Geothermal Energy PDF

BMM 4753 RENEWABLE ENERGY
Topic 3
GEOTHERMAL ENERGY
Summary
1. Introduction
2. Geothermal energy - Types of resources
3. Environmental impact of geothermal power plants
4. Operational difficulties of geothermal plants
5. Estimation of GE availability (Hot dry rock)
6. Geothermal Energy in Malaysia
7. New Developments
Topic 3 Geothermal Thermal Energy
3.1 Introduction
Earth
The Earth has a number of different layers

a. The core itself has two layers
o inner core made of solid iron
o outer core made of very hot melted rock, called magma.
3.1 Introduction
Earth
b. The mantle surrounds the core

o and is about 1,800 miles thick.
o made up of magma and rock.
3.1 Introduction
Earth
c. The crust is the outermost layer of the Earth

o the land that forms the continents and ocean floors
o 3 to 5 miles thick under the oceans
o 5 to 35 miles thick on the continents.
3.1 Introduction
Tectonic Plate Formation
Earth's crust is broken into pieces called plates

o Magma comes close to the Earth's surface near the edges of these plates
where volcanoes occur.
o The lava that erupts from volcanoes is partly magma. Deep underground,
the rocks and water absorb the heat from this magma.
3.1 Introduction
Earth Temperature
o The temperature of the rocks and water gets hotter

o hotter as it gets deeper underground.
3.1 Introduction
Geothermal Resources
Geothermal are renewable energy sources which utilise the heat within
the earth to create either a source of renewable heat or renewable
electricity.
i. Geothermal energy is generated in the Earth's core, mostly from the
decay of naturally radioactive materials like uranium and potassium.
The amount of heat within 10,000 meters of the surface contains
50,000 times more energy than all the oil and natural gas resources in
the world.
ii. The areas with highest underground temperatures are in regions with
active or geologically young volcanoes. These "hot spots" occur at plate
boundaries or at places where the crust is thin enough to let the heat
through. The Pacific Rim, called the "ring of fire" for all of its volcanoes,
has many hot spots, including some in Alaska, California, and Oregon.
3.1 Introduction
Geothermal Resources
iii. These regions are also seismically active. The many earthquakes and
the movement of magma break up the rock covering, allowing water
to circulate. As the water rises to the surface, natural hot springs and
geysers occur, such as "Old Faithful" at Yellowstone National Park. The
water in these systems can be more than 200oC.
iv. The current production of geothermal energy from all uses place third
among renewables, following hydroelectricity and biomass, and ahead
of solar and wind. Despite these impressive statistics, the current level
of geothermal use pales in comparison to its potential. The key to
wider geothermal use is greater public awareness and technical
support--two areas in which the Geo-Heat Center is very active.
3.2 Types of Resources
Current Commercial Utilization

i. Hydrothermal Reservoirs
ii. Earth Energy
Advanced Technologies Yet To Be Developed

iii. Hot Dry Rock
iv. Geopressured Brines
v. Magma
❖ Hydrothermal reservoirs are large pools of steam or hot water

trapped in porous rock. To generate electricity, the steam or hot
water is pumped to the Earth's surface where it drives a turbine
that spins an electric generator. Because steam resources are
rare, hot water is used in most geothermal power plants. Steam
and hot water power plants use different power production
technologies.
❖ These resources can be classified as low temperature (less than

