Senft’s work (Senft, 1991) showed the motivation in the use of Stirling engine. Their target was to develop an engine operating with a temperature difference of 2 C or lower. Senft (1993) described the design and testing of a small LTD Ringbom Stirling engine powered by a 60 conical reflector. He reported that the tested 60 conical reflector, producing a hot end temperature of 93 C under running conditions, worked very well.