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					Geothermal Energy
   History of Geothermal Energy Usage
                                - For thousands of years,
                              civilizations have used naturally
                              warm spring water for various
                              - This hot water was mostly used
                              for bathing and cleaning, but was
                              also used to heat living spaces

• Ancient Rome
  – Hot spring water was feed into large public bathing areas to
    provide warm bathing for everyone
  – Some large building were heated by plumbing hot water
    through the floors
Chaudes-Aigues, France
-The first district heating system
came online in the 14th century
and continues to operate to this

-The scientific study and
measurement of geothermal
energy first began in 1740,
when a researcher measured
temperatures at various
locations along a mineshaft in
France. He, and others began
to notice that, generally, the
deeper one goes, the higher
temperature one finds.
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Boise, Idaho
   - Geothermal energy usage was first found in the United States in
   Boise, Idaho in 1892
   - 40 businesses and 200 homes were heated
   - 450 homes continue to be heated today
Larderello, Italy

          - Geothermal energy was first
          used to produce electricity in Italy
          in the early 20th century. The first
          working prototype was small and
          constructed by Prince Gionori
          Conti in 1905.

          - This experimental unit paved the
          way for the first commercially
          viable unit, which in 1913 began
          producing 250kWe
    Reykjavik: The Smokey Bay
- In 1755, natural scientists drilled the first holes for hot
water wells
- In 1930, the first Icelandic buildings were heated using
geothermal energy
- In 2008, 52 water heating wells were in operation,
providing 2,400 liters per second of water ranging from
62 to 132C
- Today, 24% of Iceland’s electricity is produced from
Geothermal sources

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          20th Century Innovations

New Zealand
-Wairakei was the site of the nation’s first geothermal
site for electricity production
- The site utilized different turbine types for efficient
electricity production from varied steam pressures.
- The once magnificent Geyser Valley has been
reduced to a stream
           The Physics of Geothermal Energy
                      Sources of Earth’s internal heat.
                                   1st: The heat from impacts with
                                   large bodies such as meteors and
                                   asteroids was trapped in
                                   surrounding rock of the planet,
                                   and may have been enough in
                                   certain circumstances to
                                   completely melt the early Earth.
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                                   2nd: Remnant heat of an early
                                   Earth event known as the Iron
                                   Catastrophe. With much of early
                                   Earth still molten, denser metals,
                                   particularly iron and nickel,
                                   migrated to the center of the
                                   planet. Tremendous amounts of
                                   frictional heat was created.
                                   3rd: Compression due to gravity.
            The Physics of Geothermal Energy
                       Earth’s Atomic Engine

                                      - Detailed understanding of the
                                      nature of heat below the Earth’s
                                      surface occurred when scientists
                                      began to understand the various
                                      origins of subterranean heat.
                                      - Radiogenic heat was discovered
                                      by nuclear physicists in the 1950’s.
                                      - Radiogenic heat is generated by
                                      the decay of radioactive isotopes of
                                      uranium, potassium, and thorium,
                                      which are found deep under the
- Once radiogenic heat was            Earth’s surface, and significantly
understood, along with other          contributes to the presence of
sources, the creation, dissipation,   subterranean heat.
and movement of underground heat
was better understood.
    Bringing the Earth’s Heat to the Surface

- In some instances, passive heat extraction is used.
  - In places with “hot rocks” at the surface electricity
is created without the need for heat extraction.
- Active heat extraction requires energy input but
allows for power production at many more locations
Conversion of Heat Energy
                 - Heat is drawn from the
                 depths either actively or
                 passively through the
                 movement of hot water
                 - The heat is then used to boil
                 -The steam produced then is
                 fed to a turbine
                 -The turbine converts the
                 geothermal heat energy into
                 mechanical energy
                 - The turbine spins a
                 generator which converts
                 mechanical energy into
                 electrical energy
   Economics of Geothermal Power
• How much does a typical geothermal energy cost per kilowatt-
  hour (kWh)?
   – At The Geysers, a geothermal power plant in California, power is
     sold at $0.03 to $0.035 per kWh.
   – A power plant built today would probably require about $0.05 per
   – Coal: $0.07-0.14 , Natural Gas: $0.07 -$0.10, Nuclear $0.15+
     per kWh