90°C), moderate temperature (90°C- 150°C), and high
temperature (greater than 150°C). The uses to which these
resources are applied are also influenced by temperature. The
highest temperature resources are generally used only for
electric power generation. Current U.S. geothermal electric
power generation totals approximately 2200 MW or about the
same as four large nuclear power plants. Uses for low and
moderate temperature resources can be divided into two
categories: direct use and ground-source heat pumps.
a) Dry Steam
Steam is routed directly to the turbines, eliminating the need for
the boilers used by conventional natural gas and coal plants.
b) High-temperature Hot Water
Hot water with temperatures above 200°C are usually utilized
using a flash technology where hot water is sprayed into a low-
pressure tank. The water vaporizes to steam, which is routed to
the turbine.
c) Moderate-temperature Hot Water—hot water resources below
200°C are utilized using a binary cycle technology where the hot
water vaporizes a secondary working fluid, which then drives
the turbine.
ii. Earth Energy
❖ Direct use, involves using the heat in the water directly (without
a heat pump or power plant) for such things as heating of
buildings, industrial processes, greenhouses, aquaculture
(growing of fish) and resorts. Direct use projects generally use
resource temperatures between 38°C to 149°C . Current U.S.
installed capacity of direct use systems totals 470 MW or
enough to heat 40,000 average-sized houses.
❖ The heat contained in shallow ground—is used to directly heat
or cool homes and commercial buildings through "direct-use"
technologies such as geothermal heat pumps (GHP) and district
heating systems. Unlike other forms of geothermal energy, earth
energy is found throughout the U.S.
ii. Earth Energy
a) Geothermal Heat Pumps (GHP)

* Ground-source heat pumps use the earth or groundwater as
a heat source in winter and a heat sink in summer. Using
resource temperatures of 4°C to 38°C, the heat pump, a
device, which moves heat from one place to another,
transfers heat from the soil to the house in winter and from
the house to the soil in summer. Accurate data is not
available on the current number of these systems; however,
the rate of installation is thought to be between 10,000 and
40,000 per year.
ii. Earth Energy
a) Geothermal Heat Pumps… cont’d

* GHPs use the Earth's relatively constant ground
temperature to provide low-cost heating and cooling. In the
winter, GHPs transfer heat from the ground into homes and
buildings; in the summer, GHPs cool homes and buildings by
transferring indoor heat into the ground. GHPs can cut
heating costs by 50 percent, and cooling costs by 25 percent.
More than 200,000 GHPs are operating in U.S. homes,
schools and commercial buildings.
ii. Earth Energy
b) District Heating Systems

Many communities use district-heating systems to heat homes
or public buildings by circulating hot water through pipes.
Overall, direct-use applications use geothermal energy to supply
the energy equivalent of nearly 1 million barrels of oil.
iii. Hot Dry Rock (HDR)
iii. Hot Dry Rock
a) This energy consists of dry, impermeable rock. To use this energy,
water must be pumped into the rock at high pressures to widen
existing fissures and create an underground reservoir of steam or
hot water
b) Geothermal heat occurs everywhere under the surface of the
earth, but the conditions that make water circulate to the surface
are found only in less than 10% of the land area of the earth. An
approach to capturing the heat in dry areas is known as "hot dry
rock." The rocks are first broken up by pumping high pressure
water through them. Water is then pumped from the surface
down through the broken hot rocks. After the water heats up, it is
brought back to the surface through a second well and used to
drive turbines or to provide heat.
iii. Hot Dry Rock
c) Researchers at the Los Alamos National Lab in New Mexico have
studied hot dry rock since 1974. The Fenton Hill plant involves a
well drilled 3,500 m into rock at 220oC. Water pumped down the
well at 30oC returned to the surface at 180oC. The plant has
produced as much as 5 megawatts of power, proving the technical
feasibility of hot dry rock.
d) However, a number of barriers must be overcome before hot dry
rock can become a commercial source of power. The wells must
be quite deep, deeper than for conventional geothermal plants.
Also, the flow of heat through dry rock is slow, which means the
heat removed through the well will be slow to be renewed.
Finally, the most promising sites for hot dry rock are in dry areas
of the West, which means that water may be hard to come by.
iv. Geopressured Brines
These brines are hot, pressurized waters containing dissolved
methane. Both the heat and methane can be used for power
generation.
v. Magma
Magma is the molten or partially molten rock found below the
Earth's crust. Magma reaches temperatures up to 1200°C. While
some magma bodies exist at accessible depths, a practical way to
extract magma energy has yet to be developed.
Tectonic Plate Location
World Geothermal Power Plants
People living in these areas are receiving

electricity from geothermal power plants.
World Geothermal Power Production (8,217MW)
United States 2850.0
Philippines 1848.0
Italy 768.5
Mexio 743.0
Indonesia 589.5
Japan 530.0
New Zealand 345.0
Iceland 140.0
Costa Rica 120.0
El Salvador 105.0
Nicaragua 70.0
Kenya 45.0
China 32.0
Turkey 21.0
Portugal 11.0
Russia 11.0
Guatemala 5.0
France 4.0
Taiwan 3.0
Thailand 0.3
Zambia 0.2
3.3 Environmental Impact of Geothermal Power Plants
Applications
i. Worldwide, direct uses of geothermal water avoids the combustion of

fossil fuels equivalent to burning of 830 million gallons of oil or 4.4
million tons of coal per year.
ii. Worldwide electrical production from geothermal reservoirs avoids
the combustion of 5.4 billion gallons of oil or 28.3 million tons of coal
iii. Geothermal direct use facilities have minimal impacts on the
environment.
iv. Geothermal power plants are relatively easy on the environment.
They are successfully operated in the middle of crops, in sensitive
desert environments and in forested recreation areas.
Applications
Direct Use Geothermal Water

1. Hot Spring / Bathing
2. Agriculture
3. Aquaculture
4. Industry
5. Heating/District Heating
Indirect Use Geothermal Steam/water
6. Electrical Power Generation
1. Hot Spring Bathing
Since Roman times, we have piped the hot water into pools to better
control the temperature. These are photos of outdoor and indoor pool
and spa bathing in Japan, the US, and Europe
2. Agriculture
Peppers, tomatoes, and flowers are commonly grown in geothermally

