TERRESTRIAL HEAT

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TERRESTRIAL HEAT energy from the inside of the
Earth
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What does geothermal mean?

• The term geothermal comes from the Greek geo
  meaning earth and therine meaning heat thus
  geothermal energy is energy derived from the
  natural heat of the earth.
• The heat inside the Earth core is continually
  generated by the decay of the long lived
  radioactive isotopes of uranium,  thorium and
  potassium, which are present in the Earth.
• The heat that flows from the Earth's hot interior
  due to plate movements, zones of high heat flow,
  may be located close to the surface where
  convective circulation plays a significant role
  in bringing the heat close to the surface

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What happens with the heat?

• Without utilization, the terrestrial heat flow is
  lost to the atmosphere. In this case, the
  isotherms run parallel to the earths surface and
  the heat flow lines are perpendicular to them.
  If, instead, the heat flow can be captured, the
  isotherms are deformed and the heat flow lines
  can be diverted towards heat sinks.
• Due to variations of the earths crust thickness
  there will be different temperature profiles from
  place to place. Some areas are known to have hot
  springs and the like and volcanic activities,
  such areas will also be well suited for
  geothermal utilization.

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How does geothermal heat get up to the surface?

• Sometimes the hot magma reaches all the way to
  the surface, where we know it as lava. But most
  often the magma remains below earth's crust,
  heating nearby rock and water (rainwater that has
  seeped deep into the earth) - sometimes as hot as
  700 degrees F. Some of this hot geothermal water
  travels back up through faults and cracks and
  reaches the earth's surface as hot springs or
  geysers, but most of it stays deep underground,
  trapped in cracks and porous rock. This natural
  collection of hot water is called a geothermal
  reservoir.

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Best locations

• Geothermal systems can be found in regions with a
  normal or slightly above normal geothermal
  gradient.
• The margins of the plates correspond to weak,
  densely fractured zones of the crust,
  characterized by an intense seismic activity, by
  a large number of volcanoes and, because of the
  ascent of very hot materials towards the surface,
  by a high terrestrial heat flow. The most
  important geothermal areas are located around
  plate margins.
• World pattern of plates, oceanic ridges, oceanic
  trenches, subduction zones, and geothermal
  fields.

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Accessing geothermal energy

• If geothermal reservoirs are close enough to the
  surface, we can reach them by drilling wells,
  sometimes over two miles deep. Scientists and
  engineers use geological, electrical, magnetic,
  geochemical and seismic surveys to help locate
  the reservoirs. Then, after an exploration well
  confirms a reservoir discovery, production wells
  are drilled.
• Geothermal system can be described schematically
  as "convecting water in the upper crust of the
  Earth, which, in a confined space,transfers heat
  from a heat source to a heat sink, usually the
  free surface". A geothermal system is made up of
  three main elements a heat source, a reservoir
  and a fluid, which is the carrier that transfers
  the heat.

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Generating electricity Geothermal power plants

• In geothermal power plants, we use the natural
  hot water and steam from the earth to turn
  turbine generators to produce electricity. Unlike
  fossil fuel power plants, no fuel is burned.
  Geothermal power plants give off water vapour,
  but have no smoky emissions.
• There are several different types of plants
  flashed steam plants, dry steam plants and binary
  power plants

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Flashed Steam Plants

• Most geothermal power plants operating today are
  "flashed steam" power plants. Hot water from
  production wells is passed through one or two
  separators where, released from the pressure of
  the deep reservoir, part of it flashes
  (explosively boils) to steam. The force of the
  steam is used to spin the turbine generator. To
  conserve the water and maintain reservoir
  pressure, the geothermal water and condensed
  steam are directed down an injection well back
  into the periphery of the reservoir, to be
  reheated and recycled.
• Flash steam power plants use hot water
  reservoirs. In flash plants, as hot water is
  released from the pressure of the deep reservoir
  in a flash tank, some if it flashes to steam.

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Dry Steam Plants

• A few geothermal reservoirs produce mostly steam
  and very little water. Here, the steam shoots
  directly through a rock-catcher and into the
  turbine. The first geothermal power plant was a
  dry steam plant, built at Larderello in Tuscany,
  Italy in 1904. The power plants at the Larderello
  dry steam field were destroyed during World War
  II, but have since been rebuilt and expanded.
  That field is still producing electricity today.
  The Geysers dry steam reservoir in northern
  California has been producing electricity since
  1960. It is the largest known dry steam field in
  the world and, after 40 years, still produces
  enough electricity to supply a city the size of
  San Francisco.

