Solar Micro-Cogeneration using Small Energy scales and High Efficiency

Abstract

This experimental study focuses on a compact solar cogeneration system, which has the capacity to generate around 1 kW of electricity and up to 3 kW of heat. The system's primary objective is to facilitate decentralized and widespread production of both heat and power, achieving remarkable conversion efficiencies despite its small size. At the heart of this solar system lies a small-scale industrial Stirling engine, serving as a micro cogenerate. Originally designed for combined heat and power applications in gas boilers, this Stirling engine exhibits an impressive electrical efficiency of up to 35%. However, for its adaptation into this solar system, the Stirling engine's heat acceptor has been completely redesigned to cater to solar applications. Furthermore, a solar dish concentrator, precisely controlled by a two-axis tracking system, has been integrated into the system's configuration. Over the span of a year, the system generates an average of approximately 188 kWh/m² of electricity and around 860 kWh/m² of thermal energy. Consequently, the annual electrical efficiency reaches approximately 9%, with potential for further improvement. Simultaneously, the system achieves an annual thermal efficiency of about 46%. Notably, the collecting surface area of the solar dish measures approximately 9.6 m², which accounts for roughly 50% of the surface area required for an equivalent non-cogenerated system.