March 3rd, 2008
Stirling Cooler and Stirling Engine
The Stirling cycle machine, which can operate as either an engine or a heat pump, has aroused much interest because of its many favorable characteristics. These include:
- Minimal pollution. In the case of an engine, the exhaust gases are comparatively clean and cool.
- Silent and practically vibrationless operation in some configurations.
- Potential for low fuel or energy consumption. The maximum attainable efficiency or COP for any heat engine operating between the same temperature differential.
- Multi-fuel capability. The energy source may be almost of any form whatever, so long as it is available at a sufficiently high temperature. Stirling engines have been run on solar energy and a variety of liquid and solid fuels. This applies to heat pumping as well by the use of the duplex configuration.
- In many instances, it is possible to hermetically seal the machine thus eliminating problems arising from dirt ingress. Some of these configurations have demonstrated operating lives exceeding 10 years.
- Reversible operation allowing the same device to be used as an environmentally friendly wide temperature range refrigerator or heat pump. This feature also introduces the possibilities of regenerative braking.
- Reasonable specific power (currently between 0.067 kW(e)/kg for higher power engines down to 0.033 kW(e)/kg for lower power engines). As a low capacity heat pump (up to a few hundred Watts), the specific lift is considerably better than other heat pump technologies (30 to 40 W/kg).
- Favorable torque characteristics for transportation applications. This leads to simpler transmission designs.
- Mechanical simplicity. In some configurations gas bearings are easily implemented thus avoiding the need for oil lubrication.