Relaxation factor for geothermal use development – Criteria for a more fair and sustainable geothermal use of shallow energy resources

• A protocol for new shallow geothermal installations is proposed.
• The protocol is based on numerical modeling and a relaxation factor.
• The protocol is applied in a real urban groundwater body affected by ground source heat pumps.
• We have found a specific policy impact indicator of interest for numerical water policy assessment.

This study attempts to promote new groundwater thermal management policies for the shallow geothermal energy sector, which is currently at risk of stalling due to the existing uncertainty of its international legal status. The physical constraints affecting groundwater thermal management policies are described as a basis for a later proposal of an approval process protocol for new shallow geothermal installations. The policy proposed for this process is based on numerical modeling and a relaxation factor which reserves a fraction of shallow geothermal energy resources for possible third party installations thus preventing its monopolization. The policy is then applied to simulate a concession process in a real urban groundwater body highly affected by ground source heat pumps. A calibrated numerical groundwater flow and heat-transport model has been utilized for the evaluation of the thermal response of the aquifer to a new projected installation and the thermal interference risk associated. The results obtained from the protocol application have proven its practical value in the sustainable management of shallow geothermal energy resources and in ensuring stakeholders water rights. In addition, a specific policy impact indicator was derived that should be of interest for numerical water policy assessment initiatives.

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