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Fred Olsen is currently testing their latest wave energy converter (WEC), Lifesaver, outside of Falmouth Bay in England, preparing it for commercial operation at the Wavehub test site. Previous studies, mostly focusing on hydrodynamics and peak to average power reduction, have shown that this device has potential for increased power extraction using reactive control. This article extends those analyses, adding a detailed model of the all-electric power take-off (PTO) system, consisting of a permanent magnet synchronous generator, inverter and DC-link. Time domain simulations are performed to evaluate the PTO capabilities of the modeled WEC. However, when tuned towards reactive control, the generator losses become large, giving a very low overall system efficiency. Optimal control with respect to electrical output power is found to occur with low added mass, and when compared to pure passive loading, a 1% increase in annual energy production is estimated. The main factor reducing the effect of reactive control is found to be the minimum load-force constraint of the device. These results suggest that the Lifesaver has limited potential for increased production by reactive control. This analysis is nevertheless valuable, as it demonstrates how a wave-to-wire model can be used for investigation of PTO potential, annual energy production estimations and evaluations of different control techniques for a given WEC device.
Jonas Sjolte; Christian McLisky Sandvik; Elisabetta Tedeschi; Marta Molinas. Exploring the Potential for Increased Production from the Wave Energy Converter Lifesaver by Reactive Control. Energies 2013, 6, 3706 -3733.
AMA StyleJonas Sjolte, Christian McLisky Sandvik, Elisabetta Tedeschi, Marta Molinas. Exploring the Potential for Increased Production from the Wave Energy Converter Lifesaver by Reactive Control. Energies. 2013; 6 (8):3706-3733.
Chicago/Turabian StyleJonas Sjolte; Christian McLisky Sandvik; Elisabetta Tedeschi; Marta Molinas. 2013. "Exploring the Potential for Increased Production from the Wave Energy Converter Lifesaver by Reactive Control." Energies 6, no. 8: 3706-3733.
Most Wave Energy Converters (WECs) produce highly distorted power due to thereciprocal motion induced by ocean waves. Some WEC systems have integrated energystorage that overcomes this limitation, but add significant expenses to an already costlysystem. As an alternative approach, this article investigates the direct export option thatrelies on aggregate smoothing among several WECs. By optimizing the positioning of theWEC devices with respect to the incoming waves, fluctuations may be mutually canceledout between the devices. This work is based on Fred. Olsen’s WEC system Lifesaver, anda WEC farm consisting of 48 devices is designed in detail and simulated. The major costdriver for the electrical export system is the required oversize factor necessary for transferof the average power output. Due to the low power quality, this number can be as high as20 at the entry point of the electrical system, and it is thus crucial to quickly improve thepower quality so that the downstream power system is efficiently utilized. The simulationsundertaken in this work indicate that a high quality power output can be achieved at the farmlevel, but that a significant oversize factor will be required in the intermediate power systemwithin the farm.
Jonas Sjolte; Gaute Tjensvoll; Marta Molinas. Power Collection from Wave Energy Farms. Applied Sciences 2013, 3, 420 -436.
AMA StyleJonas Sjolte, Gaute Tjensvoll, Marta Molinas. Power Collection from Wave Energy Farms. Applied Sciences. 2013; 3 (2):420-436.
Chicago/Turabian StyleJonas Sjolte; Gaute Tjensvoll; Marta Molinas. 2013. "Power Collection from Wave Energy Farms." Applied Sciences 3, no. 2: 420-436.