Reduction of wave-induced pitch motion of a semi-sub wind platform by balancing heave excitation with pumping between floats

Stansby, Peter

doi:10.1007/s40722-021-00194-y

Cited by 3 publications

(2 citation statements)

References 16 publications

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“…Platform motion may be reduced directly in semi-subs by allowing water to oscillate internally between floats as tuned mass dampers in resonance, e.g. Fath et al (2020), or by actively pumping between floats (Stansby 2021). The latter reduces motion by 30-50% by balancing heave-induced forces in floats with relatively small power requirements as the pumps can also operate as turbines, so the net power required has only to overcome friction losses in the connecting pipes.…”

Section: Introductionmentioning

confidence: 99%

A wind semi-sub platform with hinged floats for omnidirectional swell wave energy conversion

Stansby,

2024

J. Ocean Eng. Mar. Energy

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The capacity of wind turbines on offshore wind platforms is presently much greater than that for wave energy conversion. However, wind availability with speed greater than 5 m/s, just above cut in, is typically 30–40% requiring storage to provide uniformity of supply, but this may be improved by adding swell wave energy conversion with typical availability of 90%. A hybrid platform is considered with three effectively rigid cylindrical floats connected by beams at right angles to support a wind turbine with its base on the central float, and two wave energy floats, opposite the wind floats, with beams at 90° and hinges with dampers for mechanical energy absorption on the central float. With swell periods over 10 s, pitch resonance may be achieved with the fore and aft floats about half a wavelength apart with anti-phase forcing causing a moment on hinges above water level. The NREL 5 MW wind turbine is incorporated and average swell wave power absorption in a typical significant wave height of 2 m is over 200 kW. The analysis is by time domain linear diffraction–radiation modelling validated for other multi-float configurations. Significant wave energy conversion is omnidirectional over a wide range of heading angles. An added benefit is that in larger waves associated with strong winds, when the wave energy conversion would be disengaged, the wave float rotation on free hinges reduces the hub accelerations below that for rigid floats, enabling a longer time for wind power generation.

show abstract

Section: Introductionmentioning

confidence: 99%

A wind semi-sub platform with hinged floats for omnidirectional swell wave energy conversion

Stansby,

2024

J. Ocean Eng. Mar. Energy

Self Cite

View full text Add to dashboard Cite

show abstract

“…Platform motion may be reduced directly in semi-subs by allowing water to oscillate between floats as tuned mass dampers in resonance, e.g. Fath et al (2020), or by actively pumping between floats (Stansby 2021). The latter reduces motion by 30-50% by balancing heave-induced forces in floats with relatively small power requirements as the pumps can also operate as turbines so the net power required has only to overcome friction losses in the connecting pipes.…”

Section: Introductionmentioning

confidence: 99%

A wind semi-sub platform with hinged floats for omnidirectional swell wave energy conversion

Stansby,

2023

Preprint

Self Cite

View full text Add to dashboard Cite

The capacity of wind turbines on offshore wind platforms is presently much greater than that for wave energy conversion. However wind availability with speed greater than 5 m/s, just above cut in, is typically 30-40% requiring storage to provide uniformity of supply, but this may be improved by adding swell wave energy conversion with typical availability of 90%. A hybrid platform is considered with three effectively rigid cylindrical floats connected by beams at right angles to support a wind turbine with its base on the central float, and two wave energy floats, opposite the wind floats, with beams at 90o and hinges with dampers for mechanical energy absorption on the central float. With swell periods over 10 s pitch resonance may be achieved with the fore and aft floats about half a wavelength apart with anti-phase forcing causing a moment on hinges above water level. The NREL 5 MW wind turbine is incorporated and average swell wave power absorption in significant wave heights of 2 m is over 200 kW. The analysis is by time domain linear diffraction-radiation modelling validated for other multi-float configurations. Significant wave energy conversion is omnidirectional over a wide range of heading angles. An added benefit is that in larger waves associated with strong winds, when the wave energy conversion would be disengaged, the wave float rotation on free hinges reduces the hub accelerations below that for rigid floats, enabling a longer time for wind power generation.

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Total wave power absorption by a multi-float wave energy converter and a semi-submersible wind platform with a fast far field model for arrays

Stansby

Moreno

Draycott

et al. 2021

J. Ocean Eng. Mar. Energy

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Wave energy converters absorb wave power by mechanical damping for conversion into electricity and multi-float systems may have high capture widths. The kinetic energy of the floats causes waves to be radiated, generating radiation damping. The total wave power absorbed is thus due to mechanical and radiation damping. A floating offshore wind turbine platform also responds dynamically and damping plates are generally employed on semi-submersible configurations to reduce motion, generating substantial drag which absorbs additional wave power. Total wave power absorption is analysed here by linear wave diffraction–radiation–drag models for a multi-float wave energy converter and an idealised wind turbine platform, with response and mechanical power in the wave energy case compared with wave basin experiments, including some directional spread wave cases, and accelerations compared in the wind platform case. The total power absorption defined by capture width is input into a far field array model with directional wave spreading. Wave power transmission due a typical wind turbine array is only reduced slightly (less than 5% for a 10 × 10 platform array) but may be reduced significantly by rows of wave energy converters (by up to about 50%).

show abstract

Reduction of wave-induced pitch motion of a semi-sub wind platform by balancing heave excitation with pumping between floats

Cited by 3 publications

References 16 publications

A wind semi-sub platform with hinged floats for omnidirectional swell wave energy conversion

A wind semi-sub platform with hinged floats for omnidirectional swell wave energy conversion

A wind semi-sub platform with hinged floats for omnidirectional swell wave energy conversion

Total wave power absorption by a multi-float wave energy converter and a semi-submersible wind platform with a fast far field model for arrays

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