A reconsideration of the use of domestic CHP in the UK domestic market

UK climate change policy relies on a combination of nuclear power, renewable generation (mostly wind power) and carbon capture and storage to decarbonize the electricity grid. There are technical, economic or public acceptability issues with all elements of this strategy. Advancements in gas extraction technology mean that natural gas should be available for most of this century; consequently it is worth re-examining the use of gas fired micro combined heat and power units (CHP) as a way of meeting medium term emission reduction goals.

The Carbon Trust carried out field trials of micro CHP units in domestic and small scale commercial applications in England. Units based on Stirling Engines were used in domestic applications and found to produce only modest emission savings when compared to condensing boilers and grid electricity. Internal combustion (IC) engines were used in the commercial premises and these produced nearly twice the emission savings of the Stirling engines. The IC units were used with auxiliary boilers for peak and low load duties following established commercial CHP practice.

Currently small Stirling engine micro CHP plants receive feed in tariff payments in the UK but there is no support for small (IC) engine CHP schemes.

Unfortunately the field trials did not investigate heating groups of a few houses in the same way as a commercial property. This study models this option and expands it to integrate solar water heating into the system to reduce the need to run the system purely for hot water in the summer. It was found that by using thermal stores it is possible to satisfy traditional heating patterns while only running the CHP plant at times of peak electricity demand. As such they could form a key component in the national electricity mix as well as supplying low carbon heat.