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Geothermal Energy


Geothermal Energy Based on the heat that naturally occurs in the Earth s interior Sine the Earth s interior is hotter than the surface, this heat flows form the ... – PowerPoint PPT presentation

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Title: Geothermal Energy

Geothermal Energy
  • Based on the heat that naturally occurs in the
    Earths interior
  • Sine the Earths interior is hotter than the
    surface, this heat flows form the interior
    towards the surface.
  • Heat is the result of decay of radioactive nuclei
    inside the Earth, heat left over from the
    formation of the Earth and heat from the friction
    of heavier material sinking towards the center.
  • Earths core temperature is 7200 F, which is
    close to the temperature on the Suns surface.

Radioactive Decay
  • the process in which an unstable atomic nucleus
    loses energy by emitting ionizing particles and
  • Most important source of heat inside the earth
  • loss of energy results in an atom of one type
    (parent nuclide) transforming to an atom of a
    different type, (daughter nuclide).
  • Eg a carbon-14 atom (the "parent") emits
    radiation and transforms to a nitrogen-14 atom
    (the "daughter").
  • This is a random process on the atomic level, in
    that it is impossible to predict when a given
    atom will decay, but given a large number of
    similar atoms the decay rate, on average, is

  • Not a new idea
  • Used the heat from inside the Earth for thousands
    of years for bathing (hot springs) and space
  • First electric power use was by Prince Piero
    Ginori Conti tested the first geothermal power
    generator on 4 July 1904 in Larderello, Italy.
  • In 1958 New Zealand built a plant of its own.
  • First geothermal power plant in the United States
    was made in 1922 by John D. Grant at The Geysers
    Resort Hotel.
  • In 1960, Pacific Gas and Electric began operation
    of the first successful geothermal power plant in
    the United States at The Geysers. The original
    turbine installed lasted for more than 30 years
    and produced 11 MW net power.

The Geysers
  • The Geysers is a geothermal power field located
    72 miles (116 km) north of San Francisco,
  • It is the largest geothermal development in the
  • It is currently outputting over 750 MW. It
    consists of 22 separate power plants that utilize
    steam from more than 350 producing wells.

Harnessing Geothermal Resources
  • Hot Water Reservoirs
  • Natural Steam reservoirs
  • Geopressured Reservoirs
  • Normal Geothermal Gradient
  • Hot Dry Rock
  • Molten Magma

Hot Water reservoirs
  • Heated underground reservoirs
  • Used for heating buildings, raising plants in
    greenhouses, drying crops, heating water for fish
    farms, or for industrial processes.
  • Example of a direct use system
  • a well is drilled into a geothermal reservoir to
    provide a steady stream of hot water.
  • The water is brought up through the well, piping,
    a heat exchanger, and controls delivers the heat
    directly for its intended use.
  • A disposal system then either injects the cooled
    water underground or disposes of it in a surface
    storage pond.

Natural Steam Reservoirs
  • Sources of natural steam, like the geysers
    previously discussed, used to drive a turbine.
  • Hydrothermal reservoirs consist of a heat source
    covered by a permeable formation through which
    water circulates.
  • Steam is produced when hot water boils
    underground and some of the steam escapes to the
    surface under pressure.
  • Once at the surface, impurities and tiny rock
    particles are removed, and the steam is piped
    directly to the electrical generating station

Geopressurized reservoirs
  • Geopressurized reservoirs are sedimentary
    formations containing hot water (brine-water
    saturated with salt) and methane gas.
  • Could be a source of both power and natural gas

Normal geothermal gradient/Hot Dry Rock
  • Natural geothermal gradient of about 30/km
  • A geothermal heat pump system consists of pipes
    buried in the shallow ground near a building, a
    heat exchanger, and ductwork into the building.
  • In winter, heat from the relatively warmer ground
    goes through the heat exchanger into the house.
  • In summer, hot air from the house is pulled
    through the heat exchanger into the relatively
    cooler ground. Heat removed can be used as
    no-cost energy to heat water.
  • Variation Direct exchange geothermal heat pump
    A heat pump without a heat exchanger, which
    circulates the working fluid through pipes in the
  • Hot Dry rock is the same idea, but in certain
    locations the gradient is much higher

US Geothermal Resources
  • Geothermal power requires no fuel and is
    emissions free and is not susceptible to
    fluctuations in fuel cost.
  • geothermal power station dont rely on transient
    sources of energy (wind, sun)
  • It is considered to be sustainable because the
    heat extraction is small compared to the size of
    the heat reservoir.
  • individual wells may need to recover, geothermal
    heat is inexhaustible and is replenished from
    greater depths. 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.
  • However, there has been a decrease in output
    noted at The Geysers
  • Geothermal has minimal land use requirements

