The Basque Energy Agency commissioned the Mutriku Wave Power Plant, using an Oscillating Water Column technology in 2011, and although the cumulative total power has been over 3 GW/h until 2023, the initial expectations of efficiency and LCoE have not been accomplished. This paper proposes a series of modifications to the breakwater and chamber geometry of the plant to increase energy production and efficiency. These proposed improvements were tested in experimental campaigns in the modular wave flume in the Energy Engineering Department at the University of the Basque Country, using a mock-up of the original installation. Some results also came from validated numerical simulations, showing that the response amplitude operator and the capture width ratio values were better than those in the original L-shaped power plant. The best configurations appear to be U-shaped and when harbor walls are used. In conclusion, this paper reports the proper configurations and localizations for new wave power plants that could be commercially competitive.

The research presented was conducted to quantify the effects of butterfly and gate valves located upstream water meters with diameters larger than 50 mm. Errors caused by these valves can have an enormous financial impact taking into consideration that a small percentage of variation in the error of a large meter is typically related to a significant volume of water. The uncertainty on the economic impact that a valve installed upstream of a medium size water meter leads to many water utilities to oversize the meter chambers in order to mitigate the potential negative errors. Most manufacturers approve their meters for a specific flow disturbance sensitivity class according to the standard ISO 4064-1:2018. Under this classification, a correct operation of the meters requires a certain length of straight section of pipe upstream the meter. However, this classification of the meters cannot consider all types of flow perturbances. For this study, two types of valves, butterfly and gate, were tested upstream ten brand-new water meters from six different manufacturers constructed in four different metering technologies: single-jet, Woltmann, electromagnetic and ultrasonic. In each meter unit was tested at five flow rates, from minimum to the overload flow rates. The tests were conducted with valves set in different orientations, closing degrees, and upstream distances from the water meters under study. The research shows that the valves used can produce significant deviations in the measuring errors with respect the errors found for undistorted working conditions.

A wave flume of 12.5 x 0.6 x 0.7 m (length x width x height) able to reproduce the ocean conditions of the most representative research facilities in the Basque Country (BiMEP-Biscay Marine Energy Platform and Mutriku Wave Energy Plant) has been recently installed at the laboratory of Fluid Mechanics of the Faculty of Engineering in Bilbao. This new facility has the capacity of producing a wide range of monochromatic and panchromatic waves by a piston-type wavemaker. Several ultrasonic wave probes measure the surface elevation, and the wave energy is dissipated in a passive parabolic beach in order to diminish significantly the reflection along the flume. A numerical model based on Reynolds Averaged Navier Stokes (RANS) equations has been developed to represent the turbulence and Eulerian Volume of Fluid (VOF) unsteady approach in STAR-CCM+ CFD code to track the evolution of the free surface. This numerical model has been validated with the corresponding experimental campaign covering a wide range of depths, wave heights, wavelengths and periods. Tests focused on the description of the basic hydrodynamic processes of wave generation and propagation, giving as a result the definition of the wavemaker to produce the required wave. Results were analysed together with the analytical solution based on potential flow theory. The experiments carried out in the present study establish the operational limits of the wave flume in terms of wave generation, propagation and extinction, defining the operational range of future experimental campaigns where wave interaction with floating structures, wave energy converters and mooring systems will be studied. Keywords: experimental wave flume, numerical wave flume validation, wave characterisation, BiMEP, renewable marine energy, CFD models