Journal
RENEWABLE ENERGY
Volume 198, Issue -, Pages 825-832Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.renene.2022.08.070
Keywords
Thermal energy storage; District heat; Hourly simulation; Geothermal boreholes
Funding
- Academy of Finland [315278]
- Horizon 2020 program Surefit project [894511]
- Academy of Finland (AKA) [315278, 315278] Funding Source: Academy of Finland (AKA)
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This paper explores the use of intermediate-to-deep coaxial geothermal boreholes for seasonal storage of district heat. The idea is to extract heat from bedrock, creating a temperature pothole that can be filled and used for thermal storage. Two scenarios are studied: maximizing the capacity factor of the district heating network and using intermittent wind power as a heat source. Simulation results show that with proper sizing and system power rating, the borehole can efficiently meet the heat demand.
This paper explores intermediate-to-deep coaxial geothermal boreholes for seasonal storage of district heat. Extracting heat from within the bedrock creates a temperature potholewhich 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.
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