Abstract
Groundwater heat pump systems (GWHPs) can achieve higher coefficient of performance (COP) than air-source heat pump systems by using the relatively stable temperature of groundwater. Among GWHPs, multi-well systems have lower initial investment costs than conventional closed-loop geothermal systems, because they typically require installation of fewer boreholes for the same building load. However, the performance of GWHPs depends significantly on the groundwater properties, such as groundwater temperature, permeability and water quality. Moreover, pumping and injecting of groundwater during long-term operation may lead to problems such as overflow or clogging of the wells. In order to ensure reliable energy from ground sources, the development of sustainable operation methods for multi-well systems is essential for preventing overflow and well clogging. In this study, we have developed a pairing technology that connects the injection and supply wells through a spillway. This pairing technology can be used to control groundwater levels in wells and can be sustainably operated. To accurately estimate the performance of a multi-well system with the proposed pairing technology, the heating and cooling performance of the developed system was compared to that of a standing column well (SCW) system in a field-scale experiment. Furthermore, the effects of the multi-well pairing system on groundwater levels in the injection well were analyzed by numerical simulation. Moreover, in order to decide the required conditions of the multi-well pairing system, case studies were conducted under various hydraulic conductivity and pumping conditions.
Highlights
Ground source heat pump systems (GSHPs) are equipment that uses groundwater or heat in the ground as a heat source to deal with the cooling and heating loads of buildings
The ground temperature at 10–15 m below the ground surface is characteristically constant throughout the year [1], the heat exchange efficiency of a GSHP system is better than that of an air-source heat pump (ASHP) system
The performance of the multi-well system and that of a standing column well (SCW) system were comparatively analyzed in a field-scale pairing system and that of a standing column well (SCW) system were comparatively analyzed in a experiment
Summary
Ground source heat pump systems (GSHPs) are equipment that uses groundwater or heat in the ground as a heat source to deal with the cooling and heating loads of buildings. The ground temperature at 10–15 m below the ground surface is characteristically constant throughout the year [1], the heat exchange efficiency of a GSHP system is better than that of an air-source heat pump (ASHP) system. GSHP systems are classified as open-loop systems or closed-loop systems according to the heat exchange method. In the case of a closed-loop system, more boreholes are required compared to the open-loop system, and this increases the initial investment cost of the system to deal with a similar load. Rafferty [2] quantitatively analyzed the installation costs of an open-loop system and a closed-loop system. The drilling cost for a 528 kW capacity
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