What is Geothermal?
Heat from the Earth, or geothermal — Geo (Earth) +
Geothermal resources range from shallow ground to hot
water and rock several miles below the Earth's surface, and
even farther down to the extremely hot molten rock called
•The crust is broken into enormous slabs —
tectonic plates -that are actually moving very
slowly over the mantle, separating from, crushing
into, or sliding
(subducting) under one another.
•At these plate boundaries, and in other places
where the crust is thinned or fractured, magma is
the surface than it is elsewhere. over time, it
creates large regions of hot rock.
•If the magma emerges above ground its known as
History of Geothermal Energy in the
Human beings have used geothermal energy in North America for at least
10,000 years. Paleo-Indians used hot springs for cooking, and for refuge and
respite. Native Americans have a history with every major hot spring in the
1807- John Colter visited the Yellowstone area, leading to the designation
"Colter's Hell". Also in 1807, settlers founded the city of Hot Springs,Arkansas
1842-William Bell Elliot, a member of John C. Fremont's survey party,
t bl t i ll just th f h t is
stumbles upon a steaming valley j t north of what i now S F i
California. Elliot calls the area The Geysers-a misnomer-and thinks he has found
the gates of Hell
1852 - The Geysers is developed into a spa called The Geysers Resort Hotel..
1862 - At springs located southeast of The Geysers, businessman Sam Brannan
pours an estimated half million dollars into an extravagant development dubbed
1892 - Folks in Boise, Idaho, feel the heat of the world's first district heating
system as water is piped from hot springs to town buildings.
1921 - John D. Grant drills a well at The Geysers with the intention of generating electricity.
1930 - The first commercial greenhouse use of geothermal energy is undertaken in Boise, Idaho. In
Klamath Falls, Charlie Lieb develops the first downhole heat exchanger (DHE) to heat his house.
1940 - The first residential space heating in Nevada begins in the Moana area in Reno.
1948 - Professor Carl Nielsen of Ohio State University develops the first ground-source heat pump.
J.D. Krocker, an engineer in Portland, Oregon, pioneers the first commercial building use of a
groundwater heat pump.
1970 - The Geothermal Resources Council is formed to encourage development of geothermal
resources worldwide. The Geothermal Steam Act is enacted
1975 - The Energy Research and Development Administration (ERDA) is formed.
1989 - The world's first hybrid (organic Rankine/gas engine) geopressure-geothermal power plant
begins ti t Pl
b i operation at Pleasant Bayou, Texas, using both the heat and th methane of a geopressured
tB T i b th th h t d the th f d
1991 - The Bonneville Power Administration selects three sites in the Pacific Northwest for
geothermal demonstration projects.
1992 - Electrical generation begins at the 25-MW geothermal plant in the Puna field of Hawaii.
1993 - A 23-MW binary power plant is completed at Steamboat Springs, Nevada.
1994 - DOE creates two industry/government collaborative efforts to promote the use of
geothermal energy to reduce greenhouse gas emissions.
1995 - Integrated Ingredients dedicates a food-dehydration facility. A DOE low temperature
resource assessment of 10 western states identifies nearly 9000 thermal wells and springs and 271
communities collocated with a geothermal resource greater than 50ºC.
2000 - DOE initiates its GeoPowering the West program to
encourage development of geothermal resources in the
western U. S.
2001 - GeoPowering the West brings together
representatives from industry and agencies. Secretary of the
Interior Gail Norton convened a renewable energy summit
2002 - Organized by GeoPowering the West, geothermal
development working groups are active in five states —
Nevada, Idaho, New Mexico, Oregon, and Washington. 2003
2003 - The Utah Geothermal Working Group is formed.
Renewable Energy Cost Trends
Levelized cents/kWh in constant $20001
1980 1990 2000 2010 2020 1980 1990 2000 2010 2020
10 70 15
Geothermal 60 Solar thermal Biomass
6 40 9
2 10 3
0 0 0
1980 1990 2000 2010 2020 1980 1990 2000 2010 2020 1980 1990 2000 2010 2020
Source: NREL Energy Analysis Office (www.nrel.gov/analysis/docs/cost_curves_2002.ppt)
1These graphs are reflections of historical cost trends NOT precise annual historical data.
