Wavespring technology

Providing a practical solution for phase control

For heaving wave-energy converters like the CorPower device phase control is crucial in order to harvest energy from waves of different lengths efficiently. The WaveSpring technology provides phase control by a negative spring arrangement that makes the wave energy converter responsive throughout the range of normal ocean waves.  It works without the need for real-time wave information or prediction algorithms. The negative spring module acts directly on the buoy hull and eliminates the need of cycling large energy flows through the PTO system, a challenge that has limited the practical use of phase control methods known as reactive control.

Reducing cost and complexity

For heaving wave-energy converters like the CorPower device phase control is crucial in order to harvest energy from waves of different lengths efficiently.  The WaveSpring technology provides phase control by a negative spring arrangement that makes the wave energy converter responsive throughout the range of normal ocean waves.  It works without the need for real-time wave information or prediction algorithms. The negative spring module acts directly on the buoy hull and eliminates the need of cycling large energy flows through the PTO system, a challenge that has limited the practical use of phase control methods known as reactive control.

Compared to other phase control methods such as latching and clutching, or PTO-driven reactive control, the WaveSpring principle offers similar amplification of power capture while using a smaller and less costly PTO. The device motion is continuous, which eliminates the fatigue and wear challenges associated with more abrupt motion resulting from latching or clutching control. Combined with tribological advantages this improves reliability and component lifetime. Since no real-time information on the incident waves is required for the phase control, the number of sensors and active control loops can be reduced, making the system less complex.

Increasing the power output

Extensive testing and benchmarking with alternative PTO solutions conducted within the HiWave project shows that the annual average power output of a point absorber can be increased by more than 300% using WaveSpring, as compared to systems without phase control. The Annual Energy Production per PTO force is also increased by approximately 300%. The results represent a breakthrough for wave power. The step-change improvement in performance is provided by a low-cost spring arrangement using proven components adding a minimum of cost and complexity compared to the same system without phase control. Moreover, WaveSpring provides the critical function for detuning the device in storms – making it more transparent to the large energy flux of storm waves, just like the design principle for conventional offshore structures. The detuning feature has been shown to significantly reduce the loading of the equipment during the test campaign.ing the system less complex.