Transcript Geothermal Sonia

Definition of geothermal energy
• Geothermal energy is energy
that can be obtained by man
through the use of heat
inside the Earth. The heat
inside the Earth is due to
several factors, including the
geothermal gradient, the
radiogenic heat, etc.
Geothermal comes from the
Greek ``geo´´(earth) and
``thermos´´(hot), literally
``heat of the Earth´´
•
In areas of very hot thermal
waters at little depth, it is
perforated by natural fractures
of basal rocks or within
sedimentary rocks. The hot
water or the steam can flow
naturally, by pumping or impulses
of steam and water flows
(flashing). The magma resources
(fused rocks) offer geothermal
energy of highest temperature,
but we can not take economically
advantages of it with the
existing technology.
• In most of the cases the operation should be done with two
wells so that one gets the hot water and the other reinjected the water into the aquifer, before cooling the wealth
obtained. There are many advantages with this system:
• There are less probabilities of exhausting the thermal
deposit. The water of the deposit is not exhausted because
the total amount remains.
• The possible salts or gas emissions dissolved in the water do
not appear, avoiding contaminations.
Types of geothermal deposits according
to the temperature of the water
•
•
The geothermal energy of high temperature exits in the active zones of
the crust. This temperature is between 150 and 400ºC, produce steam
in the surface and it generates electricity with a turbine.
Geothermal energy of average temperatures: is the one in which the
temperature of the aquifer’s fluids are less high, normally between 70
and 150ºC. So the steam-electricity conversion is made with a smaller
yield, and must be exploited by a volatile fluid.
• We can use the geothermal
energy of low temperatures
in zones that are bigger than
the other ones; for example,
in all sedimentary basins.
• It is considered geothermal
energy of very low
temperature when the fluids
are warmed up to
temperatures between 20
and 50ºC. This energy is used
for domestic , urban or
agricultural necessities.
• The lower temperature
sources are very suitable for
heating system.
Advantages and disadvantages
• Advantages
• It is a source that would avoid the energetic dependency of the
outside.
• The wasted productions are minimum and they caused a smaller
environmental impact than the ones that are originated by
petroleum, coal,…
• Disadvantages
• In some cases, the emission of hydrogen sulfide, that is detected
by its rotten eggs smell but you can not perceive it in large amounts
and is lethal.
• In some cases, emissions of CO2, with increased greenhouse
effect, is less than what would be issued to obtain the same energy
by combustion.
• Water contamination with substances like arsenic, ammoniac, etc.
• Thermal contamination.
• Deterioration of the landscape.
• You can not transport it (as primary energy).
• It is available only in certain places.
Geothermal energy uses
• Electricity
generation.
• Use of heat
• Heating and ACS.
• Absorption
refrigerator.
Electricity generation
• Geothermal energy was produced for
the first time in Larderello, Italy, in
1904. Since that time, the use of the
geothermal energy for electricity has
grown worldwide near 8,000megawatt of
which EE.UU generates 2,700MW.
Types of electrical plants
• Three types are used to generate power from geothermal energy:
Dry steam
flash
binary
• Plants ``in dry steam´´usually take the stream from the fractures in
the ground and it goes directly to a turbine, to move a generator. Plants
``flash´´obtains very hot water of more than 200ºC, and separats in
the steam phase with separators steam/water, and it moves a turbine.
In binary plants, the hot water flows through heat exchangers, by
boiling an organic fluid that turns the turbine.
Desalination
• Douglas Firestone began with the desalination with
the evaporation/desalination system with hot air in
1998, proving that the hot water can be used
economically to produce desalinated water in 2001.
• In 2003, the teacher Ronald A. worked with
Firestone to improve the process of geothermal
energy for desalination.
• In 2005, is fitted the 5th prototype desalination
``Delta T´´that uses a forced hot air cycle,
atmospheric pressure and a geothermal cycle of
evaporation and condensation.
Injection and water
•
In many places has happened
that magma deposits dried up.
As a result, it stops providing
geothermal water , perhaps
helped by the injection of cold
wastewater or in the hot aquifer
recharge. That means that the
reinjection recharge can cool
the resource, unless you be
careful with it. In at least one
town, the cooling was the result
of small but frequent
earthquakes. This has brought
the discussion if the plants
ownwers are responsible of the
damaged caused by an
earthquake.
Heat extinction
• Although there are sites capable of providing geothermal energy for
decades, others may dry and run. In a report, the Icelandic
government says: should be understood that geothermal energy is not
strictly renewable in the same direction as the hydraulic.
• ¿How do they work?
• The operation of a geothermal power station is done through a
very simple system: two tubes that have been introduced in the
practiced perforation, maintain their ends in a closed circuit in
direct contact with the heat source. On one end of the tube is
injected cold water from the surface, when it comes to the
bottom it is warmed up and ir rises toward the surface across
another tube, that has got a turbine with an electrical
generator. The cooled water is given back by the first tube to
repeat the cycle again.
• Disadvantages of the system
• The abyss inside the earth’s crust, where is the
usable heat, is not able to conduct the heat. In
practice, this disadvantage prevents the continuous
operation of the power station.
• Alternative variables
• In a certain way a geothermal power station
reproduces the natural operation of the geysers; in
that case the water is introduced through the cracks
of the subsurface and on having reached the heated
zones of the Earth, they are taken to boil, returning
to the outside by those holes that offer less
resistance, offering a very showy spectacle.
Geothermal power stations in
Spain
•
In the case of Spain, although there are suitable places to build in
Almeria,there are not any geothermal power station yet. In the Canary
island La Palma, many people are studying the construction of a
geothermal plant which covers part of their electricity’s needs, because
at the present time, the island dependency of fossil fuels is 95%.