Clean energy on the move

Lots of renewable energy in the news lately:

One: California is building two massive solar photovoltaic power plants, together big enough to generate 800 megawatts of power. To get a sense of the scale, consider that the current biggest PV installation in the U.S. has a capacity of 14 megawatts, and the biggest one in the world is a 23-megawatt Spanish installation. The new plant will roughly double the amount of solar PV in the U.S.

Two: Big box stores and grocery chains are getting in on the act. Hurrying to take advantage of tax incentives that expire at the end of the year, retailers like Wal-Mart, Safeway, and Whole Foods are decorating their rooftops with solar panels. Cumulatively, these efforts add up. Wal-Mart’s rooftop acreage roughly matches the size of Manhattan.

Joe Romm notes that the Times biffed this story a bit by implying that solar energy carries a high cost for retailers. In fact, the installations compare favorably with the retail electricity they displace.

Another small complaint: the article notes that retailers are combining solar panels with “other rooftop technologies like skylights and solar water heaters.” It’d be nice if these technologies got more than a one-sentence aside. Using the sun directly for heat and light can be a far more efficient than using it to generate electricity. These solutions deserve their chance to, ahem, shine.

Three: Speaking of technologies that deserve more attention, who doesn’t love a good heat pump? The Times takes a close look at a dead simple technology that can slash energy costs for buildings. Consisting of little more than some pipes run into the ground, geothermal heat exchanges provide warmth in the winter and cold in the summer, baseload power that is most available when it is most needed.

No surprise that geothermal systems are a booming business right now. Equipment manufacturers can’t keep up with demand, and the industry is hurting for trained installation personnel. Given the massive energy demands of building heating and cooling, it’s hard to imagine that geothermal energy won’t become an increasingly important part of the energy mix.

Four: Then there’s the big fancy kind of geothermal energy. Google has funded two companies working on “enhanched geothermal systems” that tap into super-hot rocks deep below the earth’s surface. Fun fact for the day: an MIT study estimates that “just 2% of the sub-surface heat in the U.S. at reasonable drilling depths would provide 2,500 times the country’s total annual energy use.”

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