I wish I could tell you that the following story happened when I was a kid, but it actually happened just a few years ago. We were back home at the family farm in Oklahoma, and my Dad had a magnifying glass that he used for reading. I liked playing with magnifying glasses as a kid, so I took my (then) 8-year-old son outside and started showing him how it worked. There was a pine tree stump in the yard, and we rigged the glass up in stationary fashion so that the sun burned a black line across the stump as it moved across the sky. We both thought this was very cool, as it indirectly showed the sun’s movement across the sky, and it also showed just how powerful the sun can be.
We did this off and on for a couple of days. One day, I heard my Mom ask “Is something burning?” Oklahoma was in the midst of a drought, and I walked outside to see the pine stump on fire, and the grass in the yard burning. The magnifying glass was a melted mass on top of the pine stump. After putting the fire out, I thought “Wow, a few large concentrating mirrors could provide a lot of energy in a small space.”
This is of course one of the applications of solar thermal energy. A number of companies are in the process of building solar thermal plants, including Nevada Solar One with their 64 megawatt plant in Nevada. While this will be the largest solar thermal plant to be constructed in over 10 years, the largest solar thermal plant in the world is a 350 megawatt plant in California’s Mojave Desert, run by Solel from Israel. Solel is also building the Mojave Solar Park, which is scheduled for completion in 2011, and will supply 553 megawatts of electricity to the citizens of California. (I presume that the 553 megawatts is in addition to the 350 megawatts of presently installed capacity).
As far as costs, Solel’s FAQ states:
Even without pricing cost externalities, the cost of solar thermal power is going down. Currently, the cost of solar thermal produced energy can be close to 12 cents (US) per k/Wh. However, many economists and investors predict that this price will continuously drop over the next ten years with increased installed capacity, to 6 cents per kW/h, as a result of technological improvements, economies of scale and volume production.
Additional information may be found at the EIA’s page on solar thermal.