Renewable Energy Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

This Renewable Energy Essay example is published for educational and informational purposes only. If you need a custom essay or research paper on this topic, please use our writing services. EssayEmpire.com offers reliable custom essay writing services that can help you to receive high grades and impress your professors with the quality of each essay or research paper you hand in.

The term re n e wable energy describes sources of energy that exist within the natural environment including the sun, wind, water, plant material, and geothermal heat. These sources are either continuously available, like heat from the sun, or are rapidly replaced after their depletion, like wood. Renewable energy is also considered clean energy. It generally does not produce carbon dioxide or other harmful pollutants or wastes. Renewables such as hydropower and wood already contribute 15 percent of total world energy production. The so-called “new renewables,” including solar and wind, while accounting for only 2 percent of energy production, are the fastest-growing sources of energy. Since the early 1990s installed capacity of both solar power and wind energy has increased by more than 20 percent annually. With concerted action, renewable energy technologies have the potential to meet half or more of the world’s energy needs within a few decades.

Hydropower

Hydropower is the most successful type of renewable energy. Humans have been using the power of flowing rivers for centuries to grind flour and turn rudimentary machinery. Hydro has been used to produce electricity for over 100 years. Rivers are dammed, impounding water in reservoirs, which is then used to turn turbines. Hydro produces 17 percent of the world’s total electricity, 10 percent of U.S. electricity, and more than 90 percent of electricity in Norway and Iceland. Forty other countries get more than 50 percent of their electricity from hydro. The cost of hydropower is low and is competitive with the cheapest fossil fuels. Hydro is a domestic source of energy, which is especially beneficial for less-developed countries faced with importing expensive oil. Dam projects have other benefits such as flood control, irrigation, recreation, and municipal water supply. Hydropower has a number of drawbacks, including the loss of farmland, displaced people, and the destruction of habitat and fisheries. Droughts pose another problem, and silt can dramatically reduce the life of a reservoir.

The Three Gorges Dam on the Yangtze River in China is the world’s largest dam project. It will produce 10 percent of China’s electricity, thus reducing dependence on dirty coal. However, the reservoir has displaced 1.5 million people and resulted in the loss of 115,000 acres of farmland, showing that hydro is not always benign. Nevertheless, the potential for hydropower is vast, especially in poorer countries. In rich countries, high construction costs and political opposition mean that fewer large dams are likely to be built in the future.

Solar Power

Solar power uses the energy of the sun for heating and to produce electricity. There are four main types of solar energy systems. Passive solar relies on the design of structures to capture heat in the winter and to keep spaces cool in the summer. For example, a greenhouse is heated by the sun. A well-designed passive system can provide nearly 100 percent of the space heating for a home. Active solar systems are most commonly used to heat water and swimming pools. They rely on flat plate collectors, generally mounted on rooftops, to circulate and heat water. Photovoltaic systems use silicon wafers or chips to convert sunlight directly into electricity. Calculators use photovoltaic cells, as do panels on homes and in places not connected to power lines. Solar thermal electric systems heat water to produce steam to generate electricity. A commercial plant in the Mojave Desert of California uses a series of curved mirrors that track the sun to produce enough power to supply electricity to 170,000 homes.

The great benefit of solar is that the energy of the sun is nearly limitless and has the potential to meet most of the world’s needs. Passive, active, and smallscale photovoltaic technologies are already widely used. Solar energy is decentralized and near the user, which could benefit nearly two billion people in less-developed countries who live in rural areas not connected to a power grid. The main problem with solar energy is that while sunlight is plentiful, it is not uniformly available. It is inconsistent, varying by region, season, time of day, and weather conditions. The ability to store power in batteries is limited, and backup systems are needed. Solar power is a good supplement to conventional systems. The other problem is that solar-generated electricity costs about four times as much as coal power. Nevertheless, costs have fallen rapidly in the past two decades and will continue to decline as technology improves.

Wind Power

Windmills have been used for nearly 2,000 years to pump water and for grinding grain. Today, wind power is the world’s fastest-growing source of electricity generation. Advanced technology has made wind power cost-competitive with coal and about half the cost of nuclear power. Europe is the leader in wind power, with three-quarters of global capacity. Wind machines in Europe generate an output equivalent to 35 large coal-burning power plants. Germany accounts for half of Europe’s total and produces 5 percent of its electricity from wind. Twenty percent of Denmark’s electricity is generated by wind. The United States is the number two world producer, but wind accounts for less than 1 percent of U.S. electricity.

Wind power has tremendous potential and could meet 20 to 30 percent of global electricity needs. The largest wind machines are 600 feet tall, have 200-foot blades, weigh 18 tons, and can generate power for 5,000 homes. The main drawback is that the wind does not blow all the time, so again, a backup system is needed. Wind machines are now being placed offshore in the ocean where winds blow more consistently. Other concerns include visual blight, noise, and potential harm to birds. Nevertheless, wind power is an important part of a mix of energy sources. It is also a good complement to solar because the wind is often blowing when the sun is not out.

Geothermal and Tidal Power

Two lesser-known sources of renewable energy are geothermal and tidal power. Geothermal power is derived from the heat of molten magma beneath the earth. Geysers and hot springs are examples of geothermal processes. Wells tap into hot water and steam under the ground, which can be used to drive steam generators or heat water and homes. Only 0.25 percent of U.S. electricity is produced by geothermal. However, 85 percent of homes in Iceland are heated by geothermal wells. El Salvador generates 40 percent of its electricity from geothermal, and this resource is important in areas of New Zealand, Japan, Russia, and Italy. Geothermal is limited to geologically and volcanically active areas. Also, hot water and steam can contain damaging minerals and the poisonous gas hydrogen sulfide.

