Seasonal High Temperature Heat Storage with Medium Deep Borehole Heat Exchangers

Bär, Kristian; Rühaak, W.; Welsch, Bastian; Schulte, Daniel O.; Homuth, S.; Sass, Ingo

doi:10.1016/j.egypro.2015.07.841

Cited by 74 publications

(29 citation statements)

References 8 publications

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“…A discharging/charging strategy is illustrated in Figure 13. When charging, the fluid should reach the bottom in a insulated inner pipe before the heat is discharged into the surrounding rock at maximum depth (Bär, 2015). In the extraction case, the cold fluid is injected into the outer pipe to utilize the borehole wall as a heat exchanger.…”

Section: Operation Of a Deep Borehole Exchangermentioning

confidence: 99%

Analysis of deep-heat energy wells for heat pump systems

Lund

Karvinen

Lehtonen

2020

2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe)

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Section: Operation Of a Deep Borehole Exchangermentioning

confidence: 99%

Analysis of deep-heat energy wells for heat pump systems

Lund

Karvinen

Lehtonen

2020

2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe)

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“…The sensitivity of the parameters is assessed, and the setup of the simulation experiment is discussed. The study is part of a project, which assesses a potential MD‐BTES system to be constructed at the Institute of Applied Geosciences, Technische Universität Darmstadt, Germany as described by Bär et al .…”

Section: Introductionmentioning

confidence: 99%

Characteristics of medium deep borehole thermal energy storage

Welsch

Rühaak

Schulte

et al. 2016

Int. J. Energy Res.

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Summary Seasonal energy storage is an important component to cope with the challenges resulting from fluctuating renewable energy sources and the corresponding mismatch of energy demand and supply. The storage of heat via medium deep borehole heat exchangers is a new approach in the field of Borehole Thermal Energy Storage. In contrast to conventional borehole storages, fewer, but deeper borehole heat exchangers tap into the subsurface, which serves as the storage medium. As a result, the thermal impact on shallow aquifers is strongly reduced mitigating negative effects on the drinking water quality. Furthermore, less surface area is required. However, there are no operational experiences, as the concept has not been put into practice so far. In this study, more than 250 different numerical storage models are compared. The influence of the characteristic design parameters on the storage system's behaviour and performance is analysed by variation of parameters like borefield layout, fluid inlet temperatures and properties of the reservoir rocks. The results indicate that especially larger systems have a high potential for efficient seasonal heat storage. Several GWh of thermal energy can be stored during summertime and extracted during the heating period with a high recovery rate of up to 83%. Medium deep borehole heat exchanger arrays are suitable thermal storages for fluctuating renewable energy sources and waste heat from industrial processes. Copyright © 2016 John Wiley & Sons, Ltd.

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“…There are two ways of upscaling BHE installations-either by increasing the number or the depth of the boreholes [3]. Although the first alternative stands for the majority of the installations today, it requires substantial land plots to install the ground loops, which poses a great challenge for its applications especially in densely populated cities and towns with scarcity of space [4][5][6].On the other hand, in order to keep sustainable operation of shallow BHEs which gradually degrades with the operating time due to the annual negatively balanced loads between heating demand in winter and cooling demand in summer, cross season thermal energy storage becomes essential [7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…It is applicable to a wide variety of geothermal resources such as dry rocks where no hydrothermal reservoir is found underground, magma bodies, and geothermal reservoirs. Ideally, DBHE extracts geothermal energy at a depth which significantly exceeds the typical BHE length of 100 m and gets down to a depth up to 1000-3000 m below the ground surface where the temperature may reach 40~80 • C [6][7][8][9][10][11]. With the advantages of much less land demand, favorable features of flexibility, potentially higher temperature available particularly for high geothermal gradient areas, and higher efficiency of heat pump units, DBHE could be made space effective with a small or negligible visual footprint [6] and shows great potential in much more heat extraction capacity in limited land plots compared to traditional shallow BHEs.…”

Section: Introductionmentioning

confidence: 99%

“…In view of the real applications that DBHE usually operates discontinuously in the heating season and stops running during the intermittent period, it An extensive thermal performance analysis is critical in need to assure long-time efficient and sustainable operation of DBHE [11][12][13][14]. Available related studies on heat transfer of DBHE have already started and mainly focus on the operation modeling of DBHE and evaluation of heat extraction output [6][7][8][9][10][11][12]. However, there is still a lack of comprehensive study on the thermal recovery characteristics of DBHE after heat extraction due to the complicated heat transfer with surrounding rock-soil of deep borehole [11,14,15].…”

Section: Introductionmentioning

confidence: 99%

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A Fast Simulation Approach to the Thermal Recovery Characteristics of Deep Borehole Heat Exchanger after Heat Extraction

Zhao

Pang

2020

Sustainability

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Necessary intermittence after heat extraction for a deep borehole heat exchanger (DBHE) is beneficial for sustainable operation. This paper centers on the fast simulation for thermal recovery characteristics of DBHE under intermittent condition. First of all, in view of the existing temperature gradient and multi-layer heterogeneity of rock underground that could never be ignored for DBHE, we extend the classical finite line source model based on heat source theory and superposition principle to account for the vertical heat flux distribution varying along depth and heterogeneous thermal conductivities in the multi-layer rock zone. Moreover, a fast simulation approach for heat transfer analysis inside the borehole coupled with the extended finite line source model is put forward to depict the transient thermal response and dynamic thermal recovery of rock outside borehole. To the authors’ knowledge, no such algorithm for deep BHE has yet been suggested in the previous literature. This approach has proven to be reliable and efficient enough for DBHE simulation under the intermittent condition. Simulation results show that at least 65 days of intermittence for the model in study should be spared after the heating season to achieve sustainable heat extraction in the next cyclic operation. Compared to the detailed solution based on full discretization numerical schemes, the relative error for borehole bottom temperature was 0.79%. In addition, comparison of the simulation results for thermal performance during the heating season in a three-year cyclic operation with 205 days intermittence shows that both the outflow temperature and heat extraction rate in the subsequent cycle after intermittence are in good agreement with the full 3D numerical solution in the reference (with a relative error of 6.36% for the outflow temperature and 9.3% for the heat extraction rate). Regarding the calculation speed, around a 13 times acceleration can be achieved. Finally, it is also promising to be applicable for thermal recovery simulation after heat extraction of vertical closed loop borehole heat exchangers at arbitrary length from shallow to deep.

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Seasonal High Temperature Heat Storage with Medium Deep Borehole Heat Exchangers

Cited by 74 publications

References 8 publications

Analysis of deep-heat energy wells for heat pump systems

Analysis of deep-heat energy wells for heat pump systems

Characteristics of medium deep borehole thermal energy storage

A Fast Simulation Approach to the Thermal Recovery Characteristics of Deep Borehole Heat Exchanger after Heat Extraction

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