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Binary Power Plants

• In a binary power plant, the geothermal water is
  passed through one side of a heat exchanger,
  where it's heat is transferred to a second
  (binary) liquid, called a working fluid, in an
  adjacent separate pipe loop. The working fluid
  boils to vapour which, like steam, powers the
  turbine generator. It is then condensed back to a
  liquid and used over and over again. The
  geothermal water passes only through the heat
  exchanger and is immediately recycled back into
  the reservoir. In some power plants, flash and
  binary processes are combined.

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Direct (non-electrical) uses of geothermal water

• Shallower reservoirs of lower temperature --
  21-149C (70-300F) are used directly in health
  spas, greenhouses, fish farms, and industry and
  in space heating systems for homes, schools and
  offices.
• It is only during the last century that we have
  used geothermal energy to produce electricity.
  But using geothermal water to make our lives more
  comfortable is not new people have used it since
  the dawn of mankind. Wherever geothermal water is
  available, people find creative ways to use its
  heat.

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Agriculture and aquaculture

• Geothermal energy is used directly in agriculture
  and aquaculture
• to help grow flowers, vegetables, and other crops
  in greenhouses while snow-drifts pile up outside
• to shorten the time needed for growing fish,
  shrimp, abalone and alligators to maturity

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Industry

• The heat from geothermal water is used worldwide
  for industrial purposes. Some of these uses
  include drying fish, fruits, vegetables and
  timber products, washing wool, dying cloth,
  manufacturing paper and pasteurizing milk.
• Geothermally heated water can be piped under
  sidewalks and roads to keep them from icing over
  in freezing weather. Thermal waters are also used
  to help extract gold and silver from ore and even
  for refrigeration and ice-making.

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Hot Spring Bathing and Spas (Balneology)

• For centuries, peoples of China, Iceland, Japan,
  New Zealand, North America and other areas have
  used hot springs for cooking and bathing. The
  Romans used geothermal water to treat eye and
  skin disease and, at Pompeii, to heat buildings.
  Medieval wars were even fought over lands with
  hot springs.
• In Europe, natural hot springs have been very
  popular health attractions. The first known
  "health spa" was established in 1326 in Belgium.
  (One resort was named "Espa" which means
  "fountain." The English word "spa" came from this
  name.) All over Eurasia today, health spas are
  still very popular. Russia, for example, has
  3,500 spas.
• Japan is considered the worlds leader in
  balneology. The Japanese tradition of social
  bathing dates back to ancient Buddhist rituals.
  Beppu, Japan, has 4,000 hot springs and bathing
  facilities that attract 12 million tourists a
  year. Other countries with major spas and hot
  springs include New Zealand, Mexico and the
  United States.

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District heating

• The oldest and most common use of geothermal
  water, apart from hot spring bathing, is to heat
  individual buildings, and sometimes entire
  commercial and residential districts.
• A geothermal district heating system supplies
  heat by pumping geothermal water -usually 60 C
  (140F) or hotter- from one or more wells drilled
  into a geothermal reservoir. The geothermal water
  is passed through a heat exchanger which
  transfers the heat to water in separate pipes
  that is pumped to the buildings. After passing
  through the heat exchanger, the geothermal water
  is injected back into the reservoir where it can
  reheat and be used again.
• Because it is a clean, economical method of
  heating buildings, geothermal district heating is
  becoming more popular in many places. The world's
  largest geothermal district heating system is in
  Reykjavik, Iceland, where almost all the
  buildings use geothermal heat. The air around
  Reykjavik was once very polluted by emissions
  from reliance on fossil fuels. Since it started
  using geothermal energy, Reykjavik has become one
  of the cleanest cities in the world.