Tidal power involves constructing a dam across the mouth of a bay to capture water at high tide. Some areas of the world, especially at far north and south latitudes, have daily tidal ranges of up to 20 feet. At low tide, water is let out through a turbine to generate electricity. Tidal power has yet to be applied commercially because it is limited to areas with large tidal ranges, and power can only be generated intermittently during the tide cycle. Also, the damming of bays and estuaries has environmental implications.

Biofuels

Energy from biomass or biofuels is derived from plant and animal products. Fifteen percent of the world’s total energy demand and 3 percent of that in the United States is currently met by biofuels. The most important biofuels are wood, biogas, ethanol, and biodiesel. Wood has been burned for thousands of years and is still the primary source of energy for half the world’s people. However, wood is severely depleted in many countries, and burning wood is a source of air pollution. Biogas is made by decomposing crop residues and manure to produce methane. Methane is also given off from landfills. Thirty-five million homes in China use village-based biogas systems for cooking, heating, and lighting. However, methane, like carbon dioxide, is a greenhouse gas. Ethanol is alcohol that is distilled from crops such as corn, sugarcane, and soybeans. In cars, it can be blended with gasoline up to 20 percent without modifying the engine. So-called flexible fuel vehicles automatically adjust to run on any mix of fuel from pure gasoline to 85 percent ethanol. Brazil has led the way in using ethanol as a transportation fuel. Fifty percent of nondiesel fuel in Brazil is ethanol, and almost all cars sold today are flex-fuel. The United States is the second leading producer, but only 2 percent of U.S. fuel is ethanol. Nevertheless, there are four million flex-fuel vehicles on the road. Global production of ethanol has doubled since 2000 and will more than double again by 2020. Biodiesel is derived from vegetable oils and can be mixed in any proportion with petroleum-based diesel or used in pure form. Europe produces 95 percent of the world’s biodiesel, and Germany is the leading producer.

Ethanol and biodiesel have a number of advantages over petroleum-based fuels. They are cost competitive, less hazardous to handle, and less polluting. They are also carbon neutral. Carbon is captured from the atmosphere by plants when they are growing and then released again when the fuel is burned. Biofuels could replace large amounts of imported oil. The technologies are proven and large-scale production is already in place. The biggest drawback is limited farmland. Crops for biofuels may someday compete with food production, and the expansion of farming into marginal lands causes soil erosion and habitat destruction. In addition, large-scale monoculture agriculture relies on petroleum-based transportation fuels, pesticides, and fertilizers, and distilleries are often powered by fossil fuels. However, in the future biofuels will be made from straw, wood, and other nonedible cellulose-type materials. If the environmental and sustainability questions can be addressed, biofuels will have even greater potential.

Hydrogen

Hydrogen is another renewable energy resource. Like natural gas or propane, hydrogen can be burned in homes and factories, and it can be shipped in existing natural gas pipelines. The by-product of burning hydrogen is water vapor, and it emits no carbon dioxide. A promising new technology is the

hydrogen fuel cell. A fuel cell resembles a battery, but it uses hydrogen and oxygen, which react with a cathode and a catalyst to produce electricity. A vehicle is powered by an electric motor. Prototype hydrogen fuel-cell vehicles are now on the market, and several European cities operate fuel cell buses. The 1937 Hindenburg airship disaster left a lasting impression that hydrogen is not safe. However, hydrogen in vehicles is no more dangerous than gasoline, which is also flammable.

The main drawback is that a large supply of hydrogen is not easily recoverable from nature. One way to obtain hydrogen is through electrolysis, which uses electricity to split water molecules. Water is very abundant, but electrolysis requires a lot of electricity, which is expensive and energy-intensive. Hydrogen made with electricity from fossil fuels results in the release of carbon dioxide and other pollutants into the atmosphere. Nuclear power could be used, but that technology is controversial. Hydrogen can also be separated from natural gas, gasoline, methane, or ethanol. Ironically, hydrogen technology can alleviate local and regional air pollution, but contribute to global warming. The only way hydrogen is truly clean is if renewable energy is used to make it.

Substantial amounts of renewable energy are available with current technologies, and hydro, wind, and biofuels are already economically competitive. A proactive energy policy is needed. Hundreds of billions of dollars annually go to subsidizing fossil fuels and nuclear power. Even a modest shift of support toward renewables could spur new industries and stimulate demand as the technology advances and costs come down. While no single source is likely to provide all of society’s energy needs, as part of a total energy package, renewable energy can contribute to lessening dependence on fossil fuels and to a cleaner and more sustainable future.

Bibliography:

Daniel Chiras, Environmental Science: Creating a Sustainable Future (Jones and Bartlett, 2006); “Crossroads for Planet Earth,” Scientific American, Special Issue (September 2005);
Susan Cutter and William Renwick, Exploitation, Conservation, Preservation: A Geographic Perspective on Natural Resource Use (Wiley, 2004);
Suzanne Hunt and Janet Sawin with Peter Stair, “Cultivating Renewable Alternatives to Oil,” in State of the World 2006 (Worldwatch Institute, 2006);
Michael Parfit, “Powering the Future,” National Geographic (August 2005);
Janet Sawin, Worldwatch Paper #169: Mainstreaming Renewable Energy in the 21st Century (Worldwatch Institute, 2004).