May 27, 2008

Enhanced geothermal energy



Enhanced geothermal systems (EGS), also sometimes called engineered geothermal systems, offer great potential for more than 100 GW of geothermal power which 40 times more than present geothermal power. Sandia national labs indicates ultimately geothermal global resources amount to 50,000 times the energy of all oil and gas resources in the world.

Ormat Technologies (775 person company, $1.8 billion market capitilization) is in talks wih Google for a possible geothermal project. Ormat is a leader in enhanced geothermal.

The EGS concept is to extract heat by creating a subsurface fracture system to which water can be added through injection wells. Creating an enhanced, or engineered, geothermal system requires improving the natural permeability of rock. Rocks are permeable due to minute fractures and pore spaces between mineral grains. Injected water is heated by contact with the rock and returns to the surface through production wells, as in naturally occurring hydrothermal systems. EGS are reservoirs created to improve the economics of resources without adequate water and/or permeability.


Ormat Technologies is featured in Cleanedge energy trends report
A 2008 survey by the Geothermal Energy Association predicted that 86 new projects underway in 12 states will more than double U.S. geothermal capacity to more than 6,300 megawatts (MW), enough to power some 6 million homes. [Probable completion over the next 5 years.] The U.S. is already the global leader in geothermal, with about 3,000 of the world’s 9,700 MW of current
generation. Overseas, Chevron dominates the landscape, with more than 1,200 MW of geothermal generation, mostly in Indonesia and the Philippines, accounting for more than 12% of the worlds geothermal electrical capacity.

Note: geothermal in the USA produced 16 billion kwh which is 2% of the nuclear power total and a few times more than solar power generated. Still if enhanced geothermal and other economical geothermal power can be added that would be a good and significant thing.

Project phases
Phase I: Identifying site, secured rights to resource, initial exploration drilling
Phase II: Exploratory drilling and confirmation being done; PPA not secured
Phase III: Securing PPA and final permits
Phase IV: Production Drilling Underway/Facility Under Construction
Unconfirmed: Proposed projects that may or may not have secured the rights to the
resource, but some exploration has been done on the site




Capacity Factor
Capacity Factor = Total Energy Produced / Energy Produced if at Full Capacity

Geothermal, hydroelectric and nuclear power provide baseload power 24 hours a day. Geothermal has an average plant uptime of 98 percent, while nuclear in the USA is 90% and coal is 70% uptime. Average geothermal electricity rates between 4-7 cents per kilowatt-hour.


Comparing Power Technologies
Technology Expected Capacity Factor (percent)
Coal 71
Nuclear 90
Geothermal 86-95
Wind 25-40
Solar 24-33
Natural Gas Combustion Turbine 30-35
Hydropower 30-35
Biomass 83


As geothermal technology progresses, resources that were once non-commercial are now being actively examined as feasible possibilities. Such resources might include the following:
• Enhanced Geothermal Systems (EGS) – Often categorized under the antiquated term
‘Hot Dry Rock,’ EGS is thought by several experts to refer to any resource that requires artificial stimulation. This includes resources that have to be fully engineered, or ones that produce hydrothermal fluid, but sub-commercially. Regarding the latter, one expert states that, ‘As we go further, there might be projects that require more and more stimulation.’ Although EGS technology is still young and many aspects remain unproven, several projects are currently underway. If EGS technology proves commercially successful, it is expected to allow significantly increased extension of and production from existing fields, as well as utilization of geothermal energy in previously implausible locations.
• Hydrocarbon/Geothermal Co-Production – There is growing interest in producing
electricity from the thermal fluid that flows from several oil & gas wells. One project is currently underway in Wyoming, with several more in the planning stages. Geothermal co-production has been predicted to be capable of providing 1000-5000 MW to the 7 states in the Texas Gulf Coast Plain alone (McKenna et al., Oil & Gas Journal, September 5, 2005). Note that there is currently no geothermal electricity production in any of those states. Also, there appears to be renewed interest in production from the geopressured resources in Texas, Louisiana and the Gulf of Mexico.
• Lower-Temperature/Flowrate Resources – With recent and continuing advances in
surface technology, new resources or those that were previously abandoned because of either sub-commercial temperatures or flow-rates are becoming increasingly viable options. Chena Hot Springs (Alaska) is currently producing 400 kW from a 165°F resource. Several projects aimed at utilizing similarly low-temperature or low-grade geothermal resources are currently in progress. Several in the industry predict that these advances will greatly increase the range of geothermal applications, some of which might include: waste heat stream recovery in industrial applications, small-scale electricity projects for communities or resorts (like Chena), and aquaculture.


Fracturing and multi-well technology has been developed for oilfield drilling


Geothermal resource map


FURTHER READING
Geothermal Energy Association

Geothermal technology part 1, 80 pages

Geothermal technology part 2, 89 pages

MIT had a study that 100GW of geothermal energy could be produced in the USA by 2050

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