Browsing by Author "Chong, Qinwan"

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    Evaluation of closed-loop U-Tube deep borehole heat exchanger in the Basal Cambrian Sandstone formation, Alberta, Canada
    (2022-10-01) Chong, Qinwan; Wang, Jingyi; Gates, Ian D.
    Abstract 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.
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    On Geothermal Heat Extraction from the Basal Cambrian Sandstone Unit in Central Alberta, Canada
    (2021-04-29) Chong, Qinwan; Gates, Ian; Clarke, Matthew; Shor, Roman; Kibria, Golam; He, Jianxun; Prodanovic, Vladan
    There is no doubt that the trend of ever-increasing energy use will continue with continued human activity. However, traditional energy resources such as fossil fuels are limited and result in serious environmental issues. As renewable energy option, geothermal resources, unlike other kinds of renewable resources, can not only provide clean but also sustained energy for both electricity and direct heating. Alberta, Canada has a long oil industry history but its continued expansion is now in question given current environmental and investment pressures. Recent studies from existing well bore information in central Alberta indicate there is potential for large-scale development of geothermal energy. In the research documented here, a detailed examination of Basal Cambrian Sandstone Unit (BCSU) of the Western Canadian Sedimentary Basin (WCSB) has been studied as a geothermal resource in Central Alberta, Canada. Three studies were conducted: 1. Evaluation of energy extraction from a geothermal resource using open loop well configurations based on analyzed geological data, 2. Numerical analysis of a closed loop U-Tube Deep Borehole Heat Exchanger (DBHE), and 3. An assessment of variable flow rate strategies for closed loop U-Tube DBHE system. The results from this research show that the reservoir is exploitable under most cases of examined well configurations. However, energy utilization is different when different well configurations are applied. For the study of open loop configurations, the temperature of produced water can meet the requirement of generating low-enthalpy power. Compared to five-well pattern systems, two-well pattern systems produce more energy with higher energy efficiency. When closed loop U-Tube DBHE system is conducted, it is more energetically effective than open loop systems. However, its low produced flow temperature and low produced energy indicating the utilization of direct heating on a small-scale. The analysis of operating variable flow rate strategies on closed loop systems reveals the complicated heat transfer performance due to the different flow rate injection during time periods. High-low stepped flow rate of the working fluid appears to have merit because enables the geothermal resource to ‘recharge’ with thermal energy during its operation.