Hydroelectric Energy

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Hydroelectric Energy

• The hydroelectric energy, is the most important
  and widely used renewable source of energy. It
  represents the 19 of the total production of
  electricity.Today all over the world exist
  roughly 45.000 big hydroelectric dams in
  operation. The country with the bigger production
  of hydroelectricity is Canada and follows the
  U.S.A and Brazil.
• It emanates from the exploitation of waters of
  rivers. The hydroelectric energy does not produce
  damaging gases and as a result has perceptibly
  smaller effect in atmosphere.

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Up to today the unexploited hydroelectric
potential of continental mainly Greece, it could
cover important percentage of total energy
consumption. In many regions of Greece small
hydroelectric power stations could be
manufactured from private individuals for the
production of electric energy as the Community of
Agistro Serres made. It has to be mentioned
here that while the electric energy is produced
the moment it is required by the consumers the
water which is saved up in tanks for future use
for the production of electric energy can be
used for irrigation at dry spells, as water
reserve , the enrichment of lakes, athletic
events, tourism etc At the same time ,the main
criterion for the manufacture or no of a
hydroelectric factory is not only the possibility
of production, cheap and clean for the
environment, energy but also the ecological
intervention in the nature for the maintenance
of nature of the region and the right Regional
growth of the country. The recent legislation
that concerns the possibility of private sector
of producing electric energy, is expected to
strengthen considerably the interest of investors
in the sector of A.P.E. A lot of Communities as
well as private individuals have expressed their
interest for the manufacture and exploitation of
small hydroelectric factories. In addition ,
usually such investments are subsidized and
part-financed by the Greek State and the European
Union. The new developmental law subsidizes 40
to 50 of the total cost of the project
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The water s "circle" in the nature has dynamic
energy, when it is found in regions with high
altitude, which is changed in kinetics, when the
water flows to lower regions. With the
hydroelectric work (water tank, dam, closed
driver of fall, water turbine, electric
generator, tailrace) we exploited the energy of
water for the production of electric current
which is channeled in the consumption with the
aim of the electric network. The transformation
of energy of waterfalls with the use of hydraulic
turbines produces the hydroelectric energy. The
hydroelectric energy is categorized in big and
small scale. S The mall scale hydroelectric
energy differs considerably from big scale
regarding the repercussions in the environment.
Big scale hydroelectric units require the
creation of dams and enormous reservoirs with
important repercussions in the direct
environment. The manufacture of dams for the
stocking of water limits the locomotion of fish,
wild life and influences the entire ecosystem.
The small scale systems are placed next to rivers
and channels and hasless repercussions in the
environment ecosystem.
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Hydroelectric units of less 30 Mw in size are
characterized small scale and are considered as
renewable sources. Fast moved water which is led
through tunnel to turn turbines, creates thus
mechanic energy. A generator changes this energy
in electric . By contrast with what happens with
mining fuels, the water is not made useless at
the production of electric energy and it can be
also used for other aims. Naturally, only in
regions with important waterfalls, rich sources
and suitable geological configuration it is
possible to manufacture water tank . Usually the
energy that is finally produced, is used only
additionally with other conventional sources of
energy, in hours of peak. In our country the
hydroelectric energy satisfies the 10 of our
energy needs.
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The advantages from the use of hydroelectric
energy are The hydroelectric power
stations are possible to be placed in operation
as soon as it is asked more electric energy,
contrary to the thermo stations of (coals, oil),
that requires time of preparation Also through
the water tanks is given the possibility to be
satisfied other needs, as water supply,
irrigation, interception of torrents, creation of
wetlands, recreation, sports. In 140 countries,
the dams provide cheap hydroelectric energy. In
world scale, provide the 19 of produced energy
and through the irrigation, the 16 of world
feeding. Certain dams continue their function
after 30-40 years, providing current and water.
The hydroelectric energy plays a serious role in
the reduction of the emission of gases that
they create the" greenhouse effect" at 13,as it
produces the equivalent of energy which in a
different case would be produced in another way
