| dc.description.abstract | Interest in exploring renewable energy resources has increased globally, especially
with recent worldwide intentions to maintain the global climate. Looking at the
oceans as a vast sustainable clean energy resource to satisfy present high humankind
energy demands has been strongly recommended. Several types of renewable energy
resources exist in the oceans: waves, tides, thermal and salinity variations, currents,
and offshore winds. Exploiting tidal currents is considered one of the most effective
approaches to the generation of electricity. Tidal turbines are deployed beneath the
sea surface to transfer the kinetic energy in tidal currents to mechanical energy
suitable for ongoing conversion to electricity and subsequent transmission. However,
choosing a suitable site to deploy these turbines is not a trivial process. Various
constraints must be satisfied subject to basic criteria dependent upon local factors,
technology limitation and economic consideration. In addition, an important issue to
consider is taking care to harness energy from tidal currents with minimum possible
impact on the surrounding environment.
The present study justifies the nomination of the Strait of Messina as an exceptional
tidal current energy resource within the Mediterranean Sea basin. The maximum
tidal current velocity at spring peak tide through the Strait may exceed 3 m/s. This
mainly results from the tidal phase-difference (180°) between the northern
(Tyrrhenian Sea) and southern (Ionian Sea) tips of the Strait, associated with a
difference of 0.27 m in tidal wave amplitudes. In addition, the complex coastline
configuration of the Strait plays an important role in enhancing tidal current
velocities. Therefore, the Strait of Messina fulfils the basic criterion (2 m/s tidal
current velocity) to be considered as a valid tidal current energy resource. This
massive tidal current energy resource is assessed in the present study.
A detailed full desk-based Environmental Impact Assessment (EIA) study is
performed using the interactive matrix approach in order to investigate the
anticipated environmental impacts on the marine ecosystem of the Strait of Messina
resulting from the harnessing of energy from its tidal currents. Through the EIA
study the different environmental components, both biotic and abiotic, which may be
affected by the energy extraction process, are explained. In addition, the proposed
key project activities are listed; the likelihood of occurrence and the magnitude of impact interaction with the environmental components are evaluated. The final
judgment matrix guides to make a right decision on the proposed project. From the
resulted matrix, the major impacts do not exceed 10% of the total anticipated effects.
The positive point is that all the expected impacts, including the majors, can be
controlled and minimised to the lowest possible limits by applying a good
monitoring programme.
The University of Edinburgh “Tidal Flow Development (TFD)” numerical model is
used to mimic the tidal environment of the Strait of Messina in different cases. The
model successfully simulates the tidal flow regime within the Strait under some
exceptional conditions. Modifications to the main numerical code and coefficients
were necessary in the present research to adjust the model according to each case
study. In the three different cases of simulation, using these exceptional coefficients,
the model simulates the main tidal characteristics of the tidal flow within the Strait.
According to the results of the numerical simulation process, tidal currents are more
intensive close to the eastern coast of the Strait of Messina near to Punta Pezzo. This
area is far from any ferry route between Italy and Sicily. The best location to deploy
tidal turbines for the energy extraction process is therefore recommended to be
within these surroundings.
Finally, a physical (laboratory) model is used to simulate the flow regime within the
Strait of Messina. The Particle Image Velocimetry (PIV) technique was applied in
the flow-table tank at the University of Edinburgh. The physical model simulates the
flow behaviour within the Strait of Messina to a satisfactory degree. The cyclonic
and anti-cyclonic motions observed at the southern extremity of the Strait are also
very well simulated.
The results of the present study assure confidence in the use of tidal currents within
the Strait of Messina as a renewable energy resource. The safety of the environment
must be ensured by following environmental guidelines, respecting the energy
extraction limits and by applying an effective monitoring programme. The later is
strongly recommended to be an adaptive one in which higher environmental
authorities are able to watch, revise and control the environmental team within the
project. These authorities are also able to postpone the project in case of any severe
environmental case. The simulation processes emphasize the effect of morphometry and topography in enhancing tidal currents in the Strait of Messina. Moreover,
numerical simulation assures that the complex morphometry and bathymetry, in
addition to the open boundaries of the Strait of Messina, are challenging issues for
modellers in order to mimic the real tidal current resource in the case of the Strait of
Messina. The study also strongly recommends applying a more effective numerical
model than TFD to assess the tidal hydrodynamical environment before and after any
proposed energy extraction process. This will certainly, with the EIA of the marine
ecosystem, help to make a right decision about the proposed project in order to
achieve the goal of using clean and clear renewable energy resources while
maintaining both natural and hydrodynamical environments to the most possible
safest degree. | en |
