Article
Energy & Fuels
Ingen Perser, Ian Alistair Frigaard
Summary: This study examines the long-term performance of a horizontal deep Borehole Heat Exchanger (BHE) in intermittent mode. A mathematical model is developed and verified using experimental results to predict the transient heat transfer process within the BHE. The study investigates the effect of various key parameters on the thermal performance of the BHE in both continuous and intermittent modes. The results show that increasing the flow rate of circulating fluid, undisturbed ground temperature, and ground thermal conductivity improves the heat extraction rate.
Article
Thermodynamics
Yongqiang Luo, Guozhi Xu, Shicong Zhang, Nan Cheng, Zhiyong Tian, Jinghua Yu
Summary: This study reveals the impacts of heating duration and heating load distribution on the long-term operation performance of a geothermal heat pump system based on deep borehole heat exchanger (DBHE) through numerical analysis and model establishment. It also explains how complex geological conditions affect the dynamic heat extraction and heat recovery of the DBHE system. Additionally, the study checks the robustness of the model and presents an initial investigation on DBHE array with heat recovery.
Article
Thermodynamics
Wanfeng Li, Zicheng Hu, Shuwen Geng, Fengyue Wang, Xiaoyuan Liu, Yibo Guo, Hao Huang, Yuchen Han
Summary: In order to solve the problem of soil thermal imbalance in cold regions, a new soil heat storage system has been proposed that absorbs heat from ambient air through a heat source tower and injects the heat into the soil through a borehole heat exchanger in the non-heating season. This paper builds a mathematical model of the integrated system of the heat source tower and borehole heat exchanger and studies the influence of borehole heat exchanger structural parameters and soil thermal properties on soil heat storage characteristics. The results show that the soil heat storage capacity and temperature difference of the system increase with certain parameters, while the borehole wall temperature increases or decreases depending on different parameters.
APPLIED THERMAL ENGINEERING
(2023)
Article
Green & Sustainable Science & Technology
Shuai Huang, Ke Zhu, Jiankai Dong, Ji Li, Weizheng Kong, Yiqiang Jiang, Zhaohong Fang
Summary: The deep borehole heat exchanger (DBHE) is an important component of medium-depth geothermal heat pump systems. It has advantages such as small land area requirement, good seasonal heat storage performance, and high efficiency in winter. Most of the current research on DBHE focuses on a single operation mode, and there are few studies on multiple operation modes. This study develops a DBHE heat transfer model and validates it using real-world data. The analysis of different run-stop ratios reveals that thermal recovery and operation stability of DBHE are negatively correlated with the run-stop ratio, while the heat loss rate is positively correlated with the run-stop ratio.
Article
Thermodynamics
Zhuo Zhou, Qinggong Liu, Yao Tao, Yuanling Peng, Tingzheng Zhou, Yong Wang
Summary: This study conducted experiments and numerical simulations on a borehole ground heat exchanger (BGHE) with shape-stabilized phase change material (SSPCM) backfill. The results showed that SSPCM effectively mitigates temperature fluctuations, especially near the heat source. The simulations also found that higher mass ratios of SSPCM can reduce temperature variations but become less cost-effective.
APPLIED THERMAL ENGINEERING
(2023)
Article
Construction & Building Technology
Haiyu Fu, Liang Fang, Mingzhi Yu, Ping Cui, Wenke Zhang, Yudong Mao, Zhaoyi Zhuang, Zhaohong Fang
Summary: This study examines the impact of heat storage in the non-heating season on the heat extraction capacity and economy of a coaxial borehole mid-deep borehole heat exchanger (MBHE). The study presents and validates a heat transfer model for the MBHE, showing high accuracy. The study analyzes the effects of operation time, annual heat storage time, temperature and flow rate of the heat storage fluid on heat extraction capacity and economy, providing recommendations for optimal parameters.
ENERGY AND BUILDINGS
(2023)
Article
Energy & Fuels
Shunsuke Tsuya, Hikari Fujii, Hiroyuki Kosukegawa, Kanako Yamashita, Saeid Mohammadzadeh Bina
Summary: The effect of pumping well operations on the performance of a borehole heat exchanger was evaluated in this study. The results showed that pumping well operations can enhance the performance of the ground source heat pump system, and a higher pumping rate can improve the heat exchange capacity of the borehole heat exchanger. Furthermore, installing a borehole heat exchanger in an area with natural groundwater flow can further enhance its performance.
