Increasing the efficiency of downhole heat exchangers by air sparging in locations without groundwater flow
Closed and open systems are available for the exploitation of shallow geothermal energy. If there is no groundwater flow, heat in closed systems can only be transferred by conduction. Unfortunately, heat conduction is a relatively slow heat transfer mechanism, which limits the heating capacity of geothermal systems. A patented method is presented, in which a closed system is combined with groundwater circulation technology. In this system, a groundwater circulation is created artificially, which increases the convective heat transfer in the soil and therefore the heat capacity of the geothermal system. In this paper a downhole heat exchanger combined with an air sparging well is numerically simulated. The groundwater circulation induced by air sparging and the heat propagation are calculated sequentially. The heat capacity of this system is compared with a normal downhole heat exchanger. Furthermore, variation calculations are performed to investigate the influence of the density of the water-air mixture in the well, permeability and conductivity of the soil. A profitability analysis rounds off the paper. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
690: Building, Construction