16.0 Geothermal Energy

Frank R. Leslie, B. S. E. E., M. S. Space Technology, LS IEEE

3/18/2010, Rev. 2.0.2

fleslie @fit.edu; (321) 674-7377

www.fit.edu/~fleslie

Oil ~$80 on 3/18/2010

In Other News . . .

Engineering firm Strategic Energy Solutions Inc. has moved into a new headquarters in Berkley MI that the owner hopes to use as a showcase for clients for state-of-the-art geothermal heating and cooling technology. A 4,000 square-foot adjacent warehouse will

house a new geothermal installation business unit.

Six geothermal pumps buried underneath a rear parking lot serve the two buildings with about 20 tons of heating and cooling capacity – the equivalent of eight to 10 homes.

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16 Overview: Geothermal

Geothermal energy is present within the land and the seaInternal heat is from initial world accretion from

gathering dust and compression of the earth and from radioactive decay

This energy can be useful in heating and cooling of air and water, but is somewhat costly to use

Active geyser areas are limited in area, but provide much hotter water or steam

The energy is inexhaustible in principle, yet local extraction will cool the immediate area in a few years

Extraction of energy from deep (~20,000 ft) hot rock is not economic yet

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16.0 Definitions: Geothermal Energy

HDR – Hot, dry rock: has no natural steam but may receive injected water to emit steam

Head – the height of water – the hydraulic height of the water (1 psi = 2.31 ft H2O)For artesian wells, the height that the water will

stand above ground level in a pipeHeat Quality – the temperature of the heatGround Source Heat Pump – extracts from ground

or rejects heat to ground to/from and air conditioning heat pump

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16.0 Geothermal Energy

Active geysers supply steam or hot water for heating in The Geysers, California (824 MWe)

“Hot, dry rock” (HDR) offers potential for injecting water and using the resultant steam to spin a turbine

At a lower thermal level, an air conditioner can extract heat from the ground for winter heating or insert energy into the ground to gain a more efficient cooling sink

www.eren.doe.gov/geothermal/ geysers20.html

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Nearby Calistoga (started 1862) has tourist spas with hot water from springs;also palm reading, water treatments, psychics, mud baths, etc.

16.0 About This Presentation

16.1 History16.2 Sources16.3 High Temperature Systems (Steam)16.4 Low Temperature Systems (Heat Pumps)16.5 Issues and Trends16.0 Conclusion

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16.1 History

Paleo-American Indians used hot springs in this areaHot Springs, Arkansas had $1 hot baths in 1830First electricity (20kW) from geothermal produced

from natural steam in Larderello, Italy in 1904 [Kruger, 1973]

New Zealand’s north island gets 6% of its electricity from geothermal energy

1920: test boring in Niland CA1922: electricity generation in The Geysers1950: 95°F, 220kW generating plant in KatangaThe Geysers CA expanded to 600MW in 1975

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16.2 Source of Geothermal Energy

Heat stems from radioactive disintegrations of atomic nuclei [Sorensen, 2000], initial cooling from agglomeration in planet formation, and other various processes

Hot spots occur where strong convective magma circulation is occurring, usually near continental plate boundaries and mountainous regions

Hot dry rock, the most common type, retains convective heat

Storage in a developed area may be depleted in 50 years

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16.2.1 Sources of Geothermal Energy

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The western states have most of the higher temperature energy

16.2.1 Sources of Geothermal Energy

http://geothermal.inel.gov/maps/west_usa.jpg

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16.2.1 Sources of Geothermal Energy

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U.S. Geothermal power plant locations: 1. The Geysers; 2, Salton Sea; 3. Heber; 4, East Mesa; 5. Coso; 6. Casa Diablo; 7, Amedee; 8, Wendel; 9. Dixie Valley; 10. Steamboat Hot Springs; 11. Beowawe Hot Springs; 12. Desert Peak; 13, Wabuska Hot Springs; 14. Soda Lake; 15, Stillwater; 16. Empire and San Emidio; 17, Roosevelt Hot Springs; 18, Cove Fort.

