Geothermal Energy

Geothermal Energy Stephen Lawrence Leeds School of Business University of Colorado Boulder, CO 80309-0419

AGENDA – Geothermal Energy
Geothermal Overview
Extracting Geothermal Energy
Environmental Implications
Economic Considerations
Geothermal Installations – Examples

Geothermal Overview

Geothermal in Context http://www.eia.doe.gov/cneaf/solar.renewables/page/geothermal/geothermal.html U.S. Energy Consumption by Energy Source, 2000-2004 (Quadrillion Btu) 0.143 0.115 0.105 0.070 0.057 Wind Energy 0.063 0.064 0.064 0.065 0.066 Solar Energy 2.845 2.740 2.648 2.640 2.907 Biomass d 0.340 0.339 0.328 0.311 0.317 Geothermal Energy 2.725 2.825 2.689 2.242 2.811 Conventional Hydroelectric 6.117 6.082 5.835 5.328 6.158 Renewable Energy 8.232 7.959 8.143 8.033 7.862 Nuclear Electric Power 0.039 0.022 0.078 0.075 0.115 Electricity Net Imports 40.130 39.047 38.401 38.333 38.404 Petroleum c 23.000 23.069 23.628 22.861 23.916 Natural Gas b 0.138 0.051 0.061 0.029 0.065 Coal Coke Net Imports 22.918 22.713 21.980 21.952 22.580 Coal 86.186 84.889 84.070 83.176 84.965 Fossil Fuels 100.278 98.714 97.952 96.464 98.961 Total a 2004 P 2003 2002 2001 2000 Energy Source

Advantages of Geothermal http://www.earthsci.org/mineral/energy/geother/geother.htm

Heat from the Earth’s Center
Earth's core maintains temperatures in excess of 5000°C
Heat radual radioactive decay of elements
Heat energy continuously flows from hot core
Conductive heat flow
Convective flows of molten mantle beneath the crust.
Mean heat flux at earth's surface
16 kilowatts of heat energy per square kilometer
Dissipates to the atmosphere and space.
Tends to be strongest along tectonic plate boundaries
Volcanic activity transports hot material to near the surface
Only a small fraction of molten rock actually reaches surface.
Most is left at depths of 5-20 km beneath the surface,
Hydrological convection forms high temperature geothermal systems at shallow depths of 500-3000m.
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm

Earth Dynamics http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm

Earth Temperature Gradient http://www.geothermal.ch/eng/vision.html

Geothermal Site Schematic Boyle, Renewable Energy, 2 nd edition, 2004

Geysers http://en.wikipedia.org/wiki/Geyser Clepsydra Geyser in Yellowstone

Hot Springs Hot springs in Steamboat Springs area. http://www.eia.doe.gov/cneaf/solar.renewables/page/geothermal/geothermal.html

Fumaroles Clay Diablo Fumarole (CA) White Island Fumarole New Zealand http://volcano.und.edu/vwdocs/volc_images/img_white_island_fumerole.html http://lvo.wr.usgs.gov/cdf_main.htm

Global Geothermal Sites http://www.deutsches-museum.de/ausstell/dauer/umwelt/img/geothe.jpg

Tectonic Plate Movements Boyle, Renewable Energy, 2 nd edition, 2004

Geothermal Sites in US

Extracting Geothermal Energy

Methods of Heat Extraction http://www.geothermal.ch/eng/vision.html

Units of Measure
Pressure
1 Pascal (Pa) = 1 Newton / square meter
100 kPa = ~ 1 atmosphere = ~14.5 psi
1 MPa = ~10 atmospheres = ~145 psi
Temperature
Celsius (ºC); Fahrenheit (ºF); Kelvin (K)
0 ºC = 32 ºF = 273 K
100 ºC = 212 ºF = 373 K

Dry Steam Power Plants
“ Dry” steam extracted from natural reservoir
180-225 ºC ( 356-437 ºF)
4-8 MPa (580-1160 psi)
200+ km/hr (100+ mph)
Steam is used to drive a turbo-generator
Steam is condensed and pumped back into the ground
Can achieve 1 kWh per 6.5 kg of steam
A 55 MW plant requires 100 kg/s of steam
Boyle, Renewable Energy, 2 nd edition, 2004