Article
Thermodynamics
Songqing Wang, Yuxuan Ji, Shijing He, Jing Gao, Yao Wang, Xuelong Cai
Summary: This paper examines the influence of various factors on the heat transfer characteristics of the vertical borehole heat exchanger (BHE) under stratified soil conditions through theoretical research, experimental research, and numerical simulations. By altering the groundwater seepage velocity, porosity, saturation, thermal conductivity, and initial soil temperature, the working conditions and heat transfer rate of the vertical BHE were established and calculated. The results show that the weight of the influencing factors follows the descending order: thermal conductivity, groundwater seepage velocity, porosity, saturation, and initial soil temperature. These findings provide an important reference for optimizing future BHE designs.
CASE STUDIES IN THERMAL ENGINEERING
(2023)
Article
Green & Sustainable Science & Technology
Changlong Wang, Han Fang, Xin Wang, Jinli Lu, Yanhong Sun
Summary: This study analyzes the influences of heat capacities of different parts of boreholes on the performance of deep coaxial borehole heat exchangers. The results show that considering the heat capacities of different parts is important for accurately estimating the heat transfer performance, especially in the early stage and for larger borehole radius.
Article
Engineering, Civil
Sara Barbieri, Matteo Antelmi, Sorab Panday, Martina Baratto, Adriana Angelotti, Luca Alberti
Summary: Geothermal resource exploitation has shown constant growth in recent years, with low-temperature geothermal energy being used as a cost-effective and green solution for building air conditioning. The design of BHE and correct interpretation of TRT are crucial for meeting building energy demand.
JOURNAL OF HYDROLOGY
(2022)
Article
Green & Sustainable Science & Technology
Chengqiang Zhi, Xiuqin Yang, Xiang Zhou, Shuyang Tu, Xu Zhang
Summary: The total length of borehole heat exchangers (BHEs) is crucial for the performance and cost-effectiveness of ground source heat pump (GSHP) systems. The current calculation method in the Chinese national standard is not economically reasonable, prompting this study to propose a revised method that incorporates a temperature penalty parameter to optimize long-term performance and minimize costs.
Article
Thermodynamics
Jiewen Deng, Chenwei Peng, Yangyang Su, Wenbo Qiang, Wanlong Cai, Qingpeng Wei
Summary: This paper investigates the heat storage characteristics of deep borehole heat exchanger (DBHE) and finds that the average heat extraction rate (Qr) of DBHE under intermittent operation is 8.6%-64.7% higher than under continuous operation. Additionally, the study quantitatively analyzes the influence of operation modes, parameters, and thermo-physical properties of DBHE on its heat storage characteristics, demonstrating the wide-range regulation ability of DBHE. Therefore, DBHE shows excellent regulation capabilities to match space heating load variations and the production rules of clean electric power.
Article
Engineering, Chemical
Antonin Kunz, Martin Klempa, Petr Bujok, Dawid Piotrowski
Summary: This study examines the impact of climate change on the dimensioning process and performance of borehole heat exchangers (BHEs), highlighting the importance of considering climate change in the design process.
Article
Thermodynamics
Yaran Wang, Yeming Wang, Shijun You, Xuejing Zheng, Shen Wei
Summary: Geothermal energy is a promising renewable source for district heating. A method to optimize the water flow rates in the coaxial deep borehole heat exchanger of a ground source heat pump system is proposed in this study. The results of the comparison of system operation before and after optimization show that the method has a significant effect on energy-saving operation.
APPLIED THERMAL ENGINEERING
(2022)
Article
Energy & Fuels
Stephan Dueber, Raul Fuentes, Guillermo Narsilio
Summary: We investigated the impact of horizontal connection pipes on shallow geothermal systems in different climate zones. The results showed that the inclusion of connection pipes reduced the load on the borehole heat exchanger (BHE) by an average of 34% in tropical climates, 19% in temperate climates, 11% in arid climates, and 4% in continental climates, leading to cost savings in drilling. However, in cities like Moscow and Heihe with severely colder conditions, the BHE load increased by 13% and 72% respectively, resulting in reduced efficiency or the need for additional drilling.
