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Developing the PTO of the first MW-level Oscillating Wave Surge Converter

Periodic Reporting for period 1 - MegaRoller (Developing the PTO of the first MW-level Oscillating Wave Surge Converter)

Reporting period: 2018-05-01 to 2019-10-31

What is the problem/issue being addressed?
Despite its attractive characteristics wave power entails significant challenges that have so far prevented it from becoming a mainstream energy source.

Why is it important for society?
Assuming 100GW of installed capacity by 2050, some studies estimated that the wave energy sector could supply 10-15% of EU power demand, reduce EU dependency on energy imports, create 500,000 jobs and contribute to diversification and decarbonization of the economy.

What are the overall objectives?
This project will focus on oscillating wave surge converters (OWSCs), and more specifically on the design, construction and validation of a high performance, cost-efficient and reliable PTO. The MegaRoller project aims to reduce the levelized cost of energy (LCOE) of the system below €150MWh, by increasing nominal device capacity, reducing the number of components, increasing the PTO reliability (lower CAPEX, OPEX and higher availability) and reducing power conversion losses.
WP1 Interaction with wave resource
In WP1, a nonlinear model of the WEC was built in WEC-Sim, enabling the assessment of the distributed loads affecting the system and of the different pressure contributions over the panel of the new MegaRoller. The model was developed to enable the assessment of survivability and reliability metrics for a range of design situations. Such load characterisation exercise was initiated with a review of critical design standards / codes and device specific design conditions to define a set of critical design load cases (DLCs). The impact of novel control algorithms was also considered and the results of wave-by-wave prediction-based control methods compared to the performance of a traditional control algorithm with stiffness and damping optimised for each sea-state.
Following documents were delivered: D1.1 Advanced wave-structure interaction WEC model – theory and user manual, and D1.2 Definition of priority DLCs and load characterisation report.
The test bench upgrade design as well as the procurement process to acquire the required elements were initiated, in close collaboration with AWE.

WP2 Design
In WP2 the conceptual hydraulic, electrical, mechanical and automation design was completed, and detailed design started. Preliminary LCC report was conducted and models for Environmental Impact Assessment (EIA) and Socio-Economic Impact Assessment (SEIA) generated.
The conceptual design of the PTO includes e.g. functional block diagrams, hydraulic, automation and electrical diagrams, selection of main components and supporting calculations. During the reporting period the detailed design was started. 3D-modelling of the PTO rack and the PTO parts was done, and continued to FEM analysis, manufacturing and assembly drawings.
Numerical electrical WEC array modelling and WEC array simulations were started. “Electricity market integration study: levelized value of energy” was conducted by SINTEF.
3-D modelling and scaled FEM for Drive Train Mechanism and resilient mounting concepts for PTO-Panel -connection solving challenges in alignment were generated.
The documents delivered: D2.1 Conceptual hydraulic design, D2.2 Conceptual electrical design, D2.3 Conceptual control system design, D2.4 Preliminary LCA report, D2.5 Conceptual mechanical design, D2.6 Environmental Impact Assessment (EIA) and Socio-Economic Impact Assessment (SEIA) models.

WP3 Implementation
Implementation work has started on the control system implementation side. LIN has developed a machine-learning algorithm to produce wave-by-wave predictions to be used in PTO damping control for optimized power capture. Deliverable 3.1 Wave Prediction Software describes the work.

WP 4 Integration
No work has been performed for this work package.

WP5 Validation & Impact Evaluation
A study on verification and validation processes has been conducted. The aim was to form an overall framework for validation activities and to clarify the purpose of validation activities and their objectives.
A functional description of the PTO system has been generated forming the basis for all reliability engineering activities.
Further on, a method has been delineated to plan and schedule monitoring activities in marine renewable energy sites.

WP6 Dissemination, Standardization & Exploitation
Partners have been involved in several events, workshops, conferences and stakeholder activities. 20 Conference talks or papers in conferences and events have been given and one joint side event was promoted and arranged in Dublin at the Ocean Energy Europe OEE 2019 conference (about 450 relevant stakeholder delegates) with 5 presentations from 4 partners. 3 blogs of the activity and scientific aspects have been written for the web-site and there are also several open articles for the general public. Video interviews of industry partners ABB, Hydroll and Hydman and the role of their product gives relevance to the industry. AW-Energy hosted a
The charge level of the hydraulic piston accumulators is normally measured by special sensor integrated to each accumulator. Test setup for testing the charge level of set of accumulators has been implemented. It seems that this is inexpensive and adequately accurate way to determine the energy content of a set of accumulators for implementation of advanced energy storage control.
LIN has developed a machine-learning algorithm to produce wave-by-wave predictions to be used in PTO damping control for optimized power capture. This algorithm is based on Echo State Networks that has been modified to mimic the auditory cortex of the brain. New ways of training the ESN has also been developed.
It has been shown by CAT that by applying wave-by-wave damping instead of traditional periodical damping coefficient it is possible to capture significantly more energy from the movement of the panel.
MegaRoller PTO test rig and PTO 3D-model