• What does it cost to plan and build a geothermal power plant?
   – Geothermal Power plants have higher initial costs for
       • land purchasing
       • development of system and analysis of area
       • Construction of power plant and pipeline
   – The initial cost for the field and power plant is around $2500 per
     installed kW in the U.S.
   – Or about $3000 to $5000/kWe for power plant less than 1 Mwe.
   – Operating and maintenance costs range from $0.01 to $0.03 per
         Dry Steam Power Plants
• Use hydrothermal fluids that are
  primarily steam.
• Process:
    – The steam is sent directly to a
      turbine, which drives the
      generator and produces
• This is the oldest type of
  geothermal power plant.
    – It was first used at Lardarello,
      Italy in 1904, and is still very
• This technology is still used at
  The Geysers in northern
• Emissions:
    – Excess Steam
    – Extremely minor amounts of
     Flash Steam Power Plants
• Hydrothermal fluids above
  360°F (182°C) can be
  used in flash plants to make
• Process:
   – Fluid is sprayed into a tank
     held at a much lower
     pressure than the fluid.
   – This causing some of the
     fluid to rapidly vaporize, or
   – The vapor then drives a
     turbine, which drives a
   – If any liquid remains in the
     tank, it can be flashed again
     in a second tank to extract
     even more energy.
      Binary-Cycle Power Plants
• Most geothermal areas contain
  moderate-temperature water
  (below 400°F).
• Energy is extracted from these
  fluids in binary-cycle power
• Process:
    – Hot geothermal fluid and a
      secondary fluid with a much
      lower boiling point than water
      pass through a heat
    – Heat from the geothermal fluid
      causes the secondary fluid to
      flash to vapor, which then
      drives the turbines.
• Since this is a closed-loop
  system, virtually nothing is
  emitted to the atmosphere.
 Economics of Direct Use and Heat
         Pump Systems
• Costs:
   – High Initial Cost for trenching and installation
      • Depends on the area (rocky soil vs. soft clay/dirt)
      • Typical costs about $2,500 per ton of capacity,
           – Typical residential building requires 3-ton unit = about $7,500.
      • A horizontal ground system will generally cost less than a
        vertical system.
   – Low Maintenance costs (repairs/electrical demand)
      • The underground piping often carries warranties of 25–50 years,
        and the heat pumps often last 20 years or more.
      • Use 25%–50% less electricity than conventional heating or
        cooling systems.
      • Reduction in energy consumption :
           – up to 44% compared to air-source heat pumps
           – up to 72% compared to electric resistance heating with standard air-
             conditioning equipment.
• State and National Tax Credits/Incentives exist
          Geothermal Direct Use
• Direct Uses:
   – Greenhouses
        • 38 greenhouses in 8 western
          states use this technology
        • vegetables, flowers, houseplants,
          and tree seedlings
   – Aquaculture
        • 28 operations are active in 10
• It is estimated that geothermal
  greenhouses save about 80% of
  fuel costs compared to typical
   – about 5% to 8% of total operating
• Industrial applications:
   –   food dehydration
   –   laundries
   –   gold mining
   –   milk pasteurizing
   –   spas
Heat Pumps – Closed Loops
Horizontal Closed Loop

•   Most cost-effective for residential installations
     –     Especially for new construction where sufficient land is
•   Layout:
     –     Trenches are dug at least four feet deep.
     –     Two pipes, one buried at six feet, and the other at four feet.
     –     OR: two pipes placed side-by-side at five feet in the ground in
           a two-foot wide trench.

•   Usually a better bet when area of usable space is limited
     –     If the soil is too shallow for trenching.
•   Used in more commercial and industrial applications.
•   Layout:
     –     Holes, 4 inches in diameter, are drilled 20 feet apart to a depth
           of 100-400 feet.
     –     two pipes are inserted and are connected at the bottom with a
           U-bend to form a loop.
     –     The vertical loops are connected with horizontal pipe, the
           manifold, placed in the trenches which is connected to the heat
           pump in the building.

