Wow - the difference between solar thermal and biofuels on one hand, and solar PV and wind on the other, is striking. The water intensity of biofuels is widely recognized (1, 2, 3), but and the solar thermal/water one had never occurred to me before (and I think about resource interdependencies a fair amount).The losses, illustrated through interesting anecdotes from Nevada and California in this NYT story, come from the evaporation that happens when steam, heated to turn a turbine, is "wet cooled" to become water again (and be reused). Unsurprisingly, "dry cooling" technology exists, and costs:
An alternative, dry cooling, uses fans and heat exchangers, much like a car’s radiator. Far less water is consumed, but dry cooling adds costs and reduces efficiency — and profits.There is also an effort to use reclaimed water in California, but this also adds costs (and takes energy, if the reclaimed water is available in a different location).
Given the increasingly looming water shortage in many parts of the world, this will certainly dampen any warm and fuzzy feelings I might associate with CSP.
Hat tip to Environmental Economics, which notes sagely that "True water pricing would push RPS portfolio to wind over solar." The chart is from this presentation.
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