1ST STIRLING SOLAR POWER PLANT A GO

Stirling Solar Goes Live: How Does it Compare to Mirrors?; Sixty solar dishes go live in Arizona. Let the debate begin.
Michael Kanellos, January 23, 2010 (Greentech Media)

"Which solar thermal technology works best? The debate will soon begin in earnest...Developer Tessera Solar has created a 1.5 megawatt power plant out of 60 SunCatcher solar thermal devices from Stirling Energy Systems. Later this year, Stirling will go into volume production which will enable Tessera to break ground on commercial scale solar plants in California (one 750 megawatt plant and one 850 megawatt plant) and Texas (a 27 megawatt plant).

"The prototype 1.5 megawatt power plant comes after a few delays and a financial glitch for Stirling…[N]ow that the plant is up, Stirling will be able to compare the results its gets from its Stirling engines [with] heliostat prototype power plants erected by eSolar in Southern California and BrightSource Energy in Israel as well as parabolic trough systems…[already] commercially deployed…[Trough and heliostat technologies] collect solar heat on mirrors and use it to heat fluid. The warmth causes the fluid to expand, which creates pressure that gets exploited to crank a turbine."

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"The SunCatcher is made up of a giant parabolic dish of mirrors (40 feet across) to concentrate the sun onto a receiver called a "power conversion unit (PCU)." Sunlight heats up the hydrogen gas in tubes in the PCU, and the gas goes through a heat exchanger to run a four-cylinder Stirling engine. The engine then drives a generator to produce electricity…Stirling engines [go] back to 1816, when Robert Stirling in Scotland designed [and built] the first machine…to pump water from a quarry."

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"Each 25-kilowatt SunCatcher is its own mini electricity-generating unit…Stirling has claimed that its system is the most efficient: a prototype converted a record 31 percent of the energy striking it into electricity. Stirling engines, however, transfer heat through the air. The others transfer heat through liquid. As a result, [the SunCatcher has no] mechanism for storing heat…Which one of these works best in which sort of environments will be one of the big issues for the solar thermal world.

"And there are other solar thermal ideas emerging as well: HelioFocus (high temperature Stirling engines linked directly to turbines)…beam down concepts…[and concentrating photovoltaic concepts]…"