Development of a Numerical Model of Geothermal Heat Pump Systems for Integrated Renewable Energy System Simulator

We have developed a numerical model of Geothermal Heat Pump (GeoHP) Systems as an element in the simulator of Integrated Renewable Energy Systems (IRES). The numerical model of GeoHP systems consists of three parts; one is heat extraction fluid in U-tube, the other is layer around the U-tube, and the other is heat pump. The model, which represents temperature variation of heat extraction fluid, is based on the one-dimensional advection-diflusion equation and the heat flow equation between the fluid and the layer. The model, which represents temperature variation of layer, is based on the equation of heat conduction in the cylindrical coordinate system. The model, which represents power variation of heat pump, is based on the capacity diagram released from the heat pump manufacturer. We have confirmed the feasibility of developed model of GeoHP systems by comparing the data calculated from the model of GeoHP systems with the real data of temperature of heat extraction fluid during the thermal response test under the condition of constant heating. It has been revealed that the calculated temperature using the model well agrees with the measured temperature profile, even though there are some inconsistencies around the beginning and after the end of heating due to the simplified model. Therefore, we have reached the conclusion that the developed model of GeoHP systems can represent the dynamic behavior of GeoHP systems enough to use for the IRES simulator.