Stirling engine manufacturer Infinia closed a $50M series B investment with a veritable who’s who of funders including: Vinod Khosla’s Khosla Ventures, Bill Gross’ Idealab and Paul Allen’s Vulcan Capital. The firm intends to use the funding to accelerate the productization of their stirling engines attached to generators for use in large scale solar thermal installations.

So what is a stirling engine anyway? It’s a loose piston setup that works on temperature differential between the two sides of the piston. Just like a regular piston engine, that reciprocating stroke can be transformed into rotation with torque. The novel approach in this case is to concentrate the sun’s heat and use that to generate the heat differential required to make the engine run. These engines have been around since the early 1800’s when Robert Stirling advanced the concept. See the illustration to the right from the Infinia website.

Infinia Unit Components

Each unit is rated at just over 3kw AC and are projected to list at around $20,000 per unit. It is believed that standard automotive parts manufacturing techniques can be used to fabricate the Infinia units. Operational costs associated with the units is believed to be low as stirling engines are low friction devices with relatively few moving parts and very loose tolerances used in design and assembly. As with all technologies, the cost should come down as the volume goes up.