heated greenhouses
3. Aquaculture
Geothermal water is also used to speed the growth of fish. These are
growing in a geothermally heated hatchery at Mammoth Lakes, California
4. Industry
This plant operates in the middle of crops in the Imperial Valley, California.
High mineral contents of some southern California geothermal reservoirs
provide salable byproducts like silica and zinc
5. District Heating
Hot water from one or more geothermal wells is piped through a heat
exchanger plant to heat city water in separate pipes. Hot city water is
piped to heat exchangers in buildings to warm the air
The first modern geothermal power plants built in Lardello, Italy. They
were destroyed in World War II and rebuilt. Today after 90 years, the
Lardello field is still producing.
The first geothermal power plants in the U.S. were built in 1962 at The
Geysers dry steam field, in northern California. It is still the largest
producing geothermal field in the world
This power plant provides about 25% of the electricity used on the Big
Island of Hawaii.
3.4 Operational Difficulties Of Geothermal Power Plants
Direct Use of Geothermal Heat
❑ Heat from geothermal springs can also be used directly for heat.
Hot spring water is used to heat greenhouses for plants, to dry
out fish and deice roads, for improving oil recovery, and to heat
fish farms and spas. In Klamath Falls, Oregon, and Boise, Idaho,
geothermal water has been used to heat homes and buildings for
over a century. New housing developments in Reno, Nevada, are
using geothermal heat from a well to heat homes.
❑ In Iceland, virtually every building in the country is heated with
hot spring water. In fact, Iceland gets 45% of its energy from
geothermal sources. In Reykjavik, for example (population
145,000), hot water is piped in from 25 kilometers away, and
residents use it for heating and for hot tap water.
How Geothermal Energy Is Captured
i. The most common current way of capturing the energy from
geothermal sources is to tap into naturally occurring
"hydrothermal convection" systems. When heated water is
forced to the surface, it is a relatively simple matter to capture
that steam and use it to drive electric generators. Geothermal
power plants drill their own holes into the rock to more
effectively capture the steam.
ii. There are three designs for geothermal power plants, all of
which pull hot water and steam from the ground, use it, and
then return it as warm water to prolong the life of the heat
source. In the simplest design, the steam goes directly through
the turbine, then into a condenser where the low-temperature
steam is condensed into water. In a second approach, the steam
and hot water are separated as they come out of the well; the
steam is used to drive the turbine while the water is sent
directly back underground.
iii. In the third approach, called a binary system, the hot water and
steam mixture is passed through a heat exchanger, where it
heats a second liquid (like isobutane) in a closed loop. The
isobutane boils at lower temperatures than water, so as steam it
is used to drive the turbine. The three systems are shown in the
graphics here.
iv. The choice of which design to use is determined by the
resource. If the water comes out of the well as steam, it can be
used directly, as in the first design. If it is hot water, it must go
through a heat exchanger. Since there are more hot water
resources than pure steam, there is more growth potential in
the heat exchanger design.
v. The largest geothermal system now in operation is a steam-
driven plant in an area called The Geysers, north of San
Francisco. Despite the name, they’re actually no geysers here,
and the heat that is used for energy is all steam, not hot water.
Although the area was known for its hot springs as far back as
the mid-1800s, the first well for power production was drilled in
1924. Deeper wells were drilled in the 1950s, but real
development didn't occur until the '70s and '80s. By 1990, 26
power plants had been built, for a capacity of over 2,000
megawatts. In 1992, the area produced enough power for a city
of 1.3 million.
vi. Because of the rapid development of the area in the '80s, and
the technology used, the steam resource has been declining
since 1988. In the Geysers, the plants use an evaporative water-
cooling process to create a vacuum that pulls the steam through
the turbine, producing power more efficiently. But this process
loses 60 to 80 percent of the steam to the air, not reinjecting it
underground. While the steam pressure may be declining, the
rocks underground are still hot. Some efforts are under way to
remedy the situation, including reinjecting water pumped in
through a 26-mile pipeline, and replacing the water-cooled
systems with air-cooled.
vii. Another problem with open systems like the ones at the
Geysers is that they produce some air emissions. Hydrogen
sulfide, along with small amounts of arsenic and minerals, is
released in the steam. At a power plant at the Salton Sea
reservoir in California, a significant amount of salt builds up in
the pipes and must be removed. While the plant initially started
to put the salts into a landfill, they now reinject the salt back
into a different well. With closed-loop systems, such as the
binary system, there are no emissions; everything brought to
the surface is returned underground.
How Geothermal Energy Is Captured - Cooper Basin, Australia
3.5 Estimation of Geothermal Energy Availability
Hot Dry Rock
Dry Rock And Hot Aquifer Analysis
Consider a large mass of dry material extending from near the earth’s
surface to deep inside the crust
Hot Dry Rock
Example Problem Hot Dry Rock
3.6 Geothermal Energy in Malaysia
Tawau in Malaysia has an electricity generation

