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Saving for a Rainy Day

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Science  18 Nov 2011:
Vol. 334, Issue 6058, pp. 922-924
DOI: 10.1126/science.334.6058.922

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Summary

The fickleness of sunlight, like the unsteadiness of wind, poses a major obstacle for renewable energy. Grid operators can take up the slack with fossil fuel or nuclear plants, but that limits the contribution of wind and solar plants. In principle, batteries could store such renewable energy, but they remain very expensive. Instead, the Andasol complex in southern Spain hoards its raw product: heat. Its "batteries"—three pairs of metal tanks containing molten salt—hold enough energy to generate electricity for about 7.5 hours, allowing the plant to provide almost round-the-clock electricity during the summer. Experts say storage systems could help concentrating solar power clear another major hurdle: cost. Increasing output by being able to generate electricity after sunset will reap economies of scale, experts say. Capital costs must also be reduced. Cheaper, simpler mirrors will be essential, as well as improved storage technology.