Enhanced Geothermal Systems

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Enhanced Geothermal Systems
Physics 160 Rodney Jamie Davies Daniel Lam Kyle
Mai
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Outline

• Technological Background
• Electrical Capacity and Costs
• Environmental Impacts
• Recommendations

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What is Geothermal Energy?

• Geo (Greek) - Earth

Thermal Of, relating to, using, producing, or
caused by heat.
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The Earth

• Parts of the earth
• Flow of magma
• Below surface Temperatures
• Gradient from hot to cold
• Heat can be ejected as steam or hot water.
• Hydrothermal reservoirs, water and hot porous
  rock.

• Yellowstone National Park

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What can we do with heat?

• conventional geothermal plants capture hot water
  from geysers or steam from vents to spin turbines

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Surface Geothermal Systems

• There are three different types surface of
  Geothermal system designs
• Flash / Steam Plants
• Dry Steam Power Plants
• Binary cycle power plant

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Flash or Steam plants

• Hot, High pressure water
• Turbines generate electricity
• Costs 4-6 cents per Kwh.

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Dry Steam Plants

• Steam passes through turbine
• 1050 -1220 degrees F

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Binary Cycle Power Plant

• Hot water (100 300 deg F)
• Heat Exchanger
• Binary liquid lower specific heat (vaporizes)

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Efficiency

• Functions like a conventional coal power plant.
• Efficiencies vary by
• input heat.
• At 400 deg. expect 23, not including parasitic
  load.

• In 2006 the US produced 2850 MW of geothermal
  electricity

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Limitations of surface geothermal

• These are surface based
• Represent low hanging fruit
• Most viable sites have been tapped
• Not as efficient as Coal, by the numbers

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Enhanced Geothermal SystemsAn Idea

• Temperature profile
• Think about the energy stored in the earth.
• How would one take advantage of this?

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Enhanced Geothermal Systems in practice

• Basically the same technology as surface
  geothermal for electricity production
• Some different nuances
• Take advantage of heat ANYWHERE

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Nuances

• Use drilling technology to access heat of the
  earth.
• Create fractures in rock under ground.
• Allows for the flow of water.
• Creates an artificial well through which water or
  fluid can be pumped.

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Drilling

• Depending on depth different solutions are
  available.

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Fracturing

• Looking for hot, tectonically stressed, and
  fractured rock.
• over time fractures seal due to secondary
  mineralization. Low permeability.
• Reopen fractures with hydraulic, thermal, and
  chemical processes.

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Enhanced Geothermal Systems in practice

• The Enhanced Geothermal System designs for the
  actual electricity generation are similar to
  surface geothermal.
• Flash or Steam Plants
• Dry Steam Power Plants
• Binary cycle power plant
• Type of plant depends on conditions

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• Electrical capacity and Cost

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Geothermal capacity

• Heat flow though the earths crust with
• Flow rate of 59 mW/m2 or 1.9 x 10-2 Btu/h/ft2
• Due to
• Convection and conduction from the mantle core
• Radioactive decay of U, Th, K
• Useful rock temperature
• 150-200 C for electricity production
• 100-150 C for other heating purposes

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Heat flow map of the US
MIT Panel of EGS
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Based on MIT report in 2006

• The worlds total geothermal resource is 13,000
  ZJ, with 200-2000 ZJ extractable
• 65-138 GWe for the worlds (1999)
• Capacity of generating 100GWe or more for the US
  by 2050
• Investment in researches cost 1billion for 15
  years in the US
• The geothermal energy at 10km under the surface
  of the US can supply the worlds need for 30,000
  years

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Electricity production

• Different types of cycle give efficiency from
  5-14 depend on temp
• Electrical output
• Where output at 40 C output geofluid

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Recoverability ( useful energy)
MWe ?th xQ rec x 1MJ/1000kJ x 1/t where Qrec
recoverable thermal energy (heat) in kWs (or
kJ)
rhomC?T ?th net
cycle thermal efficiency (fraction)
t seconds in 30 years 30
yr x 365 days/yr x 24 hrs/day x
3600 s/hr. 9.46 x 108 s
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Drilling cost

