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When someone hears
about renewable energy, your first thought is its benefits. This energy is
inexhaustible, clean and can be used on a self-management way (because they are
used in the same place where they occur). But what happens when the wind stops
blowing, or when the clouds appear to make the sun disappear completely. Well
this is where the idea of the Thermal Storage appears.
Spain is the first country in the world to use renewable
energy with a thermal
storage system by inorganic salts. Last July in Aldeire, Granada was inaugurated the plant
Andasol-1 which
runs seven and a half hours without sun. And
it has begun the construction of Gemasolar plant in Fuentes de Andalucía, Sevilla which can last up to fifteen hours
without sun.
The plant operation is very simple and efficient, in the first case Andasol Plant-1, inorganic salts such as
sodium nitrate
and potassium nitrate were stored in liquid state in a cold tank at a temperature of 293 degrees. When Sun is irradiating these salts, they are pumped to heat exchanger where the heat is absorbed and can reach 393 degrees Celsius. That is when salts are transferred to a hot tank. The same happens when the sun is not shining but in a reverse way, now is when the hot tank is transferred to the cold tank, hot salts transfer energy to the fluid and synthetic oil and steam is generated.
Figure
1: Storage tanks of Andasol 1 plant
In the second case, Gemasolar plant has very similar operation. Sunlight falls on the heliostat reflecting it to
the receiver, in the cold water
tank begins to pump the salts to the top of the tower. At the receiver tower, salts are heated to go down
to the hot
tank where they are
stored at temperatures above 500 °. Continuing the journey salts pass through the heat exchanger pipes, then when salts lose heat, water steam is generating making work the electric
generator turbine.
Heliostats
solar thermal power plant Gemasolar
With the prolongation of plant operation time in the
absence of radiation, Spain has taken a big step into the world of renewable
energy continuing its technological and commercial growth.
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