Summary: Alternative energy is useable energy from any source other than by involving the burning of fossil fuels (natural gas, coal and oil) or the splitting of atoms (nuclear power). It includes renewable energy (hydro, geothermal, biomass and wind) as well as solar energy.

Summary: The energy stored in the nucleus of an atom and released through fission, fusion, or radioactivity. In these processes a small amount of mass is converted to energy according to the relationship E = mc2, where E is energy, m is mass, and c is the speed of light (see relativity). The most pressing problems concerning nuclear energy are the possibility of an accident at a nuclear reactor or fuel plant, such as those which occurred at Three Mile Island (1979), Chernobyl (1986), and Takaimura, Japan (1999), and the potential threat to the continued existence of the human race posed by nuclear weapons

Summary: Heat generated by natural processes within the earth. Chief energy resources are hot dry rock, magma (molten rock), hydrothermal (water/steam from geysers and fissures) and geopressure (water satured with methane under tremendous pressure at great depths). The word "geothermal" literally means "Earth" plus "heat". To produce electric power from geothermal resources, underground reservoirs of steam or hot water are tapped by wells and the steam rotates turbines that generate electricity.

Summary: Solar energy - energy from the sun that is converted into thermal or electrical energy; "the amount of energy falling on the earth is given by the solar constant, but very little use has been made of solar energy"

Summary: Wind Turbines on Canary Islands. A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator.