Comparative study of hybrid ground source heat pump in cooling and heating dominant climates

Abstract

The ground source heat pump system (GSHP) has been an accepted technology to provide energy efficient and renewable air conditioning to the buildings. However, imbalanced heating and cooling load during the winter and summers especially in the regions with heating and cooling dominant climates may degrade the performance of the system over a long-term operation. Hybrid GSHP system which uses supplemental energy sources such as solar panel or cooling tower can balance the imposing load on the ground heat exchanger (GHE) and benefits the system by minimizing the GHE length in short-term and improves the overall performance in long-term. This research presents a study of application of hybrid GSHP system with an intention to compare its applicability in the regions with dominant heating and cooling loads. In this study, a student office and an actual heat pump system in Akita City, northern Japan was modeled in TRNSYS software and was validated using in-situ measured data. The hybrid system which coupled with a supplemental heating and cooling source devices was simulated to test its viability for the different heating and cooling loads in different regions within the country. The results revealed that hybrid system plays an effective role in both climates to balance the load on GHE, keeps constant the soil temperature, and consequently improves the long-term performance. Moreover, in short-term, it can reduce the GHE length and decrease drilling cost based on the meteoroidal condition of the region such as solar radiation. For instance, the GHE length was reduced to around half in cooling dominant region using cooling tower, while it was negligible in heating dominant region.