renewable energy

Some examples of renewable energy. Panels of solar cells can be used to convert the light of the Sun into electrical energy. Wind turbines are connected to generators and turn to generate electricity. In a typical hydroelectric plant, water is stored in a reservoir. The water's potential energy is converted to kinetic energy as it is piped into turbines that are connected to generators. Geothermal energy harnesses the heat of the Earth to provide heating and electricity. Biomass is organic matter that can be converted to provide heat or electricity.

Power from any source that can be replenished. Most renewable systems rely on solar energy directly or through the weather cycle as wave power, hydroelectric power, wind power via wind turbines, or solar energy collected by plants (alcohol fuels, for example). In addition, the gravitational force of the Moon can be harnessed through tidal power stations, and the heat trapped in the centre of the Earth is used via geothermal energy systems. Other examples are energy from biofuel and fuel cells. Renewable energy resources have the advantage of being non-polluting. However, some (such as wind energy) can be unreliable and therefore lose their effectiveness in providing a constant supply of energy.

Despite inherent problems with the technology behind renewable energy sources, increasing environmental pressure is forcing development at an increasing pace. By the end of 2002, worldwide wind-power generation had exceeded 30 megawatts and had reached an annual growth rate of 25%.