Control strategy of a novel dry air ground source (DAGS) system

Based on a number of studies carried out; it has been identified that Ground Source Heat Pump (GSHP) systems are widely used as one of the preferred low carbon technologies in the UK. The use of these systems is due to their economic advantages and potential reduction of carbon footprint. However, a number of the studies have highlighted that the systems are either installed incorrectly or operated and controlled improperly and therefore result in poor performance. GSHP performance is affected by the temperature of the ground and when thermally saturated its efficiency reduces significantly. This paper investigates the potential to reduce the level of thermal saturation by rejecting heat via a Dry Air Cooler (DAC) when the ground and ambient temperatures favour this. DACs are often fitted to GSHP systems to reject heat during extreme conditions to protect the system, rather than improve performance. In this investigation, an empirical Transient System Simulation (TRNSYS) model has been developed and used to investigate the control algorithms so as to identify the optimal operation and control strategies for DAGS system for enhancing the system efficiency. Specifically, the paper investigates the effect of using a DAC in conjunction with a GSHP system. This includes investigating the (i) energy input into the GSHP system, (ii) ground temperatures and (iii) Coefficient of Performance (COP). The results show significant savings can be achieved.