Closed-loop deep borehole heat exchanger (DBHE) systems for producing heat from geothermal sources have the advantage that the heat transfer fluid is contained within the loop. In this study, for the first time, a U-configuration closed-loop DBHE was examined to evaluate the energy produced per unit energy invested from a 2330-m-deep geothermal reservoir in central Alberta, Canada. A detailed earth model where the system is modeled from the surface to the geothermal source is used in a numerical simulation model to understand the efficiency of the process. The results reveal that the fluid flow reaches its highest temperature in the ascending section of the U-loop rather than the bottom section which implies that the insulation on the working fluid should start in the ascending section of the U-loop. The results demonstrate that the closed-loop system can achieve ratios of the energy produced and energy invested of 7 GJ/GJ. Although this efficiency is promising, the absolute amount of heat energy harvested is limited by the loop’s heat transfer area in the geothermal reservoir.

中文翻译：

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加拿大艾伯塔省基底寒武系砂岩地层闭环 U 型管深埋管换热器的评价

用于从地热源产生热量的闭环深埋管换热器 (DBHE) 系统具有传热流体包含在回路内的优点。在这项研究中，首次检查了 U 型闭环 DBHE，以评估从加拿大艾伯塔省中部 2330 米深的地热储层投入的单位能量产生的能量。在数值模拟模型中使用从地表到地热源对系统进行建模的详细地球模型，以了解该过程的效率。结果表明，流体流动在 U 形回路的上升段而不是底部达到最高温度，这意味着工作流体上的绝缘应该从 U 形回路的上升段开始。结果表明，闭环系统可以实现7 GJ/GJ的能源生产和能源投资比。尽管这种效率是有希望的，但所收集的热能的绝对量受到地热储层中回路传热面积的限制。