Monitoring and analysing the performance of a shallow ground geothermal heat pump system for space conditioning of buildings

Abstract

The aim of this dissertation is to monitor and analyse the performance of a shallow ground geothermal heat pump (GSHP) system. The GSHP system was installed at the premises of the Institute for Sustainable Energy situated in Marsaxlokk, Malta. The GSHP system is composed of horizontal ground heat exchangers (GHE) buried at 2m and 3m depths, connected to a reversible geothermal heat pump, which is connected to a fan coil unit system installed in a test room. An air source heat pump (ASHP) system installed in the same test room was also monitored and the heating and cooling performance of both the GSHP and ASHP systems were experimentally determined and compared based on the accumulated data. This dissertation is divided into six main chapters. In the first chapter a brief introduction of the overall aim and objective of this dissertation is given. Chapter 2 focuses on providing a description, summary and evaluation of the studies already conducted related to GSHP systems. From this chapter it was shown that parameters affecting the performance of a GSHP system included flow rate, depth of buried pipes, length of pipes and site location amongst others. In addition to this, upon comparing the performance of a GSHP system to an ASHP system, the values obtained in terms of COP were higher for the GSHP than the ASHP. Chapter 3 describes the design and installation of the GSHP system and also the type of experimental investigation that has been undertaken in order to analyse its performance. In Chapter 4, several equations related to the analysis of the performance of both the GSHP system and the AC unit were listed and described. Chapter 5 deals with analysing the performance of both the GSHP and ASHP systems by using the recorded data obtained from the calibrated equipment installed together with the equations stated in Chapter 4. In this chapter, a comparison between the results obtained for both systems was conducted and the results showed that the GSHP system obtained higher performance rating values than the ASHP system when operating in both heating and cooling modes. The last chapter of this dissertation, Chapter 6, contains a summary of all the results obtained alongside a brief conclusion which includes also some recommendations for future works as well as some areas for improvement. The first findings of this study showed that the coefficient of performance (COP) of the GSHP system reached 8.3 in the heating mode, while the energy efficiency ratio (EER) reached 5.9 in the cooling mode. On the other hand, the COP and EER achieved by the ASHP system achieved reached 3.14 and 3.33 respectively. These results show that the GSHP system can prove to be a potential alternative to the ASHP system, since the performance values obtained for the GSHP system are significantly higher than those obtained for the ASHP system in both operating modes. The ground temperature profile at 2 and 3 metres indicated that there is good thermal potential in order to operate efficiently the GSHP system in both operating modes.