ENERGY SOURCES
ENERGY SOURCES
ALTERNATIVE ENERGY SOURCES
Geothermal Energy
What is Geothermal Energy?
Geo (Greek) – earth
Thermal - relating to, using, producing, or caused by heat.
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
Sources of Earth’s Internal Energy
•70% comes from the decay of radioactive nuclei
with long half lives that are embedded within the
Earth
•Some energy is from residual heat left over from
Earths formation.
•Friction of tectonic plates
•The rest of the energy comes from meteorite
impacts.
Geysers
Clepsydra Geyser in Yellowstone
http://en.wikipedia.org/wiki/Geyser
A geyser is a type of hot spring that erupts periodically,
ejecting a column of hot water and steam into the air.
The name geyser comes from Geysir, the name of an
erupting spring at Haukadalur, Iceland; that name, in
turn, comes from the Icelandic verb gjósa, "to gush".
The formation of geysers requires a favourable
hydrogeology which exists in only a few places on
Earth, and so they are fairly rare phenomena. About
1000 exist worldwide, with about half of these in
Yellowstone National Park, USA (Glennon, J.A. 2005).
Geyser eruptive activity may change or cease due to
ongoing mineral deposition within the geyser
plumbing, exchange of functions with nearby hot
springs, earthquake influences, and human
intervention (Bryan, T.S. 1995).
Hot Springs
Hot springs in Steamboat Springs area.
http://www.eia.doe.gov/cneaf/solar.renewables/page/geothermal/geothermal.html
Fumaroles
Clay Diablo Fumarole (CDF)
http://lvo.wr.usgs.gov/cdf_main.htm
White Island Fumarole
New Zealand
http://volcano.und.edu/vwdocs/volc_images/img_white_island_fumerole.html
CDF is a fumarole in the Casa Diablo area, near the intersection of
U.S. Highway 395 and State Highway 203. Vent temperature is
measured a few times each year, has remained fairly stable between
92 and 94 degrees, and is the hottest of the 5 fumaroles that are
monitored in the Long Valley caldera. Gas chemistry has been
collected on several occasions (Farrar and others, 1985). Vent gas
temperature and chemistry of CDF are monitored because changes in
characteristics of CDF may indicate a change in the volcanic system.
This is an especially large fumarole on the inner wall of the central
crater. Image the sound of a large roaring jet engine, and you get an
impression of the noise it produces. Together with the steam, the
smell of foul eggs (caused by sulphur) and because it's not the only
fumarole in the crater, a view in the crater is like looking in hell's
kitchen. - Christian Treber Copyrights information on the above
image Location: Central Crater, White Island, New Zealand
The Earth
•Heat can be ejected as steam or hot water.
•Hydrothermal reservoirs, water and hot porous
rock. (aquifer)
It is around 4000-6000oCelsius at centre of the Earth
In general, the temperature rises one degree Celsius for every 36
metres you go down.
Where is Geothermal Energy?
• Heat generated by natural
processes occurring within
the earth
• Hot springs, geysers and
mud pots are natural
phenomena that result
from geothermal activity
Different Geothermal Energy Sources
Hot Water Reservoirs: As the name implies these
are reservoirs of hot underground water. There is a
large amount of them in the US, but they are more
suited for space heating than for electricity production.
Natural Steam Reservoirs:
In this case the
underground water changes to steam.
Hot Dry Rock: This type of condition exists in 5% of
the US. It is similar to Normal Geothermal Gradient,
but the gradient is 400C/km dug underground.
Molten Magma: No technology exists to tap into the
heat reserves stored in magma. The best sources for
this in the US are in Alaska and Hawaii.
Where Can Geothermal Energy be
Harnessed?
• Technology today allows for
small
scale
harnessing
everywhere
– Heat
pumps
(for
geothermal energy)
shallow
• Different areas have different
thermal gradients and thus
different utilization potentials
• Higher
thermal
gradients
correspond to areas containing
more geothermal energy
High Temperature Systems
• These areas are associated with the “Ring of
Fire” volcanic activities around the Pacific Rim
Basin
High Temperature Surface Geothermal
Systems
There are three different types of surface
geothermal system designs:
1. Dry-steam Power Plant
2. Flash-steam Power Plant
3. Binary-cycle Power Plant
Direct Use of Steam
Conventional geothermal plants capture hot water
from geysers or steam from vents to spin
turbines.
Dry-steam Geothermal Power Plant
• Steam passes through turbine
• 1050 -1220 degrees F
Dry-steam Geothermal Power Plant
These were the first type of plants created. They use underground
steam to directly turn the turbines. Generation of Electricity is
appropriate for sources >150oC .
