experimental testing of a linear absorber wave energy ... · a series of tests with a model of a...
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Experimental testing of a linear absorber wave energy converter: Effects of the mooring system
Abstract A series of tests with a model of a linear absorber wave energy converter (WEC) were performed at the wave tank of the Technology Research Center
of the University of A Coruña, with the objective of determining its dynamical behaviour in waves and the generated power.
Two types of tests were performed in regular waves with different heights (HW) and periods (TW). Also, irregular waves using the Jonswap spectrum
were tested.
Model description The tested model was a WEC for low wave energy potential seas denominat-
ed Butterfly and designed by Rotary Wave S.L. The device has a main body, whose geometry is similar to a spar buoy, with a pulley and two axes, one on
the bow and one on the stern. It also comprises a set of floats that can turn around these axes. The floats use the rise and fall motion of the waves to
capture the energy.
Test description Two types of tests were carried out:
Fixed: the model is fixed to the seabed with an additional structure. Floating: the model is anchored by two chain lines.
In both cases, regular waves with HW ranging from 1.3 m to 2.6 m and TW from
3.61 to 5.41 seconds were tested to determine the WEC behaviour and the
impact of the waves on it. The generated power has been studied by modify-ing the external torque applied on the WEC pulley.
The behaviour of the floating model was also tested in irregular waves, using the Jonswap spectrum, with 1.5 m significant wave height and 5.79 seconds
of peak period.
V. Díaz Casás 1 , L. Santiago Caamaño 1, M. Míguez González 1, A. Novás Cortés 2, J. Rubio Planells 2
1) Integrated Group for Engineering Research, University of A Coruña, Spain. 2) Rotary Wave S.L., Valencia, Spain.
Its survivability was studied for the case of a large solitary wave (tsunami
wave). In the floating cases, the tension in the mooring lines was calculated. Tests for the characterization of the hydrodynamic coefficients of the WEC
were also carried out.
Results In Figure 1, the WEC efficiency coefficient (CP) as a function of wave frequen-
cy to pulley frequency ratio ( λ) is shown. In floating condition, the WEC effi-
ciency decreases significantly with HW, and is less sensitive to the variation of
TW. In the fixed model, the efficiency is highly dependant on both HW and TW.
It can be concluded that in both cases, fixed and floating WEC, the efficiency
is degraded with the increase of HW and TW.
Finally, in Figure 2 and 3, roll and pitch motions of the WEC under two differ-ent regular wave conditions with the same TW and different HW are shown.
Contact information: Integrated Group for Engineering Research, University of A Coruña, Spain — [email protected]