Hybrid Ground Source Heat Pump Systems - Review

Abstract

The Ground source heat pump (GSHP) systems consist of underground thermal energy storage and any type of heat pump. These systems can be used for heating and/or for cooling. Their efficiency is very good if the building’s heating and cooling loads are well balanced on an annual basis. Unfortunately, in warm-climate or cold-climate areas there is always an imbalance and consequently there is a domination of either cooling or heating loads. In both cases a larger area of borehole heat exchangers (BHEs) is needed, which reduces the system’s efficiency. A good solution to the problem is to diminish the capital costs by means of a heat rejecter or a heat absorber, thus obtaining hybrid GSHP (HGSHP) systems. Many different components can be a part of this type of systems - solar collectors, storage with phase change materials, heat rejecters, borehole thermal energy storage as well another type of heat pump. The work presents a review of many hybrid GSHP systems constructed and used all over the world. Additionally the experience of some members of the Bulgarian research team and their international cooperation is discussed. The existing problems by using this technology and the future progress is commented, too.