The first part of this post focused on Photovoltaic Electricity. This post will take a closer look at Solar Thermal Electricity.Like solar cells, solar thermal systems use solar energy to make electricity. But as the name suggests, solar thermal systems use the sun's heat to do it.
Most solar thermal systems use solar collectors with mirrored surfaces to concentrate sunlight onto a receiver that heats a liquid. The super-heated liquid is used to make steam that drives a turbine to produce electricity in the same way that coal, oil, or nuclear power plants do.
Solar thermal systems may be one of three types: central receiver, dish, or trough. A central receiver system uses large mirrors on top of a high tower to reflect sunlight onto a receiver. This system has been dubbed a "solar power tower." Another system uses a dish-shaped solar collector to collect sunlight. This system resembles a television satellite dish. A third system uses mirrored troughs to collect sunlight. Until recently, trough systems seemed the most promising.
The world's first solar electric plant used mirrored troughs. LUZ, as the plant was called, was perfectly situated in the sunny Mojave desert of California. LUZ was the only solar plant to generate electricity economically. Dollar for dollar, it had always been cheaper to use conventional sources of energy (coal, oil, nuclear) to generate electricity. But the LUZ solar plant turned that around, producing electricity as cheaply as many new coal plants, and with no hidden pollution costs. The future looked bright for this pioneering solar plant and then the dream cracked. LUZ closed its doors at the end of 1992 because of a drop in oil prices and an over-budget construction project at LUZ's home-base.
The bottom line is...
LUZ may be gone, but most solar energy engineers believe solar power towers will be ready to take the place of trough systems very soon.
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