Regional and country-level assessments of geothermal energy potential based on UNFC principles

The United Nations Framework Classification for Resources (UNFC) is a universally acceptable and internationally applicable scheme for the sustainable management of all energy, mineral and anthropogenic resources. As of 2016, the UNFC is also applicable to geothermal energy resources. Prescribing quantification methods for resource estimates goes beyond the scope of the UNFC, as multiple best practices, as well as analytical and numerical tools already exist, which encompass the significantly wide range of geothermal geological settings, heat recovery and conversion technologies and socio-environmental contexts. Nevertheless, the Project concept embedded in the UNFC, together with the need to define the associated level of confidence in the potential recoverability of the quantities, requires users to link different types of geothermal resources with corresponding viable project development schemes. This facilitates the choice of suitable quantification methods (probabilistic, scenario or incremental), compatible with the UNFC classification principles, which is particularly relevant to regional and country-level assessments of undeveloped geothermal potential. This paper critically reviews recently published country and global geothermal resource assessments, based on different, non-UNFC methods and presents a high-level superposition of the published assessments with the unique features of the UNFC