CorPower Ocean’s C4 wave energy converter (WEC) has completed the first cycle of the ocean commissioning program at the Agucadoura site in northern Portugal.
Now proven at commercial scale, CorPower Ocean’s C4 device has demonstrated ability to tune and detune according to varying sea states, limiting response to extreme storm waves (up to 18.5 m) while amplifying motion and power capture in regular waves using novel phase control technology.
The progression marks a crucial milestone for wave energy addressing the two major obstacles that have hampered commercial adoption – survivability and efficient power generation in normal ocean conditions, CorPower Ocean said. The inflection point provides a firm signal of wave energy’s readiness for widescale adoption.
Since deployment in August 2023, all key aspects of the C4 system functions have been verified, including power export to grid, automated control and monitoring of the system, and safe operations and maintenance methods.
The collected data allowed calibration of the digital twin, an extensive numerical model used to predict the system behavior. Measured motion and power output data from the machine operating with ‘WaveSpring’ phase control has slightly exceeded predictions by the digital twin for the machinery settings used.
The first operational phase was concluded by disconnecting and towing the device to CorPower Ocean’s on-land base in Viana do Castelo for its first planned maintenance cycle. This demonstration of efficient O&M methods is a key goal of the C4 deployment program, to support scale-up to future utility scale wave farms. After completing this check-up and maintenance cycle, C4 will be redeployed at the Agucadoura site and the demonstration program continued.
Storm survivability of the C4 WEC has been verified by weathering four major storms, with confirmation of the ability to recommence operations and power export to the grid after each. The most energetic period was experienced on Nov. 4, with storm Domingos sending swell to the site with wave heights up to 18.5 m, reported by the Hydrographic Institute of Portugal as a historical record.
CorPower Ocean and its pilot access program partners have been able to verify the design principles for robust operation in extreme waves offered by the Survival mode of the device. Operating in the detuned Survival mode, which is the natural state of the system, the device displayed small response to incident waves despite the WEC hull regularly becoming fully submerged during wave peaks during these storms.
The verification of very low response to storm waves is seen as one of the most important outcomes of the C4 ocean demonstration so far. The survivability results can be compared to the measured data with C4 operating in tuned mode where up to 3 m machinery motion has been observed in 1 m incident waves. By activating the WaveSpring phase control technology, the system starts oscillating in phase with the waves, which has been confirmed to strongly amplify the machinery response to the incident waves.
The ability to tune and detune the device according to ocean conditions, limiting the response to storms and amplifying the motion and power capture in regular waves, has been demonstrated during the C4’s operational period in Agucadoura. 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.
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. A robust but simple power output controller has been used for most of the period. Power export up to 600 kW peak power has been recorded.
The configuration of the electrical drive train has been found to limit peak power to about 600 kW. During the first on-land maintenance cycle, adjustments to the drive train are planned, aiming to increase power capacity toward 850 kW. Due to the limited motion envelope and the power limitation to 600 kW, 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.
The digital twin 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 of 96% to 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. 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.
The functions for remote monitoring and control have been verified from CorPower Ocean’s control center.
The first commercial scale UMACK anchor was installed at the Agucadoura site with a sandy seabed at 45 m depth. During the first operational cycle, with the C4 device connected to the anchor, stable station keeping was verified.
The methods for tow-out and connection of the C4 system was demonstrated in August 2023. After this, the methods for manned offshore access to the system could be reviewed and approved by third party safety reviewers, which has allowed CorPower Ocean technicians to access the machine on site to perform internal inspections and minor interventions. After 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 demonstrated.
