Energy
The power to perform work, produced from natural phenomena (e.g., the Sun and the wind) or raw materials (e.g., coal and petroleum).
GEOTHERMAL AND FOSSIL ENERGY
Geothermal energy uses the Earth’s internal heat and is a renewable energy source; fossil fuels such as coal and petroleum are nonrenewable energy sources.
HYDROELECTRICITY
A nonpolluting renewable energy source, hydroelectricity accounts for 20% of the electricity consumed around the world.
NUCLEAR ENERGY
Large quantity of energy that is released in the form of heat; this occurs during a nuclear reaction (fission of atom nuclei). The heat is used to produce electricity.
SOLAR ENERGY
Harnessed solar radiation has many applications, including solar-panel heating and electricity produced with solar cells and solar furnaces.