Douglas Fischer of The Daily Climate has a great article about the growing popularity of concentrated solar thermal plants, which use mirrors to focus the sun's rays on pipes carrying oil or other heat-absorbing liquids in order to make steam, which can then power a turbine. Already some 60 projects are underway around the world, which would provide more than 5,500 megawatts of power—about ten decent-sized coal plants. It's a healthy start. As we've discussed before, solar thermal has the potential to provide a sizeable amount of carbon-free electricity, especially since it suffers from fewer intermittency problems than photovoltaic systems do—you basically take any excess hot oil and put it in a heat sink (say, a vat of molten salt), which can then be tapped for steam later when the sun stops shining. It's an efficient sort of battery.

Of course, there's the cost. As Fischer notes, a coal plant delivers baseload electricity for about three to five cents per kilowatt-hour, though that obviously doesn't include the considerable cost of carbon-dioxide emissions and other pollutants. Solar thermal, at least for now, produces electricity for about 18-21 cents per kilowatt-hour. But, in the absence of a price on carbon, solar thermal isn't competing with coal; it's competing with natural-gas peaking plants, which cost roughly the same amount and usually just run during the day when electricity demand is at its highest—precisely the time when solar thermal plants are operating at their highest capacity. So there's a lot of room for growth right now, even in the absence of a carbon policy framework (though, to be sure, plummeting gas prices throw a kink in the works). Plus, they look so darn futuristic.

--Bradford Plumer