Geothermal Energy

What is geothermal energy?

• Heat from the earth’s core heats the rock beneath the earth’s surface. This, in turn, heats water within permeable substances, which can be tapped for steam energy.

How geothermal energy is processed

• Dry-Steam Power Plants
  • Steam is piped from underground reservoirs to turbines in the plant.
  • The steam turns the turbine, which, in turn, turns a generator, creating electricity.
  • Steam is condensed and injected back into another well of the reservoir.
• Flashed-Steam Power Plants
  • Tap into pools of very hot water (greater than 182 °C), which flows up to the surface under its own pressure.
  • The pressure decreases as it rises and boils (or “flashes”) into steam.
  • This steam turns a turbine connected to a generator and produces electricity.
  • The unused water is recycled back into the pools of water beneath the surface
• Binary-cycle Power Plants
  • Uses water at a lower temperature than flash-steam plants (between about 107 °C to 182 °C)
  • A working fluid with a lower boiling point is boiled by the heat of the geothermal water.
  • The vapor created by this process turns the turbine, creating electricity.
  • Both fluids are reused, running in separate closed loops, so there are almost no air emissions

Geothermal Heat Pumps

• Uses the natural constant temperature of the top layer of rock.
• Air is circulated between the house and the ground, heating in the winter and cooling in the summer.
• Can also heat water for bathrooms, causes almost no air pollution, and only requires a small monthly electric bill.
• Can be used anywhere, not just in really hot spots.

Where geothermal energy is used

• Hawaii- 25% of electrical supply
• Nevada- 10% of electrical supply
• California- 6% of electrical supply
• Washington- HUGE potential
• Oregon, Utah, and Idaho- electricity and space heating
• Cities- i.e. New York- use geothermal heat pumps in buildings
• Overall U.S. production: 600 megawatts (about enough to heat and cool over 400,000 homes).
• Geothermal energy is used for agriculture, industrial processing, recreational pools and spas, space heating and in district heating.

Limits

• Emissions
  • Geothermal processing does emit SOME greenhouse gasses
  • BUT In comparison to the amounts emitted by fossil fuels, geothermal emissions are minuscule.
  • AND Not every process emits greenhouse gases, just flash-steam plants.
• Location
  • Geothermal sources are primarily found only where two plates meet, or the crust is stretched thin through plate tectonics.
  • Ideal locations: West coast and the Basin and Range
  • The eastern half of the US holds almost no geothermal potential
• Geothermal reserves are often located too far away from cities for efficient energy generation.
• Other locations abundant in geothermal reserves, such as Yellowstone National Park are restricted to development due to their natural or cultural value

Cost

• The initial cost of installation is high
• Oil wells are cheaper to dig, and bring in more energy to the surface per gallon
• This looks unappealing to investors, and thus, the geothermal resources are not tapped

Benefits

• Geothermal energy is almost completely clean.
• Because the process takes place underground, it reduces surface impact considerably.
• Water used in the process can be endlessly recycled
• One site- every step of the process takes place in one location, eliminating the need to excavate for raw materials or waste energy in transfer.

• Fuel price fluctuations have no affect on the cost of generating geothermal electricity.
• Changes in global energy markets do not affect the supply of geothermal energy.
• Because geothermal energy is localized, international relationships and national conditions do not affect its price.
• When accessed, and processed properly, geothermal energy is completely reliable and uninterruptible

Conclusion

• Research is constantly being performed on geothermal energy, in an effort to fully take advantage of this natural bounty of clean energy.
• Geothermal energy has not been a great player in the national energy supply due to its decentralized nature.
• It is this transition from centralized to decentralized energy that lays the greatest threat to geothermal power today.