| Title | Characterization of ground thermal conditions for shallow geothermal exploitation in the Central North China Plain (NCP) area |
|---|---|
| Authors | Wanli Wang, Guiling Wang |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Ground source heat pump (GSHP) systems; Undisturbed ground temperature; Ground thermal properties; Geological settings; Thermal response test (TRT); Constant heating-temperature method (CHTM) |
| Abstract | The North China Plain (NCP) is one of the rapid developing regions in China which has great potential for ground source heat pump (GSHP) system applications. Currently, only limited data of ground thermal properties, which is the prerequisite for GSHP systems design, can be obtained. In this study, ground thermal properties including ground temperature and thermal conductivity are measured in three representative geological regions in central NCP: SJZ (piedmont alluvial plain), HS (central alluvial plain) and CZ (coastal plain). Results show that the geothermal gradient below 45 m in depth is only 0.01°C/m in SJZ, which is smaller than that of HS and CZ with 0.02 °C/m due to the strong effect of groundwater flow. Although thermal conductivity measured by soil samples differ little in the three regions, thermal conductivity obtained by constant heating-temperature method (CHTM)-based thermal response test (TRT) ranges between 1.04 and 1.4 W/(m.K) in SJZ, and ranges between 1.55 and 1.71 W/(m.K) in HS and CZ. The lower thermal conductivity in SJZ is mainly caused by the deep groundwater table. Therefore, to obtain reasonable thermal conductivity, TRT is highly recommended in SJZ, while both laboratory and field tests are practicable methods in HS and CZ. |