Wave Energy Extraction Maximization Using Direct Transcription

2012 ◽  
Author(s):  
James T. Allison ◽  
Allen Kaitharath ◽  
Daniel R. Herber
Keyword(s):  
Optimal Control ◽  
Wave Energy ◽  
Nonlinear Models ◽  
Cost Effective ◽  
Ocean Waves ◽  
Open Loop ◽  
Energy Extraction ◽  
Optimal Control Strategy ◽  
Direct Transcription ◽  
Wave Energy Converters

Wave energy converters (WECs) extract energy from the motion of ocean waves. A variety of different WEC devices have been studied over the past several decades, with emphasis on cost-effective energy extraction. Active control has been shown to improve energy production significantly. Here we investigate energy extraction potential of a tethered heaving cylinder WEC using direct transcription (DT), an open-loop optimal control strategy. This enables direct inclusion of asymmetric constraints on power and tether force, practical considerations not considered in previous studies, and opens the door to WEC optimal control problems with more realistic nonlinear models and integration of control design with physical system design.

Wave Energy Extraction Maximization in Irregular Ocean Waves Using Pseudospectral Methods

2013 ◽  
Author(s):  
Daniel R. Herber ◽  
James T. Allison
Keyword(s):  
Optimal Control ◽  
Resonance Frequency ◽  
Wave Energy ◽  
Energy Production ◽  
Early Stage ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Irregular Waves ◽  
Energy Extraction ◽  
Control Approach

Energy extraction from ocean waves and conversion to electrical energy is a promising form of renewable energy, yet achieving economic viability of wave energy converters (WECs) has proven challenging. In this article, the design of a heaving cylinder WEC will be explored. The optimal plant (i.e. draft and radius) design space with respect to the design’s optimal control (i.e. power take-off trajectory) for maximum energy production is characterized. Irregular waves based on the Bretschneider wave spectrum are considered. The optimization problem was solved using a pseudospectral method, a direct optimal control approach that can incorporate practical design constraints, such as power flow, actuation force, and slamming. The results provide early-stage guidelines for WEC design. Results show the resonance frequency required for optimal energy production with a regular wave is quite different than the resonance frequency found for irregular waves; specifically, it is much higher.

scholarly journals Robust Adaptive PI Control of Wave Energy Converters with Uncertain and Nonlinear Dynamics

2022 ◽  
Author(s):  
Nguyen Hoai Nam
Keyword(s):  
Optimal Control ◽  
Wave Energy ◽  
Control Strategy ◽  
Pi Control ◽  
Optimal Control Strategy ◽  
Robust Optimal Control ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Robust Adaptive ◽  
Control Implementation

There exist several approaches to design the optimal control strategy to harvest wave energy with a point absorber. However they are generally based on the assumption that the WEC and the PTO dynamics are well-known. In the practical WEC control implementation, this is generally not the case. The objective of this paper is to design a robust optimal control strategy that can take into account the uncertain WEC and PTO dynamics. Our choice is a robust adaptive PI control law. The proposed controller is validated and compared through simulation for irregular sea states.

scholarly journals Robust Adaptive PI Control of Wave Energy Converters with Uncertain and Nonlinear Dynamics

2022 ◽  
Author(s):  
Nguyen Hoai Nam
Keyword(s):  
Optimal Control ◽  
Wave Energy ◽  
Control Strategy ◽  
Pi Control ◽  
Optimal Control Strategy ◽  
Robust Optimal Control ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Robust Adaptive ◽  
Control Implementation

There exist several approaches to design the optimal control strategy to harvest wave energy with a point absorber. However they are generally based on the assumption that the WEC and the PTO dynamics are well-known. In the practical WEC control implementation, this is generally not the case. The objective of this paper is to design a robust optimal control strategy that can take into account the uncertain WEC and PTO dynamics. Our choice is a robust adaptive PI control law. The proposed controller is validated and compared through simulation for irregular sea states.

Numerical Modeling to Aid in the Structural Health Monitoring of Wave Energy Converters

2013 ◽  
Vol 569-570 ◽  
pp. 595-602 ◽  
Author(s):  
William Finnegan ◽  
Jamie Goggins
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Wave Energy ◽  
Numerical Models ◽  
Wave Structure ◽  
Ocean Waves ◽  
Test Site ◽  
Structural Health ◽  
Wave Energy Converters ◽  
Energy Converters

A vital aspect of ensuring the cost effectiveness of wave energy converters (WECs) is being able to monitor their performance remotely through structural health monitoring, as these devices are deployed in very harsh environments in terms of both accessibility and potential damage to the devices. The WECs are monitored through the use of measuring equipment, which is strategically placed on the device. This measured data is then compared to the output from a numerical model of the WEC under the same ocean wave conditions. Any deviations would suggest that there are problems or issues with the WEC. The development of accurate and effective numerical models is necessary to minimise the number of times the visual, or physical, inspection of a deployed WEC is required. In this paper, a numerical wave tank model is, first, validated by comparing the waves generated to those generated experimentally using the wave flume located at the National University of Ireland, Galway. This model is then extended so it is suitable for generating real ocean waves. A wave record observed at the Atlantic marine energy test site has been replicated in the model to a high level of accuracy. A rectangular floating prism is then introduced into the model in order to explore wave-structure interaction. The dynamic response of the structure is compared to a simple analytical solution and found to be in good agreement.

scholarly journals Adaptive Optimal Control of Wave Energy Converters

2018 ◽  
Vol 51 (29) ◽  
pp. 38-43 ◽  
Author(s):  
Siyuan Zhan ◽  
Bin Wang ◽  
Jing Na ◽  
Guang Li
Keyword(s):  
Optimal Control ◽  
Wave Energy ◽  
Adaptive Optimal Control ◽  
Wave Energy Converters ◽  
Energy Converters

3D SPH Simulation of Wave Interaction Between Wave Energy Converters: Towards Optimum Wave Power Absorption in Wave Farms

2020 ◽  
Author(s):  
N. Sasikala ◽  
S. A. Sannasiraj ◽  
Richard Manasseh
Keyword(s):  
Wave Energy ◽  
Oscillation Amplitude ◽  
Excitation Frequency ◽  
Ocean Waves ◽  
Dynamic Responses ◽  
Q Factor ◽  
Floating Bodies ◽  
Sustainable Resources ◽  
Wave Energy Converters ◽  
Energy Converters

Abstract Ocean waves are one of the sustainable resources of renewable energy for carbon-free electricity. For cost-effective commercial-scale projects, Wave Energy Converters (WECs) are deployed in arrays with optimum spacing as an alternative for a large (oscillatory) device in isolation. It has been found that when the wave excitation frequency is close to the resonant frequency of the WEC, the efficiency factor of energy farms, called q-factor, increases with the oscillation amplitude of the device. It has been found that the maximum absorbed energy of WECs depends directly on array configuration as that the radiated and incident wave fields interfere to direct the energy flux in the ocean towards the floating bodies. In this paper, the fully nonlinear interaction between two 3D floating bodies in close proximity and excited near its’ resonance is studied using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH). Apart from the calculations of q factor, hydrodynamic forces acting on the floating bodies and their dynamic responses are also calculated. An optimum array of WECs is proposed.

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