Updated: October 2002
What are the benefits of using
Several attributes make it a good source of energy.
First, it's clean. Energy can be extracted without burning a
fossil fuel Geothermal fields produce only about one-sixth of
the carbon dioxide that a relatively clean natural-gas-fueled
power plant produces, and very little if any, of the nitrous oxide
sulfur bearing gases plants
or sulfur-bearing gases. Binary plants, which are closed cycle
operations, release essentially no emissions.
Geothermal energy is available 24 hours a day, 365 days a year.
Geothermal power plants have average availabilities of 90% or
higher, compared to about 75% for coal plants.
Geothermal power is homegrown, reducing our dependence on
Is geothermal energy a renewable
The source is the almost unlimited amount of heat generated
by the Earth's core. Even in geothermal areas dependent on a
reservoir of hot water, the volume taken out can be
reinjected, making it a sustainable energy source.
Where is geothermal energy available?
Hydrothermal resources - reservoirs of steam or hot water -
are available primarily in the western states, Alaska, and
Earth energy can be tapped almost anywhere with
geothermal heat pumps and direct-use applications.
Other enormous and world-wide geothermal resources - hot
dry rock and magma, for example - are awaiting further
What are the environmental impacts of
using geothermal energy?
Geothermal technologies offer many environmental advantages
over conventional power generation:
Emissions are low. Only excess steam is emitted by geothermal flash
plants. No air emissions or liquids are discharged by binary
geothermal plants, which are projected to become the dominant
technology in the near future.
Salts and dissolved minerals contained in geothermal fluids are usually
reinjected with excess water back into the reservoir at a depth well
below groundwater aquifers. This recycles the geothermal water and
replenishes the reservoir.
Some geothermal plants do produce some solid materials, or sludges,
that require disposal in approved sites. Some of these solids are now
being extracted for sale
What is the visual impact of
District heating systems and geothermal heat pumps are
easily integrated into communities with almost no visual
impact. Geothermal power plants use relatively small
acreages, and don't require storage, transportation, or
combustion of fuels. Either no emissions or just steam are
visible. These qualities reduce the overall visual impact of
power plants in scenic regions.
Is it possible to deplete geothermal
The long-term sustainability of geothermal energy
production has been demonstrated at the Lardarello field
in Italy since 1913, at the Wairakei field in New Zealand since
1958, and at The Geysers field in California since 1960.
Pressure and production declines have been experienced at
some plants, and operators have begun reinjecting water to
maintain reservoir pressure. The City of Santa Rosa,
California, pipes its treated wastewater up to The Geysers to
be used as reinjection fluid, thereby prolonging the life of the
reservoir while recycling the treated wastewater.
Types of Geothermal
Power Plants Generate Electricity from Geothermal
Direct-Use Piped Hot Water Warms Greenhouses
and Melts Sidewalk Snow
Geothermal Heat Pumps (GHPs) Use Shallow round
Energy to Heat and Cool Buildings
In the United States, geothermal energy has been used to generate
electricity on a large-scale since 1960. The US leads the world in
installed geothermal capacity with 3086.6 megawatts (MW) currently
online in nine states. Seven geothermal projects in five different states
were brought online in 2009.
Heat from the Earth—geothermal energy—heats water that has seeped
into underground reservoirs.
These reservoirs can be tapped for a variety of uses, depending on the
temperature of the water.
The energy from high temperature reservoirs (225º–600ºF) can be used
to produce electricity.
There are currently three types of geothermal power plants:
What makes a site good for geothermal
Hot geothermal fluid with low mineral and gas content,
shallow aquifers for producing and reinjecting the fluid,
location on private land to simplify permitting, proximity to
existing transmission lines or load, and availability of make-
up water for evaporative cooling. Geothermal fluid
p p g
temperature should be at least 300º F, although plants are
operating on fluid temperatures as low as 210º F.
April 2010 Geothermal Power Capacity On-Line
Dry Steam Power Plants
Dry steam plants use steam from underground wells to rotate a
turbine, which activates a generator to produce electricity. There
are only two known underground resources of steam in the
United States: The Geysers in northern California and Old
Faithful in Yellowstone National Park. Since Yellowstone is
protected from development, the power plants at The Geysers are
the only dry steam plants in the country
It was first used at Lardarello in Italy in 1904, and is still very
The Geysers in northern California, the world's largest single
source of geothermal power.
