Experimental Determination of the Efficiency and Emissions of a Residential Microcogeneration System Based on a Stirling Engine and Fueled by Diesel and Ethanol

Renewable forms of energy, such as biofuels, have the potential to displace fossil fuels in a wide variety of applications. Further benefit can be achieved through the use of combined heat and power devices, as this is accompanied with a considerable increase in energy efficiency and lower costs associated with fuel consumption. In this study, we examined the performance of a residential microcogeneration system based on a Stirling engine and fueled by diesel and ethanol. Run on diesel, and on a lower heating value basis, the system achieved a power efficiency of 12.1%, a thermal efficiency of 73.3%, and a total efficiency of 85.4%. Powered by ethanol, the corresponding efficiencies were 11.8%, 73.9%, and 85.7%, respectively. During steady state operation, the total unburned hydrocarbon emissions for both fuels were negligible, while the particulate emissions for ethanol and diesel were found to be 0.40 mg/kWh and 0.42 mg/kWh, respectively. Emissions were extremely low, as the combustor features a continu...