On end-stops and snap loads for taut-moored wave energy converters
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Contribution to journal
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Research
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peer-review
The power output from many wave energy converters (WECs) is limited by a finite stroke length in the power take-off (PTO) mechanism. As the PTO approaches
its maximum stroke length, an end-stop system needs to be engaged to avoid damage to the machinery. Still the on-set of the end-stop is a nonlinear trigger force, a stiff point in the system. In this respect it is similar to how snap loads in the mooring cables affect the system after a period of cable slack. This paper presents a detailed study into the dynamics of end-stop events and snap loads for a WEC. The WEC is a bottom-mounted linear generator connected to a surface buoy via a steel wire. By comparing a linear spring model with three dynamic mooring line models we conclude that large differences are observed in the low-tension and slack regions of the cable during moderate wave loads, while minor differences are seen in the estimated peak tension. By further varying end-stop parameters we observe that the peak tension in the line changes mildly with the axial stiffness for moderate wave heights. The peak tension is surprisingly unaffected by the introduction of a critical damping level to the end-stop system, despite the significant increase in end-stop force which causes the translator to come to a sudden stop. We discuss how the connection between maximum line force and end-stop parameters is highly dependent on the buoy
position in the wave at the instant of end-stop onset.
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Conference
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14th European Wave and Tidal Energy Conference
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Number
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14
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Location
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University of Plymouth
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Country/Territory
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United Kingdom
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City
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Virtual, Online
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Period
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05/09/2021
→
09/09/2021
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Internet address
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@inproceedings{981f9d6cd42948f084067d3df806aeba,
title = "On end-stops and snap loads for taut-moored wave energy converters",
abstract = "The power output from many wave energy converters (WECs) is limited by a finite stroke length in the power take-off (PTO) mechanism. As the PTO approachesits maximum stroke length, an end-stop system needs to be engaged to avoid damage to the machinery. Still the on-set of the end-stop is a nonlinear trigger force, a stiff point in the system. In this respect it is similar to how snap loads in the mooring cables affect the system after a period of cable slack. This paper presents a detailed study into the dynamics of end-stop events and snap loads for a WEC. The WEC is a bottom-mounted linear generator connected to a surface buoy via a steel wire. By comparing a linear spring model with three dynamic mooring line models we conclude that large differences are observed in the low-tension and slack regions of the cable during moderate wave loads, while minor differences are seen in the estimated peak tension. By further varying end-stop parameters we observe that the peak tension in the line changes mildly with the axial stiffness for moderate wave heights. The peak tension is surprisingly unaffected by the introduction of a critical damping level to the end-stop system, despite the significant increase in end-stop force which causes the translator to come to a sudden stop. We discuss how the connection between maximum line force and end-stop parameters is highly dependent on the buoyposition in the wave at the instant of end-stop onset.",
keywords = "End-stop, Floating wave energy converters, Mooring cables, Snap load, End-stop, Floating wave energy converters, Mooring cables, Snap load",
author = "Johannes Palm and Claes Eskilsson",
year = "2021",
language = "English",
pages = "1984--1 -- 1984--10",
journal = "Proceedings of the European Wave and Tidal Energy Conference",
issn = "2706-6932",
publisher = "European Wave and Tidal Energy Conference",
note = "14th European Wave and Tidal Energy Conference, EWTEC2021 ; Conference date: 05-09-2021 Through 09-09-2021",
url = "https://ewtec.org",
}
TY - GEN
T1 - On end-stops and snap loads for taut-moored wave energy converters
AU - Palm, Johannes
AU - Eskilsson, Claes
N1 - Conference code: 14
PY - 2021
Y1 - 2021
N2 - The power output from many wave energy converters (WECs) is limited by a finite stroke length in the power take-off (PTO) mechanism. As the PTO approachesits maximum stroke length, an end-stop system needs to be engaged to avoid damage to the machinery. Still the on-set of the end-stop is a nonlinear trigger force, a stiff point in the system. In this respect it is similar to how snap loads in the mooring cables affect the system after a period of cable slack. This paper presents a detailed study into the dynamics of end-stop events and snap loads for a WEC. The WEC is a bottom-mounted linear generator connected to a surface buoy via a steel wire. By comparing a linear spring model with three dynamic mooring line models we conclude that large differences are observed in the low-tension and slack regions of the cable during moderate wave loads, while minor differences are seen in the estimated peak tension. By further varying end-stop parameters we observe that the peak tension in the line changes mildly with the axial stiffness for moderate wave heights. The peak tension is surprisingly unaffected by the introduction of a critical damping level to the end-stop system, despite the significant increase in end-stop force which causes the translator to come to a sudden stop. We discuss how the connection between maximum line force and end-stop parameters is highly dependent on the buoyposition in the wave at the instant of end-stop onset.
AB - The power output from many wave energy converters (WECs) is limited by a finite stroke length in the power take-off (PTO) mechanism. As the PTO approachesits maximum stroke length, an end-stop system needs to be engaged to avoid damage to the machinery. Still the on-set of the end-stop is a nonlinear trigger force, a stiff point in the system. In this respect it is similar to how snap loads in the mooring cables affect the system after a period of cable slack. This paper presents a detailed study into the dynamics of end-stop events and snap loads for a WEC. The WEC is a bottom-mounted linear generator connected to a surface buoy via a steel wire. By comparing a linear spring model with three dynamic mooring line models we conclude that large differences are observed in the low-tension and slack regions of the cable during moderate wave loads, while minor differences are seen in the estimated peak tension. By further varying end-stop parameters we observe that the peak tension in the line changes mildly with the axial stiffness for moderate wave heights. The peak tension is surprisingly unaffected by the introduction of a critical damping level to the end-stop system, despite the significant increase in end-stop force which causes the translator to come to a sudden stop. We discuss how the connection between maximum line force and end-stop parameters is highly dependent on the buoyposition in the wave at the instant of end-stop onset.
KW - End-stop
KW - Floating wave energy converters
KW - Mooring cables
KW - Snap load
KW - End-stop
KW - Floating wave energy converters
KW - Mooring cables
KW - Snap load
UR - http://www.scopus.com/inward/record.url?scp=85120053346&partnerID=8YFLogxK
UR - https://proceedings.ewtec.org/shop/
M3 - Conference article in Journal
SN - 2706-6932
SP - 1984-1 - 1984-10
JO - Proceedings of the European Wave and Tidal Energy Conference
JF - Proceedings of the European Wave and Tidal Energy Conference
T2 - 14th European Wave and Tidal Energy Conference
Y2 - 5 September 2021 through 9 September 2021
ER -
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