IFP Energies nouvelles’ (IFPEN) ‘Wave Energy Converter Control’ project, led by Paolino Tona, has won an award for the first phase of the WEC Control Competition (WECCCOMP).
According to Paolino Tona, project manager at IFPEN, the evaluation of the experimental phase is still running.
WECCCOMP, organized by the Centre for Ocean Energy Research (COER, Ireland), the National Renewable Energy Laboratory (NREL, USA), Sandia National Laboratories (USA), and Aalborg University (Denmark), is an open competition which compares energy-maximizing controllers for wave energy converters (WECs), both in simulation, and in real time, using a scale device in a tank test situation.
“This prize confirms the excellence of IFPEN’s R&I for WEC control systems, which have a crucial part to play in industrially rolling out WECs,” IFPEN said.
Harvesting energy from waves is considered to be a promising technical solution that, ultimately, could cover from 5% to 20% of global electricity consumption.
A considerable reduction in current costs that the European Commission estimates at least a 75% reduction by 2025, will be necessary for wave energy to become competitive compared with other forms of renewable energy.
For several years, IFPEN has been working to develop solutions to a range of estimation and control problems for WEC systems, with a view to satisfying the needs expressed by certain industrial partners, the company explaines.
In particular, IFPEN has developed full control systems, designed more specifically for point absorbers and attenuators, such as the Wavestar machine. That machine is made up of a set of 20 hemispherical floats being connected to a fixed structure via hinged arms housing the Power Take-Off (PTO) systems.
The most advantageous control system for this type of WEC is a non-linear Model Predictive Control (MPC) system.
This control system was validated by tank tests at Aalborg University, on a small-scale model of a Wavestar float, subjected to the action of different irregular waves.
Power generation gains of about 20% were observed for the most representative waves, compared with the initially proposed reference control.
With a view to developing a modular approach, with control systems that are of different complexity, and that are adaptable to different machines, IFPEN has also proposed a simpler control system referred to as an “adaptive PI control” system.
This approach, which can easily be applied to the majority of WEC machines, makes it possible to improve energy harvesting by at least 10% relative to the reference control in constant sea states, and potentially by much more in changing sea states.
It should be noted that this work has also produced an additional result, by restricting a principle of conventional hydrodynamic control theory. That principle indicates that the optimum velocity of the primary converter should be in phase with the wave excitation force in order to maximize power generation. Whereas actually that is false when the conversion efficiency of the PTO is not ideal, the company added.