These plants emit only excess steam and very minor amounts of
Power Plant at The Geyers
The most common type of geothermal power plant, flash
steam plants use waters at temperatures greater than 360ºF.
As this hot water flows up through wells in the ground, the
decrease in pressure causes some of the water to boil into
steam. The steam is then used to power a generator, and any
leftover water and condensed steam is returned to the
Fluid can also be sprayed into a tank held at a much lower
pressure than the fluid, causing some of the fluid to rapidly
vaporize, or "flash.“ If any liquid remains in the tank, it can
be flashed again in a second tank to extract even more
Flash Plant Imperial valley,
Flash Plant Dixie valley, NV
Binary cycle plants
Binary cycle plants use the heat from lower-temperature
reservoirs (225º–360ºF) to boil a working fluid, which is
then vaporized in a heat exchanger and used to power a
generator. The water, which never comes into direct contact
with the working fluid, is then injected back into the ground
g j g
to be reheated.
Moderate-temperature water is by far the more common
geothermal resource, and most geothermal power plants in
the future will be binary-cycle plants.
Binary plant Big Island of
Hawaii. Provides 25% of the
Binary plant Soda Lake, NV
Enhanced Geothermal Systems
The natural hydrothermal resource is dependent on the
coincidence of substantial amounts of heat, fluids, and
permeability in reservoirs all in the same location, and the
present state of knowledge suggests that this coincidence is
not commonplace. Lots of heat not so much water.
An alternative to dependence on naturally occurring
hydrothermal reservoirs involves engineered hydrothermal
reservoirs in hot rocks. This alternative is known as
"Enhanced Geothermal Systems," or EGS.
The logical steps necessary to complete an economically-viable EGS
Finding a site.
Creating the reservoir.
Completing a wellfield
Operating the reservoir
Operating the facility
EGS reservoirs are made by drilling wells into hot rock and fracturing
the rock sufficiently to enable a fluid (water) to flow between the wells.
The fluid flows along permeable pathways, picking up in situ heat, and
exits the reservoir via production wells. At the surface, the fluid passes
through a power plant where electricity is generated. Upon leaving the
power plant, the fluid is returned to the reservoir through injection
wells to complete the circulation loop
Utah Geothermal Area
Utah has two geothermal electric plants:
the 23-megawatt Roosevelt Hot Springs
facility near Milford run by Utah Power and CalEnergy Corp., and the
Utah Municipal Power Association's Cove Fort Station, which is located
north of Beaver, Utah.
Power plants in Utah
Blundell 2 - Milford
Blundell 1 - Milford
Thermo Hot Spring –
Geothermal water contains varying concentrations of dissolved minerals and salts.
Sometimes the minerals are extracted and put to good use.
At reservoirs with higher concentrations, have the potential for clogging and corroding
power plant equipment.
Most geothermal reservoirs contain varying amounts of dissolved gases such as
hydrogen sulfide. Modern geothermal technology ensures that geothermal power plants
capture these gases
Geothermal reservoirs must be carefully managed so that the steam and hot water are
produced no faster than they can be naturally replenished or supplemented.
Geothermal power plants run day and night, so they provide reliable baseload electricity.
Most geothermal power plants can increase their output of electricity to provide more
power at times of greater demand. But geothermal power plants can’t be used
exclusively for peaking power;
If geothermal wells were turned off and on repeatedly, expansion and contraction
(caused by heating and cooling) would damage the wells.
Direct Use of Geothermal Energy
Geothermal reservoirs of low-to moderate temperature water —
68°F to 302°F - This resource is widespread in the United States
and provide direct heat for residential, industrial, and commercial
Balneology (hot spring and spa bathing)
Agriculture (greenhouse and soil warming)
Aquaculture (fi h prawn and alligator farming)
A lt (fish, d lli t f i )
Industrial Uses (mining, product drying and warming)
In addition, spent fluids from geothermal electric plants can be
subsequently used for direct use applications in so-called
Direct use of geothermal energy in homes and commercial
operations is much less expensive than using traditional fuels.
Savings can be as much as 80% over fossil fuels.
