Great article by William Tucker at The American Spectator about the myth of "renewable" energy. Energy isn't "renewable", even the Sun will run out of energy someday. The First Law of Thermodynamics posits that energy can neither be created or destroyed, it merely changes form. Great, but the Second Law of Thermodynamics posits that when energy being used to accomplish work, some of it becomes unrecoverable - to things like friction.
"In the process, however, some of the energy inevitably becomes inaccessible as "waste" or low-grade heat. Once dispersed, this energy achieves a state of high disorder or entropy. It cannot be reused, renewed, or recycled because it would take more energy to reassemble it than could be recovered."
Tucker further points out that when people talk of "renewable" energy sources, what they really mean are "inexhaustable" sources of energy. In effect, most sources of energy are related to the sun. Obviously solar power comes from the sun but also drives the water cycle, the wind, and is ultimately responsible for plant growth and thus most conventional fossil fuel energy sources derived from the breakdown of plants into petroleum and natural gas.
Solar has its uses - it is available when the need is the greatest, hot summer days, and could definitely aid us ona small scale. However, it doesn't really arrive in truly useful amounts, the kind that could be used for industrial scale purposes. Of course, we use fossil fuels for much of that, but waiting millions of years for these to be replenished isn't practical either, and there are those pesky byproducts, pollution and carbon dioxide. Biofuels aren't really a great answer either, because they compete with the alternate use of the crop as food, and buring them also releases those same pesky byproducts.
The one resource available to us that is nearly inexhaustable is that of the planet itself. Both geothermal energy and its artificially contrived corollary, nuclear power, are derived from the natural (or forced) breakdown of radiactive elements like uranium and thorium. The heat derived from these sources is transferred to water and used to drive electrical turbines. This source of energy is the only one known not dependent on the sun or solar energy stored in carbon bonds, thus it does not releasing any carbon into the atmosphere when utilized. Nuclear power is definitely the most ecofriendly of all conventional and non-conventional sources. Of course, it is also one of the most vilvified by certain segments of society, unfortunately.