These systems consists of several BHEs arranged in a grid, which are usually not deeper than 100 m. One concept is to store the heat in the underground in so called Borehole Thermal Energy Storages (BTES) (Gao et al. solar thermal energy or heat from existing combined heat and power plants (CHP) (Schmidt et al. There are already several technologies available for the seasonal storage of e.g. One of the major challenges for a sustainable and effective thermal energy supply in the future is to store the heat when it is available and to recover it when it is needed. There are not synchronous seasonal and diurnal fluctuations in the heat demand and heat supply. INTRODUCTION The energy demand for heating of buildings and domestic water accounts for about a third of the final energy consumption in Germany (AGEB 2013).
The numerical simulations were then used to economically evaluate MD-BTES and to calculate the carbon footprint of these systems. Depending on the storage design, storage efficiencies of more than 80 % and specific heat extraction rates of more than 110 W m -1 could be reached with an outlet temperature of the BHE fluid of more than 30 C during the whole extraction period. A simplified underground model was assumed and a simplified operation procedure was applied over a period of 30 years of storage operation. The influence of different parameters on the storage performance was studied by varying the BHE length, the number of BHEs and the spacing between the BHEs. Therefore, 200 different models of MD-BTES were compared, using FEFLOW for modeling the heat transport processes in the BHEs and in the underground. As no such system is put into practice so far, the efficiencies, the amount of heat that can be stored or extracted and the fluid temperatures that can be achieved by MD-BTES are unknown.
Medium deep borehole thermal energy storages (MD-BTES) have almost no impact on shallow groundwater resources and require less floor space. Schulte Kristian Bär Ingo Sass Technische Universität Darmstadt, Department of Geothermal Science and Technology, Germany ABSTRACT: The utilization of medium deep borehole heat exchangers (BHEs) as seasonal thermal energy storages is expected to have benefits compared to shallow BHE storages. 1 Technical and Economical Evaluation of Medium Deep Borehole Thermal Energy Storages Bastian Welsch Wolfram Rühaak Daniel O.
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