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A prototype 30-kW Stirling engine on test.

Infinia, under the CSP R&D FOA, is developing a 30 kW CSP system that utilizes a multi-cylinder, free-piston Stirling engine to achieve the goal LCOE of $0.07–$0.10/kWh by 2015 and $0.05–$0.07/kWh by 2020.


Infinia is taking a three-phased approach to creating an efficient, cost-effective, and highly reliable Stirling engine:

  • Phase I – Provide prototype engine preliminary design and preliminary LCOE estimate
  • Phase II – Build and demonstrate a 30-kW engine laboratory prototype
  • Phase III – Deliver and field test a production-like, prototype 30‑kW Stirling engine

A prototype 30-kW Stirling engine on test.


The Infinia design is a free-piston system utilizing helium as the working fluid. Two pistons suspended on springs are configured in a double-acting, circular arrangement. There are no cranks and no contact or wear upon surfaces, and phasing and tuning is done through the springs. Leak rates are kept sufficiently low, and this solid-state power conditioning leads to a breakthrough in reliability and durability, requiring virtually no maintenance.

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