**Preface to "New Perspectives on Geothermal Energy Exploration and Evaluation of Geothermal Potential"**

Due to the increasing need for energy in emerging countries, as well as energy transition requirements, geothermal resources' characterization and use is generating more and more interest, in both low/intermediate and high temperature fields. However, their characterization and use can be challenging. Deep geothermal resources can be hosted in highly heterogeneous volcanic complexes, sedimentary basins, or old basement rocks. Reservoir permeability can be enhanced through different engineering techniques (hydraulic, chemical, and thermal stimulation), although their application may raise problems of social acceptability. Development of interdisciplinary methodologies to characterize geothermal systems from a volcanological, geophysical, geochemical, and geo(hydro)thermal point of view is fundamental. Moreover, improvement of assessment methods is a key aspect to unlock the use of geothermal resources, including high temperature borehole thermal energy storage (HT-BTES) and direct use of thermal waters for building heating systems.

This book came up as the result of a Special Issue in the *Energies* Journal with 8 papers published during 2021. Its idea arose in the context of the IGCP636 project "Geothermal resources for energy transition", approved in 2020 by the International Geoscience Programme of the UNESCO. The main objectives of IGP636 are promoting the use of geothermal resources as a clean, baseload, and renewable energy by: (1) increasing knowledge about deep geothermal reservoirs, (2) conducting outreach activities with focus groups and community, and (3) promoting the installation of low-enthalpy geothermal systems. This book includes topics related with these three items, although only five papers are co-authored by researchers that are members of the IGCP636 group, since the Special Issue was open to contributions from any author.

> **Renato Somma and Daniela Blessent** *Editors*

*Article*
