Stirling Motor

The Scottish pastor Robert Stirling had a hot-air motor patented in 1816 whose propulsion energy was not produced from burning or a small explosion within the working cylinders as in a conventional combustion or diesel motor, but rather the heat used for propulsion is applied from outside. Both of the coupled cylinders of the Stirling motor are sealed gas-tight and filled with a constant amount of the working gas (helium). One cylinder is heated from the outside while the other remains cool. The pressure difference between the two cylinders drives two interconnected and phase-delayed pistons. In this fashion the cooled gas can be pushed into the hot cylinder, where it then can expand, and hence drive the piston and then the process repeats itself.

Since research and technology have been more involved with the use of renewable energies, this older technology has come to the forefront. A Stirling motor can be directly heated from a solar collector or work as a motor in a Block-Type Thermal Power Plant (BTTP), which produces both heat and electricity at the same time. It runs clean, quiet and maintenance-free, and it reaches very high efficiency at an electric output of just 1 kilowatt.

Until now the hot-air motor has been more of an object for tinkerers than for industrial use. Small motors for BTTP’s will be serially deliverable in 2002. In conjunction with solar power systems and biomass heating, the Stirling motor counts as one of the peripheral useable electric power plants of the future.

Further information

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