A modelling study using Feflow to examine the feasibility and sustainability of closed-loop ground source heat pump systems

The work presented in this report is part of the Thermogeology project. Ground source heat pumps are becoming an increasingly popular method of heating/cooling in the UK. However, little work has been published on the long term sustainability of such schemes, partly because insufficient time has elapsed to allow long term data to be collected but also because closed-loop schemes are not required to be regulated. The aim of the work was to determine which factors, geological, hydrogeological and scheme-specific e.g. size, spacing and operating regime were most important in ascertaining whether a vertical closed-loop ground source heat pump scheme would be successful and sustainable. The impact of interference effects when a number of boreholes are located in close proximity were also considered. Guideline values for borehole spacing are typically of the order of 5 to 10 metres but modelling studies were used to demonstrate whether such values are appropriate. The work presented in this report comprises three parts – a review of the current application of closed-loop GSHPs in the UK, an assessment of the range of parameters required for a successful scheme and scenario modelling using the heat transport model Feflow®.