The Stirling engine as a multifunctional talent.

While our machine on the test bench had just provided more than 7 kW of electrical power as a generator set, we wanted to know how it behaved as a refrigeration machine and as a heat pump. We removed the burner assembly and had a clear view of the machine’s heater heat exchanger. We used the asynchronous generator as a drive motor and started the machine with the same direction of rotation with which it was previously operated as a generator. The effect was impressive: within a few minutes, the temperature on the heat exchanger dropped to minus 160 degrees C and turned into a block of ice.

Then we allowed the machine to rest for a few hours in order to be able to return to ambient temperature without thermal stress. After reversing the polarity to the opposite direction of rotation, we started the unit again and shortly afterwards were able to measure more than 750 degrees C on the heat exchanger. The radiation temperature was so high that we had to take a step back. We have not yet determined the COP value at which the conversion of electrical energy into thermal energy takes place. If this value is significantly greater than 1, we would have created the basis for energy-saving charging of thermal storage and could at the same time use the cooling capacity on the cooler side to air-conditioning of buildings. An exciting topic…