Hydroelectricity represents the 16% of the whole world electricity
production and there has been an increase by 2.6% per year, while the
electricity production from other sources has generally increased by 3% per
year. The electricity production is proportionate to the GDP of every country
and due to the economic crisis it has decreased in countries that have suffered
from austerity like Greece. In Europe and the USA hydroelectricity has been
stagnant, whereas in Asia and South America there has been a great increase of
hydroelectricity (more than 6% per year). Many countries in Europe have fully
or almost fully exploited the economically feasible hydro potential (in Norway
hydroelectricity production is about 99% of its total electricity), but in
Greece only the 31% of the feasible hydro potential has been exploited.
Greece’s low exploitation percentage of hydropower potential would allow for
spectacular development of hydroelectricity and would resolve a lot of water
scarcity problems at the same time. However, due to the mimetism of the Greek
society for European stereotypes no development towards this level was
observed. The mimetism opposes water resources development and the most
impressive example is the Mesochora project (170 MW, 340 GWh/year, investment
500 million of Euros) in the upper Acheloos River. The dam and the hydropower
plant have been constructed and are ready to use since 2001, however they have
not been put in operation, causing a loss of 25 million of Euros each year for
the national economy.
People who are not experts in
hydrology have spread a series of fallacies that are related with
hydroelectricity and I am going to list them below:
Fallacy 1: Hydroelectric energy is
not renewable
“Hydroelectricity is not renewable. Hydro dams irreversibly destroys
wild river environments- while the water is renewable, wild rivers are not.
Dams have a finite lifetime, but the wild river cannot be replaced”.
“Hydro power is not renewable. Hydroelectric power depends on dams, and
dams have a limited life- not because the concrete crumbles, but because the
reservoir fills with silt.”
Greek legislation refers that “The hydraulic power generated by
hydroelectric plants, which have a total installed capacity more than 15 MW, is
excluded from the provisions of this act”. After these quotes it can be said
that even if we assume that dams may destroy river environments (methods that
preserve the river environments have been discovered since the mid of the 20th
century), the energy that they produce does not make it non-renewable. In
addition, no human construction (including wind turbines and solar panels) have
unlimited life and the energy production from a dam does not stop if it is
silted. The fact that the Greek legislation excludes large-scale hydropower stations
is unacceptable and apart from this, the energy production is not reported to
the EU in achieving the renewable energy targets.
Fallacy 2: Environmental problems
created by dams are irresolvable
Environmental concerns about dams have helped find solutions for real
problems such as improved ecological functioning (permanent flow for habitats
downstream, improved conditions for habitats in reservoir, passages of
migratory fish). There have also been discovered solutions for sediment
management by appropriate design and operation (sediment routing, by-pass or
pass-through, sediment dredging and transport downstream), revision/increase of
non emptied reservoir storage for improved quality of water, ecosystems and
landscape and re-naturalization of outflow regime.
Fallacy 3: Large-scale energy
storage is beyond current technology
Engineers may have not yet developed energy storage devices suitable for
storing solar and wind power, however, pumping water to an upstream location
consuming available energy, which will be retrieved later as hydropower, is a
proven and very old technology with very high efficiency and are also called
“hybrid energy systems”. This feature of hydropower makes it unique among all
renewable energies and can be implemented even in small autonomous hybrid
systems. However it is substantially more advantageous in large-scale projects.
Fallacy 4: Hydroelectric energy has
worse characteristics than wind and solar energies
Large-scale hydroelectric energy has unique characteristics among all
renewable energies and has some very important advantages. It is the only fully
controllable regulated (as contrasted to the highly variable and uncontrollable
wind and solar). It also offers high-value primary energy for peak demand as
energy is produced when is demanded and not whenever there is wind or sunlight.
Additionally, it offers the unique option of energy storage, which is an
essential need for an energy system that includes renewable energy production.
It is a system that offers high efficiency as large-scale hydropower stations
with a percentage of more than 90%, while wind turbines have a betz limit of
59% which in practice is about 20% and the commercially available solar cells
have a percentage of efficiency that is about 17%.
Fallacy 5: Small hydropower plants
are better than large
The debate about large against the small projects seems to has been won
by the latter and this is evident from everyday news, scientific documents and
particularly from legislation. However, many countries/states consider small
hydropower plants as a renewable and large as non-renewable energy resource,
where the limit in Greece is 15 MW, in California and Maine 30 MW, 80 MW in
Vermont and 100 MW in Rhode Island and New Jersey. In Greece, a total of 250
small hydropower plants have been licensed with a total installed capacity of
430 MW. Only the capacity of the Kremasta hydropower plant in Acheloos river is
437 MW and this proves the irrational environmental policy that is applied in
Greece and other countries and states. How about the environmental impact of
large and small-scale dams? Elementary knowledge of geometry reveals that if a
certain volume V is divided in n geometrically similar shapes, the total area
is proportional to n1/3 and the total perimeter is proportional to n2/3(both
increasing functions of n). This simple truth has implications on several
fields, from the area occupied by reservoirs to the hydraulic losses in
conduits, turbines and pumps. There is no doubt that one large power plant, on
one river, with an installed capacity of 437 MW has much less environmental
impact than 250 small power plants on 200 rivers and creeks, with a total
installed capacity of 430 MW. Furthermore, only large-scale systems can
efficiently store energy and work as a hybrid energy system. At the image below
we can see that for large discharge (>10 m3/sec) we can achieve
efficient storage of energy (n>0.8), while for discharge Q<1 m3/sec
the efficiency degrades rapidly.
Image 1: Efficiency and discharge in
different systems of energy production.
Conclusions
From these facts we can infer
that we need to construct more dams in order to meet increased water and food
supply needs and at the same time more hydropower plants that meet energy needs
using the most effective renewable technology. With the building of hybrid
systems we can make it possible to store a high amount of energy and
realistically replace fossil-fuel-based energy with less uncertain and varying
renewable energy. Nevertheless, we support large-scale water projects because
only these are energy-efficient and multi-purpose and can be less damaging for
the environment than small-scale projects.
References
D. Koutsoyiannis, Scale
of water resources development and sustainability:
Small is beautiful, large is great (Invited), LATSIS Symposium 2010: Ecohydrology, Lausanne, doi:10.13140/RG.2.2.20564.40320, Ecole Polytechnique Federale de Lausanne, 2010.
Small is beautiful, large is great (Invited), LATSIS Symposium 2010: Ecohydrology, Lausanne, doi:10.13140/RG.2.2.20564.40320, Ecole Polytechnique Federale de Lausanne, 2010.
https://www.basf.com/tr/tr/we-create-chemistry/creating-chemistry-magazine/resources-environment-and-climate/a-world-of-water.html
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