Closed and open systems are available for the usage of shallow geothermal energy. In closed systems heat can only be transferred conductively for the case of no groundwater flow. Unfortunately heat conduction is a relatively slow heat transfer mechanism, which causes limited heat-abstraction capacities in geothermal systems. A patented method is presented, in which a closed system is combined with groundwater-circulation technology. In this way a groundwater circulation will be created artificially, which increases convective heat transfer in the soil and therefore the heat capacity of the geothermal system. In this paper a borehole heat exchanger combined with an air sparging well is numerically simulated. The induced groundwater circulation and the heat propagation are calculated sequentially. The heat capacity of this system is compared to a normal borehole heat exchanger. Furthermore, variation calculations are performed to investigate the influence of density of the water-air-mixture in the well, permeability and hydraulic conductivity of the soil. A profitability analysis is carried out based on the numerical results.
