Alternative+energy+sources

Alternative energy refers to energy derived from sources that do not deplete natural capital or directly harm the environment. Typically the term encompasses:


 * [[image:ist2_6470863-wind-turbines-spinning.jpg width="180" height="270" align="right" caption="Harnessing the Wind"]]solar energy – photovoltaic systems (solar cells) transform sunlight directly into electricity. Solar power plants also generate electricity by using solar thermal collectors to heat a fluid which produces steam that then powers a generator. The effectiveness of solar power is dependent on location, time of day, time of year and weather conditions.
 * wind power – mainly used to generate electricity, the wind’s kinetic energy is harnessed by wind turbines to power a generator. The effectiveness of wind power is dependent on location, time of day, time of year and weather conditions.
 * geothermal – heat from within the Earth is captured for direct use in heating systems or to generate electricity where geothermal reservoirs are located within two km of the Earth’s surface.
 * biomass fuels – commonly composed of plant matter grown to generate electricity or produce heat, biomass can be converted to other useable forms of energy, such as methane gas or transportation fuels, like biodiesel or ethanol. Methane captured from decomposing landfills ([|waste gas]) is a popular form of biomass fuel.
 * wave power – harnessing the power of waves is relatively new and many methods are currently under development. One option is to bend or focus waves into a narrow channel, increasing their power and size, then either divert them into a catch basin or use them directly to spin turbines.
 * tidal energy – another new development, tidal power harnesses energy from the Moon’s gravitational pull and the rotation of the Earth as they each effect sea levels. Though more predicable than other alternative energies, efficient tidal power generation methods are still evolving. Typically, tidal generators are powered by an underwater turbine system that captures the kinetic energy of ocean tides.
 * hydro power – one of the oldest and most widely used sources of alternative energy, hydro captures the kinetic energy of moving water to power turbines and generate electricity. The renewability of hydro power is increasingly be questioned, as large scale developments cause considerable flooding and damage to river systems. [|Run of River] hydro projects are now being advocated as they reduce many of these effects.

Fossil fuels, clean coal, unconventional oil, and nuclear energy are not included within the official classification of alternative energies because of their contribution to either carbon dioxide emissions or radioactive wast. However, with the advent of new technologies and energy sources, the classifying of alternative energy is becoming increasingly controversial. Nevertheless, the term 'alternative' implies a possible substitution, or even replacement of other sources. This is a deliberate implication as the intention of alternative energies, though not yet realized, is to substitute, then replace fossil fuels before or after global reserves have been depleted.