Optimal Power Consumption in a Central Heating System with Geothermal Heat Pump

Driving a ground source heat pump in a central heating system with the minimum power consumption is studied. The idea of control is based on the fact that, in a heat pump, the temperature of the forward water has a strong positive correlation with the consumed electric power by the compressor. Thus, lowering the temperature of forward water alleviates energy consumption. The hypothesis is that the minimum water temperature is achieved when at least one of the hydronic heaters in the building works at full capacity. The setpoint of the forward water temperature is found by solving a model based optimization problem in a receding finite horizon. The optimization objective is to maintain the local control signal of the largest thermal load near full capacity. The overall control system hierarchy is composed of local PI controllers for each subsystem and an MPC controller which orchestrates the PI controllers. Simulation results for a case study with simplified subsystems' models show considerable energy savings compared to the traditional control scheme for the heat pump.