The Soony is a new breed of heat engine. Not a Brayton, a Rankine, an Ericsson nor a Stirling – of these, it most closely resembles a conventional Stirling engine, which is perhaps the simplest form of engine and currently leads the market in heat engine efficiency.

Thermodynamic engineers have worked to fully utilize the known Carnot efficiency (maximum thermal energy) ever since it was first understood nearly two hundred years ago, and the Soony offers a major breakthrough.

Current leader in efficiency, the Stirling engine was invented by a Scottish minister in 1816, but the more powerful steam engines prevailed in the 19th century. As oil became available, Otto (current gasoline engine) and diesels were the 20th century engines of choice.

Now as the 21st century sees an end to fossil fuels and the rising threat of global warming, heat engine concepts have regained interest. Stirling engines run on multiple fuels and have the highest efficiency work output. Known for low noise, long life-span, reliability, and no CO² emissions – Stirlings are now used on spacecraft and submarines, as generators for large-scale solar electric projects, and may replace the internal combustion engine in hybrid cars. Although they suffer an ~30% loss of Carnot efficiency, Stirlings have been the most efficient engines – until now.

The Soony is truly a modern engine – designed to use solar heat as fuel to produce electricity, or to recycle otherwise wasted furnace, industrial or combustion engine heat as its generating fuel. Representing a breakthrough in heat engine efficiency of 15-25% over Stirlings, the Soony engine could help bring heat recovery and solar power into the mainstream market.