Wind power isn't the expensive. Generating costs in a wind-driven turbine are about 4-5 cents per kilowatt-hour, about the same as the generating costs in coal and natural gas plants. Only geothermal energy, at 3-8 cents per kilowatt-hour, is potentially cheaper.
Advances in wind energy have been quite remarkable over the last thirty years or so. In 1980, yeah, wind power was ridiculously expensive - however, larger, more efficient turbines and a greater understanding of where and how to place wind farms has made wind power much more financially feasible.
Double check your wind power source. If you are reading the same sites I am, there is one key statement you missed. It's subsidized. The government is taxing people like you and me, to make wind power economically tenable. Without them blowing our taxed money on it, wind power isn't even remotely cheap.
But not only is wind power subsidized, it's also cost shifted. The renewable energy credit system requires that your electric company purchase renewable energy credits, which are paid to the source, even if the electricity from the source goes elsewhere. That cost, of course, is past on to us. So we actually pay for Wind Power and any renewable energy source, twice over. Through taxes, and increased electric bills.
The biggest issue with wind power is, even if it were cheap, it still can not replace a conventional power generation. Let's say that the wind is blowing hard, and the mills are spinning. Can the coal power plant, or gas power plant shut down? Even for a second? No. Because if they did, and the wind died for even a moment, the state would have a black out. Conventional power plants take 15 minutes to an hour to come up to full power. Wind on the other hand can go from full to zero in seconds.
So even when the wind generators are at full bore, the conventional power plant must remain in running standby, resulting in no saved 'fossil' fuel at all.
Direct solar energy is expensive (especially photovoltaic cells), but I'm given to understand that research into solar thermal electric generation has been promising.
True. Israel has had huge success in this area. But then, there are some key differences. Solar Thermal Power requires a huge area covered with reflective mirrors... like say a country that's mostly desert... not the US. Second, it requires tons of direct sunlight with little obstruction, like a desert country near the equator, not most of the US with cloud cover. Third, it still is more costly, unless you live in a country with very few natural resources, like Israel, not the US.
Effectively, there are only a few places where power generation could happen with good long term efficiency. New Mexico, Nevada, Texas, and even then, it would only produce a fraction of the US usage.
The amount of electricity produced by current techniques is small, yes. However, scientists estimate that 1% of the heat contained in the uppermost ten kilometeres of the Earth's crust is equivalent to 500 times the energy contained in all of Earth's oil and natural gas resources. That's a massive amount of energy, yet geothermal energy accounts for less than 1% of the world's energy generation. Clearly the problem doesn't lie in whether or not the energy is there - it lies in our ability to effectively harvest it. We rely on geysers and other underground water sources to produce electricity using geothermal energy. The discovery/development of a way to extract energy from dry, hot rocks in the crust would revolutionize geothermal energy.
http://en.wikipedia.org/wiki/Hot-Dry-Rock#Enhanced_geothermal_systems
Personally, it's my pick for the energy of the future. At least, the forseeable future.
It's ironic really, that my position on this, reverses to the eco-nut crowd. Eco-nuts are scared because CO2 is going to cause global warming and wipe out the planet. I've looked at that so many times and each time I think it's a fruity theory completely unsupportable based on scientific evidence.
Yet on this, eco-nut (not specifically you, just in general) think it's cool, but this system... concerns me. I'm not sure I like the idea of messing with the thermal workings of the Earths crust. On your link, it mentioned that the largest EGS system in Aussieland, caused repeated earthquakes, which seems to validate my hesitancy.
Using a pre-existing geothermal vent, like near geysers, is one thing, because it already existed naturally. Which ironically is banned since building the power plant will tap the energy powering the natural geysers, and causes them to stop.
But I am not so hot on the idea of drilling down to the earths crust to artificially cool tectonic plates for power generation purposes. Could there be a long term effect of doing this? Could it cause a break in the plate resulting in a new volcano? Could it cause huge earth quakes if the steam vented sideways? Could it cause thermal stress in the plate, possibly, God forbid, causing the plate to crack or break? I don't know enough about this topic really, but I am concerned.