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.

ECONOMIST: A more efficient way to make electricity in spacecraft

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.

FORBES: A Comeback For Infinia's Solar Power Heat Ray?

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.

CNN: Lab develops engine for the future