Life Cycle Energy and Carbon Analysis of Domestic Combined Heat and Power Generators

Efficient power generators have been of increasing interest recently due to growing environmental concerns. Micro Combined Heat and Power (micro-CHP) generators combine the benefits of the high-efficiency cogeneration technology and microgeneration, that is being promoted as a means of lowering greenhouse gas emissions by decentralizing the power network. Additionally, Life Cycle Assessment of energy systems is becoming a substantial part of decision making in the energy industry, helping manufacturers promote their low carbon devices, and consumers choose the most environmentally friendly options. This report summarizes a study on life-cycle energy and carbon auditing of a typical wall-hung gas-powered domestic micro-CHP device that is commercially available across Europe. Combining a very efficient condensing boiler to a Stirling engine,
the device can deliver enough heat to cover the needs of a typical household (up to 24kW) while generating power (up to 6kW) that can be used locally or sold to the grid. Assuming an annual heat production of 20 MWh the study has calculated the total energy consumption and carbon emissions over an operational lifetime of 15 years at 1606 GJ and 90 tonnes of CO2 respectively.
Assuming that such a micro CHP device replaces the most efficient gas-powered condensing boiler for domestic heat production, and the power generated substitutes electricity from the grid, the potential energy and carbon savings are 4922 - 5118 MJ/year and 522 - 543 kg CO2/year respectively, implying a
payback period of the embodied energy and carbon at 1.32 - 2.32 and 0.75 - 1.35 years respectively. Apart from the embodied energy and carbon and the respective savings, additional key outcomes of the study are the evaluation
of the energy intensive phases of the device’s life cycle and the exploration of potential improvements.