Semi-analytical model for geothermal borefields with independent inlet conditions

A model has been developed to simulate a geothermal borefield for which borehole inlet conditions can be defined independently. The borefield is modeled with a control-volume finite difference method while boreholes are modeled as analytical thermal resistances. An analytical shape factor is used to link the borehole models to the surrounding ground models. The main advantages of the proposed model are its versatility with respect to the specification of different inlet conditions and that the temperature of the disturbed ground can be known at any point of the borefield. Application examples, coupling solar collectors and heat pumps, showed that segregating the components into two loops requires 4.3% more energy from the heat pumps than a single loop arrangement for the first five years, but will require less energy after. The examples demonstrate the interest of the proposed method.