Green | February 18, 2009 | 11 comments

How to Use Solar Power...at Night?

source: http://www.sciam.com/article.cfm?id=how-to-use-solar-energy-at-night

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Near Granada, Spain, more than 28,000 metric tons of salt is now coursing through pipes at the Andasol 1 power plant. That salt will be used to solve a pressing if obvious problem for solar power: What do you do when the sun is not shining and at night?

The answer: store sunlight as heat energy for such a rainy day.

Part of a so-called parabolic trough solar-thermal power plant, the salts will soon help the facility light up the night—literally. Because most salts only melt at high temperatures (table salt, for example, melts at around 1472 degrees Fahrenheit, or 800 degrees Celsius) and do not turn to vapor until they get considerably hotter—they can be used to store a lot of the sun's energy as heat. Simply use the sunlight to heat up the salts and put those molten salts in proximity to water via a heat exchanger. Hot steam can then be made to turn turbines without losing too much of the original absorbed solar energy.

The salts—a mixture of sodium and potassium nitrate, otherwise used as fertilizers—allow enough of the sun's heat to be stored that the power plant can pump out electricity for nearly eight hours after the sun starts to set. "It's enough for 7.5 hours to produce energy with full capacity of 50 megawatts," says Sven Moormann, a spokesman for Solar Millennium, AG, the German solar company that developed the Andasol plant. "The hours of production are nearly double [those of a solar-thermal] power plant without storage and we have the possibility to plan our electricity production."
  1. groups:
    Green,   Earth and Science,   Solar Energy
  2. tags:
    Green,  Earth and Science,  Environment,  Climate Change,  3 more
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