The HOCLOOP project has completed the data analysis from the thermal response test of the Drill Heat String (DHS) performed within the scope of the full-scale pilot test at NORCE Research’s Ullrigg Test Centre in Stavanger, Norway. The results confirm that HOCLOOP’s closed-loop geothermal concept performs with the required characteristics to deliver stable, predictable, flexible, and clean geothermal energy even in areas without natural hydrothermal reservoirs, strengthening the case for geothermal deployment in a wider range of geological environments.
Pilot test validation results
In November 2024, a 500-metre DHS was installed at the Ullrigg Test Centre by Reelwell AS, with operational support from NORCE and the Institute for Energy Technology (IFE). Over the following months, the system was operated under realistic flow conditions to assess completion conditions, mechanical performance, and thermal characteristics.
A full thermal response test was completed, providing high-quality data for evaluating heat-transfer. The analysis confirms that the closed-loop configuration performs in line with expectations and can maintain efficient heat extraction without relying on underground water reservoirs.
“The Ullrigg test gave us exactly the kind of high-quality data we needed,” said Mario Silva, Project Coordinator at IFE. “We’ve validated both the thermal models and the operational performance of the Drill Heat String, showing that closed-loop geothermal technology can operate efficiently even in low-permeability environments.”
Validated models and system performance
The pilot test also confirmed that the DHS completion system operated as intended, with all components tested and evaluated under field conditions. The project’s complete modelling framework using water as the heat-transfer fluid has now been validated against the full-scale test data. In parallel, simplified and full models using CO₂ and CO₂ mixtures are nearing completion, offering promising potential for enhanced performance in different geological settings.
Deployment potential across Europe
Beyond the test site, HOCLOOP partners have completed characterization studies in France, Belgium, Germany, Italy, and Poland. These assessments provide a clearer picture of the geothermal energy production capacity of HOCLOOP’s closed-loop concept and its surface integration with regional heating, cooling, and power solutions across Europe.
The long operational lifespan of closed-loop geothermal systems – potentially spanning centuries –means that although the return on investment is gradual, the long-term energy contribution and stability become increasingly valuable over time.
A significant step toward real-world application
The successful completion and analysis of the pilot test represent a major milestone on the path to demonstrating the technology at Technology Readiness Level 5. With validated installation, performance, strong system integrity, and promising long-term potential, the HOCLOOP project confirms the feasibility, reliability, and scalability of the technology, paving the way for future pilot installations in geothermal-active regions across Europe.
About HOCLOOP:
The HOCLOOP project is a Research and Innovation Action under the Horizon Europe program (project number 101083558) coordinated by IFE, and dedicated to advancing geothermal exploitation technology, bringing together top energy and engineering experts to develop innovative methods for efficient and sustainable geothermal heat extraction.
