Energy and Society
Renewable energy systems

Enhanced Geothermal Systems (EGS) ... starting a discussion about what this might mean ... good and bad

COMMENTARY

Peter Burgess

EGS Frequently Asked Questions What is EGS technology? Enhanced Geothermal Systems (EGS) expands the potential of geothermal energy by orders of magnitude. The traditional geothermal approach relies on finding naturally occurring pockets of steam and hot water. The EGS process, by comparison, replicates these conditions by fracturing hot rock, circulating water through the system, and using the resulting steam to produce electricity in a conventional turbine. The water is then re-injected back into the rock, where the cycle begins again in a closed loop.

EGS technologies go by many names including: Engineered Geothermal Systems (EGS), Hot Dry Rock (HDR), Hot Fractured Rock (HFR), Deep Earth Geothermal, and Deep Geothermal.

To see how an EGS system works, check out our SketchUp models.

Why EGS?

EGS is a utility-scale, base-load, and renewable energy source that could produce electricity cheaper than coal. Since EGS builds the geothermal reservoir by design, EGS projects can be made large enough to produce as much power as a typical natural gas or coal power plant (500 - 1,000 MW). Everywhere on earth, the deeper you go, the hotter it gets, meaning EGS can be developed in many areas across the world. EGS is a base-load resource, meaning it can run 24 hours a day regardless of weather. A recent report by MIT on EGS estimated 2% of the heat below the continental United States could provide 2,500 times the country's total annual energy use.

Where can we do EGS?

EGS can theoretically be developed anywhere there is sufficiently hot rock (above 150 degrees centigrade). Because drilling deep is costly today, EGS is currently most economical in shallow, high temperature zones. All 50 US states have EGS resources at varying depths. As drilling technology improves, it will become more economical to develop deeper resources, unlocking the ubiquitous heat of the earth.

Is geothermal energy being used today? How much?

Yes. Geothermal energy has been used for heat and electricity for over a hundred years in volcanic regions such as California, Italy, Iceland, Mexico, the Philippines and Indonesia. Currently, approximately 9,000 MW of traditional geothermal, also known as hydrothermal, generating capacity is installed in 24 countries around the world. The United States is the world's largest producer of geothermal energy, with roughly 2,800 MW installed. Geothermal currently generates enough electricity to power roughly 2.8 million homes in the United States.

How is EGS different from traditional geothermal?

In traditional geothermal energy, also known as hydrothermal energy, pockets of hot water and steam are drilled into to produce power. The amount of power that can be produced from a hydrothermal system is dependent on the temperature and size of these pockets. Hydrothermal systems – while reliable and effective – are limited in nature, vary in size, and are geographically dispersed.

The EGS process, by comparison, replicates natural conditions by fracturing hot rock, circulating water through the system, and using the resulting steam to produce electricity in a conventional turbine. The water is then re-injected back into the rock, where the cycle begins again in a closed loop. Since EGS' only prerequisite is heat, it can theoretically be deployed anywhere there is rock hot enough to produce power. Additionally, since permeability is created by design, EGS systems can be developed in a modular fashion.

What is the resource potential for EGS?

The crust of the earth contains an enormous amount of heat. The 2007 MIT Report on The Future of Geothermal Energy estimates that only 2% of the heat 3 - 10 km below the continental United States could meet 2,500 times the United States' current total energy use. The MIT Report also found that with today's EGS technology, the United States could produce 1 - 12 million MWs of electricity. For comparison, the entire current US electrical system is about 1 million MW. All 50 US states have substantial thermal resources at varying depths. In Australia, it is estimated that 1% of that nations' thermal resource could meet 26,000 times Australia's current total energy use. To learn more about how much power could be produced by EGS, see this Google Earth Layer, U.S. Geothermal Resource (3-10km depth).

Does EGS have any major technological hurdles?

A recent MIT report found, 'there are no anticipated 'showstoppers' or fundamental constraints that will require new technologies to be discovered and implemented to achieve success.' For more information, please see the full report, The Future of Geothermal Energy.

Where is EGS being developed today?

EGS projects are producing power in France and Germany. In Australia, there are over 30 companies exploring or developing EGS resources. The first US demonstration project, run jointly by the Department of Energy, Ormat Technologies, and GeothermEx Inc., is in Desert Peak, Nevada.

How many megawatts are EGS projects generating?

The European Union's EGS project near Soultz-sous-Forets, France, recently connected their first 1.5 MW demonstration plant to the local grid. The Landau project in Germany, connected their 2.5 MW system to the grid in 2007. The leading EGS projects in Australia present thousands of MW of opportunity for renewable baseload power. The Desert Peak project in Nevada, will use EGS techniques to expand the production capacities of the existing 11 MW hydrothermal system to 50 MW.

What about the cost of EGS? Can it really be made cheaper than coal?

Yes. While EGS technology has advanced rapidly in recent years, significant opportunities for innovation remain. Advances in drilling, reservoir, and heat-to-power technologies could all significantly reduce the cost of EGS. Energy technologies generally start at higher cost but become cheaper as technology progresses and scale increases. The RE Who will Google work with in the effort to advance geothermal technology?

As part of RE What areas of geothermal technology is Google interested in?

Areas of interest include:
Advanced well and drilling technologies
High temperature technologies for extreme environments
EGS reservoir engineering, design, and modeling technologies
Fracture sensing, tracing, and mapping technologies
Energy conversion technologies for geothermal applications
Siting and geothermal prospectivity technologies
Water loss minimization technologies
Surprise technologies – advanced concepts in EGS

If so, please send your contact information and proposals to renewables@google.com.

How can I learn more about EGS and geothermal?

Here are a few resources to get you started...
Industry and Government Organizations
Australian Geothermal Energy Group
Geothermal Energy Associaion
Geothermal Resources Council
International Geothermal Association
United States Department of Energy Geothermal Technologies Program

EGS Research Projects
European Deep Geothermal Energy Programme
GFZ Germain Research Centre for Geosciences
US Department of Energy: Desert Peak
US Department of Energy: Idaho National Laboratory
US Department of Energy: National Renewable Energy Laboratory
US Department of Energy: Sandia National Laboratories

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