Enhanced geothermal system

From Wikipedia, the free encyclopedia

  (Redirected from Enhanced geothermal systems)
Jump to: navigation, search
Question book-new.svg
 This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (May 2008)
This article may contain original research or unverified claims. Please improve the article by adding references. See the talk page for details. (September 2008)

[unreliable source?]

Enhanced geothermal system

Enhanced Geothermal Systems (EGS) are a new type of geothermal power technologies that do not require natural convective hydrothermal resources. Until recently, geothermal power systems have only exploited resources where naturally occurring water and rock porosity is sufficient to carry heat to the surface.[1] However, the vast majority of geothermal energy within drilling reach is in dry and non-porous rock.[2] EGS technologies "enhance" and/or create geothermal resources in this hot dry rock (HDR) through hydraulic stimulation.

When natural cracks and pores will not allow for economic flow rates, the permeability can be enhanced by pumping high pressure cold water down an injection well into the rock. The injection increases the fluid pressure in the naturally fractured granite which mobilizes shear events, enhancing the permeability of the fracture system. Water travels through fractures in the rock, capturing the heat of the rock until it is forced out of a second borehole as very hot water, which is converted into electricity using either a steam turbine or a binary power plant system.[3] All of the water, now cooled, is injected back into the ground to heat up again in a closed loop.

EGS / HDR technologies, like hydrothermal geothermal, are expected to be baseload resources which produce power 24 hours a day like a fossil plant. Distinct from hydrothermal, HDR / EGS may be feasible anywhere in the world, depending on the economic limits of drill depth. Good locations are over deep granite covered by a thick (3–5 km) layer of insulating sediments which slow heat loss.[4] HDR wells are expected to have a useful life of 20 to 30 years before the outflow temperature drops about 10 degrees Celsius and the well becomes uneconomic. If left for 50 to 300 years the temperature will recover.[citation needed]

There are HDR and EGS systems currently being developed and tested in France, Australia, Japan, Germany, the U.S. and Switzerland. The largest EGS project in the world is currently being developed in the Cooper Basin, Australia — with the potential to generate 5,000–10,000 MW.

Contents

[edit] MIT Report

Geothermal power technologies.

A 2006 report by MIT,[5] and funded by the U.S. Department of Energy, conducted the most comprehensive analysis to date on the potential and technical status of EGS. The 18-member panel, chaired by Dr. Jefferson Tester of MIT, reached several significant conclusions.

[edit] Major Findings

  1. Resource Size: The MIT report calculated the United States total EGS resources from 3–10 km of depth to be over 13,000 zettajoules, of which over 200 ZJ would be extractable, with the potential to increase this to over 2,000 ZJ with technology improvements — sufficient to provide all the world's current energy needs for several millennia.[5] The report found that total geothermal resources, including hydrothermal and geo-pressured resources, to equal 14,000 ZJ — or roughly 140,000 times the total U.S. annual primary energy use in 2005.
  2. Development Potential: With a modest R&D investment of $1 billion over 15 years (or the cost of one coal power plant), the report estimated that 100 GWe (gigawatts of electricity) or more could be installed by 2050 in the United States. The report further found that the "recoverable" resource (that accessible with today's technology) to be between 1.2–12.2 TW for the conservative and moderate recovery scenarios respectively.
  3. Cost: The report found that EGS could be capable of producing electricity for as low as 3.9 cents/kWh. EGS costs were found to be sensitive to four main factors: 1) Temperature of the resource, 2) Fluid flow through the system measured in liters/second, 3) Drilling Costs, and 4) Power conversion efficiency.

In addition the report has a wealth of data on EGS technology, economics and prior experiments.

[edit] EGS Industry

Commercial projects are currently either operational or under development in Australia, the United States, and Germany.

The largest project in the world is being developed in Australia's Cooper Basin by Geodynamics.[6] The Cooper Basin project has the potential to develop 5–10 GW. Australia now has 33 firms either exploring for, drilling, or developing EGS projects. Australia's industry has been greatly aided by a national Renewable Portfolio Standard of 25% renewables by 2025, a vibrant Green Energy Credit market, and supportive R&D collaboration between government, academia, and industry.

Germany's 23 cent/kWh Feed-In Tariff (FIT) for geothermal energy has led to a surge in geothermal development, despite Germany's relatively poor geothermal resource. The Landau partial EGS project is profitable today under the FIT.

