Seasonal high temperature heat storage with medium deep borehole heat exchangers

Heating of buildings requires more than 25 % of the total end energy consumption in Germany. By storing excess heat from solar panels or thermal power stations of more than 110 degrees C in summer, a medium deep borehole thermal energy storage (MD-BTES) can be operated on temperature levels above 45 degrees C. Storage depths of 500 m to 1,500 m below surface avoid conflicts with groundwater use. Groundwater flow is decreasing with depth, making conduction the dominant heat transport process. Feasibility and design criteria of a coupled geothermal-solarthermal case study in crystalline bedrock for an office building are presented and discussed. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecomons.org/licenses/by-nc-nd/4.0/).