First results of wave energy experiments within Theseus

First experiments on a wave energy farm within the Theseus project

Elisa Angelelli - University of Bologna; Department of Civil, Environmental and Materials Engineering.

In the period January-March 2011, a team of the University of Bologna (Italy) was warmly received by the Aalborg University team (Denmark) to perform new tests on a wave energy farm. All the experiments were designed and carried out by the Unibo Group, composed by: Elisa Angelelli, Mirko Castagnetti and Barbara Zanuttigh. The peculiarity of these experiments was that three devices at the same time were tested, simulating a farm. The main target was to analyze the hydrodynamic around the DEXA devices, in order to examine the possibility of a combined use for energy production and coastal protection. These experimental wave energy converters are still under development. So far, a DEXA prototype was installed in March off-shore Hanstholm (Denmark) and a new one has been recently deployed off-shore Gozo, along Malta Island coast.

Three down-scale devices of the DEXA type (www.dexawave.com) were kindly supplied by the constructor Lars Clausen (DEXA Founder, inventor and Chief Technical Officer Responsible for Concept and Innovation, This email address is being protected from spambots. You need JavaScript enabled to view it.) and tested in the 3D deep wave basin. This 15.7 x 8.5 x 1.5 m steel bar reinforced concrete tank has a snake-front piston type paddle system with a total of ten actuators, enabling generation of short-crested waves. The experiments were carried out in two scales (1:60 with three devices, and 1:30 with only one device), with different wave obliquity (incident wave propagation 0°-15°-30°) and, in case of the 1:30 scale, with two different mooring systems (spread and CALM). The facility measurements consisted of up to 27 wave gauges to record water level during the tests and a 1:30 scaled Power Take Off system to measure the energy efficiency. In short, the DEXA device seems to be promising both for energy conversion (hydraulic efficiency up to 30%) and for coastal protection (average wave transmission around 80%) especially when placed in a wave farm. In order to extend the experimental dataset, simulations with the software MIKE21 BW are scheduled for the next semester. These will also investigate the design and the effects of a hypothetical wave farm installation in one of Theseus project study sites. The complete elaboration of the experiments and the results and their elaboration are enclosed in the Report ID2.2 Report on physical tests on innovative coastal structures, preliminary version– WT2.1 “Hydrodynamic around a wave energy farm of DEXA devices”.