
Various meanings of the term free energy include:
In engineering fields related to power generation, free energy means an energy source available directly from the greater environment and which cannot be expected to be depletable by humans. Free energy in this sense may be categorised as renewable energy, although most renewable energy sources would not normally be called free energy sources.
Free Energy Wikipedia
Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels. Typically, official uses of the term, such as qualification for governmental incentives, exclude fossil fuels and nuclear energy whose undesired consequences are high carbon dioxide emissions, the major contributing factor of global warming according to the Intergovernmental Panel on Climate Change, and difficulties of radioactive waste disposal. Over the years, the nature of what was regarded alternative energy sources has changed considerably, and today because of the variety of energy choices and differing goals of their advocates, defining some energy types as "alternative" is highly controversial.
The term "alternative" presupposes a set of undesirable energy technologies against which "alternative energies" are opposed. As such, the list of energy technologies excluded is an indicator of what problems that the alternative technologies are intended to address. Controversies regarding dominant forms of energy and their alternatives have a long history.
Alternative Energy Wikipedia
'Blue energy' seems feasible and offers considerable benefits PhysOrg - October 30, 2009
Generating energy on a large scale by mixing salt and fresh water is both technically possible and practical. The worldwide potential for this clean form of energy - 'blue energy' or 'blue electricity' - is enormous.
Powering a Green Planet: Sustainable Energy, Made Interactive Scientific American - October 27, 2009
'Smart Grid' Gets $3.4 Billion Jolt Live Science - October 27, 2009
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