EFFECTS OF CEMENT CONDUCTIVITY ON THE THERMAL PERFORMANCE OF AGS SYSTEMS

Abstract

Geothermal energy applications have gained significant importance within the renewable energy sector. This growth is caused primarily by supply constraints in fossil-fuel-based energy sources. Recent advancements focus on developing various techniques to extract subsurface heat. Advanced designs and innovative materials are constantly emerging to support these novel applications. This highlights the necessity to carefully analyse all system components. Closed-loop geothermal systems also referred to as Advanced Geothermal Systems (AGS), can be configured in various design methods to extract this energy. This study evaluates the influence of casing cement thermal conductivity on the thermal performance of closed-loop systems. The study compares three cement options using fixed design parameters as low-conductivity (0.8 W/mK) and high-conductivity (2.8 W/mK), and a hybrid model. Also, the surrounding rock formation is modelled with a homogeneous thermal gradient along the wellbore, analysed both for low (35 K/km) and high (75 K/km ) thermal gradient scenarios. The results demonstrate that varying cement thermal conductivity impacts the overall thermal output by 8.3 to 12.6%. The hybrid configuration provides a further 1 to 1.5% improvement compared to uniform high conductivity cement, demonstrating the benefit of selecting cement conductivity based on the local direction of heat transfer.