Thursday, September 10, 2009

The Sun or the Atom

It looks like we might finally see a solar power installation built on a large enough scale to enable meaningful comparisons between it and our current largest low-emission energy source, nuclear power. Tuesday's announcement by First Solar, Inc. that it had negotiated a memorandum of understanding with the Chinese government to install up to 2,000 MW of capacity in Inner Mongolia could take solar out of the world of rooftops and into direct competition with central power plants. It also provides an opportunity to assess this technology on a more consistent basis with our other full-scale energy options, even if it's clear that they ultimately serve somewhat different portions of the power market.

For years I've been reading suggestions for covering large swaths of desert with solar panels, and this looks like the largest realistic proposal so far, involving 25 square miles of desert near the city of Ordos, China. While the Desertec project in North Africa might ultimately be much bigger, that still looks like a much more remote possibility, at this point, though it was also clear from First Solar's press release that their project in China will start at a modest scale of 30 MW and work its way up from there. I can't help wondering if some of the project's later phases might be contingent on continuing to reduce the cost of solar power from today's levels. As I noted recently, even with solar module costs below $1/Watt for First Solar's thin-film technology, non-module costs can still push total installed costs above $4/W. That would put the Ordos project in roughly the same category as a new nuclear power plant in terms of total cost, not just notional output.

And while we're looking at output, we ought to consider how comparable an installation of 2,000 MW of solar panels anywhere on earth would really be to two coal-fired power plants, as was mentioned in several news reports on this story. Although I couldn't find data specifying the actual annual number of peak-sun hours for Ordos City, a glance at this solar irradiance map of China suggests that this location gets around 6 kW/m2/day, equal to 6 peak-sun hours per day, on average. That gives this project an average capacity factor of 0.25, which means that 2,000 MW of peak solar power would generate roughly the same amount of electricity annually as one 700 MW coal-fired power plant or a single 550 MW nuclear power plant, if there were such a thing. Perhaps this project's biggest benefit is in its scalability. Unlike a new nuke, which would probably take about as long to build, the Chinese won't need to wait until the project was completed in 2019 to get useful electricity from it. Each sub-project would stand on its own, and the first one could start generating within a year or two.

On balance, then, this huge solar project could produce as much peak power as a pair of nuclear power plants (or large coal-fired plants)--though still quite a bit less than either of those technologies over the course of a year--while costing about as much as one large nuclear reactor, even allowing for significant cost improvement between the time the first and last solar panels are installed. How useful such a facility will be is largely a function of whether that region of China has a greater need for lots of power when the sun happens to shine, or reliable power around the clock. I'm as pleased as anyone that China appears to be diversifying its energy mix away from coal, even to a modest degree, and there's certainly nothing about building such a facility that precludes expanding nuclear power, since in the long run the country is likely to need lots more of both. Still, in terms of bang for the buck and without factoring in what this one project might do to help bring down the cost of solar power elsewhere, it hardly seems an obvious choice.

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