Tech Briefs Magazine - October 2021 - 27a

DESIGN OPTIMIZATION
FIGURE 1          
            
          
FIGURE 2  
    
   
  
» FEEDBACK LOOP: THE EVOLVING
PRIORITIES OF THE DELTA WORKS
As would be expected from such a large and complex project,
construction of the Delta Works has lasted for decades (Figure
1). The project's priorities have continued to evolve over the 70+
years since it began. Along with providing protection from sea
storms, the Delta Works have also changed the regional ecosystem
- not always for the better. " In the 1950s and '60s, when the
project was designed, it was completely new. Nobody in the world
had done this type of waterworks before, " explains Van Halewijn.
" Concern for the environment was not like it is today. "
Aside from the semiopen barriers mentioned above, the
original Delta Works included dams that blocked off some
estuaries. This created new boundaries between salty seawater
and freshwater from the rivers. Behind the dams, areas that
had previously been subject to tidal action instead became
freshwater lakes. " Nowadays we see that was a mistake, " Van
Halewijn says. Since the 1970s, sluices have been installed in
a number of dams. These controlled passages are kept open
under normal conditions and are closed only during storms. By
reintroducing tidal cycles to the basins behind the dams, the
sluices have restored the salty conditions preferred by oysters,
mussels, and other coastal sea life.
» ENCORE AND WATER2ENERGY: RENEWABLE
ENERGY FROM VULNERABLE PLACES
While Zeeland's circumstances are unusual, rising sea levels
caused by climate change are threatening coastal regions
worldwide. The infrastructural expertise of the Netherlands,
learned from many centuries of bargaining with the sea, is
more globally relevant than ever before. In this context, it is
no surprise to see the Dutch lead cross-border initiatives like
Energizing Coastal Regions with Offshore Renewable Energy
(ENCORE).
A joint project funded through the Interreg 2 Seas program
and led by marine renewable energy expert MET/SUPPORT,
ENCORE recognizes the North
Sea region's vulnerability
to climate change, as well
as its potential as a source
of energy production. The
project, with partners from
the U.K., France, Belgium,
and the Netherlands, affirms
that 25% of European energy
demand could be met with
offshore renewable sources
by 2050. Three participating
companies are developing
offshore solar power, wave
energy technology, and a river
turbine. The third company,
Water2Energy, seeks to produce
power from the tidal flows
through Delta Works sluices.
» THE DARRIEUS
ROTOR: ADAPTING
A WIND TURBINE
FOR WATER
A place defined by the
restless movement of water
seems like an ideal setting
for hydroelectric production.
However, while tapping
into the potential of tidal
power seems simple, actual
conditions present many
challenges. Conventional
hydroelectric technology
(Figure 2) is not well suited
to installation in Delta Works
sluices. " The most common
design for water turbines
is the Kaplan-type rotor, "
explains Van Halewijn. " It
looks like the propeller used
to power a ship. It turns very
fast and if you place it in a
confined space, like the sluices
in our dams, it could damage
fish and other sea life, " he
says. To address these issues,
Water2Energy has instead
developed a vertical-axis
water turbine (VAWT) that
incorporates a Darrieus-type
rotor (Figure 3).
Named after Georges
Jean Marie Darrieus, who
patented the Darrieus
rotor for wind turbine use
in 1926, this design offers
potential benefits for water
applications as well. From
Water2Energy's perspective,
the most significant
advantage of a Darrieus rotor
is that its open structure
and motion would be far
less dangerous to fish than
that of a Kaplan-type rotor.
Would it be able to meet the
ambitious power production
goals of the ENCORE project?
To balance the need to
maximize electrical output
while minimizing ecological
harm, a number of challenges
inherent to the Darrieus
design had to be addressed.
COMSOL NEWS 27a
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Tech Briefs Magazine - October 2021

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