Modeling and testing of a micro-cogeneration Stirling engine under diverse conditions of the working fluid

Micro-cogeneration Stirling engines are promising for residential applications. This work focuses on the experimental and numerical analyses of a commercial unit generating 8 kW of hot water and 1 kW of electricity burning natural gas. Measurements are coupled to a detailed model based on a modification of Urieli and Berchowitz’s work. The results indicate that the thermal efficiency is influenced by the water loop inlet temperature, varying from 90% at 30°C to 84% at 70°C (HHV-based). The measured and simulated powers of the engine are in the 900-964 W range depending on the water temperature and differ by less than 4%. Net electric efficiency of the engine is 15% and of the whole cogeneration unit above 9% (HHV-based). Helium instead of Nitrogen as working fluid is expected to increase the performance.