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ORIGINAL RESEARCH article

Front. Energy Res.
Sec. Sustainable Energy Systems
Volume 12 - 2024 | doi: 10.3389/fenrg.2024.1430707
This article is part of the Research Topic Clean Energy and Low-carbon Transportation View all 6 articles

Heat transfer and system performance of a novel solar ground-source heat-pump system with borehole heat-exchangers using a combined parallel and series connection

Provisionally accepted
Chunling WU Chunling WU 1*Mengyao Song Mengyao Song 2Lu Jin Lu Jin 3Qiang Fu Qiang Fu 1Longhu Zhu Longhu Zhu 1
  • 1 China Academy of Building Research Tianjin Institute, Tianjin, China
  • 2 Guangzhou City Construction College, Guangzhou, China
  • 3 Shanghai Municipal Engineering Design Institute (Group) Co., Ltd, Shanghai, China

The final, formatted version of the article will be published soon.

    A novel BHEs is proposed that can overcome the problems associated with the low heat-transfer efficiency of borehole heat-exchangers (BHEs) that are connected in series (BHEs-S) and the low heat-transfer temperature differences of BHEs that are connected in parallel (BHEs-P). The new BHE uses a combined series and parallel connection (BHEs-CSP), which can further be classified into individual in-series and in-parallel zones. A numerical model of the new BHEs-CSP is then developed to optimize the key design parameters such as borehole spacing, number of series stages, and heat-extraction methods. The results show that, with the optimal configuration, the average soil temperature with a BHEs-CSP is 6.70 °C higher than for a BHE that is connected in parallel. Furthermore, the heat-transfer efficiency can be improved by 4.1 % compared to BHEs that are connected in series. It is recommended that the distance between buried pipes in the series area and parallel area should be 5.25m, and the series number of buried pipe groups should be 4. To study the overall performance of the solar-assisted ground-source heat-pump with a BHEs-CSP (SAGSHP-CSP), a TRNSYS model is developed. The results show that the optimal area- and heat-storage-ratios (for in-series zone to in-parallel zone), using SAGSHP-CSP, are 1:4 and 3:2, respectively. Under these conditions, the system coefficient of performance (SCOP) is over 5.2 and the COP and SCOP is improved by 9.8 % and 13.0 % compared to GSHP systems with BHEs-P. Furthermore, an improvement by 18.4 % and 18.2 %, compared to the GSHP system with BHEs-S, is reported.

    Keywords: Borehole heat exchangers, Solar-assisted ground-source heat-pump, Combined series and parallel connection, Design parameter optimization, heat transfer

    Received: 10 May 2024; Accepted: 21 Jun 2024.

    Copyright: © 2024 WU, Song, Jin, Fu and Zhu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Chunling WU, China Academy of Building Research Tianjin Institute, Tianjin, China

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