16.2.2 Mammoth Pacific Power Plant, CA

“Located in the eastern Sierra Nevada mountain range in California, showcases the environmentally friendly nature of geothermal power.” ---- ASES policy, 2005

16.3 High Temperature Systems

These areas are associated with the “Ring of Fire” volcanic activities around the Pacific Rim Basin

Geyser-temperature steam is contaminated with salts that cause corrosion of turbines or engines

Removing these salts to protect the machinery is costly

Types of geothermal systemsDirect from steam undergroundFlash-steam systems take in deep-well hot water

(high enthalpy) that is above the boiling point to heat clean water into steam in a heat exchanger

Binary systems that heat a low-boiling-point fluid like butane or propane to drive a closed-loop turbine

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16.4 Low Temperature Heat Extraction/Rejection

The classic use of earth/water is as a heat sink or source for air conditioning or heating

Pipes embedded in the earth carry refrigerant or water and conduct heat from the hotter to cooler substance

Since the earth (or water) has a high specific heat in comparison with air, there is good thermal transfer

In winter, heat is extracted from the earth by the chilled refrigerant, while in the summer, the hot refrigerant conducts heat to the earth

Houses have been built partially underground to moderate the winter and summer temperaturesDennis Weaver built an “Earthship” house with

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16.4.1 Basic Refrigeration Concept

Specific heats determine the storage of thermal energyAir – 0.018 Btu per cubic footWater – 62.42 Btu per cubic foot, or 3472 times

higherHeat pumping works through phase change of the

refrigerant; boiling to gas or condensing to liquidTypical refrigerants have boiling points of -40 degrees

FWhen the refrigerant is compressed, heat is released

and it liquefies; when decompressed through an expansion valve, it cools as it changes to a gas

Reversing the direction of refrigerant travel through the system changes operation from an air conditioner to a heat pump

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http://www.popsci.com/

16.4.2 Basic Refrigeration Diagram

Long pipes buried in the ground carry water to and from a heat exchanger

The refrigerant absorbs heat from or rejects heat to the water

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http://www.geothermalheatpump.com/how.htm

16.5 Issues and Trends

HDR (hot, dry rock) cools locally as the temperature falls with energy extractionWells may require redrilling to find new hot

regions and to let more heat enter the depleted region

Since the locations are limited, this source of energy may not be economically available

Extraction often requires fracturing of deep rock layers to allow water in and steam out

Since sources are geographically limited, the energy is best used locally; too difficult to pipeline elsewhere

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16.C Conclusion: Geothermal

Geothermal energy is limited in extent as extracting the heat usually exceeds the replenishment rate

Hot, dry rock (HDR) is widespread and offers new resources in areas where geyser activity is unknown

Direct low-temperature heat transfer for home systems is practical as long as low maintenance is designed into the system

Sources of high temperature water or steam are limited and the cost of extraction, maintenance, and operation will remain high in comparison with other sources of energy

Geothermal energy likely to remain at 1% of world energy [Kruger, 1973]

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Olin Engineering Complex 4.7 kW Solar PV Roof Array

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Questions?

References: Books

Boyle, Godfrey. Renewable Energy, Second Edition. Oxford: Oxford University Press, 2004, ISBN 0-19-26178-4. (my preferred text)

Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76, 333.79’4’0973.

Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY: John Wiley & Sons, Inc., 920 pp., 1991

Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., 1993. 0-930031-64-4, TJ820.G57, 621.4’5

Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136

Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-12-656152-4.

Texter, [MIT] Kruger, Paul and Carel Otto, eds. Geothermal Energy. Stanford CA:

Stanford University Press, 1973, 333.7 0-8047-0822-3. Bockris, J. O’M. Energy – The Solar-Hydrogen Alternative. NY: John Wiley &

Sons1975. ISBN 0-4700-08429-4. 333.7. TJ810.B58

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References: Websites, etc.

http://www.eere.energy.gov/geothermal/ Government Labhttp://www.geothermalheatpump.com/how.htm Good explanation of practical usehttp://www.acmehowto.com/howto/appliance/refrigerator/overview.htmUniversity of Nevada at Reno Desert Research Institutehttp://www.bnl.gov/est/MEA.htm Brookhaven Laboratorieshttp://geothermal.inel.gov/ INEELhttp://www-esd.lbl.gov/ER/geothermal.html Lawrence Livermore Labshttp://www.sandia.gov/geothermal/ Sandia National Labshttp://www.nrel.gov/geothermal/ National Renewable Energy Labshttp://www.eere.energy.gov/geothermal/webresources.html More Resources________________________________________________________________________________

______________geothermal.marin.org/ on geothermal energymailto:energyresources@egroups.com rredc.nrel.gov/www.dieoff.org. Site devoted to the decline of energy and effects upon populationwww.ferc.gov/ Federal Energy Regulatory Commissionsolstice.crest.org/dataweb.usbr.gov/html/powerplant_selection.html

http://www.eere.energy.gov/geothermal/history.html

http://www.consrv.ca.gov/DOG/geothermal/index.htm

ftp://ftp.consrv.ca.gov/pub/oil/maps/Geothermal/G3-1.pdf

http://www.dennisweaver.com/habitat.html

http://www.worldbank.org/html/fpd/energy/geothermal/

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