Xcel switches on hybrid solar-coal power plant - Minneapolis / St. Paul Business Journal
The mirrors focus the sun’s heat on a line of tubes filled with food-grade mineral oil. The oil is heated to about 575 degrees Fahrenheit, then the heat is transferred, heating water to about 360 degrees, according to Xcel.
The project includes eight rows of mirrors, 500 feet long, covering 6.4 acres, according to Xcel (NYSE: XEL).
The solar-heated water then is transferred to the 49-megawatt power plant’s existing coal-fired boiler, and heated to higher temperatures to produce the steam needed to spin turbine blades that generate electricity. Using solar-heated water cuts the amount of coal needed to produce steam, according to Xcel.
The combined, integrated use of solar power and coal is expected to increase the power plant’s efficiency by up to 5 percent, reduce the use of coal by 900 tons per year, and cut the plant’s carbon dioxide emissions by 2,000 tons per year.
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