The potential of intermediate-to-deep geothermal boreholes for seasonal storage of district heat

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2022-10
Major/Subject
Mcode
Degree programme
Language
en
Pages
8
825-832
Series
Renewable Energy, Volume 198
Abstract
This paper explores intermediate-to-deep coaxial geothermal boreholes for seasonal storage of district heat. Extracting heat from within the bedrock creates a “temperature pothole” which can be filled and utilized for thermal storage. Unlike in shallow boreholes, the pothole effect minimizes losses and offers a novel heat-storage concept. Exploiting this idea, two scenarios are studied: one to maximize the capacity factor of the district heating network and another to utilize intermittent wind power as a heat source on annual basis. With the borehole serving as a load-shifting storage facility in both cases, simulating the minimum annual delivery temperature as a function of the borehole depth and the system's average power rating enables determining the necessary sizing for the borehole to function as a storage for space heating on annual basis. The first-principle simulation results show that, in co-operation with the borehole, intermittent wind power as well as a district heat network operating at full capacity throughout the year both could cover the hourly heat demand with effectively 100% storage efficiency, provided that the borehole depth and system power rating are chosen in proportion.
Description
| openaire: EC/H2020/894511/EU//Surefit Funding Information: The work of EH was supported by the Academy of Finland grant no. 315278 . The work of JH was supported by the Horizon 2020 program Surefit project , grant no. 894511 . EH also wishes to thank Prof. Mika Järvinen for the illuminating discussions on the topic. Publisher Copyright: © 2022 The Authors
Keywords
District heat, Geothermal boreholes, Hourly simulation, Thermal energy storage
Other note
Citation
Hirvijoki , E & Hirvonen , J 2022 , ' The potential of intermediate-to-deep geothermal boreholes for seasonal storage of district heat ' , Renewable Energy , vol. 198 , pp. 825-832 . https://doi.org/10.1016/j.renene.2022.08.070