I had trouble locating the article I read -- it was about a year ago that I saw it, in a geoscience magazine -- which mentioned the prospects of geothermal energy for Texas. The advantage of geothermal over other renewable energies is that the energy source is more reliable, whereas the wind in Texas tends to blow strongest in the spring and fall, generally in the evening, and the sun can be intermittent and unreliable on a daily basis. Certainly geothermal energy is limited to areas where the temperature gradient is high enough that we can feasibly and economically drill down (< 6 km) to a good temperature (200 C at a minimum, 300 C is better). These requirements narrow the location down to Eastern Texas and Louisiana, as well as an extensive portion of the Basin and Range area of the Western United States.
Texas has literally thousands of holes already drilled in the land from old oil wells. In much of Eastern Texas, the article commented on how many of these wells happen to be artesian (that is, the water level naturally rises to the surface of the land). This would be advantageous for heat extraction. In geothermal energy, colder water is pumped from the surface down to depth where it heats up before returning to the surface. If the natural water level of the land is too far below ground there can be complications with obtaining enough fluid, controlling the flow of fluid, and increased cost of development.
It seems that while the technology exists to develop geothermal energy in Texas, there remain major hurdles in the permiting and regulations of such development. Additionally, were such a system to be developed on a large scale it would require significant investments in infrastructure to connect the source wells to urban energy demand. Of course, this is also a problem for wind and solar energy.
I will make a point of tracking down the article and posting it soon. In the meanwhile, does anyone else have much knowledge of geothermal? There may be other problems with its development, but there are case examples of geothermal plants in Nevada and California that have demonstrated successful and economical energy production for several decades now.
One worthwhile link if you are interested is: http://www1.eere.energy.gov/geothermal/