Waves in the nearshore
are directionally focused and have a huge horizontal force because of the effect
of the sea bottom. The EDS is designed for dealing with such wave characteristics.
The EDS combines a heaving float, supported by an arm hinged on a fixed
structure, and a surging paddle, top-hinged on the same arm, between the float
and the fixed hinge. The supporting arm is aligned along the wave propagation
direction.
The EDS is scalable according to the available wave power, with typical float diameter ranging from 3 to 8 m.
The energy is extracted by a PTO (Power take-off) connected to the arms of the bodies. This works through the rotation of a single main shaft to which is connected a permanent magnet generator controlled by an A.F.E. system.
Tests on the scale
model of the EDS, carried out at the Hydraulics Laboratory of the Politecnico
di Milano, have revealed a maximum capture width ratio CWR (efficiency) of more than 40%, measured as the rate
between the power absorbed by the EDS and the oncoming wave power. The main
publications on the EDS are:
-
Marchesi
E., Negri M.,
Malavasi S., 2020. Development and analysis of a numerical model for a two-oscillating-body
wave energy converter in shallow water. Ocean
Engineering 214, 107765. https://doi.org/10.1016/j.oceaneng.2020.107765
-
Negri M., Malavasi
S., 2018. Wave energy harnessing
through oscillating bodies. Energies
11, 2730. https://doi.org/10.3390/en11102730.
-
Malavasi S., Negri M.,
2015. Double system wave energy converter for the breaker zone. Special Issue
Ocean energy: Ongoing research in Italy. Rivista EAI, ENEA. https://doi.org/10.12910/EAI2015-047
One or more modules of
EDS can be installed outside the breakwaters of the port at a sufficient
water depth (about one diameter D of the float). The number of
EDS to install will depend on the need of electricity.
A preliminary simple estimate
of the mean annual power Pout that can be produced with the
EDS, utilizing a section of breakwater of length L, is the
following:
Pout= Pw ∙ L/2 ∙CWR
Where:
-
Pw [kW/m] is the mean annual available wave power for
unit crest width [kW/m]
-
L [m] is the length of the coast occupied (the
factor ½ is because some space between the EDS modules is needed). Therefore,
the total available wave power is Pw ∙ L/2
-
CWR is the mean annual capture
width ratio of the EDS, which can be interpreted as the mean annual absorption efficiency
of the EDS.
The mean annual available wave power Pw at the port is included in the range 1—2 kW/m (see the references). The table below reports two examples of calculation, assuming different values of the mean annual available wave power. It is assumed an annual mean efficiency CWR=30%. The optimal diameter D of the EDS increases as available wave power increases. The calculations are made considering a section L=100 m of the breakwaters.
Although this is a
first estimation and must be refined, it gives an idea of the power that can be
produced. This calculation considers the annual mean power. Actually, the power
extracted will present oscillations during the year, and a large part of the
energy will be produced in winter.
|
Case 1 |
Case 2 |
|
Mean annual wave
power available |
PW [kW/m] |
1 |
2 |
Mean annual power produced |
Pout [kW] |
15 |
30 |
Energy produced
in a year |
Eout [MWh/year] |
131 |
263 |
Diameter of the float |
D [m] |
3 |
4 |
Number of EDS modules |
n |
17 |
13 |
References
- - Ponce de Leon S., Orfila A., Simarro G., 2016. Wave energy in the Balearic Sea. Evolution from a 29
year spectral wave hindcast. Renewable
Energy 85,1192-1200. http://dx.doi.org/10.1016/j.renene.2015.07.076
- - Cascajo R., García E., Quiles
E., Morant F., Correcher A. 2020. Wave Energy Assessment at Valencia Gulf and Comparison
of Energy Production of Most Suitable Wave Energy Converters. Int. J. Environ.
Res. Public Health 2020, 17, 8473; http://dx.doi.org/ijerph17228473
Waves are a clean, renewable source of energy. Excluding the phases of construction and installation of the EDS, the transformation of wave energy into electricity does not involve CO2 emissions. The EDS has a minimal impact on the landscape and on the marine environment. The mechanical and electrical parts of the energy transformation are not in contact with the water.
https://www.tecnomac.it/it/eds-energy-double-system.html
Tecnomac S.r.l. has patented and developed
the EDS. Tecnomac was born in 1990 and has always been active in the field of
innovation. Tecnomac is specialized in designing and building special equipment
and multiple toolinh and special machines to run production processes
automatically.
Contact: info@tecnomac.it
http://www.fluidlab.polimi.it/main-topics/wave-energy-converter
The scientific investigation of the EDS has
been made at the Department of Civil and Environmental Engineering of Politecnico
di Milano. A laboratory scale model and a numerical model of the EDS have been developed.
The scale model of EDS has been tested at the Hydraulics laboratory of Politecnico
di Milano.
Contacts: marco.negri@polimi.it (marco.negri82@libero.it),