Sodium heat pipe solar receiver for a SPS V-160 Stirling engine - Development, laboratory and on-sun test results

The design, laboratory tests, and on-sun tests of a heat pipe solar receiver for a Stirling Power Systems V-160 Stirling engine are reported. The heat-pipe-receiver-Stirling-engine unit has been tested successfully in the laboratory using an electrical radiant heater as a power source. Four different operating temperatures of the helium working gas from 625 C to 730 C have been tested. A steady-state performance evaluation was done for all four temperatures. Machine efficiencies (Stirling plus generator) at full power of 27 percent to 30 percent have been determined. Transient, start up and shut down behavior have been studied. Later the unit has been tested successfully in a 7.5 m diameter parabolic dish with an operating temperature of 700 C, where 8 kW net electric power output at 930 W/sq m with an aperture diameter of 120 mm have been reached. The receiver efficiency was about 83 percent at full power. The vapor temperature in the heat pipe was 40 K to 80 K above the operating temperature of the helium, depending on the power. Clear days with insolation levels up to 930 W/sq m as well as cloud passages at high insolation levels and startup from low temperature have been performed without heat pipe failure.