Dry Steam Schematic Boyle, Renewable Energy, 2 nd edition, 2004

Single Flash Steam Power Plants
Steam with water extracted from ground
Pressure of mixture drops at surface and more water “flashes” to steam
Steam separated from water
Steam drives a turbine
Turbine drives an electric generator
Generate between 5 and 100 MW
Use 6 to 9 tonnes of steam per hour

Single Flash Steam Schematic Boyle, Renewable Energy, 2 nd edition, 2004

Binary Cycle Power Plants
Low temps – 100 o and 150 o C
Use heat to vaporize organic liquid
E.g., iso-butane, iso-pentane
Use vapor to drive turbine
Causes vapor to condense
Recycle continuously
Typically 7 to 12 % efficient
0.1 – 40 MW units common
http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp

Binary Cycle Schematic Boyle, Renewable Energy, 2 nd edition, 2004

Binary Plant Power Output http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm

Double Flash Power Plants
Similar to single flash operation
Unflashed liquid flows to low-pressure tank – flashes to steam
Steam drives a second-stage turbine
Also uses exhaust from first turbine
Increases output 20-25% for 5% increase in plant costs

Double Flash Schematic Boyle, Renewable Energy, 2 nd edition, 2004

Combined Cycle Plants
Combination of conventional steam turbine technology and binary cycle technology
Steam drives primary turbine
Remaining heat used to create organic vapor
Organic vapor drives a second turbine
Plant sizes ranging between 10 to 100+ MW
Significantly greater efficiencies
Higher overall utilization
Extract more power (heat) from geothermal resource

Hot Dry Rock Technology
Wells drilled 3-6 km into crust
Hot crystalline rock formations
Water pumped into formations
Water flows through natural fissures picking up heat
Hot water/steam returns to surface
Steam used to generate power
http://www.ees4.lanl.gov/hdr/

Hot Dry Rock Technology Fenton Hill plant http://www.ees4.lanl.gov/hdr/

Soultz Hot Fractured Rock Boyle, Renewable Energy, 2 nd edition, 2004

2-Well HDR System Parameters
2×10 6 m 2 = 2 km 2
2×10 8 m 3 = 0.2 km 3

Promise of HDR
1 km 3 of hot rock has the energy content of 70,000 tonnes of coal
If cooled by 1 ºC
Upper 10 km of crust in US has 600,000 times annual US energy (USGS)
Between 19-138 GW power available at existing hydrothermal sites
Using enhanced technology

Direct Use Technologies
Geothermal heat is used directly rather than for power generation
Extract heat from low temperature geothermal resources
< 150 o C or 300 o F.
Applications sited near source (<10 km)

Geothermal Heat Pump http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp

Heat vs. Depth Profile Boyle, Renewable Energy, 2 nd edition, 2004

Geothermal District Heating Boyle, Renewable Energy, 2 nd edition, 2004 Southhampton geothermal district heating system technology schematic

Direct Heating Example Boyle, Renewable Energy, 2 nd edition, 2004

Technological Issues
Geothermal fluids can be corrosive
Contain gases such as hydrogen sulphide
Corrosion, scaling
Requires careful selection of materials and diligent operating procedures
Typical capacity factors of 85-95%

Technology vs. Temperature http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Direct Fluid Use
Heat Exchangers
Direct Use Water Low Temperature 50-150 o C (120-300 o F).
Binary Cycle
Direct Fluid Use
Heat Exchangers
Heat Pumps
Power Generation Direct Use Water Intermediate Temperature 100-220 o C (212 - 390 o F).
Flash Steam
Combined (Flash and Binary) Cycle
Direct Fluid Use
Heat Exchangers
Heat Pumps
Power Generation Direct Use Water or Steam High Temperature >220 o C (>430 o F). Technology commonly chosen Common Use Reservoir Fluid Reservoir Temperature

Geothermal Performance Boyle, Renewable Energy, 2 nd edition, 2004

Environmental Implications

Environmental Impacts
Land
Vegetation loss
Soil erosion
Landslides
Air
Slight air heating
Local fogging
Ground
Reservoir cooling
Seismicity (tremors)
Water
Watershed impact
Damming streams
Hydrothermal eruptions
Lower water table
Subsidence
Noise
Benign overall
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm

Renewable?
Heat depleted as ground cools
Not steady-state
Earth’s core does not replenish heat to crust quickly enough
Example:
Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW
http://en.wikipedia.org/wiki/Geothermal

