ABSTRACT
It is recognised by many international organisations (World Bank, UNESCO, etc.) that by 2050, climate change will have a dramatic effect on not just human beings but also on world geopolitics. Although geothermal energy should be able to play a major role in addressing this issue, this has not been the case to date due to a disparity in the availability of environmentally friendly geothermal energy in relation to the high demand for energy from the high density populated areas of the world (China, India, Europe, etc.). At present, the higher demand for energy in these areas is normally met with hydrocarbon resources with associated emissions of greenhouse gases and other contaminants into the atmosphere, which in turn has led to the climate change effect.
Worldwide conventional geothermal (hydrothermal) development is mainly in areas characterised by volcanism and/or crustal extension and thinning, both of which lead to anomalously high heat flow from the interior of the Earth towards the surface. In these locations, the depth required to access high-temperature resources is relatively shallow. Economically, this is a distinct advantage; however, such resources have a limited geographic extent and often do not coincide with the most densely populated areas. Therefore, geothermal’s contribution to the reduction of CO2 is relatively insignificant on a global scale.
Research is being carried out in many countries and regions to determine if significantly more geothermal energy can be made economically more accessible in the non-volcanic regions of the world. One of these concepts is the engineered geothermal system (EGS), whereby deep, naturally permeable faults are hydraulically manipulated at depth to emulate natural conventional hydrothermal systems, allowing injected cold water to be heated at depth and returned to the surface in production wells as high-temperature heat for commercial application.
Following a public-funded European R&D project at Soultz-sous-Forêts in France, several small commercial EGS projects are now operational in Germany and France. All are located within the Rhine Graben, which is known to host deep, permeable faults that can be enhanced to enable commercial flow rates of geothermal fluids. These projects have clearly demonstrated that deep fault systems can maintain sufficient in-situ fluid productivity for them to be regarded as long-term and sustainable local energy resources. Additionally, the value of international collaboration has been shown to be helpful in addressing scientific and engineering problems. Although these projects are relatively small (~5 MWe, supplying around 10,000 homes), they have the potential to be scaled up into much more significant sources of energy.
This demonstrates that EGS has great potential for geothermal energy production outside of volcanic areas. However, for this to become universally applicable, it needs to be demonstrated in various geological environments (not only the Rhine Graben).
The authors of this chapter agree that for EGS technology to be effective and help mitigate the climate change issue, large-scale international collaboration is essential. It is proposed that a cooperation structure be established under a consortium consisting of bodies such as the International Energy Agency, the World Bank, the United Nations and others, providing the priority and credibility needed. The broad objective would be to identify and characterise suitable deep fault systems in the vicinity of densely populated areas. This would lead to the establishment of EGS demonstration projects in key areas initially and commercial projects subsequently. Establishing an International EGS Centre of Excellence where scientists and engineers can come together to exchange experiences and drive the technology forward is proposed as a way to facilitate large-scale international cooperation and technology transfer.
Based on experience gained at various sites, a scenario is put forward in this chapter that could help the take up of EGS technology worldwide and thus assist the climate mitigation plan.
