Long Term Performance of Ground Source Heat Pump Systems

Ground source heat pump systems offer a sustainable way to reduce heating and cooling demand for buildings through the use of the ground as a seasonal thermal store. Access to the thermal store is made via ground heat exchangers, which are then connected to a heat pump and the building heating and cooling delivery system. Well performing ground source heat pump systems should offer efficiencies of around four or more, meaning substantial energy savings. However, studies of post installation performance by government agencies and other researchers suggest that this degree of energy efficiency is not being realised in many cases. This underperformance may be due to a number of reasons including, problems with design or specification, inappropriate control systems, or final building use incompatibility to design stage assumptions. These issues can all be compounded by the difficulty of accurately determining the thermal demand of buildings before their occupancy.

Historically, ground source heat pump systems in the UK have been installed without any due regard to following up monitoring. This has meant that valuable lessons about design and operation have not been learnt. GI Energy Ltd and the University of Leeds have been gathering performance data for a number of installed ground source heat pump systems. This offers an unrivalled opportunity to assess the appropriateness of current design and control systems in routine use, compare operational conditions to those assumed during design and to make recommendations for better practice in the future.

The PhD project will interpret the energy performance of a number of operating ground source heat pump systems in the UK and determine the factors involved with successful schemes. Analysis of datasets from the buildings will also allow systematic validation of design approaches based on real performance, something currently lacking in the industry.

The project aims are to:
1. Apply analytical method to data sets from case study buildings to determine the performance of the heat pumps systems, and potential causes for underperformance/over-performance;
2. Develop and validate building and ground heat exchanger models to explore the reasons behind the underperformance, and to test scenarios not available from the field datasets.
3. Create a summary of transferrable recommendations to optimise performance of the heat pump systems;
4. Design a smart monitoring system and monitoring regime, incorporating the recommendations to achieve greater efficiencies.

The project will be of interest to building developers, ground source heat SMEs, building designers and operators who will be able to use the results to achieve better building energy performance.