potential of up to 67 MW from geothermal
resources following the discovery of a geothermal
site in Apas
Topic 3 Geothermal Energy
a) In Malaysia, Tenaga Nasional Bhd (TNB) has identified four potential
geothermal power generation sites that could collectively generate
more than 2 MW of electricity, at a confidence level of 60%. The
locations of the four sites in the peninsula area were not disclosed.
Once testing raises the confidence level to 90%, TNB would begin
drilling. Expectations are that the projects to be on line by 2016. TNB’s
move into geothermal energy was part of its long-term strategy to
diversify into renewable energy sources, given the environment of
rising coal and gas prices. TNB had earmarked four sites to set up
geothermal power plants which will utilise steam generated from hot
springs. There are more than 40 thermal springs in Peninsular
Malaysia. Most of these springs are good potential sites to generate
geothermal power as part of the nation’s plan to enhance its
renewable energy potential.
b) Each geothermal plant would have the potential to generate more than
two megawatts of electricity. A large hot spring can generate up to 20
megawatts of power. The need to look at other viable renewable
energy options is gaining -importance, given adverse public opinion on
the use of nuclear power, post-nuclear disaster in Japan. The foray into
geothermal power is in line with the government’s plan to increase
renewable energy’s contribution to Malaysia’s power generation mix
from less than one per cent currently to 5.5 per cent (985MW) by 2015.
Tawau has an electricity generation potential of up to 67 MW from
geothermal resources following the discovery of a geothermal site in
Apas by a study by the Mineral and Geoscience Department. A study
has found a reservoir about 2,000 to 3,000m below the earth’s surface
with water at temperatures of 220 to 236 degrees Celsius which was
more than enough heat to generate electricity.
3.7 Recent Developments
1. Comparing statistical data for end-1996 (SER 1998) and the present
Survey, there has been an increase in world geothermal power plant
capacity (+9%) and utilisation (+23%) while direct heat systems show a
56% additional capacity, coupled with a somewhat lower rate of
increase in their use (+32%).
2. Geothermal power generation growth is continuing, but at a lower
pace than in the previous decade, while direct heat uses show a
strong increase compared to the past.
3. Six countries with the largest electric power capacity are: USA with 2
228 MWe is first, followed by Philippines (1 863 MWe); four countries
(Mexico, Italy, Indonesia, Japan) had capacity (at end-1999) in the
range of 550-750 MWe each. These six countries represent 86% of the
world capacity and about the same percentage of the world output,
amounting to around 45 000 GWhe.
3.7 New Developments
4. Strong decline in the USA in recent years, due to overexploitation of
the giant Geysers steam field, has been partly compensated by
important additions to capacity in several countries: Indonesia,
Philippines, Italy, New Zealand, Iceland, Mexico, Costa Rica, El
Salvador. Newcomers in the electric power sector are Ethiopia (1998),
Guatemala (1998) and Austria (2001). Total of 22 nations are
generating geothermal electricity sufficient for 15 million houses.
5. Three countries with the largest amount of installed power: USA (5
366 MWt), China (2 814 MWt) and Iceland (1 469 MWt) cover 58% of
the world capacity, which has reached 16 649 MWt, enough to
provide heat for over 3 million houses. Out of about 60 countries with
direct heat plants, beside the three above-mentioned nations, Turkey,
several European countries, Canada, Japan and New Zealand have
sizeable capacity.
6. With regard to direct use applications, a large increase in the number
of GHP installations for space heating (presently estimated to exceed
500 000) has put this category in first place in terms of global capacity
and third in terms of output. Other geothermal space heating systems
are second in capacity but first in output. Third in capacity (but second
in output) are spa uses followed by greenhouse heating. Other
applications include fish farm heating and industrial process heat. The
outstanding rise in world direct use capacity since 1996 is due to the
more than two-fold increase in North America and a 45% addition in
Asia. Europe also has substantial direct uses but has remained fairly
stable: reductions in some countries being compensated by progress
in others.
7. In R&D, the hot dry rock (HDR) project at Soultz-sous-Forêts near the
French-German border has progressed significantly. Besides the
ongoing Hijiori site in Japan, another HDR test has just started in
Switzerland (Otterbach near Basel).
8. The total world use of geothermal power is giving a contribution both
to energy saving (around 26 million tons of oil per year) and to CO2
emission reduction (80 million tons/year if compared with equivalent
oil-fuelled production).

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What are the different layers of the Earth?

What are the different layers of the Earth?

What are geothermal resources and where are they located?

What are geothermal resources and where are they located?

BMM 4753 RENEWABLE ENERGY

The Earth has a number of different layers

b. The mantle surrounds the core

c. The crust is the outermost layer of the Earth

Earth's crust is broken into pieces called plates

o The temperature of the rocks and water gets hotter

Current Commercial Utilization

Advanced Technologies Yet To Be Developed

❖ Hydrothermal reservoirs are large pools of steam or hot water

❖ These resources can be classified as low temperature (less than

a) Geothermal Heat Pumps (GHP)

a) Geothermal Heat Pumps… cont’d

b) District Heating Systems

People living in these areas are receiving

i. Worldwide, direct uses of geothermal water avoids the combustion of

Direct Use Geothermal Water

Peppers, tomatoes, and flowers are commonly grown in geothermally

Tawau in Malaysia has an electricity generation

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