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Geothermal heat pumps

• The heat pumps are machines that move heat in a
  direction opposite to that in which it would tend
  to go naturally, i.e. from a cold space or body
  to a warmer one. A heat pump is effectively
  nothing more than a refrigeration unit. Any
  refrigeration device (window air conditioner,
  refrigerator, freezer, etc.) moves heat from a
  space (to keep it cool) and discharges that heat
  at higher temperatures. The only difference
  between a heat pump and a refrigeration unit is
  the desired effect, cooling for the refrigeration
  unit and heating for the heat pump. A second
  distinguishing factor of many heat pumps is that
  they are reversible and can provide either
  heating or cooling in the space.
• Geothermal heat pumps reduce electricity use
  30-60 compared with traditional heating and
  cooling systems, because the electricity which
  powers them is used only to move heat, not to
  produce it. The U.S. Environmental Protection
  Agency rates geothermal heat pumps among the most
  efficient of heating and cooling technologies.

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Advantages of geothermal energy

• RENEWABILITY AND SUSTAINABILITY Earths heat is
  continuously radiated from within, and each year
  rainfall and snowmelt supply new water to
  geothermal reservoirs. Production from individual
  geothermal fields can be sustained for decades
  and perhaps centuries. The U.S. Department of
  Energy classifies geothermal energy as renewable.
• CONSERVATION OF RESOURCES When we use renewable
  geothermal energy for direct use or for producing
  electricity, we conserve exhaustible and more
  polluting resources like fossil fuels and
  uranium. Installed geothermal electricity
  generation capacity around the world is
  equivalent to the output of about 10 nuclear
  plants.
• PROTECTION OF THE ENVIRONMENT Geothermal direct
  use facilities have minimal or no negative
  impacts on the environment. Geothermal power
  plants are relatively easy on the environment.
• Protection of the Air and Atmosphere. Hydrogen
  sulphide gas (H2S) sometimes occurs in geothermal
  reservoirs. It is subject to regulatory controls
  for worker safety because it can be toxic at high
  concentrations. Equipment for scrubbing H2S from
  geothermal steam removes 99 of this gas. Carbon
  dioxide CO2 occurs naturally in geothermal steam
  but the geothermal plants release amounts less
  than 4 of that released by fossil fuel plants.
  And there are no emissions at all when
  closed-cycle (binary) technology is used.
• Visual Protection. A geothermal plant sits right
  on top of its fuel source no additional land is
  needed such as for mining coal or for
  transporting oil or gas. When geothermal power
  plants and drill rigs are located in scenic
  areas, mitigation measures are implemented to
  reduce intrusion on the visual landscape.
• LOW COSTS the price of geothermal power
  decreased with about 25 in the last 2 decades
  due to the development of the technology used and
  the involvement of the government in the research
  regarding this domain.

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Future of geothermal energy

• The outlook for geothermal energy use depends on
  at least three factors
• The Demand for energy will continue to grow.
  Economies are expanding, populations are
  increasing (over 2 billion people still do not
  have electricity), and energy-intensive
  technologies are spreading. All mean greater
  demand for energy.
• The Inventory of accessible geothermal energy is
  sizable. Using current technology geothermal
  energy from already-identified reservoirs can
  contribute as much as 10 of the United States
  energy supply. And with more exploration, the
  inventory can become larger. The entire world
  resource base of geothermal energy has been
  calculated in government surveys to be larger
  than the resource bases of coal, oil, gas and
  uranium combined
• The Competitive Position depends primarily on
  cost
• Costs Shorter and Longer Term. Production of
  fossil fuels (oil, natural gas and coal) are a
  relative bargain in the short term. Like many
  renewable resources, geothermal resources need
  relatively high initial investments to access the
  heat, hot water and steam. But the geothermal
  "fuel" cost is predictable and stable. Renewable
  geothermal energy is a better long term
  investment.
• Costs Direct and Indirect. The monetary price we
  pay to our natural gas and electricity suppliers,
  and at the gas pump, is our direct cost for the
  energy we use. Geothermal energy is a clean,
  indigenous, renewable resource without hidden
  external costs.
• Costs Domestic and Importing. Investment in the
  use of domestic, indigenous, renewable energy
  resources like geothermal energy provides jobs,
  expands the regional and national economies, and
  avoids the export of money to import fuels.

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Conclusion

• Energy demand is increasing rapidly worldwide.
  Some energy and environmental experts predict
  that the growth of electricity production and
  direct uses of geothermal energy will be
  revitalized by international commitments to
  reduce carbon dioxide emissions to avert global
  climate change and by the opening of markets to
  competition.

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Made by Diana GiurghitaAnca Muntean