VGB POWERTECH 7 (2020) - International Journal for Generation and Storage of Electricity and Heat

A journey through 100 years VGB | Hydropower | VGB POWERTECH · Issue 10 (2006)
Hydro-power in Europe
logical requirements. One emerging concept
in terms of innovation is the tidal energy converter.
It consists in recovering the energy of
tidal currents using a technology which combines:
– hydraulics,
– offshore techniques (for the pipe-laying
operation),
– and wind processes.
Having said this, since the density of water is
1,000 times greater than air, the machines are
more compact: for a 1 MW machine, two rotors
having a diameter of 18 m are used for a
water turbine compared to a rotor of 60 m for
a wind turbine. Another advantage is the predictability
of production and the reduced visual
and environmental impact.
The drawbacks include the difficulties encountered
during installation, and also maintenance
which may be delicate.
In order for a site to be considered attractive,
the speed of the tidal currents must be greater
than 2 m/s.
In autumn 2006, an important step forward
will be taken with the installation in Northern
Ireland of the pre-industrial SeaGen water
turbine (1.2 MW; Figure 5). If the tests
carried out at sea and the industrialisation
phase of SeaGen are successful, a first tidal
energy facility producing around 10 MW will
be installed in Wales by EDF Energy in
2008. In France, EDF aims to operate tidal
energy before 2010.
Integration of the New
Environmental Aspects
From the very outset, hydro-power links the
notions of power generation with environmental
and nature conservation. The reservoirs
created by hydro-power are in some cases
biotopes worthy of protection today. Other
aspects, e.g. flood prevention, were always
guiding principles when planning hydro-power
plants. Storage power plants, for example,
can make a significant contribution to
managing flooding incidents, as the example
from Voralberg shows (Figure 6).
Nonetheless, the demands to take account of
ecological needs when operating, and above
all building, hydro-power plants have grown
in recent years. This largely involves three
points:
– increase of residual water in the old river
bed,
– making it possible for water animals to
pass through,
– general improvement in water body morphology.
Setting the direction in this area for hydropower
too is the European Water Framework
100 %
90 %
80 %
50 %
10 %
0 %
Example:
Vorarlberg,
August 2005
Directive (WFD). It demands and enables a
new definition of the balance between ecology
and water usage. A prerequisite for this is
avoidance of a one-sided, ecological fixation
in its implementation. This requires that hydro-power
plant operators intensively support
that implementation. That applies in particular
to the currently forthcoming phases of
“economic analysis” and “monitoring”. The
hydro-power plant operators must preserve
and expand the specific know-how needed to
do this. The goal is to prevent major differences
in implementation in Europe and to
exploit the opportunities for a pragmatic and
balanced process of implementation. The
WFD offers opportunities to do that, especially
through recognition of the Heavily Modified
Water Body and the separate appraisal
of hydro-power usage as an exceptional circumstance
per section 4.7.
The hydro-power plant operators stand for an
integrated approach to improving waterbody
Actual discharge
Retention through
storage power plant
Flood peak reduced by
approx. 15 %
Natural discharge
Figure 6. Flood control by storage plants. The storage power plant prevented towns
and villages from flooding reducing the flood peak by 15 % (Vorarlberg, 2005).
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Ecology
Improved water ecology in
the old river bed
Often addional CO 2
emissions through
substitute power
Partial compensation by
using the residual water for
power generation
Time
ecology. Improvements should first be agreed
at sites where a significant ecological improvement
can be achieved at the lowest cost.
Complex effects need to be considered when
making these decisions, as the example of increasing
residual water shows (Figure 7).
On the one hand, an increase in the residual
water in the old river bed improves the waterbody
ecology, but on the other hand this water
is no longer available for power generation,
thus leading to lost production and often
additional CO 2 emissions because of the substitute
power required. Depending on the specific
circumstances at the site, this generation
loss can be partly compensated for by use of
the residual water to generate power. But this
is only possible with high and additional specific
investments. Overall, high residual water
requirements can put the viability, especially
of smaller plants, in question. Only a balanced
increase of the residual water can integrate
all these aspects.
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Economy
High residual water
requirements can challenge
the economic viability
especially of small plants
Increase always leads to
loss of production
New, specifically higher
investments in the use of
residual water for power
generation
Figure 7. Pros and Cons of a increase of residual water flow demand for a balanced solution.
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