Construction and testing of a dish/Stirling solar energy unit

This study is concerned with the construction of a simple solar energy conversion system consisting of a parabolic dish concentrator and a Stirling engine. For this purpose, a parabolic dish concentrator consisting of planar mirror segments was built and coupled with a Stirling engine recently developed by the authors for solar energy conversion and domestic cogeneration. By mounting the engine to the bottom of the dish concentrator, the solar rays were directly reflected onto the hot end of the displacer cylinder. For the design of an appropriate parabolic dish concentrator reflecting solar rays onto the hot zone of a displacer cylinder and satisfying their uniform distribution, an equation was derived. The energy conversion unit constructed was tested under 820 W m(-2) solar radiation. The engine started to run at 93 degrees C hot end temperature. At steady running conditions, the hot end temperature of the displacer cylinder became stable at similar to 156 degrees C. The variation of shaft power with engine speed and charge pressure was evaluated. The engine produced a maximum shaft power of 23.59 W at 344 rev min(-1) engine speed and 2 bar helium charge pressure.