• Same for oil, gas and geothermal wells
• Depends on
• Well type
• Depth
• Location of wells

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Drilling of oil/gas wells vs. EG wells
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Cost and performance of 1MW geothermal plant as a
function of temp
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Geothermal energy and economics

• Reduce in energy price
• Meet market price after 2nd year
• long-term stability
• and characteristic power curve run all year
  round

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Power curves

• EGS electrical power

• Traditional electrical power

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Economics-the long run

• High capital cost (fixed cost)
• Low variable cost
• Low maintenance
• Heating/cooling capacity

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Deep Geothermal Energy

• The Environmental Impacts

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Solid and Gas Emissions

• No chance of contamination from solid discharge.
• Geothermal fluids contains less harmful
  greenhouse gases.
• No Nitrogen Oxide and Sulfur Dioxide. Less acid
  rain.
• Binary Plants have no Carbon Dioxide, however
  others have 0.2lb/kW-h.

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Comparison of Gas Emissions
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Landscape Impact and Land Use

• Requires relatively less land.
• Less environmental alterations and adverse
  effects.
• Produces more power per surface acre compared to
  nuclear and coal.

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Comparison of Land Requirement for Baseload Power
Generation
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Thermal Pollution

• It is one of the biggest concerns due to
  considerable loss of thermal heat.
• Taller cooling towers are needed to contain the
  waste heat.

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Noise Pollution

• Noise does occur during initial construction and
  drilling.
• Noise is minimum.

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Land Subsidence and Induced Seismicity

• In early days of geothermal energy sinking of
  land was a major problem (subsidence). This was
  caused by severe drop in reservoir pressure due
  more fluid removal. However, now through
  re-injection we keep the pressure balanced.
• Possibility of microseismic events from opening
  of fractures and acoustic noise when drilling.

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Disturbance to Wildlife Habitat and
Vegetations

• Loss of habitat and vegetation is relative minor
  and non-existence.
• Although there will be some alteration to the
  vegetation, most can restored.
• Available technology and waste management
  significantly reduces and damage to the ecosystem.

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Geothermal Plants In Harmony with Nature
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Recommendations

• An analysis on the reasons to move forward in the
  development of deep geothermal systems

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Expansion of Available Resources
Triangles and circles refer to locations that are
potent locations for geothermal energy
extraction. Triangles are the locations that are
already being exploited and circles are
locations unexploited (Barbier, 2002)
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New potential Deep Geothermal extraction or
Enhanced Geothermal System locations
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Immense potential

• Although Geothermal Energy is not renewable, the
  available resource is large
• 2,000 zettajoules available for extraction. (MIT)
  Enough to power human civilization for thousands
  of years
• 100,000 MWe is projected to be extracted in the
  next 50 years

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Environment

• Low risks of water contamination and low air
  pollution
• Most of the major noise pollutions are during
  construction only
• Seismicity due to EGS operation is minor and not
  definite

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Technology Disadvantages and Advantages

• Disadvantages
• For mid to low grade resources, wells deeper than
  4 km are required.
• EGSs are very new, time will be required to
  develop its potential and stability
• Advantages
• Deep Geothermal energy extraction could use
  existing drilling technologies for high grade
  resources.

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Competitive Costs

• MIT did simulations that project the 100,000 MWe
  could be achieved by investing a relatively small
  amount of 800 million to 1 billion for EGSs for
  the next 15 years.
• In the next 50 years, the costs to produce 1 kWh
  is estimated to range from 5 to 8 cents.
• While seemingly not competitive as operating
  costs of the 3 cents/kWh of nuclear and coal
  plants, the costs of 5-8 cents doesnt include
  the environmental costs that tag along with coal
  and nuclear power plants.
• -In comparison for 2006
• 494 Million was used for Nuclear waste disposal
• 6.5 Billion was used for Environmental
  Management

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In Summary

• Further development of Deep Geothermal Energy
  should be highly considered because of its
• Potential to allow new access to large resources
• Environmentally friendly traits
• Competitive costs in the long run
• Ability to use existing technologies to begin
  extraction soon