Novel hybrid coaxial-U-shaped closed-loop geothermal system for enhanced energy extraction: a numerical analysis

ABSTRACT

Insulated U-shaped closed-loop geothermal system (UCLGS) is an efficient and environmentally friendly method of harnessing geothermal energy. However, heat available in the rock surrounding the insulated production pipe has not been extracted yet. Therefore, this study proposed a novel hybrid coaxial-U-shaped CLGS (HCLGS) to enhance the overall thermal performance of CLGS. The HCLGS comprises an insulated UCLGS for harnessing energy from the reservoir rock, alongside a coaxial double pipe system designed to extract additional thermal energy from the rock enveloping the insulated production pipe of the UCLGS. Further, the study explored the thermal feasibility of the proposed HCLGS in various rock formations for geothermal energy extraction at different depths. The results showed that the HCLGS installed in the pyroxenite rock produced primary hot fluid with a maximum temperature of 94°C and secondary hot fluid at a temperature of 38.5°C for the base case, achieving a COP of 1.15. The proposed HCLGS can extract up to 18% higher thermal power than the insulated UCLGS, with a COP ranging from 1.11 to 1.16. Finally, the proposed hybrid system significantly harnessed the additional heat available in the rock encompassing the insulated production pipe of UCLGS.

KEYWORDS:

• Renewable energy
• geothermal energy
• heat extraction
• closed-loop geothermal system
• hybrid coaxial and U-shaped system

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2024.2340124.

Additional information

Notes on contributors

Srinivas Chappidi

Srinivas Chappidi currently pursuing PhD in the Department of Civil Engineering, SVNIT, Surat. His research interest includes Geothermal energy extraction, Slope stability, Tunnelling and underground construction and Ground improvement techniques.

Ankesh Kumar

Dr. Ankesh Kumar is currently working as an Assistant Professor in the Department of Civil Engineering at IIT Palakkad, Kerala, India. He received his PhD from IIT Delhi in 2019. His research interests encompass rock mechanics and underground structures, petroleum-related rock mechanics and energy geotechniques.

Jogender Singh

Dr. Jogender Singh is currently working as Assistant Professor in the department of chemical engineering of SVNIT, Surat. After completing his Ph.D. from IIT Delhi, he worked in Tecnológico De Monterey, Mexico as Postdoctoral Researcher. His research interest includes Process Intensification, Heat Transfer and Fluid flow, Microfluidics and Geothermal energy extraction.