Roland N. Horne [Chair], Thomas Davies Barrow Professor of Earth Sciences, Stanford University

Geothermal energy is the ‘underground’ renewable energy source – out of view, and sometimes out of mind. Yet in parts of the world, geothermal energy makes up between 20% (El Salvador, New Zealand, Philippines) and 35% (Tibet, Iceland) of all electricity generated within a country. The US states of California and Nevada both generate about 5% of their electricity from this source. We will hear from Kenya, which is pursuing geothermal energy aggressively, and effectively plans to electrify much of its economy using this indigenous renewable resource. Challenges to the broader application of geothermal energy are partly geological, partly technological, and partly political. Not all regions enjoy the geological conditions for high temperature resources. Not all resources are straightforward for development, and would require the application of stimulation technology. And not all communities are willing to embrace geothermal development if they believe it may impact natural hot spring resources that are important to their way of life. Nonetheless, these challenges are not insurmountable, and we will discuss ideas to move forward with this important renewable energy source.

Keith Evans, Senior Scientist, Department of Earth Sciences, ETH Zürich

Guðmundur Ó. Friðleifsson, Chief Geologist, HS Orka hf

The geothermal industry in Iceland joined forces some 15 years ago and established the Iceland Deep Drilling Project (IDDP). The main purpose is to find out if it is economically feasible to extract energy and chemicals out of hydrothermal systems at supercritical conditions from within geothermal systems in volcanic terrains (www.iddp.is). In order to study such systems in nature an advanced drilling technology needs to be applied and a novel fluid handling and evaluation system designed. The basic idea is to drill deep enough into the roots of such high temperature systems and bring the fluid to the surface as 400-600°C superheated steam, at subcritical   pressures (<220 bar). In the case of low permeability systems, by injecting cold fluid into the hot rocks, fractures can be induced to complete the thermal mining cycle. If successful, it may be possible to increase the power outputs of suitable geothermal wells by an order of magnitude, without increasing their environmental foot prints. The IDDP lessons learned so far and future prospects are described in my presentation at ICEF-2015 annual meeting. In 2009, drillhole IDDP-1 was drilled into 900°C hot magma with a spectacular result, which is briefly summarized in this video release: https://www.youtube.com/watch?v=3d8hC71xGpc.