PHYS 1110
Lecture 20
Professor Stephen Thornton
November 13, 2012
Reading Quiz
Which country has the greatest amount
of geothermal produced electricity
installed?
A)
B)
C)
D)
E)
Philippines
Iceland
Italy
Turkey
United States
Reading Quiz
Which country has the greatest amount
of geothermal produced electricity
installed?
A)
B)
C)
D)
E)
Philippines
Iceland
Italy
Turkey
United States
Homework 4 due Tuesday, November
13, 2012.
Quiz on solar (Ch. 7) and wind energies
(Ch. 8) on Thursday, Nov. 13
Homework 5 on Ch. 8 due Thursday,
Nov. 13.
Geothermal energy has been used for
cooking and bathing for centuries, but can also be used in
large power plants to produce electricity, and the steady
temperatures just under the ground in our backyards can
be used as thermal reservoirs to both heat and cool our
homes using a heat pump.
Geothermal energy accounts
for at least 25% of the
electrical capacity in Iceland,
the Philippines, and El
Salvador. The United States
produces more geothermal
electricity than any country
in the world, more than 3
GW in eight states.
Geothermal heat – used in 78 countries
Geothermal power – 11 GW in 24 countries
Geothermal heat includes heat pump groundbased thermal reservoirs.
Geothermal electrical power capacity
for US and World.
The upper 3 m of the Earth has a nearly
constant temperature between 500F (100C) and 600F (160C),
but below that are large resources.
Crust: 5 – 70 km thick
Mantle: 3000 km thick, rocks
Core:
outer (2300 km) is liquid.
inner (1200 km) is solid.
The Earth’s temperature gradient is ~22 0C/km.
Radioactive decay heating of 40K, 232Th, 235U, and 238U are
primarily responsible for the heating. The center of the Earth
has a temperature of at least 5000 0C (maybe as high as 7000
0C) with a pressure as high as 360 GPa, which causes the inner
core to still be a solid instead of melting into a liquid.
Hot springs occur when the rising heated water is
collected on Earth’s surface into a pool. The springs can be calm or
boiling, depending on the temperature. The hot water dissolves
material as it rises to the surface and often contains minerals, which
people use for medicinal purposes.
Many hot springs
are too hot or too
acidic for bathing,
but others are very
relaxing. This one
is in Japan.
Fumaroles are vents that emit steam and other gases
(such as sulfur dioxide and hydrogen sulfide formed after interacting
with sulfur). When superheated water emerges from the ground, the
pressure drops turning the hot water into steam. This is sometimes
associated with chemical activity and brightly colored rocks in the
surface water. They contain water hotter than hot springs.
Mud pots are similar to hot springs or
fumaroles but have only a small amount of water.
This results in an acidic, viscous, often bubbling,
slurry (Yellowstone).
Volcanoes and their eruptions are the most
obvious visualizations of geothermal energy. They occur
due to an opening in the Earth’s surface, often releasing
huge amounts of lava, ash, and gases to escape to the
Earth’s surface. Iceland is on the Mid Atlantic Ridge of the
Ring of Fire and did not even exist as an island 20 million
years ago.
Quiz
The upper 3 m of the Earth has
approximately what temperature?
A)
B)
C)
D)
E)
550F
550C
50F
50C
5K
Quiz
The upper 3 m of the Earth has
approximately what temperature?
A)
B)
C)
D)
E)
550F
550C
50F
50C
5K
Quiz
The temperature about 4000 km inside the
Earth from its surface has approximately
what temperature?
A)
B)
C)
D)
E)
400F
4000C
400000F
40000C
50000 K
Quiz
The temperature about 4000 km inside the
Earth from its surface has approximately
what temperature?
A)
B)
C)
D)
E)
400F
4000C
400000F
40000C
50000 K
Quiz
Which of the following is not directly due
to geothermal processes?
A)
B)
C)
D)
E)
hot springs
volcanoes
earthquakes
geysers
fumaroles
Quiz
Which of the following is not directly due
to geothermal processes?
