Like fuel cells, another 19th-century invention that promised more than it delivered, the Stirling engine has been a device in search of an application.

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In an off-grid village in India, for example, biogas from an anaerobic digester could be burned to drive the Stirling engine to generate power.

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In the conventional Stirling engine, a fixed amount of helium is compressed in a cool chamber and then transferred to a chamber heated by an external burner.

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So Ford modified the system for the Wayne plant, substituting a Stirling engine for the fuel cell.

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But the heat-driven Stirling engine design opens up possibilities for alternative fuels.

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The concept behind the engine derives in part from a principle outlined by Robert Stirling in 19th century Scotland.

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One option is to combine a Stirling engine with a solar concentrator resembling a satellite dish that can harness the power of 1, 000 suns.

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