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 Iceland’s electricity is produced from Geothermal sources

7. 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

8. 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.
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
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 Earth’s 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 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

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: $ , 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 360°F (182°C) 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 400°F).
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 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

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.
Holes, 4 inches in diameter, are drilled 20 feet apart to a depth of 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
If the site has an adequate water body, this may be the lowest cost option.
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.

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)26

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 ground’s constant temperature (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 building.
Example of a ground-source heat pump.