Peter Lynn ARCHIVE
This is a core engine/generator and individual components from a Whispergen CHP (combined heat and power unit). It comprises four cylinders disposed axially around the generator shaft and driving it via a 'wobble yoke'. An original invention by Donald Clucas, the wobble yoke is mechanically efficient, has a long life and enables 100% engine balance. The four finned cylinder heads are machined from solid billets of a creep resistant alloy able to operate at 700 Celsius. These cylinder heads were very expensive to manufacture not least because of their internal fins- visible in the separate head in this display.
The equivalent total swept volume (capacity) of this engine is 0.17 litre. Fired by gas or diesel, and running at between 1500rpm and 2000rpm it could generate up to 1kw of electricity (DC or AC depending on the model). Water heating capacity was 8kw from the engine exhaust plus an additional 5kw from a booster.
Stirling engines are external combustion engines that operate on a closed cycle.
A volume of working fluid (nitrogen at 28bar in this case) is alternatively heated and cooled at engine speed, causing pressure differences that drive the pistons.
History: Ashburton born engineer Don Clucas began working on this design in 1988 for his PhD. CHPs have a fuel-efficiency advantage over direct water heating systems because the 1000+degree available from combustion is applied first to the engine (which drives the generator). The engine's exhaust is then used for water heating (which can't efficiently use temperatures much above 100 degrees). CHP's (the 'power station in your kitchen') also reduce the losses and costs inherent in national electricity grid systems.
As the design took shape, the project moved from Ashburton to Christchurch and investment for commercialisation became available from electricity companies.
After considerable development by a large team of engineers, manufacture of AC (domestic) and DC (boat) CHPs for sale began around 2000.
Manufacture ceased when sufficient sales failed to materialise after the 2008 world financial crisis.
Peter Lynn for the Roger Mahan Heritage Centre, July 2023.
