A descriptive and comparative analysis of three common control techniques for an on/off controlled Ground Source Heat Pump (GSHP) system

• Three common capacity control methods for Ground Source Heat Pump systems are described.
• A generic model of the system is used to compare annual performance of the control methods.
• Degree–minute and floating hysteresis are better control methods than the constant hysteresis.
• Constant control parameters in the controller can lead to a poor annual performance of system.
• It is recommended to use dynamic and adaptive control parameters in the system controller.

In the present paper, three common methods in order to control an on/off controlled Ground Source Heat Pump (GSHP) system called “Constant hysteresis”, “Floating hysteresis”, and “Degree–Minute” methods are comprehensively described. Then, the generic model already developed by the authors is used in order to do the dynamic simulation of the systems with three different control methods over a year and making the comparison between them. The results from annual modeling of the systems show that the mean temperature of the heating water supplied to the building for the system controlled with degree–minute method is always close to the required temperature, regardless of the climatic boundary conditions over a typical year, whereas, the average supply temperature for the system with constant hysteresis method is mostly higher or lower than the required temperature, depending on the boundary condition. Regarding the annual energy use, the degree–minute and constant hysteresis methods have the lowest and highest annual energy use respectively. Switching from constant hysteresis to floating hysteresis method, the annual energy use will become lower and the mean temperature of the heating water supplied to the building will be closer to the required one.