December 12, 2007 | 6 Comments
Some readers might know what a Stirling engine is and how it works. For a pretty complete review of the history and engineering designs, some of which are in production today, see the Wikipedia – Stirling Engine.
Meanwhile, a Stirling engine most simply explained, is an engine that uses a working gas that travels back and forth between two cylinders warmed going one way to add energy and cooling while going the other using the difference in pressure to drive the pistons within into motion. For examples and animation see Wikipedia’s – Sterling Engine.
Air motors are designs that use compressed air to drive an output shaft. Some newer designs are extremely efficient and offer the real possibility of operating in a hybrid design in place of batteries. But the thermodynamic price, the heating of gas to compression and the cooling in expansion greatly diminish the efficiency. Undeterred by the thermodynamic issues some inventors will be offering short-range vehicles imminently, that while not solving the thermodynamic issue, offer low cost vehicles that have very low operating expenses.
These new designs just beg the question, could the Stirling engine principles be applied?
The problem of air motors with the thermodynamic losses and the matter that the compressed air needs a means to be compressed which uses energy might be neatly solved when the Stirling principle is applied to a pair of such motors.
In particular I am impressed by the near friction free design of Angelo Di Pietro of Brooklyn Australia. This design is reputed to be the current height of efficiency; minimalist and might very well offer a stunning Stirling principle opportunity. A pair of these astonishing little engines rigged with a regenerator (heat exchanger) and a gas heating system might offer a path to very high efficiency Stirling engines, which could be used in a broad array of applications. The small dimensions and likely, low cost manufacturing might even offer the prospect of a retrofit industry for current motor vehicle, construction and farm engines.
Another Stirling advantage is that the combustion is a continuous process that is much easier to build for efficiency and to control emissions. For example, your car might, in optimal form, be 25% efficient, but 95+% efficient furnaces are readily available. The technology and engineering to add the heat efficiently to a Sterling’s re-circulating gas is already in use. There is a lot of available gain if top air motor designs can be designed to work as Sterling engines. Please click on Mr. Di Pietro’s EngineAir site and offer encouragement.