The AltaRock Energy effort is a demonstration project being conducted to prove out the company's proprietary technology at the site of an existing geothermal project owned and operated by NCPA in The Geysers, and does not include power generation. However, any steam produced by the project will be supplied to NCPA's flash turbines under a long-term contract.[7]

Current EGS projects
Project Type Country Size (MW) Plant Type Depth (km) Developer Status
Soultz R&D France (EU) 1.5 Binary 4.2 ENGINE Operational
Desert Peak R&D United States 11-50 Binary DOE, Ormat, GeothermEx Development
Landau Commercial Germany (EU) 3 Binary 3.3  ? Operational
Paralana (Phase 1) Commercial Australia 7-30 Binary 4.1 Petratherm Drilling
Cooper Basin Commercial Australia 250-500 Kalina 4.3 Geodynamics Drilling
The Geysers R&D; Commercial United States (Unknown) Flash 3.5 - 3.8 AltaRock Energy, NCPA Drilling (June 2009)

[edit] Research And Development

[edit] Australia

The Australian government has provided research funding for the development of Hot Dry Rock technology. [1][2]
On 30 May 2007, then Australian opposition environmental spokesperson and current Minister for the Environment, Heritage and the Arts Peter Garrett announced that if elected at the 2007 Australian Federal Election, the Australian Labor Party would use taxpayers money to subsidise putting the necessary drilling rigs in place. In an interview, he promised:
"There are some technical difficulties and challenges there, but those people who are keen on getting Australia into geothermal say we've got this great access to resource and one of the things, interestingly, that's held them back is not having the capacity the put the drilling plants in place. And so what we intend this $50 million to go towards is to provide a one for one dollars. Match $1 from us, $1 from the industry so that they can get these drilling rigs on to site and really get the best sites identified and get the industry going."[8]

[edit] United States

[edit] Early Days—Fenton Hill

The United States pioneered the first EGS effort--then termed Hot Dry Rock--at Fenton Hill, New Mexico with a project run by the federal Los Alamos Laboratory.[9] It was the first attempt anywhere to make a deep, full-scale HDR reservoir, and efforts there spanned 1974 through 1992, in two phases. Ultimately, the project was unable to generate net energy, and the project was terminated.

[edit] Working at the Edges—Using EGS Technology to Improve Hydrothermal Resources

EGS funding languished for the next few years, and by the next decade, U.S. efforts focused on the less ambitious goal of improving the productivity of existing hydrothermal resources. According to the Fiscal Year 2004 Budget Request to Congress from DOE's Office of Energy Efficiency and Renewable Energy, [10]

EGS are engineered reservoirs that have been created to extract heat from economically unproductive geothermal resources. EGS technology includes those methods and equipment that enhance the removal of energy from a resource by increasing the productivity of the reservoir. Better productivity may result from improving the reservoir’s natural permeability and/or providing additional fluids to transport heat.[11]

In Fiscal Year 2002, this vision translated into completing "preliminary designs for five competitively selected projects employing EGS technology," and the selection of one project for "full-scale development" at the Coso Hot Springs geothermal field at the U.S. Naval Weapons Air Station in China Lake, Calif., and two additional projects for "preliminary analysis from a new solicitation" at Desert Peak in Nevada and Glass Mountain in California. Funding for this effort totaled $1.5 million. [12]

In Fiscal Year 2003, $3.5 million was appropriated to launch the Coso project, with the aim of improving the permeability of an existing poorly performing well, and to complete the conceptual design and feasibility studies at the Desert Peak and Glass Mountain sites.[13]

The Fiscal Year 2004 request for $6 million was to "[s]tep up work on EGS cost-shared projects' at the three sites, to include "drilling and reservoir stimulation experiments" at one and drilling a production well at another.[14]

The U.S. Department of Energy USDOE issued two Funding Opportunity Announcements (FOAs) on March 4 2009 for enhanced geothermal systems (EGS). Together, the two FOAs offer up to $84 million over six years, including $20 million in fiscal year 2009 funding, although future funding is subject to congressional appropriations. [15]

The DOE followed up with another FOA on March 27, 2009, of stimulus funding from the American Reinvestment and Recovery Act for $350 million, including $80 million aimed specifically at EGS proejcts,[16]

[edit] United Kingdom

Cornwall is set to host a 3MW demonstration project that could pave the way for a series of 50MW commercial-scale geothermal power stations in suitable areas across the country.[17][18]

[edit] European Union

The EU's EGS R&D project at Soultz-sous-Forêts, France, has recently connected its 1.5 MW demonstration plant to the grid. The Soultz project has explored the connection of multiple stimulated zones and the performance of triplet well configurations (1 injector/2 producers).[19]

Portugal - Portuguese government has awarded, December 2008, an exclusive license to Geovita Ltd, to prospect and explore geothermal energy in one of the best areas in continental Portugal. An area of about 500 square kilometers that is being studied together by Geovita and Coimbra's University — Science and Technology Faculty — Earth Sciences Department, and foresees the installation of an Enhanced Geothermal System (EGS).