A)
B)
C)
D)
E)
hot springs
volcanoes
earthquakes
geysers
fumaroles
History
Hot springs: US Indians, Chinese spa, Romans
District heating system: Boise (1892), Klamath Falls,
Oregon (1900)
The first geothermal electricity was produced in 1904 in Lardello in
Southern Tuscany, Italy. Steam and hot water springs were known to be
produced at this site since Roman times. Hot steam escaping the Earth’s
surface turned a turbine that powered five light bulbs in 1904. By 1911 a
geothermal power station was constructed at Lardello. It remained the
world’s only industrial geothermal power plant until a plant was built in
New Zealand in 1958. A 250 kW power plant was constructed in 1913 to
provide power for the Italian electric railroad system. Today, almost
5,000 GWh are produced at Lardello each year, enough to provide
electricity to about one million homes. Surface water is pumped down to
very hot granite rocks that are located close to the surface. The water is
warmed to more than 2000C, and the returning steam turns turbines that
produce electricity.
The Pacific Gas and Electric Company built
the United State’s first successful geothermal power plant
at the Geysers in California in 1960. Its successors
remain in operation today and will be discussed shortly.
Ground Source Heat Pump
æ Qc ö
æ Tc ö
÷
÷
ç
ç
÷
÷
W = Qh - Qc = Qh çç1= Qh çç1÷
÷
÷
÷
è Qh ø
è Th ø
Qc is the heat removed from a cold reservoir at temperature
Tc and Qh is the heat deposited to a hot reservoir at
temperature Th. If we want to minimize the work done, and
therefore the amount of electricity we have to pay for, we
want the cold and hot reservoirs to have approximately the
same temperature. When it is very cold outside, heat
pumps have to do a considerable amount of work. The
work done to heat our houses to 720F inside is much less
when the cold reservoir is 570F (underground thermal
reservoir) rather than 50F in the atmosphere.
Heat pumps are classified by their
coefficient of performance COP = Qh / W
There are more than 600,000 groundsource heat pumps in operation in the United States
today, and they are increasing at the rate of 60,000 new
ones each year. They have higher initial capital costs,
but the savings make them cost effective after only a
few years. They are relatively easy to install, especially
in new construction. They do require digging up yards
in order to place the pipes in the ground. Even now,
many heating and cooling contractors are not familiar
with the installation procedures. Mostly the heat
exchange is done with the ground, but it can also be
done with a pond or even a swimming pool that does
not freeze over in the winter.
Geothermal reservoirs close to the surface of Earth
having temperatures up to about 1500C (3000F) are used for direct heat
in residences, industry and commerce. Its use is widespread in the
United States for a wide variety of applications including food
processing, gold mining, greenhouses, and fish and alligator farms.
Useful geothermal resources are plentiful in the western United States.
A survey of 10 western states in the US identified almost 1000 low- to
moderate- temperature geothermal sources with hundreds of direct use
sites in the more than 9,000 thermal known wells and springs. In 2004
approximately 70 countries used 270,000 GJ of geothermal energy
directly for space heating, heating swimming pools, and for industrial
and agricultural applications.
Direct-use systems normally have three components:
• A production facility, usually a well, to bring hot water to the surface.
• A mechanical system (pipes, heat exchanger, controls) to deliver the
heat to a place of use.
• A disposal system (injection well or storage pond) for the spent
geothermal fluid.
A district heating system melts the snow on a
sidewalk in Klamath Falls, Oregon. Note the snow is not
melted on the sidewalk beyond, the road, or the parking lot.
The hottest known geothermal regions on Earth
are shown in red. These are likely to be best sources for
electrical production.
Quiz
Which of the following countries gets the
largest percentage of its electricity from
geothermal sources?
A)
B)
C)
D)
E)
Philippines
United Kingdom
Italy
Turkey
United States
Quiz
Which of the following countries gets the
largest percentage of its electricity from
geothermal sources?
A)
B)
C)
D)
E)
Philippines
United Kingdom
Italy
Turkey
United States
Estimated temperatures over the United
States at a depth of 6 km.
Satellite imaging and aerial photography
must be closely examined for prospective
geothermal sites.
Geothermal exploration is similar to that of
oil and gas – but 50 years behind!
