Hot Dry Rocks for Electricity Generation

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Hot Dry Rocks for Electricity Generation

• Australian Energy News
• June 2002
• Engineers Australia
• February 2003

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Hot ones

• Thousand of cubic kilometres of hot dry rocks lie
  buried beneath 3 to 5 km of the earth surface in
  Cooper Basin in SA
• Horizontal stresses in the granite allow to
  create deep horizontal reservoirs heat
  exchangers
• The very best place in the world to develop large
  scale HDR electricity generation 24 hours per
  day renewable energy source

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Where is the hottest?
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Geology

• At between 4.5 and 4.9 km underground the
  temperature is 270 degrees
• Heat is trapped inside the granites by an
  overlying blanket (at least 3 km thick) of
  insulating sedimentary rocks
• The rocks are subject to the high horizontal
  stresses needed to create a multiple horizontal
  heat exchangers in France and Japan semivertical
  orientation (not so efficient) occurs
• Under these conditions, it takes tens of millions
  of years to build up the temperature to more than
  200 oC

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The pilot project

• Demonstration facility 13 MW 8 km south of
  Innamincka by Geodynamics
• Cost of the first geothermal well 5.4mln
• The Habanero well 1 is named after the worlds
  hottest chilli pepper
• Pilot project 11.5mln by public float plus
  5mln AusIndustry RD grant
• The estimated total cost of electricity
  generation (capital and operating) 6.18
  cents/kWh in a three-well 47mln system

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Habanero 1
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Binary geothermal power plants

• Two closed loops
• The first loop circulates water to extract heat
  from the deep hot rocks. As it operates under
  pressure, the superheated water (gt200 degrees)
  remains a liquid, with no steam generated
• The second loop uses liquids with a low boiling
  point (like in fridges and air conditioners) that
  drive a turbine as it boils out of the heat
  exchanger

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Binary geothermal power plant
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Three stages

• Stage 1 development of an underground heat
  exchanger followed by the drilling of a
  production well and providing the output through
  circulation (by May 2004)
• Stage 2 a demonstration 13 MW power plant will
  be developed and second production well drilled
  (18-24 months)
• Stage 3 commercial plant to produce 300 MW (37
  wells), total cost 770mln, connection to the
  national grid (total electricity costs
  4-5cents/kWh

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The potential

• One cubic kilometre of hot granite at 250 degrees
  has the stored energy of 40 million barrels of
  oil when the heat is extracted to a temperature
  of 140 degrees
• Copper Basin has a thermal source equivalent to
  50 billion barrels of oil (USA oil reserves are
  20 billion barrels)
• Australia has several thousand cubic km of high
  heat producing granites with the potential to
  meet the total electricity demand of the country
  for hundreds of years
• Further reading www.geodynamics.com.au