Although the analysis presented in Chapter 7 is highly idealized, it is quite appropriate for providing some insight into the geometrical requirements of the ultra low temperature differential Stirling engine illustrated in Figures B.1–B.3. Nicknamed the P-19, this engine has proven itself capable of operating down to a temperature difference of just 0.5 °C (less than 1 °F) between its warm and cool sides. The P-19 was the first to run from heat absorbed while resting on the palm of a human hand. The P-19 was first publicly demonstrated at the 25th Intersociety Energy Conversion Engineering Conference held in Reno, Nevada, in August 1990.

BACKGROUND

A low temperature differential (LTD) Stirling engine may be characterized as one that operates more or less optimally with a temperature difference of less than 100 °C between its hot and cold end. Ivo Kolin was the first to design and build such an engine. At the Inter-University Center in Dubrovnik in 1983 he demonstrated the first of his engines operating with hot water as the heat source and cold water as the heat sink (Kolin, 1983). The engine continued to run until the temperature difference between the source and sink dropped to 15 °C.

Kolin's first engine inspired a number of research projects over the next decade to further develop LTD Stirling engines (Senft, 1996).