Co-design has been successfully utilised in wind turbines to improve efficiencies and reduce levelised cost of energy (LCoE). Currently, wave energy converter (WEC) controllers are designed once the physical device is mostly finished. Introducing a co-design philosophy to WEC design could help bring down it’s LCoE to competitive levels

Forehand, David

Onslow, Matthew

Stock, Adam

Heriot Watt Pure

Co-design of controllers in wave energy converters

University of Strathclyde Institutional Repository

Matthew OnslowSupervisors: Adam Stock, David ForehandCo-design of Controllers in Wave Energy ConvertersWind & Marine Energy Systems CDT, Rm 3.36, Royal College BuildingUniversity of Strathclyde,  204 George Street, Glasgow, G1 1XWmatthew.onslow@strath.ac.uk[1] – Hong et al, Review on electrical control strategies for wave energyconverting systems, Renewable and Sustainable Energy Reviews, 2014 [2] – Mason & Dhoop, Occurrence of Bimodal Seas around the English Coastline, 2018[3] – Guedes Soares, Representation of double-peaked sea wave spectra, Ocean Engineering, 1984[4] - Marine Offshore Renewable Energy (MOREnergy Lab), Politecnico di Torino [5] – FloWave Ocean Energy Research Facility, https://www.flowavett.co.uk/3. The PhDThis PhD will investigate the potential improvements from taking a holistic approachto the design of a WEC.Designing controllers that incorporate PTO efficiency Package controllers into a toolbox for use by othersValidation of controllers as part of HAPiGYMInvestigation of the interaction between different WEC geometries and controllersReview of the benefits of a holistic design processHAPiWECThis PhD is aligned with the EPSRC funded HAPiWEC(Holistic Advanced Prototyping and Interfacing forWave Energy Control) project.The HAPiWEC team is proposing that through theimplementation of rapid-prototyping hardware andremotely accessible user control, novel controlalgorithms can be created, demonstrated, andvalidated at unprecedented levels of efficiency.FloWave Ocean Energy Research Facility at the University of Edinburgh [5]A ‘comparative evaluation’ will be launching later thisyear, where participants will be able to test their owncontrol algorithms remotely on a WEC based at theFloWave research facility. The comparative evaluation,called ‘HAPiGYM,’ will have a variety of availablemetrics for participants to pick from, allowing them todecide which factors are most important to their controlscheme.Aligning with the HAPiWEC project will allow for theopportunity to contribute controllers to the HAPiGYMreference controller set, providing the opportunity tovalidate the PhD’s controllers in a wave tank.1. Why Co-design?Co-design has been successfully utilised in wind turbinesto improve efficiencies and reduce levelised cost ofenergy (LCoE). Currently, wave energy converter (WEC)controllers are designed once the physical device ismostly finished. Introducing a co-design philosophy toWEC design could help bring down it’s LCoE tocompetitive levels.The figure above shows the improvement in energycapture from controlling a WEC. Studies have suggestedimprovements in energy capture ranging from 14 – 50%depending on technology [1]. Using a co-designmethodology could lead to further enhancements.Figure from [1]2. Pieces of the puzzleWave ResourceVery little can be done to alter the waveresource, having a solid understanding of it’snature will influence choices madeelsewhere in the design process.For example, in bimodal sea states (thosewith two dominant wave frequencies), theconditions a WEC experiences is much morecomplex, possibly requiring the use of a moresophisticated controller. On the right, thefigure shows the occurrence of bimodal seasacross the English coastline, showing at somesites, the occurrence is significant enough toneed to be considered [2]. More broadly, inthe North Atlantic, bimodal seas occur 40%of the time in low wave heights [3].Power Take-off (PTO)There is a multitude of different PTO technologies to choose from, for examplehydraulics, linear generators, or rotary generators. The choice of which dependsupon many factors, such as the expected forces upon the PTO, and optimaloperating frequency.GeometryThere are many different types of WEC, each withtheir own optimal conditions and controlstrategies. On the left, there are four completelydifferent designs that all fall under the banner of‘WECs.’Deciding on which design, and then thedimensions of that design have implications forthe other components, for example the forces thePTO will experience, and the resonant frequencyof the device.ControllerControllers are in charge of making the moment by moment decisions in how a WECoperates, so it is important it has been designed with a detailed description of all ofthe WEC’s components to ensure it can operate at peak efficiency.Similarly, different control algorithms operate better under different situations, forexample in model predictive control a model is used to predict the best decisions tomake. Designing the WEC with a simpler geometry would allow for this model tooperate much more effectively.Figure from [2]Graphics from [4]

https://strathprints.strath.ac.uk/84423/1/Onslow_etal_FWM_2023_Co_design_of_controllers_in_wave_energy_converters.pdf

Co-design of controllers in wave energy converters

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Heriot Watt Pure

University of Strathclyde Institutional Repository

Heriot Watt Pure