Typically include three components:
A production facility — usually a well — to bring the hot water
to the surface;
A mechanical system — piping, heat exchanger, controls — to
deliver the heat to the space or p
A disposal system — injection well or storage pond — to
receive the cooled geothermal fluid.
A 1996 survey found that these applications were using
nearly 5.8 billion megajoules of geothermal energy each year
— the energy equivalent of nearly 1.6 million barrels of oil!
Native Americans used hot springs. Some tribes considered hot springs to be
neutral territory where no wars were allowed. 2000-2005 Geothermal Eduation
There are thirty-eight greenhouses, many covering several
acres, are raising vegetables, flowers, houseplants, and tree
seedlings in 8 western states.
Using geothermal resources instead of traditional energy
sources can saves about 80% of fuel costs Which would
equate to about 5% to 8% of total operating costs.
The relatively rural location of most geothermal resources
also offers advantages, including clean air, few disease
problems, clean water, a stable workforce, and, often, low
Milgro Nurseries near Newcastle, Iron County
covering over 24 acres, growing chrysanthemums, poinsettia, calilysis and tulips.
Milgro is the largest potted plant grower in the U.S. and in
addition to its 1,000,000-sq ft geothermally-heated facility in
Newcastle, it also maintains substantial conventionally-heated
operations near Los Angeles.
2000-2005 Geothermal Eduation Office
About 20% of U.S. fish and seafood consumption is now
farm-raised, aquaculture is becoming a recognized segment
of the livestock complex.
There are twenty-eight active aquaculture operations using
geothermal energy in 10 states
Highly dependent upon the quantity and quality of water
Closeup of a prawn grown in a research project with
geothermally heated water at the GeoHeat Center,
Oregon Institute of Technology. 2000-2005 Geothermal
Multiple varieties of fish
Alligator farming Buhl, Idaho &
Alamosa springs, CO
Fish Breeders of Idaho Inc., Hagerman, Idaho
This site is ideal for warm water species. The wells (expect one) are near the
top of the canyon; so, water flows down a quarter mile with an 80 ft drop.
Raceways are interspersed with rocky brook-like channels that help add oxygen
utilized by the fish.
Stocking starts with the water flow at the top with channel catfish, followed by
lower oxygen tolerant blue catfish (350,000 - 400,000 lb/yr combined), to
even more tolerant tilapia (100,000 - 200,000 lb/yr) near the bottom, then to
settling ponds where solid waste is removed More oxygen is added and water
cooled in the rocky brook on its way to the river. Starting in 1994, in the lower
portion, water is diverted to alligator houses (1,000 6-footers/yr) and outdoor
ponds for 1,000 lb 10 - 14 ft breeding stock. The alligators are fed dead fish
from this site and from the numerous nearby cold water fish farms (trout).
Since the fish are cleaned on site, the alligators are also fed the entrails.
In winter, about 1,000 gpm of cold water from shallow springs is mixed with
geothermal to maintain correct growing temperatures. In summer, 4,000 -
5,000 gpm is obtained from an irrigation canal.
Industrial and Commercial Uses
Industrial applications include food dehydration, laundries,
gold mining, milk pasteurizing, spas, and others.
Dehydration, or the drying of vegetable and fruit products, is
the most common industrial use of geothermal energy. The
earliest commercial use of geothermal energy was for
swimming pools and spas. In 1990, 218 resorts were using
geothermal hot water.
This plant in Brady, Nevada, provides dried onions
to Burger King.
2000-2005 Geothermal Education Office
District and Space Heating
In the U.S., more than 120 operations, with hundreds of
individual systems at some sites, are using geothermal energy for
district and space heating.
District systems distribute hydrothermal water from one or more
geothermal wells through a series of pipes to several individual
houses and buildings or blocks of buildings
Space heating uses one well per structure.
Geothermal district heating systems can save consumers 30% to
50% of the cost of natural gas heating.
The potential for district heating in the western U.S. was
published in a 1980s inventory which identified 1,277 geothermal
sites within 5 miles of 373 cities in 8 states.
Pipes of geothermal water can
be installed under sidewalks and
roads to keep them from icing
over in winter, like this sidewalk
in Klamath Falls, Oregon.
