A new electrical power source for long term unattended operation

This paper reports results of research a t Harwell on thermal energy conversion, which began i n 1966 and has led t o t h e s u c c e s s f u l development of an e f f i c i e n t heat engine/alternator system capable of delivering s e v e r a l t e n s o f w a t t s o f a l t e r n a t i n g c u r r e n t w i t h a n efficiency much g r e a t e r t h a n t h a t o f a l t e r n a t i v e methods. This system has no r o t a t i n g or s l i d i n g s u r - faces, so requires no lubrication, and i s b e l i e v e d t o be capable of operating continuously for many years without wear or need f o r a t t e n t i o n . I t is capable of using heat from a v a r i e t y of sources and i s s e l f -s t a r t - ing on application of heat. Three electrically-heated research machines have been built and run, the third delivering an output of 27 w a t t s a .c . w i t h a n e f f i c - iency of 13.5%. Two development machines have been b u i l t and are running, one propane-heated and delivering 31.75 watts a .c ., and one with a r a d i a t i o n s h i e l d for operation with a radioisotope heat source, which delivers 18 w a t t s a .c . Both g i v e a n o v e r a l l e f f i c i e nc y of 10% including a l l l o s s e s from the heat sources.