Any energy source, organism, or substance found in nature that people use.
An energy source that can be replaced in nature at about the same rate it is used.
Any energy source that exists in a fixed amount or that is used up faster than it can be replaced in nature.
A nonrenewable energy source formed from ancient plants and animals that were buried in Earth's crust for millions of years.
The process of protecting, restoring, and managing natural resources so they last as long as possible.
The process of recovering materials that ordinarily would be thrown away.
The process of splitting the nucleus of a radioactive atom, forming lighter elements and releasing a huge amount of energy.
Electricity produced by moving water.
A specially constructed sandwhich of silicon and other materials that uses sunlight as an energy source.
Energy produced by heat within Earth's crust.
Organic matter that can be used as fuel.
hydrogen fuel cell
A device that produces electricity by combining hydrogen and oxygen.