| Planning & projects
waves, has been clearly demonstrated during the C4’s operational period in Agucadoura. The verification of the amplified motion and power capture by the phase control system is seen as a key outcome from the HiWave-5 demonstration project. The tuning and detuning feature of CorPower Ocean’s WECs can be compared to wind turbines, where all modern turbines have a function to pitch the blades to alter the response to the wind conditions, limiting loads in storms while optimizing yield in regular conditions. We believe that adding such a similar function to wave energy is key for making it a reliable and competitive source of clean energy.
Power performance
During this commissioning period the primary focus has been on verifying safe and reliable operations in all ocean conditions and to rigorously test each system function. The device has been operated with limited motion envelopes, providing extra safety margins by limiting the maximum allowed velocity and machinery stroke, and a robust but simple power output controller has been used to control the machine for most of the period. Power export up to 600kW peak power has been recorded. The configuration of the electrical drive train has been
found to limit peak power to about 600kW. During the first on-land maintenance cycle adjustments to the drive train are planned, aiming to increase power capacity towards 850kW. Due to the limited motion envelope and the power limitation to 600kW, tuned operation has been limited to moderate sea states during this first operational period. In the sea states where tuned operation could be verified the measured power output has slightly exceeded predictions from the digital twin using the same machinery settings.
Calibration of digital twin The digital twin (a detailed numerical model) of the
system has been calibrated using the measured data on motion, power and internal machinery dynamics. The power conversion chain has been found to be accurately represented, with a close match between measured and simulated data, showing a typical goodness of fit in the range of 96-99%. This indicates that the Power Take Off components are accurately represented, with appropriate losses and efficiency maps. The hydrodynamic models have been found to slightly underestimate the power absorption from ocean waves into the WEC hull, which has resulted in measured motion and power in the ocean slightly exceeding predictions from the digital twin, for the measured sea states and the specific machinery settings used. Adjustments to non-linear correction functions of the hydrodynamic model can be expected going forward, based on the measured data and further informed by ongoing research on non-linear hydrodynamics in collaboration with leading academic groups.
Remote monitoring & control The functions for remote monitoring and control
have been verified from CorPower Ocean’s control centre. The C4 system was initially monitored 24/7 by operators, which could later be reduced to periodic check-ins as the commissioning program advanced and the supervisory system sent alarms to operators in case of events requiring attention.
The UMACK anchor The first commercial scale UMACK anchor developed
by CorPower Ocean in collaboration with European partners was installed at the Agucadoura site with a sandy seabed at 45m depth. Further details on this geotechnical innovation can be found here CorPower Oceans commercial scale UMACK anchor deployed. During the first operational cycle, with the C4 device connected to the UMACK anchor, stable station keeping was verified.
Operations & Maintenance (O&M) The methods for tow-out and connection of the C4
system was successfully demonstrated in August 2023 CorPower Ocean’s Wave Energy Converter Deployed in Portugal. After this, the methods for manned offshore access to the system could be reviewed and approved by third party safety reviewers, which has subsequently allowed CorPower Ocean technicians to access the machine on site to perform internal inspections and minor interventions. Following completion of the test cases of the first commissioning phase, the methods for releasing and towing back the device for a planned on-land check- up and maintenance cycle have been successfully demonstrated. The release process involves remotely actuating a quick-connector located between the bottom of the mooring system and the UMACK anchor, allowing the device to surface. The operational period has provided valuable learning on O&M-methods towards efficient low-cost operations of utility scale wave farms in the future.
Next steps The C4 system is now going through a planned on-land
check-up sequence. Adjustments and upgrades will also be performed based on the learnings collected from the first cycle of operation. When completed the system will be redeployed in Agucadoura, and the system will be taken through a ramp-up phase to demonstrate full power capacity including further advancement in control methods. When the commissioning program has been completed, a Power Performance Assessment phase will be initiated following the IEC/TS 62600-100 standard.
Above: The functions for remote monitoring and control have been verified from CorPower Ocean’s control centre
Below: The first commercial scale UMACK anchor developed by CorPower Ocean in collaboration with European partners was installed
First phase results
Summary of results from the first phase of C4 operations and commissioning: All key system functions verified. Ability to tune and detune according to varying sea states verified: Limiting response to extreme storm waves while amplifying motion and power capture in regular waves using novel phase control technology. Storm survivability: Proven in significant wave heights (Hs individual waves (Hmax)
) up to 11m and up to 18.5m.
Power export to the grid: peak power generation of 600 kW demonstrated; measured power output slightly exceeding predictions by the digital twin, for the specific machinery settings used during the period. Automatic tracking of tide, tidal regulator following tide variations. Remote control and monitoring from control centre. Digital twin calibrated for motion and power. UMACK anchor: Stable station-keeping verified. Operations & maintenance: successful demonstration of manned offshore access methods; successful disconnection & tow-back for planned on-land O&M cycle.
www.waterpowermagazine.com | April 2024 | 31
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