geothermal energy - site.iugaza.edu.pssite.iugaza.edu.ps/mabualtayef/files/re-ch06.pdf · 5....
TRANSCRIPT
Geothermal Energy
Dr. Mazen Abualtayef Environmental Engineering Department
Islamic University of Gaza, Palestine
Adapted from a presentation by
Professor S.R. Lawrence Leeds School of Business, Environmental Studies
University of Colorado, Boulder, CO, USA
AGENDA – Geothermal Energy
• Geothermal Overview
• Extracting Geothermal Energy
• Environmental Implications
• Economic Considerations
• Geothermal Installations – Examples
Geothermal Overview
Geothermal in Context
• Geo = earth, thermos = heat
• Geothermal energy is the extractable
portion of the heat stored in the ground.
Geothermal in Context
http://en.wikipedia.org/wiki/World_energy_consumption
World energy consumption
Geothermal in Context
Global geothermal electric capacity
http://en.wikipedia.org/wiki/Geothermal_power
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 originates from radioactive decay of elements
• Heat energy continuously flows from hot core
– Conductive heat flow تدفق الحرارة بالتوصيل
– Convective انتقال حراري 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, 2nd edition, 2004
نبع ماء حار
Geysers
http://en.wikipedia.org/wiki/Geyser
Clepsydra Geyser in Yellowstone
500 geysers in yellow stone park out 1000 geysers worldwide
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, 2nd edition, 2004
Enthalpy: Catchment
Extracting Geothermal Energy
Methods of Heat Extraction
http://www.geothermal.ch/eng/vision.html
من تشكيل
الصخور المحيطة
من المياه الجوفية
الحراريةحركة المياه من
خالل محاكاة
الصخور
المتصدعة
Units of Measure
• Pressure
– 1 Pascal (Pa) = 1 Newton / square meter
– 100 kPa = ~ 1 atmosphere
– 1 MPa = ~10 atmospheres
• Temperature
– Celsius (ºC); Fahrenheit (ºF); Kelvin (K)
– 0 ºC = 32 ºF = 273 K
– 100 ºC = 212 ºF = 373 K
Plants Types: 1. Dry Steam Power Plants
• “Dry” steam extracted from natural reservoir
– 180-225 ºC
– 4-8 Mpa
– 200+ km/hr
• 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, 2nd edition, 2004
Dry Steam Schematic
Boyle, Renewable Energy, 2nd edition, 2004
2. 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 to
produce each MW of electrical power
Single Flash Steam Schematic
Boyle, Renewable Energy, 2nd edition, 2004
The steam is
condensed,
creating a
partial vacuum
and thereby
maximizing the
power
generated by
the turbine-
generator.
The steam is usually condensed either in a direct contact condenser, or a heat exchanger type condenser.
In a direct contact condenser the cooling water from the cooling tower is sprayed onto and mixes with the
steam. As an alternative to direct contact condensers shell and tube type condensers are sometimes used.
3. Binary Cycle Power Plants
• Low temps – 100o and 150oC
• Use heat to vaporize organic liquid – E.g., iso-butane, iso-pentane
• Use vapor to drive turbine – Causes vapor to condense
– Recycle continuously
• Typically 7~12% 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, 2nd edition, 2004
>2000m
Binary Plant Power Output
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
4. 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, 2nd edition, 2004
5. 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
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
6. 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 شقوق
• 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, 2nd edition, 2004
2-Well HDR System Parameters
• 2×106 m2 = 2 km2
• 2×108 m3 = 0.2 km3
Boyle, Renewable Energy, 2nd edition, 2004
Impedance: معاوقة لتيار كهربائي
Promise of HDR
• 1 km3 of hot rock has the energy content of 70,000 tons 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
Boyle, Renewable Energy, 2nd edition, 2004
Direct Use Technologies
• Geothermal heat is used directly rather
than for power generation
• Extract heat from low temperature
geothermal resources
– < 150 oC
• Applications sited near source (<10 km)
• Using heat pump technology to utilize
geothermal heat for air conditioning and
refrigeration applications
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Geothermal Heat Pump
http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
Vertical Geothermal Loop
Video
Video
Ramallah example
Installation
Heat vs. Depth Profile
Boyle, Renewable Energy, 2nd edition, 2004
Geothermal District Heating
Boyle, Renewable Energy, 2nd edition, 2004
Southhampton geothermal district heating system technology schematic
Direct Heating Example
Boyle, Renewable Energy, 2nd edition, 2004
Technological Issues
• Geothermal fluids can be corrosive
– Contain gases such as hydrogen sulphide
– Corrosion
• Requires careful selection of materials
and diligent operating procedures
• Typical capacity factors of 85-95%
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Technology vs. Temperature
Reservoir
Temperature
Reservoir
Fluid
Common
Use
Technology
commonly chosen
High Temperature
>220oC
Water or
Steam
Power Generation
Direct Use
• Flash Steam
• Combined (Flash
and Binary) Cycle
• Direct Fluid Use
• Heat Exchangers
• Heat Pumps
Intermediate
Temperature
100-220oC
Water Power Generation
Direct Use
• Binary Cycle
• Direct Fluid Use
• Heat Exchangers
• Heat Pumps
Low Temperature
50-150oC
Water Direct Use
• Direct Fluid Use
• Heat Exchangers
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Geothermal Performance
