Experimental results from sea trials of an offshore wave energy system

Waters, Rafael; Stålberg, Magnus; Danielsson, Oskar; Svensson, Olle; Gustafsson, Stefan; Strömstedt, Erland; Eriksson, Mikael; Sundberg, Jan; Leijon, Mats

doi:10.1063/1.2432168

Cited by 162 publications

(107 citation statements)

References 16 publications

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“…From this point onwards, for simplicity, "standard deviation" is used for the term "normalized standard deviation". [15] and [21] rather than in a non-linear fashion as in the above experiment with two converters and as in [22][23]. Each data point is the half-hour mean value of electrical power converted to heat in each of the WEC dump loads.…”

Section: Methodsmentioning

confidence: 99%

Experimental results from the operation of aggregated wave energy converters

Rahm¹,

Svensson²,

Boström³

et al. 2012

IET Renew. Power Gener.

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Experimental results from the operation of aggregated wave energy converters. IET Renewable Power Generation ABSTRACTWave energy comes in pulses and is unsuitable for direct conversion and transmission to the grid. One method to smooth the power is to deploy arrays of wave energy converters (WECs), the geometrical layout and damping optimization of which many have studied analytically and numerically, but very few by experiments at sea. In this paper, the standard deviation of electrical power as function of various parameters is investigated. Two offshore experiments have been conducted. During the longer run, three WECs were operated in linear damping during 19.7 days. It is shown that the standard deviation reduces with the number of WECs in the array up to three WECs. The reduction compared to single WEC operation was found here to be 30% and 80% with two and three WECs respectively as a mean for an arbitrary array member. It is found that in sea states above approximately 2 kW/m, the standard deviation is independent of sea state parameters. This is contradictory to a previous study on the same device. The results are however in accordance with numerical results of the SEAREV device but show larger reduction in standard deviation with number of WECs. This could be due to suboptimal damping conditions.

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Section: Methodsmentioning

confidence: 99%

Experimental results from the operation of aggregated wave energy converters

Rahm¹,

Svensson²,

Boström³

et al. 2012

IET Renew. Power Gener.

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“…In contrast, rotational systems with a constrained throw show greater capability in transferring energy to the resistance load. In these systems, the ratio of the optimum load resistance and the internal resistance of the generator can be written according to equation (21) and (32) as follows:…”

Section: Discussionmentioning

confidence: 99%

Output power and efficiency of electromagnetic energy harvesting systems with constrained range of motion

Hendijanizadeh¹,

Sharkh²,

Elliott³

et al. 2013

Smart Mater. Struct.

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Abstract. In some energy harvesting systems, the maximum displacement of the seismic mass is limited due to the physical constraints of the device. This is especially the case where energy is harvested from a vibration source with large oscillation amplitude (e.g., marine environment). For the design of inertial systems, the maximum permissible displacement of the mass is a limiting condition. In this paper the maximum output power and the corresponding efficiency of linear and rotational electromagnetic energy harvesting systems with a constrained range of motion are investigated. A unified form of output power and efficiency is presented to compare the performance of constrained linear and rotational systems. It is found that rotational energy harvesting systems have a greater capability in transferring energy to the load resistance than linear directly coupled systems, due to the presence of an extra design variable viz. the ball screw lead. Also, in this paper it is shown that for a defined environmental condition and a given proof mass with constrained throw, the amount of power delivered to the electrical load by a rotational system can be higher than the amount delivered by a linear system. The criterion that guarantees this favorable design has been obtained.

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“…In other devices, including the one described in this paper, relative linear motion is exploited. Direct drive linear generator have been used for energy conversion in these devices [5]. However, in applications where the frequency of vibrations, and hence the relative speed are low, a direct drive generator can be quite large and expensive relative to the amount of power produces, i.e.…”

mentioning

confidence: 99%

An inertial coupled marine power generator for small boats

Sharkh

Hendijanizadeh

Moshrefi-Torbati

et al. 2011

2011 International Conference on Clean Electrical Power (ICCEP)

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Abstract-This paper proposes a device to harvest energy from the vertical motion of small boats and yachts. The device comprises a sprung mass coupled to an electrical generator through a ball screw. The mathematical equations describing the dynamics of the system are derived. The equations are used to determine the optimum device parameters, namely its mass, spring constant, ball screw lead, within practical constraints. Simulation results are presented to determine the maximum power that can be generated and the optimum load resistance as a function of boat vibration frequency.

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Experimental results from sea trials of an offshore wave energy system

Cited by 162 publications

References 16 publications

Experimental results from the operation of aggregated wave energy converters

Experimental results from the operation of aggregated wave energy converters

Output power and efficiency of electromagnetic energy harvesting systems with constrained range of motion

An inertial coupled marine power generator for small boats

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