Geothermal Energy

1
Geothermal Energy
2
History of Geothermal Energy Usage
- For thousands of years, civilizations have
used naturally warm spring water for various
purposes - 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

3

• Chaudes-Aigues, France
• The first district heating system came online in
  the 14th century and continues to operate to this
  day.

-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.
4

• 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

5
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

6
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 Icelands electricity is produced
  from Geothermal sources

7
20th Century Innovations

• New Zealand
• Wairakei was the site of the nations 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

8
The Physics of Geothermal Energy
Sources of Earths 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.
• 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.

9
The Physics of Geothermal Energy
Earths Atomic Engine

• Detailed understanding of the nature of heat
  below the Earths surface occurred when
  scientists began to understand the various
  origins of subterranean heat.
• Radiogenic heat was discovered by nuclear
  physicists in the 1950s.
• - Radiogenic heat is generated by the decay of
  radioactive isotopes of uranium, potassium, and
  thorium, which are found deep under the Earths
  surface, and significantly contributes to the
  presence of subterranean heat.

- Once radiogenic heat was understood, along with
other sources, the creation, dissipation, and
movement of underground heat was better
understood.
10
Bringing the Earths 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

11
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 water
• 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

12
Economics of Geothermal Power Plants

• 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 kWh.
• 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 kWh.

13
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 electricity.
• This is the oldest type of geothermal power
  plant.
• It was first used at Lardarello, Italy in 1904,
  and is still very effective.
• This technology is still used at The Geysers in
  northern California.
• Emissions
• Excess Steam
• Extremely minor amounts of gases.

14
Flash Steam Power Plants

• Hydrothermal fluids above 360F (182C) can be
  used in flash plants to make electricity.
• 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 "flash."
• The vapor then drives a turbine, which drives a
  generator.
• If any liquid remains in the tank, it can be
  flashed again in a second tank to extract even
  more energy.

15
Binary-Cycle Power Plants

• Most geothermal areas contain moderate-temperature
  water (below 400F).
• Energy is extracted from these fluids in
  binary-cycle power plants.
• Process
• Hot geothermal fluid and a secondary fluid with a
  much lower boiling point than water pass through
  a heat exchanger.
• 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.

16
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 2550 years, and the heat pumps often last 20
  years or more.
• Use 2550 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
• http//www.dsireusa.org/

17
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 states.
• It is estimated that geothermal greenhouses save
  about 80 of fuel costs compared to typical
  greenhouses
• about 5 to 8 of total operating costs.
• Industrial applications
• food dehydration
• laundries
• gold mining
• milk pasteurizing
• spas

18
Heat Pumps Closed Loops

• Horizontal Closed Loop
• Most cost-effective for residential installations
• Especially for new construction where sufficient
  land is available.
• 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.
• Vertical
• 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.
• Pond/Lake

19
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.

20
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

21
Atmospheric Pollution

• The practice of extracting fluid from deep earth
  can cause dissolved (non-condensable) gases to
  escape into the atmosphere
• Major CO2, CH4, NH3, H2S
• Minor Hg vapor, C6H6 benzene
• Implications
• Climate change
• Acid rain
• Health risks
• A relatively minor source of greenhouse gases

22
Emission Comparison
Source Geothermal Resources Council
23
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

24
LO-CAT Function Diagram
25
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 damage.
• 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.

26
Krafla Geothermal Station(northeast Iceland)
27
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 district
• 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 activity)

28
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 activity
• Motivated by the AltaRock Energy company incident
• Failure to properly disclose the earthquake risk
  to local residents
• Increased seismic activity blamed on the project,
  which was subsequently cancelled by U.S.E.D.

29
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.

30
Sharp Sustainability Education Center

• Geothermal Field - A geothermal system provides
  heating and cooling for the building, making use
  of the grounds constant temperature
  (approximately 55F 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 building.
• Example of a ground-source heat pump.