Most of the Earth's energy comes from the Sun
Solar power, that's
obvious, but the energy in coal originally came from the Sun too. Prehistoric
plants stored the Sun's energy in their leaves, and when they died and
eventually formed coal seams, that energy was still there. So when we burn coal
(or any fossil fuel), we're releasing chemical energy that was stored in plants
millions of years ago.
The same goes for Wind and Wave power. Waves occur because of winds, and winds blow because the Sun warms our atmosphere. Warm air tends to rise, and winds are due to other air moving in to replace it. Most power stations burn coal, oil or natural gas to run the generators.
Others use uranium, or the flow of water. Electricity is sent around the country using high-voltage power lines. Nearly all of the power we use comes from large power stations, although some places such as isolated farms, or hospitals, have their own diesel generators.
Hydropower
Hydropower, hydraulic power or water power is power that is derived from the force or energy of moving water, which may be harnessed for useful purposes.
Prior to the widespread availability of commercial electric power, hydropower was used for irrigation, and operation of various machines, such as watermills, textile machines, sawmills, dock cranes, and domestic lifts.
Another method used a trompe, which produces compressed air from falling water, which could then be used to power other machinery at a distance from the water.
Geothermal Power
Geothermal power (from the Greek roots geo, meaning earth, and
thermos, meaning heat) is power extracted from heat stored in the
earth. This geothermal energy originates from the original formation of the
planet, from radioactive decay of minerals, and from solar energy
absorbed at the surface. It has been used for space heating and bathing
since ancient Roman times, but is now better known for generating
electricity. Worldwide, geothermal plants have the capacity to generate
about 10 GW as of 2007, and in practice generate 0.3% of global electricity
demand. An additional 28 GW of direct geothermal heating capacity is
installed for district heating, space heating, spas, industrial processes,
desalination and agricultural applications.
Geothermal power is cost effective, reliable, and environmentally friendly, but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expand the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of conventional fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.
Prince Piero Ginori Conti tested the first geothermal generator on 4 July 1904, at the Larderello dry steam field in Italy. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California, United States. As of 2004, five countries (El Salvador, Kenya, the Philippines, Iceland, and Costa Rica) generate more than 15% of their electricity from geothermal sources.
Wind power
Wind power is the
conversion of wind energy into a useful form of energy, such as
electricity, using wind turbines. At the end of 2008, worldwide
nameplate capacity of wind-powered generators was 121.2 gigawatts (GW).
In 2008, wind power produced about 1.5% of worldwide electricity
usage; and is growing rapidly, having doubled in the three years
between 2005 and 2008. Several countries have achieved relatively
high levels of wind power penetration, such as 19% of stationary
electricity production in Denmark, 11% in Spain and Portugal, and 7%
in Germany and the Republic of Ireland in 2008. As of May 2009,
eighty countries around the world are using wind power on a
commercial basis.
Large-scale wind farms are connected to the electric power transmission network; smaller facilities are used to provide electricity to isolated locations. Utility companies increasingly buy back surplus electricity produced by small domestic turbines. Wind energy as a power source is attractive as an alternative to fossil fuels, because it is plentiful, renewable, widely distributed, clean, and produces no greenhouse gas emissions. However, the construction of wind farms is not universally welcomed due to their visual impact and other effects on the environment.
Wind power is non-dispatchable, meaning that for economic operation, all of the available output must be taken when it is available. Other resources, such as hydropower, and standard load management techniques must be used to match supply with demand. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand, additional costs for compensation of intermittency are considered to be modest.
