Dynamic response and power production of a floating integrated wind, wave and tidal energy system

IEEE Trans. Sustain. Energy

Gao

et al. 2019

Self Cite

Liang Li et al.: Wave force prediction effect on the energy absorption of a wave energy converter with real-time control Abstract-Real-time control has been widely adopted to enlarge the energy extraction of a wave energy converter (WEC). In order to implement a real-time control, it is necessary to predict the wave excitation forces in the close future. In many previous studies, the wave forces over the prediction horizon were assumed to be already known, while the wave force prediction effect has been hardly examined. In this paper, we investigate the effect of wave force prediction on the energy absorption of a heaving point-absorber WEC with real-time latching control. The real-time control strategy is based on the combination of optimal command theory and first order-one variable grey model GM(1,1). It is shown that a long prediction horizon is beneficial to the energy absorption whereas the prediction deviation reduces extracting efficiency of the WEC. Further analysis indicates that deviation of wave force amplitude has little influence on the WEC performance. It is the phase deviation that leads to energy loss. Since the prediction deviation accumulates over the horizon, a moderate horizon is thus recommended.Index Terms-real-time control, wave energy converter, energy absorption, renewable energy, wave force prediction I. IntroductionT is expected that the global demand for energy will climb up to 25 percent by 2040 and the world is pursuing economic and renewable energy sources to keep up with this considerable demand growth [1]. Among various of ocean energy resources, sea waves take the advantage of high power density and all-day availability. To extract energy from ocean waves, WECs with various operation mechanisms have been developed. Li et al. [2] showed the power output of an oscillating-body WEC installed on a spar-type floating wind turbine. Boren et al. [3] presented a testing of a scaled vertical axis pendulum WEC. He et al. [4] utilized a floater breakwater to harvest energy from the waves. Experimental study of the concept was performed.Control action is introduced to the WEC to enlarge the energy absorption and broaden the bandwidth. Babarit et al. [5] studied how the declutching control influenced the energy absorption of a WEC in regular and irregular waves. Zou et al.[6] investigated constrained and unconstrained optimal control of a heaving point-absorber. Park et al. [7] proposed an phase L. Li, Z. M. Yuan (corresponding author), and Y. Gao, are with Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, (e-mail: liang.li@strath.ac.uk; zhiming.yuan@strath.ac.uk; yan.gao@strath.ac.uk ).control by estimating the wave period using velocity and acceleration information.The latching control was first proposed by Budal and Falnes [8]. They found that one condition for maximizing energy absorption was to keep the velocity in phase with the wave excitation force. Therefore, the latching control is a kind of phase control. Hoskin and Nichols [9] used op...

Section: Introductionmentioning

confidence: 99%

Wave Force Prediction Effect on the Energy Absorption of a Wave Energy Converter With Real-Time Control

IEEE Trans. Sustain. Energy

Gao

et al. 2019

Self Cite

“…Their study showed that the combined operation of the rotating flaps resulted in an increase of the produced power without affecting the critical response quantities of the semi-submersible platform significantly. Li et al [13] proposed a hybrid offshore renewable energy device by combining a floating wind turbine, a WEC and two tidal turbines. It was shown that the overall power production was increased while the platform motions were reduced.…”

Section: Introductionmentioning

confidence: 99%

Investigation on long-term extreme response of an integrated offshore renewable energy device with a modified environmental contour method

Gao

et al. 2019

Renewable Energy

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Considering the massive simulations required by the full long-term analysis, the environmental contour method is commonly used to predict the long-term extreme responses of an offshore renewable system during life time. Nevertheless, the standard environmental contour method is not applicable to the wind energy device due to the non-monotonic aerodynamic behaviour of the wind turbine. This study presents the development of a modified environmental counter method and its application to the extreme responses of a hybrid offshore renewable system. The modified method considers the variability of the responses by checking multiple contour surfaces so that the non-monotonic aerodynamic behaviour of the wind turbine is considered. The hybrid system integrates a floating wind turbine, a wave energy converter and two tidal turbines. Simulation results prove that the modified method has a better accuracy.

“…Liu et al (2017) developed an OpenFOAM-based simulation tool for the fully coupled model of floating wind turbines. The dynamic response and extreme structural response of an integrated floating turbine were investigated numerically in (Li et al, 2018a;Li et al, 2018c). Their integrated concept was based on the combination of a floating wind turbine, two tidal turbines and a wave energy converter.…”

Section: Introductionmentioning

confidence: 99%

Dynamic and structural performances of offshore floating wind turbines in turbulent wind flow

Liu

et al. 2019

Ocean Engineering

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A realistic turbulent wind field differs from a steady uniform one, in terms of the wind shear, the turbulence intensity and the coherence structure. Although it has been clear that an offshore floating wind turbine will behave differently in the turbulent wind, the individual effect of the above three items are not investigated sufficiently until now. The primary objective of the present research is to investigate in details how the wind shear, the turbulence intensity and the coherence influence the dynamic and structural responses of offshore floating wind turbines. Aero-hydro-servo-elastic coupled simulation of a semi-submersible floating wind turbine is run in time-domain. The wind shear has a limited effect on the global responses of the floating wind turbine although its influence on each individual blade is considerable. Comparatively, the floating wind turbine is quite sensitive to the turbulence intensity. In a wind field with high turbulence intensity, the platform motions become more violent and the structural loads are increased substantially. The proper orthogonal decomposition method is used to investigate the coherence quantitatively. A partial coherence structure helps to reduce the flow variation seen by the rotor and thereby beneficial to the safety of the floating wind turbine.