Vapor dominated resources where steam production is not contaminated
Steam is 1050°F - 1220° F
Steam passes through turbine
Steam expands
Blades and shaft rotate and generate power
Cooling towers generate waste heat
Most common and most commercially attractive (Godfrey Boyle)
Used in areas where geysers do not exist
Need water to inject down into rock
Well is deep
Takes more time to inject water in well
Flash-steam Geothermal Power Plant
• Hot, High pressure water
• Turbines generate electricity
• Costs 4-6 cents per Kwh.
Flash-steam Geothermal Power Plant
These are the most common plants. These systems pull deep, high
pressured hot water that reaches temperatures of 360˚F or more to the
surface. This water is transported to low pressure chambers, and the
resulting steam drives the turbines. The remaining water and steam are
then injected back into the source from which they were taken.
Use very hot (more than 300° F) steam and hot water resources
Steam either comes directly from the resource, or the very hot, highpressure water is depressurized ("flashed") to produce steam.
Steam then turns turbines, which drive generators that generate electricity.
Only significant emission from these plants is steam (water vapor).
Minute amounts of carbon dioxide, nitric oxide, and sulfur are emitted, but
almost 50 times less than at traditional, fossil-fuel power plants.
The flash steam power plant uses hot water reservoirs as a source of
power. When the hot water comes up from the earth into the flash tank,
there is a drop in pressure which causes some of the water to turn into
steam. This steam is then used to spin the turbine much like in the Dry
Steam power plant. The water is then returned to the earth to be used
again later. This is the most used type of geothermic power plant since
there are a lot of hot water reservoirs.
Binary-cycle Geothermal Power Plant
• Hot water (100 – 300 deg F)
• Heat Exchanger
• Binary liquid lower specific heat
(vaporizes)
Binary-cycle Geothermal Power Plant
This system passes moderately hot geothermal water past a liquid, usually an
organic fluid, that has a lower boiling point. The resulting steam from the organic
liquid drives the turbines. This process does not produce any emissions and the
water temperature needed for the water is lower than that needed in the Flash
Steam Plants (2500F – 3600F).
Uses lower-temperatures, but much more common, hot water resources (100° F –
300° F).
Hot water is passed through a heat exchanger in conjunction with a secondary
(hence, "binary plant") fluid with a lower boiling point (usually a hydrocarbon such
as isobutane or isopentane).
Secondary fluid vaporizes, which turns the turbines, which drive the generators.
Remaining secondary fluid is simply recycled through the heat exchanger.
Geothermal fluid is condensed and returned to the reservoir.
Binary plants use a self-contained cycle, nothing is emitted.
Energy produced by binary plants currently costs about 5 to 8 cents per kWh.
Lower-temperature reservoirs are far more common, which makes binary plants
more prevalent.
Limitations of Surface Geothermal
Power Plant
• Dependent on location.
• Most viable sites have been tapped.
• Not as efficient as coal fired power plant.
Geothermal Power from Hot Dry Rocks
The simplest models have one injection well
and two production wells. Pressurized cold
water is sent down the injection well where the
hot rocks heat the water up. Then pressurized
water of temperatures greater than 200˚F is
brought to the surface and passed near a liquid
with a lower boiling temperature, such as an
organic liquid like butane. The ensuing steam
turns the turbines. Then, the cool water is again
injected to be heated. This system does not
produce any emissions. US geothermal
industries are making plans to commercialize
this new technology.
How Energy is extracted from Hot Dry Rocks
•Direct Sources function by
sending water down a well
to be heated by the Earth’s
warmth.
•Then a heat pump is used
to take the heat from the
underground water to the
substance
• Then after the water it is
cooled is injected back into
the Earth.
Overview of Geothermal systems
1900’s
Dry Steam Systems:
≥ 200 °C
• Hot Dry Rock/Enhanced
Geothermal Systems
1960’s
1980’s
Flash Systems:
1) Single‐Flash vs.
Dual‐Flash
Systems
2) Combined Cycle
Systems
≥ 180 °C
Binary Systems:
1) Organic Rankine
cycle technology
2) Kalina Cycle
technology
≥ 87 °C
• Other Technology Directions
like direct use
The Kalina cycle uses water and ammonia at various ratios and a
registered thermodynamics facility to reduce thermodynamic irreversibility
and therefore increase overall thermodynamic efficiency. There are
multiple variants of the Kalina cycle systems available specifically
applicable to increase the efficiencies of different types of heat source that
would have previously been lost as waste thermal energy.
