ethanol, another transportation fuel, comes from fermented corn or sugarcane. Crops such as willow trees and switchgrass are also cultivated for biomass energy generation.
Biomass energy has many environmental benefits when compared with fossil-fuel energy. It contributes little to air pollution, as it releases 90 percent less carbon dioxide than do fossil fuels. Energy crops, such as prairie grasses, require fewer pesticides and fertilizers than do high-yield food crops such as wheat, soy beans, and corn, so they cause less water pollution. Energy crops also add nutrients to the soil. About 4 percent of the energy used in the United States is biomass energy.
(The entire section is 184 words.)
Solar Energy (Encyclopedia of Environmental Issues, Revised Edition)
One of the most promising and popular kinds of renewable energy is solar energy, which uses radiant energy produced by the sun. Solar energy was used as early as the seventh century b.c.e., when a magnifying glass was used to concentrate sunlight to light fires. In 1767, Swiss scientist Horace-Bénédict de Saussure invented the first solar collector, a device for storing the sun’s radiation and converting it into a usable form, such as by heating water to create steam. In 1891, American inventor Clarence Kemp patented the first commercial solar water heater.
Sunlight can be converted directly into electricity at the atomic level by photovoltaic (PV) cells, also called solar cells. The photovoltaic phenomenon was first noted in the eighteenth century and became more practical with the use of silicon for the cells in the twentieth century. The cells are joined together in panels, often connected together in an array. They can be placed on rooftops and connected to a grid. In the twenty-first century, solar cells are used worldwide in home and commercial electrical systems, satellites, and various consumer products.
Solar energy has numerous environmental benefits. Photovoltaics produce electricity without gaseous or liquid fuel combustion or hazardous waste by-products. Decentralized PV systems can be used to provide electricity for rural populations, saving more expensive conventional energy for industrial, commercial,...
(The entire section is 375 words.)
Wind Energy (Encyclopedia of Environmental Issues, Revised Edition)
One of the fastest-growing types of renewable energy during the 1990’s, wind energy has been used by humans for centuries. Windmills appear in Persian drawings from 500 c.e., and they are known to have been used throughout the Middle East and China. The English and the French built windmills during the twelfth century, and windmills were indispensable for pumping underground water in the western and Great Plains regions of the United States during the nineteenth and early twentieth centuries. These windmills converted wind into mechanical power.
The modern windmills used to convert wind energy into electricity are called wind turbines or wind generators. In 1890 Poul la Cour, a Danish inventor, built the first wind turbine to generate electricity. Another Dane, Johannes Juul, built the world’s first alternating current (AC) wind turbine in 1957. In the twenty-first century, large wind plants are connected to local electric utility transmission networks to relieve congestion in existing systems and to increase reliability for consumers. Wind energy is also used on a smaller scale by home owners in what is known as distributed energy; home-based wind turbines, with batteries as backup, can lower electricity bills by up to 90 percent.
The use of wind energy has long-term environmental benefits. Unlike nuclear and fossil-fuel electricity generation plants, wind generation of electricity does not consume fuel, cause acid...
(The entire section is 449 words.)
Hydropower (Encyclopedia of Environmental Issues, Revised Edition)
Long before electricity was harnessed, in about 4000 b.c.e., ancient civilizations used hydropower, or energy from moving or flowing water, in the waterwheel, the first device employed by humans to produce mechanical energy as a substitute for animal and human labor. Running water in a stream or river moves the wooden paddles mounted around a waterwheel, and the resulting rotation in the shaft drives machinery. The earliest waterwheels were used to grind grain, and the technology went on to be used worldwide for that purpose, as well as to supply drinking water, irrigate crops, drive pumps, and power sawmills and textile mills.
In the nineteenth century, the water turbine replaced the waterwheel in mills, but then the steam engine replaced the turbine in mills. The hydraulic turbine reemerged, however, to power electric generators in the world’s first hydroelectric power stations during the 1880’s. By the early twentieth century, 40 percent of the U.S. electricity supply was hydroelectric power. Modern large hydropower plants are attached to dams or reservoirs that store the water for turning the turbines and are connected to electrical grids or substations that transmit the electricity to consumers.
Hydropower is the leading renewable energy source for generating electricity. It has both negative and beneficial effects on the environment. Building dams and reservoirs changes the environment and can harm native habitats...
(The entire section is 307 words.)
Geothermal Energy (Encyclopedia of Environmental Issues, Revised Edition)
Geothermal energy comes from heat produced deep inside the earth. Deep wells and pumps bring underground hot water and steam to the earth’s surface to heat buildings and generate electricity. Some geothermal energy sources come to the surface naturally, including hot springs, geysers, and volcanoes. The ancient Chinese, Native Americans, and Romans used hot mineral-rich springs for bathing, heating, and cooking. Food dehydration became the major industrial use of this form of energy. In 1904, the first electricity from geothermal energy was generated in Larderello, Italy.
