ABSTRACT
The Stirling engine has been identiŽed as an excellent candidate for conversion of solar thermal energy to electric power at the 500 W to 5 kW level. As for space applications, NASA has recently developed a system that will utilize Stirling engines for deep-space missions. Those engines are expected to run without the need for refueling or any maintenance for a period of 14 years, continuously. Attributes of the engine that make it a strong candidate for such terrestrial and space applications are its high efŽciency and the fact that heat is added to the cycle externally. Critically important to the performance of the cycle is the regenerator, a component within which thermal energy is extracted from the working ¨uid as it ¨ows from the hot end of the engine to the cold end and then returned to the working ¨uid when the working ¨uid proceeds back to the hot portion of the engine. Use of a regenerator greatly increases the Stirling efŽciency. It is the regenerator that is considered by many designers to be the critical component to target for improvement in the next generation of Stirling engine (and cooler) systems. A survey of performance for small (<100 We) engines indicates that regenerator thermal inefŽciency contributes 1.5% to engine thermal inefŽciency while pressure drop losses contribute about 11% engine inefŽciency.
