Meitian dizhi yu kantan (Apr 2025)
Operation strategy simulation of the heating system for moderately deep geothermal resources
Abstract
BackgroundThe active utilization of moderately deep geothermal resources for heating serves as a critical measure to achieve the goals of peak carbon dioxide emissions and carbon neutrality. Meanwhile, the effectiveness of the operation strategies of the heating system using these resources directly influences heating performance and significantly affects the energy consumption of the heating system. It is necessary to prevent resource waste while utilizing geothermal energy. MethodsBased on a heating project using moderately deep geothermal resources in the Guanzhong Basin, Shaanxi Province, this study established a dynamic simulation model using the TRNSYS transient simulation software. Then, this study simulated the heating performance and energy consumption of the heating system under five operation strategies and conducted systematic analyses of the temperatures, energy consumption, and operational mechanisms. Results and Conclusions The results indicate that during the early and late stages of the heating season, the operation strategy of direct heat exchange via a geothermal well exhibited the highest heating performance. This strategy enabled the room temperature on the user end to reach 32℃, with a peak coefficient of performance (COP) of 19. In contrast, cascading utilization based on a geothermal well and heating pump units was suitable in the case where the water temperature at the outlets of the buried tubes gradually decreased in the middle stage of the heating season. This strategy can maintain the room temperature on the user end at about 30℃ over a short period, with a maximal and minimal COP of 12.75 and 9.06, respectively. In the late stage of the continuous heat supply using a single geothermal well, the heating operation strategy relying primarily on heat pump units can be adopted. This strategy allowed the room temperature on the user end to range from 20 ℃ to 28 ℃ in the short term, with a maximal and minimal COP of 6.99 and 5.22, respectively. In addition, the operation strategy should be dynamically adjusted based on the water temperature at the outlets of buried pipes and the room temperature on the user end under varying application contexts. The overall energy consumption revealed that direct heat transfer via a geothermal well should be preferred and that the start frequency and operational duration of heat pump units should be minimized. For the cascading utilization, one pump unit should be started first, and it is necessary to minimize the number of heat pump units in operation. For the operation strategy of single-well heating, heating relying on heating pump units in the middle to late stage of the heating season led to increased energy consumption. Therefore, an intermittent operation strategy based on multiple wells should be employed where possible. The results of this study can be used to adjust and optimize the operation strategies of the coaxial casing-type buried pipe heat exchanger system for moderately deep geothermal resources while also providing a reference for the design of operation strategies.
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