Solar Thermal Waste Heat Engine works at low temperature, low pressure

The compact, lightweight 18 lb (8 kg) Waste Heat Engine is a six-cylinder radial steam engine capable of running on waste heat as low as 225 °F (107 °C) and pressure as low as 25 psi (172 kPa). The engine achieves maximum efficiencies at 600 °F (316 °C) and steam pressure of 200 psi (1.4 MPa), at which point one Waste Heat Engine can generate 16 hp (12 kW), 30 lb-ft (41 Nm) of torque, and a little over 10 kW of electrical output. The only drawback is the typically low 12% energy efficiency common with most reciprocating steam engines. On the plus side the piston-based steam engine operates at a maximum of 3000 rpm which means it is well suited to drive any standard generator.

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