High Specific Power Multiple-Cylinder Free-Piston Alpha Stirling

NASA seeks highly efficient, long life solar dynamic power conversion systems. The requirements for these missions emphasize low mass and high conversion efficiencies. A reliable and highly efficient Stirling convertor would provide mission planners with less costly spacecraft power options than currently exist. Current Stirling technologies have demonstrated a beginning of life specific power level of 4.2 W/kg, and a useful life greater than 10 years. The proposed effort will result in the preliminary design for an innovative multiple-cylinder alpha free-piston Stirling engine (AFPSE) for high power applications. The program approach minimizes development risk by combining proven technologies, experiences and innovative concepts of Sunpower Inc. and Global Cooling BV (GCBV) with AFPSE. The proposed system is a compact, highly efficient, long life, low mass Stirling machine for a high power conversion system. This configuration having multi-pistons in separate cylinders connected by rejector and acceptor is not only very simple due to one moving part in one cylinder with no displacer, but also highly adaptable due to its versatile shape. This machine is very innovative because it is anticipated to achieve a specific power greater than 100W/kg as well as a heat input to electrical output conversion efficiency greater than 30%.