Although not as popular a renewable energy source as wind or solar energy, geothermal energy has significant advantages and benefits for the environment. Because the earth’s heat and temperatures are basically constant, geothermal energy is reliable and inexhaustible; it is also not affected by changes in climate or weather. It is very cost-efficient as well; heat pumps can be operated at relatively low cost. The steam and water used in geothermal systems are recycled back into the earth.
Geothermal plants are environmentally friendly. Because they do not burn fuel to generate electricity, they release little or no carbon dioxide and other harmful compounds. Geothermal plants produce no noise pollution and have minimal visual impacts on the surrounding environment, because they do not occupy large surface areas.
The U.S. Environmental...
(The entire section is 351 words.)
Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Craddock, David. Renewable Energy Made Easy: Free Energy from Solar, Wind, Hydropower, and Other Alternative Energy Sources. Ocala, Fla.: Atlantic, 2008.
Da Rosa, Aldo Vieira. Fundamentals of Renewable Energy Processes. 2d ed. Boston: Elsevier Academic Press, 2009.
Langwith, Jacqueline, ed. Renewable Energy. Detroit: Greenhaven Press, 2009.
MacKay, David J. C. Sustainable Energy—Without the Hot Air. Cambridge, England: UIT Cambridge, 2009.
Nelson, Vaughn. Wind Energy: Renewable Energy and the Environment. Boca Raton, Fla.: CRC Press, 2009.
Pimentel, David, ed. Biofuels, Solar, and Wind as Renewable Energy Systems: Benefits and Risks. New York: Springer, 2008.
(The entire section is 88 words.)
Definition (Encyclopedia of Global Warming)
Renewable energy is derived from inexhaustible sources, such as solar energy, wind, biomass, geothermal energy, and the ocean’s tides. Solar energy is captured through passive or active means and can be used as heat or electricity. Passive solar energy can be captured by constructing buildings and houses, so heat radiating from the Sun can be used to heat interiors through the strategic placement of windows. Active solar energy comes from the use of photovoltaic (PV) technology, concentrating systems, solar water heaters, and solar cookers.
Only PV technology and concentrating systems can produce electricity from the Sun’s heat. PV technology consists of solar cells made of silicon or thin films made from semiconductor materials. Concentrating systems, also known as central solar power (CSP), use mirrors to concentrate sunlight onto a liquid to produce steam, which can then be used to power a turbine and generate electricity.
Wind power is created through the use of wind turbines, which create electricity when the blades are turned by blowing wind. Biomass includes all living or dead plant material and organic waste from humans. Biomass, such as wood and other plants, can be burned in heat and electricity operations, or it can be converted into biofuel to be used in an internal combustion engine. Geothermal energy is the internal heat energy of the Earth. It can be taken directly from vents in the Earth’s crust, where...
(The entire section is 350 words.)
Significance for Climate Change (Encyclopedia of Global Warming)
Many experts and world leaders view renewable energy as a major solution for mitigating climate change. The use of fossil fuels to satisfy human energy needs is one of the major contributors to greenhouse gas (GHG) accumulation in the atmosphere. Renewable energy, with the exception of biomass, does not create GHGs in the process of creating heat or electricity as fossil fuels do, because nothing has to be burned. Although biomass must be combusted, it has the potential to emit less GHGs than do fossil fuels, though how much less is heavily debated.
If renewable energy sources are used as substitutes for fossil fuels, the amount of GHG emissions would be reduced and presumably so would climate change. Renewable energy is also seen as a solution to the worldwide growth in energy demand that has the potential to contribute even more GHG emissions. As more developing countries seek electrification for household and industrial uses and find needs for motorized transportation, their demand for energy will increase their use of fossil fuels and their GHG emissions. Renewable energy is thus a potential solution to allow for development to continue while reducing its impact on the climate.
Although political agreements such as the Kyoto Protocol do not require that renewable energy be used to reduce GHG emissions, it is expected that renewable sources will have to become part of the energy mix to achieve the...
(The entire section is 360 words.)
Further Reading (Encyclopedia of Global Warming)
Boyle, Godfrey. Renewable Energy. New York: Oxford University Press, 2004. Provides a comprehensive explanation of the different kinds of renewable energy and the concepts behind them. Colorful graphics contribute to enhanced understanding of the topic.
Inslee, Jay, and Braken Hendricks. Apollo’s Fire: Igniting America’s Clean Energy Economy. Washington, D.C.: Island Press, 2007. Emphasizes the bold leadership and commitment that will be required to move the United States toward a more sustainable energy economy.
Leggett, Jeremy. The Empty Tank: Oil, Gas, Hot Air, and the Coming Global Financial Catastrophe. New York: Random House, 2005. Thoroughly explains the oil topping point, the financial and environmental risks of global warming, the role of government and business in promoting continued fossil fuel use, and the solutions to the problem.
Sweet, William. “Going All Out for Renewables, Conservation and Green Design.” In Kicking the Carbon Habit. New York: Columbia University Press, 2006. This chapter provides a thorough examination of the successes of the wind industry and the disappointing development of the photovoltaic market.
(The entire section is 167 words.)