•   If the site has an adequate water body, this may be the
    lowest cost option.
•   Layout:
     –     A supply line pipe is run underground from the building to the
           water and coiled into circles at least eight feet under the
           surface to prevent freezing.
            Open Loop System
    Uses well or surface water as
  the heat exchange fluid.
• Once it has circulated through
  the system, the fluid is
  returned to a recharge well or
  is discharged on the surface.
• Available where:
    – a sufficient supply of clean
      water is found
    – All local codes and regulations
      meeting groundwater discharge
      is me.
        Environmental Impact
• Overall, geothermal power is a sustainable,
  flexible, environmentally-friendly resource.
• Main disadvantages:
 – Emission of pollutant gases into atmosphere
 – Emission of toxic compounds to surface level
 – Possible cause of land instability
 – Reliant on electricity power sources
         Atmospheric Pollution
• The practice of extracting fluid from deep earth can cause
  dissolved (non-condensable) gases to escape into the
  – Major: CO2, CH4, NH3, H2S
  – Minor: Hg vapor, C6H6 benzene
• Implications:
  – Climate change
  – Acid rain
  – Health risks
• A relatively minor source of greenhouse gases
           Emission Comparison

Source: Geothermal Resources Council
            Emission Solutions
• Closed-loop designs (ground-source heat pumps)
• Emission scrubber technology (for power plant usage)
  – Terra-Gen Power facility employs the LO-CAT® process to
    oxidize gaseous H2S into solid form.
  – H2S + ½O2  H2O + So
  – 99% removal efficiency of H2S
  – 15 years of proven effectiveness operating at the China Lake
    Naval Weapons Center in southeastern California
LO-CAT Function Diagram
   Emission of Toxic Chemicals
• The heated water from geothermal sources may contain
  boron, arsenic, mercury, antimony, and salt.
• Once the energy is extracted, the cooled water can
  cause these trace toxins to come out of solution.
• High concentrations of toxins can cause environmental
• Solution: extracted (cooled) geothermal fluid is commonly
  injected back into the source
  – This closed-loop recycling technique prevents toxin
     emission and prolongs the viable life of the source.
Krafla Geothermal Station
   (northeast Iceland)
          Land Instability Issues
     (threats to the built environment)
• Subsidence
  – Downward motion of ground surface (due to a
    reduction in subterranean volume/pressure)
  – In Staufen im Breisgau, Germany, geothermal drilling is
    blamed for causing surface deviations in the historical
• Increased seismic activity
  – Hydraulic fracturing can occur when power facilities
    introduce new bores into rock
  – Viable geothermal heat sources may be located near
    volcanically-active sites (predisposed to seismic
             Seismic Concerns
• In Jan. 2010, The United States Energy Department
  enacted new safety measures:
  – Permitting
  – Community education
• Intent to minimize the risk of drilling-induced seismic
• Motivated by the AltaRock Energy company incident
  – Failure to properly disclose the earthquake risk to local
  – Increased seismic activity blamed on the project, which
    was subsequently cancelled by U.S.E.D.
      Recent Geothermal News
• As of March 22, 2010, The World Bank announced their
  effort to provide $400 million to Indonesia for geothermal
  power infrastructure.
• Indonesia contains an estimated 28,100 MW of
  geothermal capacity (equivalent to 12 BBO)
• Goals:
  – To derive 9,500 MW from geothermal sources by 2025
  – Reduce growth of greenhouse gas emissions by 26%
    during the next ten years
• This effort recognizes the potential of geothermal power,
  a promising but understated resource.
     Sharp Sustainability Education Center
• Geothermal Field - A
  geothermal system
  provides heating and
  cooling for the
  building, making use of
  the ground’s constant
  (approximately 55°F
  6 feet below grade). In
  summer, excess heat
  from the building is
  pumped into the cooler
  ground; in winter, heat
  from the ground is
  pumped into the
• Example of a ground-
  source heat pump.