Thursday, November 30, 2006

Stirling Engines and Photovoltaics

One big advantage of systems that use Stirling Engines have over Photovoltaics is that many Stirling based systems have a battery built into the basic design. For example High Temperature Helostat and Dish systems use a salt-graphite mass at their focus as the hot-end block of their Stirling Engines. The mass behaves as a thermal battery

The state change temperature of salt from solid to liquid (molten) is 900 C. Like any solid to liquid state change, it absorbs a great amounts of energy. The physics of salt means that salt behaves in a constant desirable way between 600 C to 1500C. The thermal battery is heated by solar input during the day. Overnight, the Stirling Engine continues to draws off heat energy and generate power. The thermal battery's internal temperature falls accordingly. The follow days solar input reheats the salt graphite mass.

So these kinds of Stirling designs are potentially more cost effective for base load applications than Photovoltaics and Wind.


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