Comparison of Simulation-based Design Procedures for Hybrid Ground Source Heat Pump Systems

Abstract

1. ABSTRACT Due to their higher efficiency, ground source heat pump (GSHP) systems offer an attractive alternative to conventional systems for residential and commercial heating and cooling applications. However, the higher first cost of GSHP systems has been a significant constraint for wider application of the technology. One way to reduce the first cost is to reduce the imbalance in the ground thermal loads by incorporating a supplemental heat source or sink into the system, which creates a hybrid ground-source heat pump (HGSHP) system. This work presents a new, computationally efficient method for sizing HGSHP systems based on a hybrid time step simulation. This design method utilizes an optimization routine to configure the ground heat exchanger (GHE) length and the size of the supplemental device so that the system meets both the desired maximum and minimum heat pump entering fluid temperature limits as closely as possible. This method is compared to existing methods for a cooling-constrained HGSHP system serving a three-story office building in four U.S locations. The proposed method produces the closest life-cycle cost to a cost-optimized design method in three of four cases, while requiring substantially less computation time. The other methods occasionally, but inconsistently, provide close cost matches.