Experimental study on Stirling engine generator and solar receiver system for future space applications

A fundamental study on solar Stirling power generation system has been performed as a part of the space solar power technology program in National Aerospace Laboratory (NAL). The research work involves both a solar receiver and Stirling power generation technologies. The former work is focused on developing a high efficiency solar receiver for future space energy experiments on the Japan Experiment Module-Exposed Facility of the International Space Station. It is composed of a cavity receiver, thermal energy storage and sodium heat pipes, and aims at transporting solar heat to a bottoming system with the minimized heat loss. A ground test model of the solar receiver will be experimentally evaluated in NAL. In parallel, semi-free piston Stirling engine generators have been experimentally studied as one of the candidate converters for future space power generation. Through a series of bench tests, the thermodynamic efficiency of 32% and system efficiency of 20% was obtained. Based on these achievements, the design work for an improved Stirling generator system is underway.