Boyle, Renewable Energy, 2nd edition, 2004
Current Geothermal Projects
Environmental Implications
Environmental Impacts
• Land
– Vegetation loss
– Soil erosion
– Landslides
• Air
– Slight air heating
– Local fogging
• Ground
– Reservoir cooling
– Seismicity (tremors)
(الهزات)الزلزالية
• Water using water for drilling
purpose:
– Watershed impact
– Divert streams
using water from reservoir:
– Lower water table
– Subsidence هبوط
• Noise -- Disturbance to
animals & humans
• Benign overall
بشكل عام غير خطر
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/refill heat to crust
quickly enough
• Example:
-- The government of Iceland states It should be
stressed that the geothermal resource is not
strictly renewable in the same sense as the hydro
resource. It estimates that 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
Geothermal Calculator
A geothermal
calculator was
developed by
© Mazen
Abualtayef
and you can
find it here http://site.iugaza.edu.ps/mab
ualtayef/files/PV-calculator.xlsx
Economics of Geothermal
Cost Factors • Temperature and depth of resource: A shallow resource means minimum drilling costs. High temperatures
mean higher energy capacity
• Type of resource (steam, liquid, mix):
A dry steam resource is generally less expensive to develop as reinjection pipelines, separators and reinjection wells are not required
• Chemistry of resource: A resource with high salinity fluids, high silica concentrations, high gas
content, or acidic fluids can pose technical problems which may be costly to overcome
• Permeability of rock formations: A highly permeable resource means higher well productivity
• 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
http://www.worldbank.org/html/fpd/energy/geothermal/
Cost of Water & Steam
Cost
(US $/ton
of steam)
Cost
(US ¢/ton
of hot water)
High temperature
(>150oC)
3.5-6.0
Medium
Temperature
(100-150oC)
3.0-4.5 20-40
Low Temperature
(<100oC)
10-20
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Table Geothermal Steam and Hot Water Supply Cost where drilling is required
Cost of Geothermal Power
Unit Cost
(US ¢/kWh)
High Quality
Resource
Unit Cost
(US ¢/kWh)
Medium
Quality
Resource
Unit Cost
(US ¢/kWh)
Low Quality
Resource
Small plants
(<5 MW)
5.0-7.0 5.5-8.5 6.0-10.5
Medium
Plants
(5-30 MW)
4.0-6.0 4.5-7 Normally not
suitable
Large Plants
(>30 MW)
2.5-5.0 4.0-6.0 Normally not
suitable
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Direct Capital Costs
Plant
Size
High Quality
Resource
Medium Quality
Resource
Low Quality
Resource
Small plants
(<5 MW)
Exploration : US$400-800
Steam field:US$100-200
Power Plant:US$1100-1300
Total: US$1600-2300
Exploration : US$400-1000
Steam field:US$300-600
Power Plant:US$1100-1400
Total: US$1800-3000
Exploration : US$400-1000
Steam field:US$500-900
Power Plant:US$1100-1800
Total:US$2000-3700
Med Plants
(5-30 MW)
Exploration : US$250-400
Steamfield:US$200-US$500
Power Plant: US$850-1200
Total: US$1300-2100
Exploration: : US$250-600
Steam field:US$400-700
Power Plant:US$950-1200
Total: US$1600-2500
Normally not suitable
Large Plants
(>30 MW)
Exploration:: US$100-200
Steam field:US$300-450
Power Plant:US$750-1100
Total: US$1150-1750
Exploration : US$100-400
Steam field:US$400-700
Power Plant:US$850-1100
Total: US$1350-2200
Normally not suitable
Direct Capital Costs (US $/kW installed capacity)
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Indirect Costs
• Availability of skilled labor
• Infrastructure and access
• Political stability
• Indirect Costs
– Good: 5-10% of direct costs in developed countries
– Fair: 10-30% of direct costs
– Poor: 30-60% of direct costs in developing countries
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Operating/Maintenance Costs
O&M Cost (US
c/KWh)
Small plants
(<5 MW)
O&M Cost (US
c/KWh)
Medium Plants
(5-30 MW)
O&M Cost (US
c/KWh)
Large
Plants(>30
MW)
Steam field 0.35-0.7 0.25-0.35 0.15-0.25
Power Plant 0.45-0.7 0.35-0.45 0.25-0.45
Total 0.8-1.4 0.6-0.8 0.4-0.7
http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Geothermal Installations
Examples
Geothermal Power Examples
Boyle, Renewable Energy, 2nd edition, 2004
Geothermal Power Generation
• World production of 8 GW
– 2.7 GW in US
• The Geysers (US) is world’s largest site
– Produces 2 GW
• Other attractive sites
– Rift region منطقة الصدع 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, 2nd edition, 2004
Geothermal Summary
Geothermal Prospects
• Environmentally very attractive
• Attractive energy source in right locations
• Likely to remain an adjunct مساعد 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, 2nd edition, 2004
Volcanic Geothermal System
Boyle, Renewable Energy, 2nd edition, 2004
Temperature Gradients
Boyle, Renewable Energy, 2nd edition, 2004
http://www.earthsci.org/mineral/energy/geother/geother.htm
UK Geothermal Resources
Boyle, Renewable Energy, 2nd edition, 2004
Porosity vs. Hydraulic Conductivity
Boyle, Renewable Energy, 2nd edition, 2004
Performance vs. Rock Type
Boyle, Renewable Energy, 2nd edition, 2004
Deep Well Characteristics
Boyle, Renewable Energy, 2nd edition, 2004
Single Flash Plant Schematic
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
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, 2nd 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