that would create greenhouse gases
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The disadvantages that usually are presented
are The big cost of the manufacture of dams
and the equipment of the stations of generation
of electricity, as well as, the time that is
required up to the completion of work The
intense environmental alteration in the region of
tank (potential locomotion of populations,
areas revalorization, change in the use of the
ground, in the flora and fauna of the regions
but also local climate, fulfillment of tanks
with brought matters, increase of seismic
danger, etc). The international practice today
is directed in the manufacture of small dams.
The hydroelectric dams built in order to provide
electricity -water for irrigation but also in
order to check the flow of rivers, they limit the
floods and the droughts- have disproportionately
acquired a big effect in the environment.
Globally they have submerged more than 400.000
square kilometers of ground, mainly fertile.
Globally the one fifth of fish of sweet water
either have been disappeared or are threatened
seriously. Nearly 40 to 80 million persons have
abandoned their houses because of dams, forced
to settle in other , less fertile regions. On the
other hand the big dams have led to the loss of
forests and biotopes but also to the biodiversity
of the waters of the rivers. The big dams, in
the majority of cases, failed systematically to
contribute to the re-establishment of the
negative consequences for the populations that
were moved because of them. With roughly 80
millions persons to have been moved from their
houses and many more who live in the lower parts
of the flow of the river to suffer from the
indirect repercussions (eg loss of fish catches),
the efforts of mitigation of repercussions were
ineffective.
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Small Hydroelectric power station The hydraulic
energy, the energy of water, is a renewable,
and decentralised source of energy that served
and serves man loyally in his course of
progress . Many hydraulic wheels, watermills,
sawmills, klwstoy!fantoyrgej'a and other
mechanisms of hydro movement continue even today
to use the force of water, contributing
considerably in the progress of the local
economy of many regions, in an absolutely
friendly to the environment way. In many parts
the of Greek country certain traditional, but
also modern installations of Small Hydroelectric
Work continue developing the energy of water for
the production of mechanic work but mainly for
the production of electric current nowadays. The
exploitation of small hydrodynamic sources of
mountainous Greece passes from the concretisation
decentralised, developed small hydroelectric
power stations of multiple expediency, that can
function and for the simultaneous cover watering
irrigatory and other local needs. In the wider
region of Sjdirokastro 4 small hydroelectric
works function that use a) the water from the
lake Kerkini and b) the water of the tributaries
water of Strimonas river in the region of
Angistro.
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Operation of Hydroelectric units The
hydroelectric units use the energy of water and
by using a simple method change this energy into
electric current. This units are based on the
movement of water that turns a turbine which
brings in operation a generator. Most
hydroelectric units use a dam which retains a big
quantity of water creating thus a big reservoir.
Certain doors in the dam open and because of the
gravity the water passes in a driver which leads
it to a turbine. As it passes from the driver it
creates a big pressure. The water falls on the
propeller s of a turbine and makes it turn. This
movement is transported in the generator which is
connected with the turbine with an axis.
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The most usual type of turbine for hydroelectric
units is the turbine Francis which resembles to
a big disk with convex . Such a turbine can weigh
up to 172 tons and make 90 rotations per minute.
While the propellers of the turbine are turning,
the magnets of the generator are turned round an
inductor placing in movement electrons and
creating the alternating electric current. The
transformer takes the alternating current and
changes it into current of high potential.
Outside each hydroelectric unit exist four
cables the three phases of current that are
created simultaneously plus the neutral for the
three.
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Most hydroelectric units function in this way.
However ,another type of hydroelectric unit
exists. In a conventional hydroelectric unit the
water from the reservoir passes from the turbine
and leads again to the river. The new
hydroelectric units use two reservoirs. The
higher reservoir which assembles the water that
retains the dam and is used for the production of
electric current. The lower reservoir which
assembles the water that leaves from the
turbines, send it behind in the river. A reverse
turbine channels this water again behind in the
higher reservoir. Returning the water behind the
unit has more water for use in periods of peak.