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I've read a bit about Solar PV, Wind Turbines and Hydroelectric in this thread so far, but there's a technology from the 17th century slowly making a comeback in some of the hotter parts of the world...Solar Thermal energy.
There's currently a plant just outside of Barcelona created to be a massive Solar Oven, just like the cheap boxes that cook food you can make for about $10-only instead of cooking your food, this one supplies energy. The Tech is simple, efficient and non-polluting-massive, heat-absorbent towers full of water are surrounded by rows of reflective surfaces to focus and maximize the effect...the resulting superheated steam(comparable to the results we get from Fission) drive turbines for rather respectable amounts of power. During the night, insulated tanks full of pre-heated boiling water (which were siphoned from the Daytime loads) drive the turbines in a continuous load.
The plant has been considered quite a success by the Spanish government, and a second plant is under construction-the Backup Tanks are using a "milkshake" of heavy Salt/liquid Slurry this time for a more even Thermal Absorbtion/release curve than the previous model...
Then there's the Australian plant under way soon, pretty much a Greenhouse Funnel. Transparent panels will allow the Desert's rays to superheat the air in an area about a mile across, where it will rise through a gradually narrowing aperture, gaining speed from the compression as it goes...by the time it exits the six-foot wide aperture at the top, the air will be at near-Hurricane speeds. The entire last hundred yards of this 'throat' will be lined with Industrial reinforced Wind Turbines. In theory, energy production should completely cease about twenty minutes after Sunset-but the Daytime output is supposed to be tremendous! Guess we'll find out the results in a few more years on that one...
I suspect that Thermal Mass is going to get some long belated respect from architects in the next few years, as it's still the best way to regulate Temperature in a dwelling. As to existing structures, Geothermal might make a bit of a comeback-and i'm not talking about active heat sources here, i'm talking about the ground's tendency to remain at a steady temperature! Several designers have Retro-fitted existing structures with about 1000 yrds or so of PVC, buried about 20 ft underground and then tied into a high-efficiency heat pump...this results in a steady-state temp of 65-70F all year for very little energy!
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