What is it about?
Small-scale combined heat and power (micro-CHP or mCHP) plants generate heat in the process of localised electricity production that can usefully be captured and employed for domestic space and water heating. Studies of the relative merits of three alternative network-connected mCHP plants are reviewed based respectively on an Internal Combustion engine (ICE), a Stirling engine (SE), and a Fuel Cell (FC). Each plant will, in most cases, result in lower carbon dioxide (CO2) emissions, relative to those from the most efficient condensing boilers. In addition, they lead to operational cost savings for the consumer, depending on house type. However, their capital costs are presently more expensive than a conventional boiler, with the FC being prohibitively so.
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Why is it important?
Highly distributed energy systems, employing various micro-generators, may be able to reduce domestic energy demand and CO2 from the housing sector. Very small ‘combined heat and power’ (CHP) systems are therefore one class of micro-generator that can supply heat and power to a single residential home at significantly increased efficiency and reduced carbon emissions compared with separate supply. Such micro-CHP (mCHP) systems can be used to replace (mainly NG-fired) central heating boilers typically installed in UK dwellings. The ICE and SE variants display the greatest economic and environmental benefit. Nevertheless, the performance and costs associated with these innovative technologies have rapidly improved over the last decade or so. Comparisons are also made with heat pumps that are seen as a major low-carbon competitor by the United Kingdom (UK) Government. Finally, the potential role of micro-CHP as part of a cluster of different micro-generators attached to contrasting dwellings is considered. The review places mCHP systems in the context of the UK transition pathway to net-zero CO2 emissions by 2050, whilst meeting residential energy demand. However, the lessons learned are applicable to many industrialised countries.
Perspectives
Each of the micro-CHP systems varies in terms of their electricity generation efficiencies, and supply differing proportions of electricity and heat. They are therefore suitable for different housing types and sizes. all three mCHP systems were capable of lowering CO2 emissions (relative to those from the most efficient condensing boilers)—about 450 kg for every thousand hours used in the case of a SE-based system installed in a reasonably well insulated home. They also lead to cost savings for the consumer of about 61% over conventional energy supplies, depending on the house type. However, their capital costs are at present more expensive than that for a conventional boiler, with the FC being prohibitively so. The ICE and SE mCHP variants were found to exhibit the greatest economic and environmental benefit. In view of the present enthusiasm of the British Government for heat pumps, comparisons have also been made between such devices and mCHP plants. Finally, the potential role of mCHP an element of clustered micro-generators in dwellings of different types was considered, based on the recent research. The present review places micro-CHP systems in the context of transition pathways to a net-zero CO2 emissions future in terms of meeting UK residential energy demand by 2050. They are just one low-carbon option available from amongst a range of 'zero and low carbon' (ZLC) technologies; some of whose strengths and weaknesses have been illustrated here.
Professor Emeritus Geoffrey P Hammond
University of Bath
Read the Original
This page is a summary of: Small-Scale Combined Heat and Power Systems: The Prospects for a Distributed Micro-Generator in the ‘Net-Zero’ Transition within the UK, Energies, August 2022, MDPI AG,
DOI: 10.3390/en15166049.
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