Abstract
Cogeneration using solar dish Stirling engine is a proven technology showing good energy conversion performance in those Countries where the solar resource is particularly high. Many international agencies report that in the regions where the direct solar radiation is higher than 1900 kWh/(m2 year), the solar concentration technologies for the production of electrical power will be a valuable solution for the greenhouse gases emission mitigation and the reduction of the fossil fuel use. However, up to now, the production cost of a solar dish system showed a lack of economic competitiveness if compared to other solar technologies. In order to reduce cost, economies of scale must be achieved, standardization of the components must be adopted and very cheap but effective solutions must be introduced. In this work, an innovative, cheap and performing solution to reduce the cost of a free piston Stirling engine (FPSE) solar receiver system is proposed. The receiver was studied to suite the hot end of a 1kW FPSE which was originally designed as a household cogeneration systems. The concentrated solar energy receiver is made by a copper mass, welded by induction brazing on the Stirling hot head; this receiver acts as a conductive mass that brings the heat flow from the solar receiver aperture to the engine’s head internal copper foils where the working fluid flows. Also a cavity receiver was designed to reduce the effect of re-irradiation and convection losses to the ambient. By means of a CFD simulation the performance of the copper receiver and the cavity is studied; an un-steady state simulation is performed taking into account the thermal flow required to feed the engine. It is shown that the thermal losses can be limited also in windy conditions and that the performance of the FPSE is granted. The heat flow rate, the thermal losses and the thermal transient time are reported for the most performing solution.