Solar energy application a stirling engine

In this study, an experimental setup was constituted for solar energy application of a beta type Stirling engine developed in the project supported by The Scientific and Technological Research Council of Turkey (TUBITAK). The experimental setup was consist of a Stirling engine, a fresnel lens, a platform and test equipments. Solar radiation was directly focused into a cavity taking part at the top of displacer cylinder. Performance tests were conducted with three different cavities made of copper, aluminum and stainless steel. For copper cavity the maximum power, torque and thermal efficiency were obtained as 22 W, 1.09 Nm and 2.95 %, respectively at 4.7 bars charge pressure and 185 ºC hot end temperature of the displacer cylinder. For aluminum cavity the maximum power, torque and thermal efficiency were obtained as 64.37 W, 2.93 Nm and 8.67 %, respectively at 6 bars charge pressure and 425 ºC hot end temperature. For the cavity made of stainless steel (ASTM 304) the maximum power, torque and thermal efficiency were obtained as 39.95 W, 1.67 Nm and 5.45 %, respectively at 5.4 bars charge pressure and 205 ºC hot end temperature of the displacer cylinder. For the conical stainless steel (ASTM 304) cavity the maximum power, torque and thermal efficiency were obtained as 40.74 W, 2.26 Nm and 5.79 %, respectively at 5 bars charge pressure and 315 ºC hot end temperature of the displacer cylinder. The efficiency of the system was found to be lower than expectation. It is estimated that the focusing error, back reflection of some solar radiations and thermal losses are major reasons of insufficient performance.