Analysis on variations of ground temperature field and thermal radius caused by ground heat exchanger crossing an aquifer layer

Ma, Zongyuan; Jia, G.S.; Cui, Xin; Xia, Zhenhua; Zhang, Y.P.; Jin, Liwen

doi:10.1016/j.apenergy.2020.115453

Cited by 26 publications

(5 citation statements)

References 28 publications

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“…The effective radius of each well is dependent on the rate of groundwater flow in the area, itself a function of the porosity and density of the aquifer. Ma et al [38] recorded the impact of increasing groundwater flow rate, finding that the thermal influence radii increased from 7.4 m to 143 m with an increase of groundwater velocity from 3.15 m/a to 315 m/a. Bakr et al [39] studied 19 ATES systems installed within a 3.8 km 2 area in The Hague, The Netherlands.…”

Section: Sub-surface Characterisationmentioning

confidence: 99%

A review of thermal energy storage technologies for seasonal loops

Mahon

O’Connor

Friedrich

et al. 2022

Energy

181

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Section: Sub-surface Characterisationmentioning

confidence: 99%

A review of thermal energy storage technologies for seasonal loops

Mahon

O’Connor

Friedrich

et al. 2022

Energy

181

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“…In the above references, convective heat transfer in rocks and soil was ignored in the presence of groundwater flow. However, groundwater flow has a critical impact on the heat transfer process between GHEs and surrounding rocks and soil, according to some investigative results on the GHEs [19,20]. You et al [21] found that the temperature drop of soil located upstream and near the ground heat exchanger could be alleviated by groundwater flow.…”

Section: Introductionmentioning

confidence: 99%

Effects of Boundary Conditions on Performance Prediction of Deep-Buried Ground Heat Exchangers for Geothermal Energy Utilization

Qin

Zhang

et al. 2023

Energies

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An accurate prediction for deep-buried ground heat exchangers (DBGHEs) is the premise for efficient utilization of geothermal energy. Due to the complexity of the geological composition spanning thousands of meters, the configuration of boundary conditions plays a critical role in evaluating DBGHE thermal performance. This paper proposed a three-dimensional model of full-scale DBGHE involving both conductive and convective heat transfer in aquifuge and aquifer layers. The constant inlet temperature and constant heating power boundaries in the DBGHE domain, and the surface–bottom temperature and heat flux boundaries in the rock-soil domain were examined. It was found that the differences in the performance prediction caused by different DBGHE boundary conditions were closely related to the system’s operating time. The relative differences in heat extraction amount and average borehole temperature of 2000 m DBGHE caused by the two inlet boundaries on the 30th day were, respectively, 19.5% and 18.3%, while these differences on the 120th day were decreased to 8.4% and 9.9%, respectively. It was found that the constant inlet temperature boundary was more appropriate than the constant heating power condition for estimating aquifer effects on the performance of DBGHE. For the rock-soil domain, the results showed that the heat extraction amount of DBGHE under the heat flux boundary was 12.6%–13.6% higher than that under the surface–bottom temperature boundary. Particularly, when considering the velocity change of groundwater in the aquifer, the relative difference in heat extraction amount increments caused by the two types of rock-soil boundaries can reach 26.6% on the 120th day. It was also found that the thermal influence radius at the end of a heating season was hardly affected by either the DBGHE inlet or rock-soil domain boundary conditions.

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“…The ground heat exchangers (GHEs) are extensively employed in geothermal systems for building cooling or heating. Compared with shallow GHEs, the deep GHEs can be used for heating with higher performance, because they utilize the geothermal energy in the high-temperature soils and rocks in IOP Publishing doi:10.1088/1755-1315/1074/1/012001 2 deep strata [2,3]. Due to this point, the deep GHE has been regarded as a superior solution for building heating in China [5,6].…”

Section: Introductionmentioning

confidence: 99%

A case study on long-term performance optimization of a geothermal heating system

Jia

Duan²,

Xue

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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The optimal use of geothermal energy necessitates the performance evaluation and economic analysis of the geothermal heating systems. This work presented a field study of the long-term operating performance of a geothermal heating system in Xixian New Area, China. Nine deep coaxial ground heat exchangers (GHEs) with depths of 2,500 m were adopted for space heating to the residential buildings, with a total heating area and heating load of 136,097.71 m2 and 6,082 kW, respectively. The system’s 30-year running performance at various volumetric flow rates and operating modes was simulated. Through response surface analysis and multi-objective optimization, the levelized cost of energy (LCOE) and payback period were obtained based on the thermal performance analysis. It is concluded that the operating parameters have a significant impact on the system economy. When the daily operating time reduces from 24 hours to 8 hours, the payback period will be lowered from more than 25 years to approximately 11 years. When the volumetric flow rate is 35 m3·h-1, the examined system achieves the lowest LCOE. The minimum values of LCOE are 13.2 $/GJ, 11.6 $/GJ, 9.4 $/GJ, 7.8 $/GJ and 5.6 $/GJ when the system operates 24 hours (continuous operation), 20 hours, 16 hours, 12 hours and 8 hours a day, respectively. With the optimal flow rate, the average heat exchange rate of the single GHE increases from 295 kW to 519 kW after 30 years of operation when the daily operating time is reduced from 20 hours to 8 hours. The proposed method and findings can be used to guide the high-efficiency operation, which is conducive to reducing operating costs of geothermal heating systems.

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Analysis on variations of ground temperature field and thermal radius caused by ground heat exchanger crossing an aquifer layer

Cited by 26 publications

References 28 publications

A review of thermal energy storage technologies for seasonal loops

A review of thermal energy storage technologies for seasonal loops

Effects of Boundary Conditions on Performance Prediction of Deep-Buried Ground Heat Exchangers for Geothermal Energy Utilization

A case study on long-term performance optimization of a geothermal heating system

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