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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - WaveBoost (Advanced Braking Module with Cyclic Energy Recovery System (CERS) for enhanced reliability and performance of Wave Energy Converters)

Teaser

Summary

WaveBoost aims at providing a step-change improvement to the reliability and performance of PTOs (Power-TakeOffs), by developing and validating an innovative braking module with a Cyclic Energy Recovery System (CERS). While built and tested on the platform of the existing CorPower technology, the CERS braking module can be integrated in many types of Wave Energy Converters (WECs). Especially for point absorbers - undisputedly the WEC type with best prospects for large-scale development - WaveBoost will solve a central reliability challenge, the socalled \'end-stop\' problem (excessive, uncontrolled forces when linear movement reaches end of stroke). Further, dedicated reliability assessment methods will be developed and applied. CERS is an energy redistribution system that will allow WECs to absorb more energy from high energy wave cycles, temporarily storing excessive energy in the first step of the PTO chain, then releasing it for conversion through the remaining steps of the PTO in low energy wave cycles. Similar systems are being used in other sectors (e.g. automotive) but have not been applied to ocean energy. The additional damping force required to safely stop the motion of WECs in storm waves may be several times larger than the PTO force used to convert wave motion into electricity. By providing the extra damping needed from the CERS module, system survivability and reliability of critical components are significantly improved. Another consequence is a size reduction of the PTO for the same power rating, and an increase of the Annual Electricity Production (AEP). The technology allows WECS to operate at higher average loading, increasing average conversion efficiency. Further, the grid compliance of electricity produced is significantly improved through this new energy storage concept. The improvements described above are expected to significantly reduce shock loads on WECs, increase in AEP of 25% and reduce LCOE more than 30% compared to the state of art.

Work performed

The CERS system has been evaluated through an initial risk and failure modes analysis, where critical components and functions were identified. These critical components have been further analyzed and evaluated for reliability and robustness, as input to the continued design, prototyping and test program. The system reliability is critical to get to a point where a third party can issue a statement of feasibility, and the test program is designed to secure robustness as well as functionality and efficiency. The time domain model has been developed an iterated through several design proposals to give correct design input in terms of design load cases, component dimensioning and selection and system architecture. The numerical design and parameter tuning is an ongoing activity that will ensure LCOE optimization of the system. The system requirements have bene identified and broken down to module (sub-system) requirements, iterations have been done on both requirements and preliminary design when investigating manufacturability and cost of goods for different solutions. Engineering calculations have been performed to size components and include FEM and CFD as well as handbook calculations and dimensioning against DNV standards and European directives. The integration and functional test planning revealed critical components that need specific robustness and life length testing that could not be performed by suppliers in their normal product verification. Custom test rigs have been designed and built to test the very specific properties and performance of components for the marine renewable energy sector. Condition monitoring is key for performance and robustness of the wave energy converter, the requirements for a full scale device has been investigated and the control system is being tested in the reliability test rigs. The overall techno-economical tools have been prepared and the LCOE analysis is continuously evolving to stay on target for a sustainable energy production.

Final results

A) The Novel CERS braking module for Wave Energy Converters
In response to the R&D needs identified, the WaveBoost project will focus on developing a new subsystem to deliver significant and measurable improvements in reliability and survivability, performance and cost. As an additional benefit, and further contributing to improvements in cost and availability, significant improvements in grid integration will be delivered. The novel Cyclic Energy Recovery System (CERS) braking module consists of building blocks that are well understood in other sectors including automotive, air-planes and rail road infrastructure but has, to date, not been applied to WECs. This provides the opportunity for a new generation of end-of-stroke braking system, delivering improvements of the current state-of-the-art. In many cases, it can be argued that for the wave energy sector no performance benchmarks are yet established. It is the ambition of WaveBoost to fill this gap in key areas for credible future predictions, as well as set higher limits of performance indicators already existing.

B) A new business model
During the development of CorPower Oceanâ€™s WEC technology, the interest from other developers as well as other industries have led to the consideration of a new business model for CorPower Ocean: that the technology development may be better valorized by being a supplier of PTOs or subsystems instead of being a full WEC system supplier. Such shift could allow for better focus and optimization of resources and skills, while reducing the high uncertainty both upstream (technical risks and funding) and downstream (market risks). In the short term however, due to the lack of commercial wave energy systems where the CERS module could be integrated and due to the lack of verification in full scale, CorPower Ocean is continuing with the development of the entire WEC system. Once proven in first arrays, the opportunity to narrow the focus to the PTO or subsystems may be attractive.

C) An advanced hardware-in-the-loop (HIL) test rig for WECs
Further advance to the sector will be providing new methods and testing infrastructure. By enhancing the HIL test rig with a wet chamber, the project will enable EMEC to provide valuable new services to the industry, providing a new infrastructure to accelerate technology development at a lower cost and risk.

D) New and improved methods for the sector
Also, the application of reliability assessment and improvement methods from other sectors including automotive by SP (VMEA, see WP 6) and offshore wind by EDP will be established for wave energy converters and first benchmarks provided to the sector, advancing the sector\'s credibility. Methods and tools on performance assessment (WP5) and LCOE modelling (WP6) will also be enhanced and validated, allowing WAVEC and the University of Edinburgh (UEDIN) improve their services.