Wiktionary
n. 1 Energy derived from any source other than fossil fuels 2 Energy derived from any renewable source; i.e other than fossil fuels or nuclear fission
WordNet
n. energy derived from sources that do not use up natural resources or harm the environment
Wikipedia
Alternative energy is any energy source that is an alternative to fossil fuel. These alternatives are intended to address concerns about such fossil fuels, such as its high carbon dioxide emissions, an important factor in global warming. Ocean, wind and solar power are some sources of alternative energy.
The nature of what constitutes an alternative energy source has changed considerably over time, as have controversies regarding energy use. Because of the variety of energy choices and differing goals of their advocates, defining some energy types as "alternative" is considered controversial.
Alternative Energy is a symphony for electronica and orchestra in four movements by the American composer Mason Bates. The work was commissioned by the Chicago Symphony Orchestra, for whom Bates was then composer-in-residence. It was premiered by the orchestra under conductor Riccardo Muti at Symphony Center in Chicago, February 2, 2012.
Usage examples of "alternative energy".
They get some energy through my skin, from sunlight, and they release any glucose they can spare-but that's not nearly enough for me to live on, and they need an alternative energy source when they're in darkness.
Thorny was going to NA---Narcotics Anonymous--and volunteering at a local recycling and alternative energy company.
Like medical research, alternative energy sources, the space program .
There are a host of alternative energy sources just waiting to be adopted.