Infinia 3kw Solar Stirling Generator

Infinia 3kw Solar Stirling Generator

Engine number: Y115, made in 2010.

Made by: Infinia Corp. Kennewick, Washington State, USA. (2007 to 2013).

Height with tower: 6.4metres

Mirror diameter: 4.7m

Weight: 864kg

Cost in 2010: US $20,000 (introductory offer).

Infinia was founded in 2007 with US $50 million capital from various venture capital investors.

Its business plan was to develop and manufacture solar Stirling generators of around 3kw to suit domestic and small holding purchasers that would be 20% to 30% more cost effective than photo voltaics (solar panels).

 The engine at the heart of this development was a free piston Stirling engine the same as the Y176 stand-alone engine in this collection.  These engines are the result of many years of development starting with William Beale’s 1964 invention of the free piston Stirling engine and progressing through huge effort by NASA who were interested in their potential use for deep space probes using isotope heat sources. 

 NASA developed their contactless seals- with fits so exact between the piston and displacer and their respective cylinders that there is no leakage- and no contact.  This enables an oil-less environment and more than 15 years of continuous running without maintenance.

Infinia engines are welded closed during manufacture and cannot later be opened.  They are charged with Helium at 55 bar and this one is still holding at more than 50 bar after 15 years.   Compared to other Stirling engines, especially 19th century ones, Infinia free piston engines have impressive output for their size and impressive efficiency: 24% claimed. 

Although the contactless seals are an amazing technological achievement, with the piston and displacer held to precise straight-line motion solely by supporting springs, they can be easily damaged by dust, asymmetric thermal changes and shock loads.  The stand-alone Infinia engine (Y176) in this collection ran briefly here before seizing- presumably because of contact between the seal surfaces (It will probably now become a cutaway engine).   

Unfortunately, reducing prices for photo voltaics (solar panels) made Infinia solar Stirling generators uncompetitive and they were not a commercial success (a common story for Stirling engine projects).   Infinia Corp closed in 2013, with their designs and IP moving to Qnergy, an Israeli company with a presence in the US- who have found commercial applications for these free piston Stirling engines, though not in the solar thermal field. 

Peter Lynn for the Mahan Heritage Centre 2025