Low Temperature Heat Extraction/Rejection
• The classic use of earth/water is as a heat sink or
source for air conditioning or heating
• Pipes embedded in the earth carry refrigerant or water
and conduct heat from the hotter to cooler substance
• Since the earth (or water) has a high specific heat in
comparison with air, there is good thermal transfer
• In winter, heat is extracted from the earth by the
chilled refrigerant, while in the summer, the hot
refrigerant conducts heat to the earth
• Houses have been built partially underground to
moderate the winter and summer temperatures
•Geothermal Heat Pumps:
- produces 4 times the energy that they consume.
-initially costs more to install, but its maintenance cost is 1/3 of the
cost for a typical conventional heating system and it decreases
electric bill. This means that geothermal space heating will save the
consumer money.
Heat pumps (for shallow geothermal energy), At a lower thermal
level, an air conditioner can extract heat from the ground for winter
heating or insert energy into the ground to gain a more efficient
cooling sink
Geothermal’s Positive Attributes
Geothermal production of energy is 3rd highest among renewable energies. It is
behind hydro and biomass, but before solar and wind.
• Useful minerals, such as zinc and silica, can be extracted from underground
water.
• Geothermal energy is “homegrown.” This will create jobs, a better global trading
position and less reliance on oil producing countries.
• In large plants the cost is 4-8 cents per kilowatt hour. This cost is almost
competitive with conventional energy sources.
• Geothermal plants can be online 100%-90% of the time. Coal plants can only be
online 75% of the time and nuclear plants can only be online 65% of the time.
• Flash and Dry Steam Power Plants emit 1000x to 2000x less carbon dioxide than
fossil fuel plants, no nitrogen oxides and little SO2.
• Geothermal electric plants production in 13.380 g of Carbon dioxide per kWh,
whereas the CO2 emissions are 453 g/kWh for natural gas, 906g g/kWh for oil
and 1042 g/kWh for coal.
• Binary and Hot Dry Rock plants have no gaseous emission at all.
• Geothermal plants do not require a lot of land, 400m2 can produce a gigawatt of
energy over 30 years.
Availability of Geothermal Energy
• On average, the Earth emits 1/16
W/m2. However, this number can
be much higher in areas such as
regions near volcanoes, hot
springs and fumaroles.
• As a rough rule, 1 km3 of hot rock
cooled by 1000C will yield 30 MW
of electricity over thirty years.
• It is estimated that the world
could produce 600,000 EJ
(exajoule) (1 EJ = 1018 J) over 5
million years.
• There is believed to be enough
heat radiating from the center of
the Earth to fulfill human energy
demands for the remainder of
the biosphere’s lifetime.
Geothermal’s Harmful Effects

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Brine can salinate soil if the water is not injected back into the reserve after
the heat is extracted.
Extracting large amounts of water can cause land subsidence, and this can
lead to an increase in seismic activity. To prevented this the cooled water
must be injected back into the reserve in order to keep the water pressure
constant underground.
Power plants that do not inject the cooled water back into the ground can
release H2S, the “rotten eggs” gas. This gas can cause problems if large
quantities escape because inhaling too much is fatal.
One well “blew its top” 10 years after it was built, and this threw hundreds of
tons of rock, mud and steam into the atmosphere.
There is the fear of noise pollution during the drilling of wells.
Geyser-temperature steam is contaminated with salts that cause corrosion of
turbines or engines
Geophysical/geological data availability
Access to finances
Technologies – drilling (for EGS)
Direct uses of geothermal energy is appropriate
for sources below 150˚C
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Space heating
Air conditioning
Industrial processes
Drying
Greenhouses
Aguaculture
Hot water
Resorts and pools
Melting snow
EXPLORATION
ENERGY SYSTEMS
Geothermal technologies
Drilling
• mud-pumping technology
• better drill bits for hard rocks and
higher temperatures
Enhanced geothermal systems
• demo facility
• system operation
Geothermal heat pumps
Geothermal Energy Plant
Geothermal energy plant in Iceland
http://www.wateryear2003.org/en/
Geothermal Well Testing
Geothermal well testing,
Zunil, Guatemala
http://www.geothermex.com/es_resen.html
Heber Geothermal Power Station
52kW electrical generating capacity
http://www.ece.umr.edu/links/power/geotherm1.htm
Geysers Geothermal Plant
The Geysers is the largest producer of geothermal power in
the world.
http://www.ece.umr.edu/links/power/geotherm1.htm
Geothermal Greenhouses
Geothermal greenhouse
in Nigrita, Greece
Cultivation of spirulina
algae using geothermal
heat
Geothermal application in
the food industry
Geothermal tomato drying
in Northern Greece
The finished
product
Geothermal application in
the food industry
Fish factory in Laugar, Iceland
Geothermal fish drying in
Northern Iceland
The finished product
Geothermal Energy for the
German Parliament
Heat- and Cold Storage, heat source
waste heat from Combined Heatand Power-Generation (CHP) during
summertime