Electricity has traditionally been generated by burning fossil fuels, but fears about the environment cost to the planet and the sustainability of continued fossil fuel consumption have prompted research into cleaner methods of generating electricity from renewable resources. Burning fossil fuels not only depletes resources but also releases carbon dioxide that had previously been locked in the Earth’s crust. Renewable resources are sources of energy that cannot be significantly depleted by generating power from them. Such energy sources include radiation from the Sun, power from the wind, waves and tides, and water falling under gravity, and heat from the Earth itself. Generating electricity from these resources causes significantly less pollution than fossil fuel combustion.
Enormous amounts of energy reach the outer atmosphere of the Earth from the Sun. The quantity reaching the surface depends upon the ozone layer, dust, clouds and latitude. Even in temperate latitudes it can amount to 500 W/m2. This energy is readily available for producing hot water and spa heating using simple solar panels. Installation costs are high, however, and the energy available decreases in winter when the requirement is greatest. Much higher temperatures are needed for power generation and these can be achieved by focusing the Sun’s rays with concave mirrors.
Solar cells convert the Sun’s energy directly into electricity. These have been used to power small experimental cars through electric motors of about 1 hp. Photoelectric cells are already widely used in light meters and solar powered calculators where very small currents are sufficient but they are n yet economic for power generation.
Ocean thermal energy
The Sun causes the surface temperatures of oceans to be considerably higher than the temperatures at great depths. This temperature difference could be used in a thermodynamic cycle to generate electricity. Watch the video below to learn more about ocean thermal energy.nbsp;
Tidal barrages use the difference between water levels at high and low tide to generate electricity. They are constructed across the mouths of tidal estuaries. When the tide is rising, water is allowed through the barrage, filling the estuary behind it. As the tide falls, floodgates are closed and a head of water builds up behind the barrage. Water is then allowed to flow back to the sea, driving turbines that are connected to generators as it does so.
In mountainous countries substantial amounts of power can be generated from the potential energy of water stored by dams. See the video below to learn more about hydroelectric energy.nbsp;
The vertical motion of the sea can be utilised to generate power in several ways. One system uses the relative movements of floating rafts to convert the wave energy. Very large amounts of energy are theoretically available, particularly in the winter season.
At a few locations round the world, known as ‘hotspots’, upwelling within the Earth’s mantle brings molten rock close to the surface. Water circulating underground at these sites is heated, giving rise to hot springs and geysers. This geothermal energy is captured nu using the naturally occurring steam to drive turbines that generate electricity.
Wind power has been harnessed for many centuries and is now seriously considered for the generation of electricity. Wind farms are becoming an ever more common sight. They are built on high ground, open plains, coastal ridges, or even offshore. Wind farms can provide small communities with power or supplement the main grid. The costs of wind generated power is falling and the technology could mature into a significant source of electrical power.
Recommended Books on Renewable Energy
- The Crash Course: The Unsustainable Future Of Our Economy, Energy, And Environment
- Renewable Energy: Power for a Sustainable Future, Second Edition
- Alternative Energy For Dummies
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