[edit] Seismicity

Some seismicity is inevitable and, indeed, expected in EGS, which involves pumping fluids at pressure to enhance or create permeability through the use of hydraulic fracturing techniques. Depending on the rock properties, and on injection pressures and fluid volume, the reservoir rock may respond with tensile failure, as is common in the oil and gas industry, or with shear failure of the rock's existing joint set, as is thought to be the main mechanism of reservoir growth in EGS efforts.[20] [21]

In several cases, significant events have occurred.

Largest Events at EGS Sites Worldwide[22]
Site Maximum Magnitude
Cooper Basin, Australia 3.7
Basel, Switzerland 3.4
Rosemanowes, United Kingdom 3.1
Soultz-sous-Forêts, France 2.9

Experience in the field has shown that seismicity associated with hydraulic stimulation can be mitigated and controlled through predictive siting and other techniques. According to the MIT report,[23]

With current technology, it appears feasible that the number and magnitude of these induced events can be managed. In fact, based on substantial evidence collected so far, the probability of a damaging seismic event is low, and the issue – though real – is often one more of public perception.

[edit] Basel earthquakes

The case at Basel bears special mention because the induced seismicity led the city (which is a partner) to suspend the project and conduct a seismic hazard evaluation, which resulted in the cancellation of the project in December 2009.[24]

Although the Basel project had established an operational approach before proceeding with the geothermal stimulation for addressing induced earthquakes of concern, it had not performed a thorough seismic risk assessment beforehand,[25] even though most of the city was destroyed in 1356 by a magnitude 6.5 earthquake. Basel is in a known earthquake zone (see Basel earthquake) and sits atop a historically active fault.

On 8 December 2006, only 6 days after the main stimulation started on 2 December, the HDR project in Basel was suspended when an earthquake tripped a 4-level "traffic light" scheme established for halting operations in the event of unacceptable induced earthquake occurrences.[26] Trip points of Richter Magnitude ML 2.9 and a peak ground velocity of 5 millimeters per second were established by the project as independent criteria for a "red alert" that entailed halting fluid injection and bleeding-off to minimum wellhead pressure. Lesser operational curtailments were triggered for lower magnitude and peak ground velocity thresholds.

Earlier that day, a "yellow alert"--the second level--was called at 03:06 local time after a 2.6 ML event with peak ground velocity of 0.55 mm/s, which exceeded the "soft" 2.3 ML and 0.5 mm/s thresholds. As a precaution, the injection rate was reduced at 04:04.[26]

Following further events that were larger than 2.0 ML, a level-three "orange alert" was declared—the injection was stopped at 11:34 and the well shut-in, maintaining the pressure. However, a 2.7 ML event occurred at 15:46, followed by a 3.4 ML event at 16:48, and so in accordance with the response strategy, the well was bled off as soon as practicable.[26]

The largest event [27] [28] prompted concern from local residents. Further tremors exceeding magnitude 3 were recorded on 6 January (measuring 3.1),[29] 16 January 2007 (3.2), and 2 February 2007 (3.2).[30][31][32]

The six borehole seismometers installed near the Basel injection well to monitor the natural background seismicity and the geothermal stimulation recorded more than 13,500 potential events connected with the geothermal project, from which 3,124 were of sufficient quality to permit [hypocenter] determinations in the period 2-12 December 2006[26], which spanned the main stimulation and the decline in the event rate. During the post-stimulation period from 13 December 2006 onward, a further 350 locatable events were detected up to 2 May 2007, by which time events were occurring sporadically at around one per day. In all, locations for more than 3,500 events were determined.

Of these more than 3,500 events, only the 200 largest (magnitudes between 0.7 and 3.4) were also observed by the earthquake networks of the Swiss Seismological Service and the Seismological Service of Baden-Wuerttemberg,[33] The remainder were too small to be observed or felt at the surface. For the period through 24 January 2007, there were 168 earthquakes with magnitudes> 0.6, 15 with ML >2, and three with ML > 3. All of these were within 1 km of the wellbore, and at depths between 4 and 5 km, near the well bottom[34]. There were only 9 events with an ML of 2.5 or larger in the borehole vicinity for the period through 2007. Five occurred in December 2006,[35] two in January 2007, and one each February and March.[36]

Damage claims arose from the largest of the events. Eventually, some 2,700 claims were processed by the project's insurer for an estimated 7 million - 9 million Swiss francs (about 6.5 million to 8.3 million U.S dollars)[37]

The Basel HDR project was under review[38] which resulted in a cancellation of the project in December 2009.[24]

[edit] CO2 EGS

The recently established Center for Geothermal Energy Excellence at the University of Queensland, has been awarded $18.3 million (AUS) for EGS research, a large portion of which will be used to develop CO2 EGS technologies.

