Analysis of Geo-Energy System with Focus on Borehole Thermal Energy Storage

Abstract: Ground source heat pump (GSHP) systems have become more popular lately both for residential space heating and for commercial applications. GSHP systems can use water, ground or the bedrock as a thermal source. The energy extracted is regarded as a renewable energy-source and it consists of both stored solar energy and a share of geothermal energy. A borehole thermal storage (BTES) consists of boreholes drilled in a specific pattern with a few meters in-between. A BTES can be used for both heating during winter and cooling during summer. The stable temperature of the bedrock provides good performance as long as the balance between extracted and injected heat is kept. With increasing size of GSHP-systems it is desirable to simulate the systems and to perform optimization and life cycle analysis to justify investments. There are several existing software that can simulate a BTES but they are either working with too large time steps or they are too complicated for industrial usage. Within this thesis a short time-step model of a BTES is constructed based on existing research. The model is validated using existing simulation software and then demonstrated within a simplified GSHP-system.