Geologists and geophysicists examine closely
volcanic regions like this one on a hillside in El Hoyo,
Nicaragua for likely places for power plants.
Data from all kinds of surveys (electrical,
magnetic, chemical, and seismic) must be gathered and
studied in various ways.
Drilling is crucial for determining the
suitability of the region for geothermal energy power
production. It must be determined whether the geothermal
reservoir will be hot enough to support commercial
electrical production. Small-diameter temperature (or
thermal) gradient holes (TGH) are drilled to various
depths to determine the temperature gradient in the region.
Thermal characteristics of the material brought up from
drilling are quickly examined to determine the geothermal
characteristics and the extent of the resource. The TGH
may be drilled in steps, and at first may only go to a depth
of a few hundred meters. Sometimes the TGH may be
drilled deeper in an attempt to penetrate the geothermal
reservoir. But the depth is dependent on the geologic and
hydrologic conditions.
Quiz
Which of the following is the closest to the
maximum temperature at 6 km depth in the
United States (do not consider volcanoes,
etc.)?
A)
B)
C)
D)
E)
250C
2500C
25000C
25,0000C
250,0000C
Quiz
Which of the following is the closest to the
maximum temperature at 6 km depth in the
United States (do not consider volcanoes,
etc.)?
A)
B)
C)
D)
E)
250C
2500C - actually 3250C
25000C
25,0000C
250,0000C
Divide into groups and discuss:
Flash geothermal power plant
Dry steam geothermal power plant
Binary geothermal power plant
Flash/binary combined geothermal
power plant
Enhanced geothermal systems
Co-Production with Oil and Gas Wells
Oil and gas fields already in production may be another potential source of geothermal
energy, because a significant amount of hot water or suitable high-pressure conditions
are present. This could possibly allow for the production of geothermal produced
electricity at the same time that oil and gas is extracted. In many cases, the extraction
of oil and gas may even be enhanced. The 2007 MIT mentioned earlier estimated that
the United States may even be able to produce 44 GWe of electricity by 2050 by coproducing electricity, oil, and natural gas. The study went so far as to suggest that such
advanced geothermal systems could supply 10% of US baseload electricity by 2050,
given sufficient research and development over the next 10 years.
As part of the American Recovery and Investment Act of 2009, $400 million of new
funding was allocated to the US DOE’s Geothermal Technologies Program. Of these
funds, $90 million may go to up to 10 demonstration projects to develop and test EGS
technology. Another $50 million will fund up to 20 other demonstration projects, which
includes co-production.
The Southern Methodist University Geothermal Energy Program has identified many
GW of possible energy by co-production. There are currently two geothermal coproduction demonstrations sites underway in the United States: at the Rocky Mountain
Oil Test Center in Wyoming and the Jay oil field in Florida.
Electrical Production Today
Most geothermal power plants use flash technology (New
Zealand). Most new growth is in binary plants that can utilize
low and moderate temperatures.
Potential in Asia and Pacific Islands is immense. Philippines
is heavily involved.
Central America and Caribbean have large potential and need.
5 GW under development in USA.
Europe is involved, especially Italy, Turkey and Iceland.
Environmental Impact
Some gases.
Subsidence, motion & sinking of Earth.
Germany, New Zealand, Switzerland
(near Basel, 10,000 seismic events in 6
days of water injection), Australia,
almost none in the Geysers (best
monitored in world).
Quiz
Which of the following processes has the
most geothermal power plants currently
installed?
A)
B)
C)
D)
E)
Flash
Dry steam
Binary
Flash/binary combined
Enhanced geothermal systems
Quiz
Which of the following processes has the
most geothermal power plants currently
installed?
A)
B)
C)
D)
E)
Flash
Dry steam
Binary
Flash/binary combined
Enhanced geothermal systems
The future is not clear.
• Costs for producing electricity are high.
• Good for heating source and groundbased heat pumps.
• Small-scale plants (< 5 MW) in rural areas.
• Need Enhanced Geothermal Systems.
• Need co-production with oil and gas wells.
Lots of pros and cons. Look at them. Pros
outweigh cons. Need tax incentives, subsidies,
research and development.