SE-14-031 -- Should the Optimization Horizon in Optimal Control of Ground-Coupled Heat-Pump Systems Cover the Interseasonal Time Scale?

Optimizing the control of ground-coupled heat-pump systems requires consideration of the building dynamics, to maintain thermal comfort, and the borehole heat exchanger dynamics, to exploit seasonal underground thermal energy storage. For the implementation of model predictive control (MPC) the question arises whether the optimization horizon should cover the interseasonal time scale to achieve optimal system operation. This paper addresses this question for a hybrid ground-coupled heat pump (HyGCHP) system with a backup gas boiler and a backup (active) chiller for a cooling dominated office building. The optimal system operation-- found by solving the optimization problem for a prediction horizon of one year--is compared to the operation obtained with MPC with a receding horizon of one week. The results show that the operation computed with one-week horizon is identical to the operation found with one-year horizon. This indicates that for the considered HyGCHP system there is no optimization potential at the seasonal time scale.