  • The geothermal fluid is corrosive and, worse, is
    at a low temperature compared to steam from
    boilers, this limits the efficiency of heat
    engines in extracting useful energy during the
    generation of electricity. Much of the heat
    energy is lost, but could be used for
    co-generation purposes
  • Construction of the power plants can adversely
    affect land stability in the surrounding region.
    This is mainly a concern with Enhanced Geothermal
    Systems, where water is injected into hot dry
    rock where no water was before.
  • Dry steam and flash steam power plants also emit
    low levels of carbon dioxide, nitric oxide, and
    sulphur, although at roughly 5 of the levels
    emitted by fossil fuel power plants. However,
    geothermal plants can be built with
    emissions-controlling systems that can inject
    these substances back into the earth, thereby
    reducing carbon emissions to less than 0.1 of
    those from fossil fuel power plants.
  • Hot water from geothermal sources will contain
    trace amounts of dangerous elements such as
    mercury, arsenic, and antimony which, if disposed
    of into rivers, can render their water unsafe to
  • Locations may eventually cool down

  • Plant matter grown to generate electricity or
    produce biofuel
  • Examples trash such as dead trees and branches,
    yard clippings and wood chips, plant or animal
    matter used for production of fibers, chemicals
    or heat.
  • Biomass may also include biodegradable wastes
    that can be burnt as fuel.
  • It excludes organic material which has been
    transformed by geological processes into
    substances such as coal or petroleum.

Energy from Biomass
  • Comes initially from the sun
  • Solar energy is stored as chemical energy in the
  • This chemical energy is released when the biomass
    is burned or converted to another fuel that is
  • Process starts with the conversion of sunlight to
    chemical energy in the plant we call this

Review of Photosynthesis
  • Plant takes in water and carbon dioxide. The
    energy in visible light excites atoms in the
    water and carbon dioxide which allows bonding to
    take place. As a result, compounds with hydrogen,
    carbon and oxygen are formed (called
    carbohydrates), along with oxygen and water.
  • The simplest carbohydrate formed is sugar, and
    these compounds are the plants fuel.

  • About 30 of the energy in the incident sunlight
    is stored in biomass.
  • Not a new idea, remember way back in the semester
    when we looked at sources of energy production in
    the US? Wood was a primary source of energy until
  • If you look at the average crop yield for all the
    harvested land in the US, you find that nearly
    all our energy needs could be furnished from

Municipal Waste
  • Our solid waste (garbage) needs a home-we
    normally put it in a landfill (polite name for a
  • Landfill sites are diminishing for a variety of
    reasons, but our waste production is increasing.
  • Unfriendly to the environment
  • Can contaminate groundwater
  • Nasty smell
  • Harbor diseases and disease carrying rodents
  • Can contain toxic chemicals
  • Emit methane (produced in the decay of organic
    materials and is not only toxic, but a greenhouse

Municipal waste
  • This waste has energy stored in it, which can be
    released of the waste is burned.
  • Energy produced is modest, but this solves
    another environmental problem.
  • Plants are expensive to construct and maintain,
    most cities do not have the money to get one
    started. Rely on private investors or companies

Creating Fuel from Biomass
  • Ethanol common form of alcohol, it is an
    oxygenated hydrocarbon (a hydrocarbon with oxygen
  • Also known as ethyl alcohol, pure alcohol, grain
    alcohol, or drinking alcohol,
  • volatile, flammable, colorless liquid.
  • type of alcohol found in alcoholic beverages and
    in modern thermometers.
  • Fermentation of sugar to ethanol is one of the
    earliest organic reactions employed by humanity

  • Usually produced from corn, though other grains
    can be used. (Brazil is a major user of Ethanol,
    and uses sugar cane to produce their ethanol)
  • Entire plant is ground up and mixed with water.
  • Cooked to convert starch to sugars via enzymatic
  • Sugars are converted to alcohol via fermentation.
  • Distillation removes the rest of the material
    from the alcohol.

Ethanol as a Fuel additive
  • Ethanol increases the oxygen content of gasoline,
    and leads to more complete combustion and reduces
    CO2 emissions.
  • Mixtures are defined by E, where is the
    percent of ethanol in the fuel.
  • So E100 is 100 ethanol
  • E10 (10 ethanol) is a particular type of mixture
    called gashol.
  • Current gasoline engines cannot run on pure
    ethanol since to maximize its energy conversion
    efficiency, higher compression ratios are needed,
    which wont work for gasoline engines.

Debate rages
  • Will it really solve all our problems?
  • Is it cheaper?
  • Is it cost effective?
  • What about the issue of using a food source
    (corn) for fuel?

Methane from Biomass
  • Methane makes up 85 of the natural gas extracted
    from the ground.
  • In the presence of water and absence of oxygen,
    organic material will ferment naturally.
  • Such organic materials include
  • Crops
  • Agricultural waste (animal or vegetable)
  • Waste from lumber mills
  • waste from breweries
  • Algae
  • Sludge from sewage treatment plants
  • Municipal waste
  • Fermentation by bacteria in the absence of oxygen
    is called anaerobic fermentation

Methane from Biomass
  • Same heating value as natural gas
  • High conversion efficiency(50-70 of the useful
    energy is converted)
  • High cost
  • Useful in systems that can generate their own
    power - for example sewage plants

  • Diesel fuel made from vegetable oil, recycled
    cooking grease or oil and animal fat
  • Used as a fuel additive, designate the same way
    we designate ethanol fuels-i.e B where is the
    amount of biodiesel in the diesel fuel.
  • B20 widely used in trucks and school buses
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