Thursday, June 19, 2008

Advanced Geothermal Under Study

EGS are systems of engineered reservoirs created by drilling deep wells into hot rock, fracturing the rock, and circulating a fluid through the wells to extract heat. __GCC
The US Department of Energy is offering up to $90 million to advance the state of the art in enhanced geothermal energy production. By the year 2050, enhanced geothermal may generate 20% of the electricity produced by US utilities.
The DOE report found that there are three critical assumptions about EGS technology that require thorough evaluation and testing before the economic viability of EGS can be confirmed:

1. Demonstration of commercial-scale reservoir. This requires stimulation and maintenance of a large volume of rock (equivalent to several cubic kilometers) in order to minimize temperature decline in the reservoir. Actual stimulated volumes have not been reliably quantified in previous work.

2. Sustained reservoir production. The MIT study concludes that 200°C fluid flowing at 80 kg/sec (equivalent to about 5 MWe) is needed for economic viability. No EGS project to date has attained flow rates in excess of ~25 kg/sec.

3. Replication of EGS reservoir performance. EGS technology has not been proven to work at commercial scales over a range of sites with different geologic characteristics. __GCC
The actual available energy in the hot dry rock layers far exceeds all energy used by humans on Earth. It will require new technology to retrieve that energy, however. Geothermal is baseload energy--available 24 hours a day, every day. Until we have space-based solar, or until utility scale electrical storage is cheaper than dirt, that advantage puts geothermal far ahead of other renewables.

Let's see, 20% of US electricity from enhanced geothermal, 20% of US electricity from waste heat recovery--before you know it, you're talking about real power.



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