Economics of Geothermal

Cost Factors
Temperature and depth of resource
Type of resource (steam, liquid, mix)
Available volume of resource
Chemistry of resource
Permeability of rock formations
Size and technology of plant
Infrastructure (roads, transmission lines)
http://www.worldbank.org/html/fpd/energy/geothermal/cost_factor.htm

Costs of Geothermal Energy
Costs highly variable by site
Dependent on many cost factors
High exploration costs
High initial capital, low operating costs
Fuel is “free”
Significant exploration & operating risk
Adds to overall capital costs
“Risk premium”
http://www.worldbank.org/html/fpd/energy/geothermal/

Risk Assessment http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm

Geothermal Development http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm

Cost of Water & Steam http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm Table Geothermal Steam and Hot Water Supply Cost where drilling is required 10-20 Low Temperature (<100 o C) 20-40 3.0-4.5 Medium Temperature (100-150 o C) 3.5-6.0 High temperature (>150 o C) Cost (US ¢ /tonne of hot water) Cost (US $/ tonne of steam)

Cost of Geothermal Power http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm Normally not suitable 4.0-6.0 2.5-5.0 Large Plants (>30 MW) Normally not suitable 4.5-7 4.0-6.0 Medium Plants (5-30 MW) 6.0-10.5 5.5-8.5 5.0-7.0 Small plants (<5 MW) Unit Cost (US ¢ /kWh) Low Quality Resource Unit Cost (US ¢ /kWh) Medium Quality Resource Unit Cost (US ¢ /kWh) High Quality Resource

Direct Capital Costs Direct Capital Costs (US $/kW installed capacity) http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm Normally not suitable Exploration : US$100-400 Steam field:US$400-700 Power Plant:US$850-1100 Total: US$1350-2200 Exploration:: US$100-200 Steam field:US$300-450 Power Plant:US$750-1100 Total: US$1150-1750 Large Plants (>30 MW) Normally not suitable Exploration: : US$250-600 Steam field:US$400-700 Power Plant:US$950-1200 Total: US$1600-2500 Exploration : US$250-400 Steamfield:US$200-US$500 Power Plant: US$850-1200 Total: US$1300-2100 Med Plants (5-30 MW) Exploration : US$400-1000 Steam field:US$500-900 Power Plant:US$1100-1800 Total:US$2000-3700 Exploration : US$400-1000 Steam field:US$300-600 Power Plant:US$1100-1400 Total: US$1800-3000 Exploration : US$400-800 Steam field:US$100-200 Power Plant:US$1100-1300 Total: US$1600-2300 Small plants (<5 MW) Low Quality Resource Medium Quality Resource High Quality Resource Plant Size

Indirect Costs
Availability of skilled labor
Infrastructure and access
Political stability
Indirect Costs
Good: 5-10% of direct costs
Fair: 10-30% of direct costs
Poor: 30-60% of direct costs
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm

Operating/Maintenance Costs Operating and Maintenance Costs http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm 0.4-0.7 0.6-0.8 0.8-1.4 Total 0.25-0.45 0.35-0.45 0.45-0.7 Power Plant 0.15-0.25 0.25-0.35 0.35-0.7 Steam field O&M Cost (US c/KWh) Large Plants(>30 MW) O&M Cost (US c/KWh) Medium Plants (5-30 MW) O&M Cost (US c/KWh) Small plants (<5 MW)

Geothermal Installations Examples

Geothermal Power Examples Boyle, Renewable Energy, 2 nd edition, 2004

Geothermal Power Generation
World production of 8 GW
2.7 GW in US
The Geyers (US) is world’s largest site
Produces 2 GW
Other attractive sites
Rift region of Kenya, Iceland, Italy, France, New Zealand, Mexico, Nicaragua, Russia, Phillippines, Indonesia, Japan
http://en.wikipedia.org/wiki/Geothermal

Geothermal Energy Plant Geothermal energy plant in Iceland http://www.wateryear2003.org/en/

Geothermal Well Testing http://www.geothermex.com/es_resen.html Geothermal well testing, Zunil, Guatemala

Heber Geothermal Power Station http://www.ece.umr.edu/links/power/geotherm1.htm 52kW electrical generating capacity

