Electricity Generating Sources
Most of the electricity in the United States is generated by steam turbines. Petroleum (oil), coal, and natural gas are burned in large furnaces to generate steam, which pushes on the blades of a turbine. In the United States, coal is the primary source used to generate electricity. Besides being burned to heat water for steam, natural gas can be also burned to produce hot combustion gases that pass through a turbine, turning the blades to generate electricity.
According to the United States Country Analysis Brief by the Energy Information Administration, in 2003, the United States generated 3,848 billion kilowatt hours (Kwh) of electricity, including 3,691 billion Kwh from the electric power sector plus an additional 157 billion Kwh coming from combined heat and power (CHP) facilities in the commercial and industrial sectors. For the electric power sector, coal-fired plants accounted for 53% of generation, nuclear 21%, natural gas 15%, hydroelectricity 7%, oil 3%, geothermal and "other" 1%.
There are two types of energy resources, renewable and non-renewable. Non-renewable resources come out of the ground as liquids, gases and solids. These resources are crude oil (petroleum), natural gas, propane and coal. Petroleum, coal, propane and natural gas are considered fossil fuels because they formed from fossils (remains or impressions of organisms of past geologic ages). Another non-renewable source is nuclear fission power. These sources cannot be replenished in a short period of time. Renewable resources are not subject to depletion in a human timescale. These sources include the sun's ray, waves, rivers, tides, wind, biomass and the heat from radioactive decay in the Earth's core.
Methods of Generating Energy
We have talked about the generation of energy using steam turbines. There are alternatives methods of generating energy; some of these methods use renewable resources and some of them don't. Let's take a look at the following:
Heat contained within the earth can be recovered and put to work. This heat is called geothermal energy. Geothermal power is originated beneath the surface of the earth. It comes from buried heat energy. There are five forms of geothermal energy:
* Earth energy
* Geo pressured brines
* Hot dry rock and magna
* Hydrothermal reserves
Today, only hydrothermal reserves and earth energy are being used. The word "geothermal" means "earth and "heat". People have used the geothermal resource for centuries and it is the world's largest energy resource. Geothermal power is a renewable resource and it is environmentally friendly. It is generated in geothermal plants in some areas of the country like California, Hawaii, Nevada and Utah. Geothermal power is produced when enough heat rises close to the surface of the earth and heats underground water causing steam that can be used at steam-turbine plants. Unlike a coal generating plant, a geothermal plant does not produce emissions of sulfur dioxide, carbon dioxide and nitrogen oxides.
Solar power is obtained from the energy of the sun. Solar technologies use the sun's energy and light to provide heat, light, hot water, electricity, and even cooling. The energy from the sun is not always available and it is widely scattered, however, solar power is renewable and environmentally friendly. There are several solar technologies, for example:
* Photovoltaic solar cells, which directly convert sunlight into electricity.
* Passive solar heating, cooling and day lighting is how buildings are designed to incorporate design features that promote passive solar and day lighting. For example, using large south-facing windows and building materials that absorb and slowly release the sun's heat. All of these methods do not use mechanical means; passive solar designs can lower heating bills by 50%.
* Concentrating Solar power is a technology that uses reflective materials like mirrors to concentrate the energy from the sun. The heat energy obtained can be converted to electricity.
* Solar Hot Water and Space Heating and Cooling: Solar hot water heaters use the sun to heat water or fluid in collectors.
Bioenergy technologies use renewable biomass resources -wood, municipal solid waste (garbage), and agricultural waste (like corn cobs and wheat straw) - to produce different types of energy, like electricity, liquid, solid and gaseous fuels, chemicals, heat, and other materials. Bio-energy has the second place after hydropower, in renewable U.S. primary energy production. It is also a renewable resource and environmentally friendly.
Wind power uses the energy contained in the wind for practical purposes like generating electricity, charging batteries, grinding grain or pumping water. A wind turbine is very similar to a windmill; they operate together in wind farms to produce electricity for utilities. Homeowners or remote villages can use smaller turbines to produce energy. Wind power is also a renewable resource and environmentally friendly.
Hydropower is a process where flowing water is used to spin a turbine that is connected to a generator. There are two systems in which hydropower can be divided:
* Dams: Flowing water accumulates in reservoirs or dams. The water falls through a pipe and applies pressure against the blades of a turbine. The blades drive the generator and produce electricity.
* Run-of-River: The force of the river current applies pressure to the blades of a turbine and produces electricity.
Hydropower faces a controversy when classifying it into a renewable resource. It is produced from elemental, natural, and recurrent resources like rainfall and snowfall. Its fuel is not depleted during the production of electricity. However environmentalists say that the construction of dams as well as the change of course in rivers causes irreversible damages to the wildlife and the ecosystems.
Nuclear power is produced when heating water through a process called nuclear fission generates steam. Nuclear power is generated in a nuclear power plant. This plant has a reactor that contains a core of nuclear fuel, primarily enriched uranium. When continuous fission takes place, it forms a chain reaction and releases heat. This heat is used to turn water into steam; the steam then spins a turbine and generates electricity. Nuclear plants do not burn fuel so they do not release emissions like fossil-fueled power plants do. But the uranium mining, uranium enrichment and uranium transportation processes are associated with fossil fuel emissions. Uranium is a non-renewable resource that cannot be replenished. It is radioactive and toxic and it is extracted from open-pit underground mines. After the uranium is mined, it is sent to a processing plant so it can be concentrated into a useful fuel (called uranium oxide pellets). This is known as the uranium enrichment process and it generates radioactive waste. The enriched fuel is then transported to the nuclear plant.
As we know, conventional electricity generation is based on the combustion of fossil fuels, which is the number one industrial source of air pollution. Green power is electricity that is generated from resources such as geothermal, biomass, solar, wind, and low-impact hydro facilities. It uses renewable energy technologies and its purpose is to reduce the environmental impacts associated with electricity generation. It is an alternative solution to the supply of energy.