12 - Hybrid ground-source heat pump systems

Abstract

Hybrid ground-source heat pump (HGSHP) systems have been proposed in a number of configurations to achieve more economic and efficient solutions than ground-source heat pump (GSHP) systems using borehole heat exchangers alone, especially in situations where a building's heating and cooling demands are not well balanced. HGSHP can adopt various supplemental heat sources and sinks according to the climatic conditions and the balance of energy demands. For buildings located in hot climate regions, the HGSHP can use a cooling tower as a supplemental heat rejecter to improve the ground thermal environment and cooling performance. The design and control of the HGSHP have to be optimized properly to balance the ground thermal environment and minimize the life cycle cost. Important issues in the optimization are the control strategy, the loop configuration between the ground flow loop and supplemental flow loop, and the sizing of the ground heat exchanger and supplemental equipment. Well designed and optimized HGSHPs can provide substantial economic benefits and improved ground energy balance. Borehole heat exchanger sizing procedures for hybrid systems are also discussed in chapter “Vertical borehole ground heat exchanger design methods,” Section 2.7. Dual-source GSHP equipment is discussed in chapter “New trends and developments in ground-source heat pumps.”