It is becoming increasingly apparent to the International Geothermal Association that a lack of clear global guidelines and standards is holding back the assessment and development of geothermal energy as a viable energy option at a global scale. The planning and funding of future energy infrastructure on a global scale (for example, by development banks and aid agencies) is based to a large extent on the comparative potential of different energy options in different locations. A proper comparison of those options requires globally consistent methods for assessing and classifying energy potential. The fossil fuel, nuclear and many renewable energy sectors, for example, have clearly defined standard methodologies for assessing energy potential in a globally consistent manner.

A global assessment of geothermal potential is currently hindered on at least two fronts. Firstly, national agencies in many parts of the world have no experience or guidelines as to how to assess, quantify and classify their local geothermal potential. Secondly, those agencies that have assessed geothermal potential within their jurisdictions have developed and used their own local methodologies and terminologies that are not necessarily comparable with, or appropriate for, other jurisdictions.

This special issue of Geothermal Energy Science aims to collate in one place papers on a range of methods commonly applied to estimate geothermal potential, and a range of existing and proposed schemes to classify those estimates according to confidence and other factors.