Impact of micro-CHP systems on domestic sector CO2 emissions

The effects of applying combined heat and power systems, based on Stirling engines and fuel cells, to single UK dwellings are investigated by using heat and power demand data recorded on a 1-min time base across a full year. The control regime has a major influence upon economic and CO2 savings for Stirling engine systems due to their high heat–power ratio. For the considered home, the contributions made by a 1 kWe Stirling engine system to the daily demands for heat and power ranged from 54% to 100% and from 3% to 73% respectively. Future systems based on fuel cells are predicted to achieve greater savings, because they can operate for relatively long periods during mild and warm weather without generating surplus heat. Estimates of the annual savings amount to £90/574 kg CO2 for a 1 kW Stirling engine system and £142/892 kg CO2 for a prospective 1 kW fuel cell system, when compared to a non-CHP base case of employing a condensing boiler of 90% efficiency and network electricity. These respective savings represent 9% and 16% of emissions attributable to the single UK dwelling, which is highly significant relative to other individual measures that can be deployed in the domestic sector.