Literature review on a U-shaped closed loop geothermal energy development system

Geothermal energy is becoming more attractive nowadays. Compared with enhanced geothermal recovery method, developing geothermal energy using a closed loop heat exchanger possesses unique advantages, such as no fluid exchange with the geothermal reservoir. U-shaped closed loop geothermal energy development system was proposed in recent years with high energy efficiency. In this paper, we reviewed the U-shaped closed loop geothermal energy development system from literature and, then, conducted a case study based on previous models. It is found that: (a) the effective heating distance is an important parameter that can be used for economic analysis; (b) the effective heating distance grows with producer number; (c) the wellbore starting from the turning point to well-head should be insulated; (d) a higher temperature can be obtained not only from by increasing the effective heating distance, but also by decreasing mass flow rate to a reasonable level; (e) the turning point will come earlier when the mass flow rate is smaller, while it will come later when the mass flow rate is larger.