Wave Energy from the North Sea: Experiences from the Lysekil Research Site

Leijon, Mats; Boström, Cecilia; Danielsson, Oskar; Gustafsson, Stefan; Haikonen, Kalle; Langhamer, Olivia; Strömstedt, Erland; Stålberg, Magnus; Sundberg, Jan; Svensson, Olle; Tyrberg, Simon; Waters, Rafael

doi:10.1007/s10712-008-9047-x

Cited by 123 publications

(76 citation statements)

References 23 publications

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“…A linear generator can take advantage of the heave motion of the wave and therefore linear generators are used in several different wave energy converters [4][5][6][7]. Drawbacks with linear generators for wave power is that they become very large due to the high forces and low velocities [8,9] and that the induced voltage varies in both frequency and amplitude [10][11][12][13]. Another drawback with linear generators is the partial stator overlap that can occur depending on the design [14].…”

Section: Introductionmentioning

confidence: 99%

Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study

Frost

Ulvgård

Sjökvist

et al. 2017

JMSE

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This paper presents a study on how the power absorption and damping in a linear generator for wave energy conversion are affected by partial overlap between stator and translator. The theoretical study shows that the electrical power as well as the damping coefficient change quadratically with partial stator overlap, if inductance, friction and iron losses are assumed independent of partial stator overlap or can be neglected. Results from onshore experiments on a linear generator for wave energy conversion cannot reject the quadratic relationship. Measurements were done on the inductance of the linear generator and no dependence on partial stator overlap could be found. Simulations of the wave energy converter's operation in high waves show that entirely neglecting partial stator overlap will overestimate the energy yield and underestimate the peak forces in the line between the buoy and the generator. The difference between assuming a linear relationship instead of a quadratic relationship is visible but small in the energy yield in the simulation. Since the theoretical deduction suggests a quadratic relationship, this is advisable to use during modeling. However, a linear assumption could be seen as an acceptable simplification when modeling since other relationships can be computationally costly.

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Section: Introductionmentioning

confidence: 99%

Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study

Frost

Ulvgård

Sjökvist

et al. 2017

JMSE

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“…The measurement ranges were decided from generator specifications and from the wave climate at the offshore test site [5]. The three-phase AC measurements required a range of ±1.2 kV and ±350 A. DC measurements required a range of 0-2 kV and 0-400 A.…”

Section: Measurement Objectivementioning

confidence: 99%

“…At Uppsala University, Uppsala, Sweden, full scale offshore operation of wave power has been studied since 2006 [5,6]. The wave energy converters (WECs) considered, described in [7], are of the point absorber type, which makes each unit limited in size and power production.…”

Section: Introductionmentioning

confidence: 99%

Offshore Measurement System for Wave Power—Using Current Loop Feedback

Ulvgård¹,

Kamf²,

Leijon³

2016

Electronics

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This paper presents the design and testing of a measurement system for wave power generators. The work is part of a project to build a robust and cheap measurement system for offshore monitoring of wave power farms. Due to the harsh offshore environment, low accessibility and high cost for installation and maintenance, it is of key importance to minimize power consumption, complexity and cost of each measurement unit. For the first prototype, the objective was to measure voltage, current and translator position inside the linear wave power generator. For this, two printed circuit boards (PCBs) were developed, using a two wire current loop transmitter setup. They were tested separately and in a three phase setup inside a wave power generator during onshore tests. To ensure stability, speed and accuracy in the signal transfer, the PCBs were tested for linearity, frequency response and step response. In addition, power consumption was measured, for operational time evaluation. Results show good agreement between expected and measured performance, with an input range of ±1560 V and ±420 A for alternating current measurements and a bandwidth of 10 kHz and 7 kHz, for voltage and current measurements, respectively. The power consumption was measured to 0.5 W for each measurement unit, at 24 V feed.

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“…Figure 2 shows a photo of buoys and translators on the harbor before offshore deployment in Norway. Since 2006, the WEC system developed at Uppsala University has undergone several offshore experiments at the research site in Lysekil, Sweden [7][8][9][10][11], covering different aspects on wave energy conversion including the environmental aspects [12,13], wave power park layout analysis [14], manufacturing [15,16] and deployment [6] processes, WEC survivability in extreme seas [17], and efficiency of WECs subjected to tides [18]. An application of a direct drive PMLG for wave energy conversion (mainly used for the Archimedes Wave Swings) was suggested in [19].…”

Section: Introductionmentioning

confidence: 99%

Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power

et al. 2017

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The wave energy converter (WEC) studied and developed at Uppsala University in Sweden is a point absorbing buoy connected to a linear generator (LG) on the seabed. Previous studies have improved the sustainability of the generator, changing its magnets from Nd 2 Fe 14 B-magnets to ferrites. In this paper, the magnetic circuit of the linear generator is further studied. Ferrite magnets of two different types (Y30 and Y40) are studied along with different shapes of pole shoes for the system. The finite element method (FEM) simulations in a program called Ace are performed. The results show that a linear generator including both Y30 and Y40 magnets and shortened T-shaped pole shoes can generate a similar magnetic energy in the airgap as a linear generator only containing Y40 magnets and rectangular pole shoes. This shows that the magnetic circuit can be altered, opening up sizes and strengths of magnets for different retailers, and thereby possibly lowering magnet cost and transportation. This work was previously presented as a conference at the European Wave and Tidal Energy Conference (EWTEC) 2017 in Cork, Ireland; this manuscript has been carefully revised and some discussions, on magnet costs for example, have been added to this paper.

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Wave Energy from the North Sea: Experiences from the Lysekil Research Site

Cited by 123 publications

References 23 publications

Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study

Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study

Offshore Measurement System for Wave Power—Using Current Loop Feedback

Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power

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