Analytical simulation of groundwater flow and land surface effects on thermal plumes of borehole heat exchangers

A new analytical model is presented for simulation of ground thermal effects from vertical borehole heat exchangers (BHEs). It represents an extension of the moving line source equation and efficiently describes the coupled transient effects from geothermal energy extraction, subsurface heat conduction, horizontal groundwater flow and spatially variable land use. It is successfully verified by comparison with an equivalent numerical model and validated by application to a field case with detailed long-term temperature monitoring. Non-dimensional sensitivity analysis reveals the coupled influence of advection and conduction for different assumptions of the land surface. Especially accelerated heat flux from asphalt or buildings at the land surface is shown to have a remarkable impact on the thermal conditions in the ground. Together with the flow velocity of the groundwater, it determines the intensity, form and steady-state of the thermal anomaly induced from BHE operation.