Research conducted at Los Alamos National Laboratories and Lawrence Berkeley National Laboratories examined the use of supercritical CO2, instead of water, as the geothermal working fluid with favorable results. CO2 has numerous advantages for EGS:

  1. Greater power output
  2. Minimized parasitic losses from pumping and cooling
  3. Carbon sequestration
  4. Minimized water use

[edit] See also

[edit] References

  1. ^ Lund, John W. (June 2007), "Characteristics, Development and utilization of geothermal resources", Geo-Heat Centre Quarterly Bulletin (Klamath Falls, Oregon: Oregon Institute of Technology) 28 (2): 1–9, ISSN 0276-1084, http://geoheat.oit.edu/bulletin/bull28-2/art1.pdf, retrieved 2009-04-16 
  2. ^ Duchane, Dave; Brown, Don (December 2002), "Hot Dry Rock (HDR) Geothermal Energy Research and Development at Fenton Hill, New Mexico", Geo-Heat Centre Quarterly Bulletin (Klamath Falls, Oregon: Oregon Institute of Technology) 23 (4): 13–19, ISSN 0276-1084, http://geoheat.oit.edu/bulletin/bull23-4/art4.pdf, retrieved 2009-05-05 
  3. ^ http://www1.eere.energy.gov/geothermal/egs_animation.html
  4. ^ 20 slide presentation inc geothermal maps of Australia
  5. ^ a b Tester, Jefferson W. (Massachusetts Institute of Technology) et al (2006) (14MB PDF). The Future of Geothermal Energy - Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century. Idaho Falls: Idaho National Laboratory. ISBN 0-615-13438-6. http://geothermal.inel.gov/publications/future_of_geothermal_energy.pdf. Retrieved 2007-02-07. 
  6. ^ Beardsmore, Graeme (September 2007), "The Burgeoning Australian Geothermal Energy Industry", Geo-Heat Centre Quarterly Bulletin (Klamath Falls, Oregon: Oregon Institute of Technology) 28 (3): 20–26, ISSN 0276-1084, http://geoheat.oit.edu/bulletin/bull28-3/art4.pdf, retrieved 2009-05-07 
  7. ^ http://altarockenergy.com/AltaRockEnergy.2009-03-19.pdf
  8. ^ "Garrett discusses Labor's stance on climate change", Lateline, 30 May 2007
  9. ^ Tester 2006, pp. 4-7 to 4-13
  10. ^ "FY 2004 Congressional Budget Request - Energy Supply Energy Efficiency and Renewable Energy". U.S Department of Energy. 2003-02-03. pp. 244. 
  11. ^ FY2004DOE 2003, p. 131
  12. ^ FY2004DOE 2003, pp. 131-131
  13. ^ FY2004DOE 2003, p. 132
  14. ^ FY2004DOE 2003, p. 132
  15. ^ "EERE News: DOE to Invest up to $84 Million in Enhanced Geothermal Systems". 2009-03-04. http://apps1.eere.energy.gov/news/news_detail.cfm/news_id=12279. Retrieved 2009-07-04. 
  16. ^ "Department of Energy - President Obama Announces Over $467 Million in Recovery Act Funding for Geothermal and Solar Energy Projects". 2009-05-27. http://www.energy.gov/news2009/7427.htm. Retrieved 2009-07-04. 
  17. ^ "Tories pledge support for deep geothermal energy projects". New Energy Focus (www.newenergyfocus.com). May 15, 2009. http://newenergyfocus.com/do/ecco.py/view_item?listid=1&listcatid=32&listitemid=2641&section=Carbon%2CIndustry%2COn-site%20%26%20Micro. Retrieved 2009-06-11. 
  18. ^ "Geothermal power plant that could run 5,000 British homes to be built in Cornwall". Daily Mail (Associated Newspapers Ltd). June 2, 2009. http://www.dailymail.co.uk/sciencetech/article-1190107/Geothermal-power-plant-run-5-000-British-homes-built-Cornwall.html. Retrieved 2009-06-11. 
  19. ^ See French Wikipedia: Soultz-sous-Forêts — Soultz is in the Alsace région of France.
  20. ^ Tester 2006, pp. 4–5 to 4-6
  21. ^ Tester 2006, pp. 8-9 to 8-10
