Overview of solutions to improve efficiency of ground source heat pump system

ZHANG Yuping; YANG Xiao; LIU Jun; LIU Boyang; TANG Fujiao; TAN Yiqiu

doi:10.13809/j.cnki.cn32-1825/te.2023.06.003

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Overview of solutions to improve efficiency of ground source heat pump system
Vol. 13, Issue 6, Pages: 726-740(2023)
Published：2023
DOI： 10.13809/j.cnki.cn32-1825/te.2023.06.003
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DOI：

ZHANG Yuping, YANG Xiao, LIU Jun, et al. Overview of solutions to improve efficiency of ground source heat pump system[J]. Petroleum Reservoir Evaluation and Development, 2023, 13(6): 726-740. DOI： 10.13809/j.cnki.cn32-1825/te.2023.06.003.

摘要

浅层地热可被用于路面融雪除冰，建筑供热、制冷等。闭环垂直地埋管是浅层地热资源利用最常见形式，其在终端负荷作用下与岩土体进行热量交换。单根地埋管获取地热资源能力有限，多根埋管组合形式（地埋管群）被广泛应用于地源热泵系统。然而，地下温度场受管群与岩土换热性能影响，在设计、运行等不合理条件下可导致岩土体温度场不平衡，进而造成地源热泵系统能效降低，甚至失效。因此，管群设计、运行等方案优化是解决地温场不平衡问题的必要途径。基于国内外相关研究成果，梳理管群优化设计方法、储能和去能方法、辅助热源和冷源方法、运行控制策略。其中，管群优化设计方法主要聚焦管群间距设计、排布方式等；储能和去能方法主要介绍利用太阳能、工业废热等外部热源和冷源对地下岩土体进行加热和降温等的最新研究成果；辅助热源和冷源部分重点介绍太阳能、冷却塔等在地源热泵系统中的应用；运行控制策略主要分析地源热泵系统运行控制方案，包括峰点冷热负荷运行、间歇性运行、分区运行、系统控制策略等方案。总结了管群优化设计方法、运行控制策略等，剖析了各方案的优点与不足，可为管群岩土体温度场不平衡解决方案与地源热泵系统能效提升途径提供参考。

Abstract

Shallow geothermal energy

with applications ranging from road snow melting and deicing to building heating/cooling

primarily utilizes closed-loop vertical buried pipes for resource exploitation. These pipes function by exchanging heat with the subterranean zone under specific cooling or heating loads. Given the limited capacity of a single vertical ground heat exchanger to harness geothermal resources

arrays of these exchangers are more commonly employed to effectively tap into shallow geothermal resources. However

the underground temperature field can be significantly affected by the heat exchange process between the ground heat exchanger array and the surrounding soil. Improper design and operational conditions can lead to an imbalance in the underground temperature field

potentially resulting in energy deficiencies and the malfunctioning of Ground Source Heat Pump Systems（GSHPS）. Therefore

optimizing the design and operation scheme of ground heat exchanger array is the key to solve the imbalance of underground temperature field. The review summarizes the domestic and foreign research results

outlining various methods for energy storage and removal

incorporating auxiliary heating and cooling sources

and exploring relevant optimization techniques. The borehole array design optimization methods include primarily the distance between the pipe and the borehole layout. The energy storage/removal section mainly introduces the latest research results of borehole heat exchanger array by using external heat/cold sources such as solar energy and industrial waste heat. The auxiliary method mainly describes the latest researches on the application of resources like solar energy and heating towers. The operation control strategy mainly analyzes the operation control of the ground source heat pump system

including the peak cooling and heating load operation

intermittent operation

partition operation

system control strategy

etc. By thoroughly examining these optimization approaches and operational control strategies

the review provides a comprehensive analysis of the advantages and disadvantages of each scheme. This detailed evaluation serves as a valuable reference for improving the energy efficiency of GSHPS

ensuring sustainable and effective utilization of shallow geothermal resources.