All-electric Wave Energy Converter array with energy storage and reactive power compensation for improved power quality

Sjolte, Jonas; Tjensvoll, Gaute; Molinas, Marta

doi:10.1109/ecce.2012.6342716

Cited by 15 publications

(9 citation statements)

References 4 publications

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“…In our earlier publication [13], we showed that the peak to average ratio would be directly reduced by a factor of 3-5 due to natural power smoothing between the devices. The peak-to-average ratio could be further improved towards 1.5 by implementing a small energy storage, as shown in our work [14]. As will be demonstrated in the following, the peak power rating for the current configuration is close to three, which will require a rated installed converter capacity of about twice the average exported power.…”

Section: Arraymentioning

confidence: 77%

“…Still, this will require a converter with twice the cost compared to an average exported power, and measures to further improve the power quality should be kept in mind. Our previously published paper [14] indicates a final peak-to-average ratio for the array between 1.5 and 3 after energy storage is included, the exact figure being a result of economic optimization. The total aggregate wave farm power is calculated by adding up the six array outputs.…”

Section: Resultsmentioning

confidence: 99%

“…The power transfer chain is believed to be economically efficient, although some components within the wave farm require significant over-capacity. Earlier studies of annual power have shown annual full-load export capacity of approximately 3500 hours per year [14], and with the improvements that the farm configuration brings, it is believed that an annual full-load export capacity of more than 4000 hours per year will be attainable. This is better than land-based wind turbines which, on average, provide approximately 2500 full-load hours per year [20], and is believed to be competitive with offshore wind farms.…”

Section: Discussionmentioning

confidence: 99%

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Power Collection from Wave Energy Farms

2013

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Most Wave Energy Converters (WECs) produce highly distorted power due to the reciprocal motion induced by ocean waves. Some WEC systems have integrated energy storage that overcomes this limitation, but add significant expenses to an already costly system. As an alternative approach, this article investigates the direct export option that relies on aggregate smoothing among several WECs. By optimizing the positioning of the WEC devices with respect to the incoming waves, fluctuations may be mutually canceled out between the devices. This work is based on Fred. Olsen's WEC system Lifesaver, and a WEC farm consisting of 48 devices is designed in detail and simulated. The major cost driver for the electrical export system is the required oversize factor necessary for transfer of the average power output. Due to the low power quality, this number can be as high as 20 at the entry point of the electrical system, and it is thus crucial to quickly improve the power quality so that the downstream power system is efficiently utilized. The simulations undertaken in this work indicate that a high quality power output can be achieved at the farm level, but that a significant oversize factor will be required in the intermediate power system within the farm.

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Section: Arraymentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Power Collection from Wave Energy Farms

2013

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“…Olsen [18]. Lifesaver is a toroid shape WEC equipped with five individual all-electric Power Take-Off (PTO) units.…”

Section: Model Of the Wave Power Generationmentioning

confidence: 99%

Stochastic Rating of Storage Systems in Isolated Networks with Increasing Wave Energy Penetration

et al. 2013

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Abstract:The future success of wave energy in the renewable energy mix depends on the technical advancements of the specific components and systems, on the grid access availability and, ultimately, on the economical profitability of the investment. Small and remote islands represent an ideal framework for wave energy exploitation, due both to resource availability and to the current high cost of electricity that mostly relies on diesel generation. Energy storage can be the enabling technology to match the intermittent power generation from waves to the energy needs of the local community. In this paper real data from La Palma, in the Canary Islands, are used as a basis for the considered test case. As a first step the study quantifies the expected power production from Wave Energy Converter (WEC) arrays, based on data from the Lifesaver point absorber developed by Fred. Olsen. Then, a stochastic optimization approach is applied to evaluate the convenience of energy storage introduction for reducing the final cost of energy and to define the corresponding optimal rating of the storage devices.

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“…Previous estimations have been made for the Lifesaver concept [23], and some preliminary investigations have also been performed into a potential increase in annual energy production using reactive control. However, the latter paper does not take into account the generator force limitation or generator losses, and these factors become very significant under reactive control in particular [24].…”

Section: Energy Calculations-potential Increase In Annual Energy Prodmentioning

confidence: 99%

Exploring the Potential for Increased Production from the Wave Energy Converter Lifesaver by Reactive Control

et al. 2013

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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.

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All-electric Wave Energy Converter array with energy storage and reactive power compensation for improved power quality

Cited by 15 publications

References 4 publications

Power Collection from Wave Energy Farms

Power Collection from Wave Energy Farms

Stochastic Rating of Storage Systems in Isolated Networks with Increasing Wave Energy Penetration

Exploring the Potential for Increased Production from the Wave Energy Converter Lifesaver by Reactive Control

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