  22. ^ Bromley, C.J. & Mongillo, M.A. (February 2007), "All Geothermal Energy from Fractured Reservoirs - Dealing with Induced Seismicity", IEA Open Journal 48 (7): 5, https://byustudies.byu.edu/http://www.iea.org/impagr/cip/pdf/Issue48Geothermal.pdf 
  23. ^ Tester 2006, p. 5-6
  24. ^ a b Glanz, James (2009-12-10), "Quake Threat Leads Swiss to Close Geothermal Project", The New York Times, http://www.nytimes.com/2009/12/11/science/earth/11basel.html?_r=1 
  25. ^ Bromley 2007, p. 5
  26. ^ a b c d Dyer, B. & Schanz, U. et al. (2008), "Microseismic imaging of a geothermal reservoir stimulation", The Leading Edge 27 (7): 856–869, doi:dx.doi.org/10.1190/1.2954024, http://www.seismo.ethz.ch/products/publications/pdf/earthquake2007.pdf 
  27. ^ "Hot Rock Firm Looks at Earthquake Risk". Sydney Morning Herald. 2007-01-02. ISSN 0312-6315. http://www.smh.com.au/news/Business/Hot-rock-firm-looks-at-earthquake-risk/2007/01/02/1167500096355.html. Retrieved 2009-07-04. 
  28. ^ "Man-made tremor shakes Basel". Swissinfo.ch. 2006-12-09. http://www.swissinfo.ch/eng/search/detail/Man_made_tremor_shakes_Basel.html?siteSect=881&sid=7334248&cKey=1165839658000. Retrieved 2009-07-04. 
  29. ^ "Geothermal project shakes Basel again". Swissinfo.ch. 2007-01-06. http://www.swissinfo.ch/eng/front/detail/swissinfo.html?siteSect=105&sid=7407138. Retrieved 2009-07-04. 
  30. ^ Ladner, Florentin (2007-11-16). Geological and hydraulic evaluation of the Basel 1 geothermal reservoir. Geneva. http://www.geothermal.ch/fileadmin/docs/downloads/genf_2007pp.pdf. Retrieved 2009-07-04. 
  31. ^ Mukuhira, Yusuke et al. (2008). "Characterization of Microseismic Events with Larger Magnitude Collected at Basel, Switzerland in 2006". GRC Transactions 32: 87–94. http://niweb.kankyo.tohoku.ac.jp/PDF/GRCVol32MUKUHIRA.pdf. 
  32. ^ Schanz, Ulrich; Ben Dyer, Florentin Lander, Markus Haring (2007). Part 2: Microseismic aspects of the Basel 1 geothermal reservoir Presentation at the 5th Swiss Geoscience Meeting. http://www.geothermal.ch/fileadmin/docs/downloads/geoschanztalk.pdf. 
  33. ^ Swiss Seismological Service. "Die vom Schweizerischen Erdbebendienst erfassten Daten [The Swiss Seismological Service recorded data]". Das Deep-Heat-Mining-Projekt in Basel [The Deep-Heat Mining Project in Basel]. http://www.seismo.ethz.ch/basel/index.php?m1=analyse&m2=data. Retrieved 2009-07-04. 
  34. ^ Swiss Federal Institute of Technology, Zurch (2007-02-06). DHM-Basel: Statement 1. http://www.seismo.ethz.ch/basel/articles/Pressekonf_Basel_20070125.pdf. 
  35. ^ Baer, M. et al. (2007), "Earthquakes in Switzerland and surrounding regions during 2006", Swiss J. Geosci 100: 517–528, http://www.seismo.ethz.ch/products/publications/pdf/earthquake2006.pdf 
  36. ^ Deichmann, N. et al. (2008), "Earthquakes in Switzerland and surrounding regions during 2007", Swiss J. Geosci 101: 659–667, http://www.seismo.ethz.ch/products/publications/pdf/earthquake2007.pdf 
  37. ^ Jahresbericht 2007 der Geopower Basel AG [Annual Report 2007]. GeoPower Basel. http://www.geopower-basel.ch/media/de/download_pdf/drucksachen/geopower_jb-07_web.pdf. Retrieved 2009-06-30. 
  38. ^ "Geothermie". Basel-Stadt Departement für Wirtschaft, Soziales und Umwelt. http://www.wsu.bs.ch/geothermie. 

[edit] External links

v • d • e
Geothermal power
Geothermal power NesjavellirPowerPlant edit2.jpg
By country
Technologies
Energy Concepts
Portals: Energy • Sustainable development
Retrieved from "http://en.wikipedia.org/wiki/Enhanced_geothermal_system"