Heat pump led heat networks will be a key feature of the UK’s future energy strategy, with c.20% of heat forecast to be delivered via heat networks and with many likely to utilise heat pump technologies.

This electrification of heat will place a significant additional burden on grid infrastructure.

Utilising rooftop photovoltaic (PV) or solar thermal technologies could help to reduce the grid electricity load on these heat pump led systems. Since roof-space in urban environments is often small compared to the network demand size, it is unclear which technology would provide the best outputs, carbon reductions and lifetime cost benefit, especially in relation to changing demand profiles resulting from the UK’s response to COVID-19.

A technoeconomic feasibility assessment has been carried out on the usage of PV and solar thermal as supplementary technologies on different sized heat networks in the London area.

The model found that increasing PV capacity had a larger effect on reducing both carbon emissions and total system cost over 30-years than solar thermal.

Despite this, the model also found that increasing air source heat pump (ASHP) capacity gives the largest carbon emissions reduction whilst simultaneously reducing upfront capital expenditure (CapEx) due to the reduction of the carbon offsetting costs between 80% and 95% heat fractions.

Consequently, maximising the performance of the heat pump before considering PV capacity is advised. Achieving a >95% ASHP heat fraction with rooftop PV was found to provide the most optimal carbon and cost reductions on any scheme.

This research was featured in CIBSE Technical Symposium 2021 and later by the CIBSE Journal.