Geysers Geothermal Plant The Geysers is the largest producer of geothermal power in the world. http://www.ece.umr.edu/links/power/geotherm1.htm

Geyers Cost Effectiveness Boyle, Renewable Energy, 2 nd edition, 2004

Geothermal Summary

Geothermal Prospects
Environmentally very attractive
Attractive energy source in right locations
Likely to remain an adjunct to other larger energy sources
Part of a portfolio of energy technologies
Exploration risks and up-front capital costs remain a barrier

Next Week: BIOENERGY

Supplementary Slides Extras

Geothermal Gradient http://www.earthsci.org/mineral/energy/geother/geother.htm

Geo/Hydrothermal Systems http://www.freeenergynews.com/Directory/Geothermal/

Location of Resources http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp

Ground Structures Boyle, Renewable Energy, 2 nd edition, 2004

Volcanic Geothermal System Boyle, Renewable Energy, 2 nd edition, 2004

Temperature Gradients Boyle, Renewable Energy, 2 nd edition, 2004

http://www.earthsci.org/mineral/energy/geother/geother.htm

UK Geothermal Resources Boyle, Renewable Energy, 2 nd edition, 2004

Porosity vs. Hydraulic Conductivity Boyle, Renewable Energy, 2 nd edition, 2004

Performance vs. Rock Type Boyle, Renewable Energy, 2 nd edition, 2004

Deep Well Characteristics Boyle, Renewable Energy, 2 nd edition, 2004

Single Flash Plant Schematic http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm

Binary Cycle Power Plant http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp

Flash Steam Power Plant http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp

Efficiency of Heat Pumps Boyle, Renewable Energy, 2 nd edition, 2004

Recent Developments
Comparing statistical data for end-1996 (SER 1998) and the present Survey, it can be seen that there has been an increase in world geothermal power plant capacity (+9%) and utilisation (+23%) while direct heat systems show a 56% additional capacity, coupled with a somewhat lower rate of increase in their use (+32%).
Geothermal power generation growth is continuing, but at a lower pace than in the previous decade, while direct heat uses show a strong increase compared to the past.
Going into some detail, the six countries with the largest electric power capacity are: USA with 2 228 MWe is first, followed by Philippines (1 863 MWe); four countries (Mexico, Italy, Indonesia, Japan) had capacity (at end-1999) in the range of 550-750 MWe each. These six countries represent 86% of the world capacity and about the same percentage of the world output, amounting to around 45 000 GWhe.
The strong decline in the USA in recent years, due to overexploitation of the giant Geysers steam field, has been partly compensated by important additions to capacity in several countries: Indonesia, Philippines, Italy, New Zealand, Iceland, Mexico, Costa Rica, El Salvador. Newcomers in the electric power sector are Ethiopia (1998), Guatemala (1998) and Austria (2001). In total, 22 nations are generating geothermal electricity, in amounts sufficient to supply 15 million houses.
Concerning direct heat uses, Table 12.1 shows that the three countries with the largest amount of installed power: USA (5 366 MWt), China (2 814 MWt) and Iceland (1 469 MWt) cover 58% of the world capacity, which has reached 16 649 MWt, enough to provide heat for over 3 million houses. Out of about 60 countries with direct heat plants, beside the three above-mentioned nations, Turkey, several European countries, Canada, Japan and New Zealand have sizeable capacity.
With regard to direct use applications, a large increase in the number of GHP installations for space heating (presently estimated to exceed 500 000) has put this category in first place in terms of global capacity and third in terms of output. Other geothermal space heating systems are second in capacity but first in output. Third in capacity (but second in output) are spa uses followed by greenhouse heating. Other applications include fish farm heating and industrial process heat. The outstanding rise in world direct use capacity since 1996 is due to the more than two-fold increase in North America and a 45% addition in Asia. Europe also has substantial direct uses but has remained fairly stable: reductions in some countries being compensated by progress in others.
Concerning R&D, the HDR project at Soultz-sous-Forêts near the French-German border has progressed significantly. Besides the ongoing Hijiori site in Japan, another HDR test has just started in Switzerland (Otterbach near Basel).
The total world use of geothermal power is giving a contribution both to energy saving (around 26 million tons of oil per year) and to CO2 emission reduction (80 million tons/year if compared with equivalent oil-fuelled production).
http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp

Geothermal Energy

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