2000-2005 Geothermal Education Office
District heating Boise, Id
Direct-use growth in the United States
Geothermal fluids in Utah are regulated as “a special kind of
underground resource.” The use of or injection of the fluid
constitutes a beneficial use of the waters of the state and as
such water rights are required from the State Division of
In addition, rights to a geothermal resource or fluids are
based upon the principle of “correlative rights” conveying the
right of each landowner to produce his equitable share of
underlying resources. Well construction and permitting is
regulated by the Division of Water Resources of the
Department of Natural Resources.
Geothermal heat pumps
Have been in use since the late 1940s. Geothermal heat pumps (GHPs) use the constant
temperature of the earth as the exchange medium instead of the outside air temperature.
This allows the system to reach fairly high efficiencies (300%-600%) on the coldest of
winter nights, compared to 175%-250% for air-source heat pumps on cool days.
The technology relies on the fact that the Earth (beneath the surface) remains at a
relatively constant temperature throughout the year, warmer than the air above it during
the winter and cooler in the summer, very much like a cave. The ground, in other words,
acts as a heat source in winter and a heat sink in summer.
There l 0 000 h l heat ll d h
Th are approximately 50,000 geothermal h pumps installed in the United S d States
The system includes three principal components:
Geothermal earth connection subsystem
Geothermal heat pump subsystem
Geothermal heat distribution subsystem.
Using the Earth as a heat source/sink, a series of pipes,
commonly called a "loop," is buried in the ground near the
building to be conditioned. The loop can be buried either
vertically or horizontally. It circulates a fluid (water, or a
mixture of water and antifreeze) that absorbs heat from, or
relinquishes heat to, the surrounding soil, depending on
whether the ambient air is colder or warmer than the soil.
Heat Pump Subsystem
For heating, a geothermal heat pump removes the heat from
the fluid in the Earth connection, concentrates it, and then
transfers it to the building. For cooling, the process is
Heat Distribution Subsystem
Conventional ductwork is generally used to distribute heated
or cooled air from the geothermal heat pump throughout the
Residential Hot Water
Geothermal heat pumps can be used to provide domestic hot
water when the system is operating
Excess heat from the geothermal heat pump's compressor is
transferred to the house's hot water tank.
Provides no hot water during the spring and fall when the
geothermal heat pump system is not operating
Manufacturers are beginning to offer "full demand" systems
that use a separate heat exchanger to meet all of a
household's hot water needs. These units cost-effectively
provide hot water as quickly as any competing system.
Types of Geothermal Heat Pump Systems
There are four basic types of ground loop systems.
open loop option.
All of these approaches can be used for residential and
commercial building applications.
Closed-Loop Systems Horizontal
This type of installation is generally most cost-effective for
residential installations, particularly for new construction
where sufficient land is available. It requires trenches at least
four feet deep. The most common layouts either use 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. The Slinky™ method of looping pipe
allows more pipe in a shorter trench, which cuts down on
installation costs and makes horizontal installation possible in
areas it would not be with conventional horizontal
Large commercial buildings and schools often use vertical systems
because the land area required for horizontal loops would be
Vertical loops are also used where the soil is too shallow for
trenching, and they minimize the disturbance to existing
Holes (approximately four inches in diameter) are drilled about 20
feet apart and 100–400 feet deep. Into these holes go two pipes
that are connected at the bottom with a U-bend to form a loop.
The vertical loops are connected with horizontal pipe (i.e.,
manifold), placed in trenches, and connected to the heat pump in
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. The coils should only
be placed in a water source that meets minimum volume,
depth, and quality criteria.
This type of system uses well or surface body water as the
heat exchange fluid that circulates directly through the GHP
Once it has circulated through the system, the water returns
to the ground through the well, a recharge well, or surface
Practical only where there is an adequate supply of relatively
clean water, and all local codes and regulations regarding
groundwater discharge are met.
Installed Geothermal HVAC Capital Cost:
Conventional HVAC Capital Cost Bid:
Annual HVAC Energy Cost ( (2001-2002):)
Annual HVAC Energy Cost of Comparable Conventional School:
$200,500 ($0.86/ft2) ($9.26/m2)
Annual HVAC Energy Savings:
Estimated Simple Payback Period: