Techno-economic analysis of a solar district heating system with seasonal thermal storage in the UK

Heat demand in buildings is responsible for around 40% of all energy use in middle to high latitude countries. The combination of district heating systems with solar thermal energy and seasonal thermal energy storage has successfully reduced the carbon intensity of heating in different countries, such as Denmark, Germany and Canada. The potentials of such systems to decarbonise the heat demand in the UK has also been highlighted in different reports. Nevertheless, bottom-up quantitative studies to support or dismissive these potentials are very limited. The quantification can be provided by simulating a solar district heating system using UK-specific inputs, such as heat demand and weather profiles. In this study, a validated simulation model is used to study the performance of solar district heating systems with seasonal thermal storage deployed in the UK. The case study is based on the Drake Landing Solar Community in Okotoks, Canada, which has a relatively high solar fraction. The results show that the system is technically feasible to be implemented in the UK but that it has lower technical performance. A systematic analysis of the influence of the main components on the system performance shows that not only the solar supply and heat demand need to be balanced but also that the long-term storage needs to be appropriately sized. The relatively lower solar fraction could be offset by installing more long-term storage and implementing the system to supply new-built houses with better energy performance rather than the current building stock of older homes. Financially, the system still needs to be supported by encouraging policies to make it competitive with incumbent technologies. The results and the validated model open the possibility to design bespoke solar district heating systems for the UK and other countries in middle to high latitudes.