And Ausra, headquartered in Palo Alto, California, has perhaps the most promising solar thermal design we’ve ever seen.
Solar thermal power uses mirrors to reflect sunlight onto heat exchangers, in order to heat a thermal transfer fluid to drive a turbine, which turns a generator to produce electricity. Only about 500 megawatts of solar thermal power capacity exist in the world today, most of it at Kramer Junction in California’s Mohave Desert.
Compared to total worldwide energy production, solar thermal electricity production is negligible, only about one 20th that of photovoltaic energy production, which itself represents less than one-twentieth of one percent of worldwide energy production. But this is about to change, and solar thermal technology will race photovoltaic technology neck and neck, as together they grow to a significant share of global energy production.
There are three basic ways to concentrate solar energy - one is a “power tower” where a boiler sits atop a tower surrounded by 2-axis tracking mirrors that each individually move each day to reflect the sun’s light onto the boiler. Another design is a field of parabolic mirrors, each of them equipped with a 2-axis mechanism to track the sun all day, with each of them having a heat exchanger positioned at a single reflective focal point a few feet away from the center of the dish.
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