W. Sheng

SW MARE Marine Technology

Wave energy provides a renewable and clear power for the future energy mix and fights against climate change. Currently, there are many different wave energy converters, but their costs of extracting wave energy are still much higher than other matured renewables. One of the best indicators of calculating the generating cost of wave energy is the ‘...

This book provides the materials and examples for understanding the fundamentals of the fluid-structure interactions, especially on the wave-structure interaction, which is based on the potential flow theory, and the applications of the wave-structure interaction in wave energy conversion, such as the optimisation and control of the PTO for maximis...

The study of wave-structure interactions involving nonlinear forces would often make use of the popular hybrid frequency–time domain method. In the hybrid method, the frequency-domain analysis could firstly provide the reliable and accurate dynamic parameters and responses; then these parameters and responses are transformed to the parameters to es...

Current panel methods for wave-structure interactions employ the potential flow theory, which provide fast, reliable and relatively accurate predictions for the marine structures, and now some open source packages, NEMOH and HAMS, are available. In this research, the relative utility and performance of NEMOH and HAMS is compared with the well-known...

Biomimetics and creatures could contribute to novel design inspiration for wave energy converters, as we have seen numerous examples in applications of other branches of engineering. However, the issue of how to obtain valuable biological entities, or bionic design cases, that could produce inspiration for novel designs, may be challenging for the...

An effort has been recently paid to derive and to better understand the Navier-Stokes (N-S) equation, and it is found that, although the N-S equation has been proven to be correct by numerous examples, some concepts and principles behind the equation may not be correct or consistent. For instance, from an analysis of the simple classic Couette flow...

An effort has been recently paid to derive and to better understand the Navier–Stokes (N–S) equation, and it is found that, although the N–S equation has been proven to be correct by numerous examples, some concepts and principles behind the equation may not be correct or consistent. For instance, from an analysis of the simple classic Couette flow...

The International Energy Agency Technology Collaboration Programme for Ocean Energy Systems (OES) initiated the OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters (WECs). The long-term goal is to assess the accuracy of and establish confidence in the...

The Backward Bent Duct Buoy (BBDB) oscillating water column (OWC) wave energy converter (WEC) has been invented following the so-far most successful OWC navigation buoys in wave energy utilisation, with aims to build large and efficient OWC wave energy converters for massive wave energy production. The BBDB device could use its multiple motion mode...

Highlights: Comparative study and assessment of six control strategies developed for the biradial turbine in the Mutriku OWC plant. --- Two are adaptive controllers, other two are latching controllers, one uses a RL scheme and one is a non-linear MPC. ---- Numerical simulations are done on a variety of sea states to support a performance and reliab...

The paper presents a detailed analysis of the dynamics and control of air turbines and electrical generators in oscillating-water-columns (OWCs). The aim is to explain the performance of an OWC device based on the physical behaviour of each system component. The Mutriku wave power plant was chosen as the test case. The power plant is a breakwater l...

It has been well accepted that wave energy may have the potential to significantly contribute to the future renewable energy mix but so far it remains as the largest untapped renewable resources since the current wave energy technologies are technically immature for reliable and economic energy production. The greatest challenges would be how the p...

This research work presents an investigation into the effects of wave spectra on energy conversion for wave energy converters and shows it may be important what theoretical spectrum should be used for a better assessment of a wave energy converter (WEC) in the given sea conditions in a proposed deployment site. To illustrate the problem and the sol...

This research presents the power performance of the backward-bent duct buoy (BBDB) oscillating water column (OWC) wave energy converters (WECs). To achieve that, following steps are detailed: firstly, power conversion from wave power into pneumatic power by coupling the hydrodynamics and the thermodynamics in the air chamber using a linear air turb...

A model testing campaign of the Tupperwave device was carried out to prove the working principal and validate a numerical modelling that had previously been developed. An appropriate and challenging scaling method was applied to the floating device to correctly model the air compressibility in the Tupperwave PTO. In parallel, a model scale conventi...

This work focuses on an array of point absorbers, with linear permanent magnet generators (LPMG) connected to the grid via back to back voltage source converters, controlled using economic model predictive control (MPC) that produces optimal electrical power generation. The main contribution of this paper is the comparison of the performance provid...

COMMITTEE MANDATE Concern for load analysis and structural design of offshore renewable energy devices. Attention shall be given to the interaction between the load and structural response of fixed and floating installations taking due consideration of the stochastic nature of the ocean environment. Aspects related to prototype testing, certificati...

This study investigates the possibility of using pitch and roll motions to increase the airflow in floating oscillating water columns by configuring 4 spar buoy type columns into a quadrangle shaped device. For this analysis, the Boundary Element Method (BEM) solver Ansys Aqwa is used. The BEM solver uses numerical methods based on potential flow t...

This is the first joint reference paper for the Ocean Energy Systems (OES) Task 10 Wave Energy Converter modeling verification and validation group. The group is established under the OES Energy Technology Network program under the International Energy Agency. OES was founded in 2001 and Task 10 was proposed by Bob Thresher (National Renewable Ener...

For cost savings and ease of operation, nearshore regions have been considered as ideal regions for deploying wave energy converters (WECs) and wave farms. As the water depths of these regions may be frequently limited to 50 m or less, they can be considered as being transitional/intermediate to shallow when compared to the wave lengths of interest...

The Mutriku breakwater wave power plant is located in the Bay of Biscay, in Basque Country, Spain. The plant is based on the oscillating water column (OWC) principle and comprises 16 air chambers, each of them equipped with a Wells turbine coupled to an electrical generator with a rated power of 18.5 kW. The IDMEC/IST Wave Energy Group is developin...

This paper presents a new method for improving the assessment of energy and resources of waves in the cases of finite water depths in which the historical and some ongoing sea wave measurements are simply given in forms of scatter diagrams or the forms of (significant) wave heights and the relevant statistical wave periods, whilst the detailed spec...

This paper presents an investigation on how to optimize the power takeoffs (PTOs) to maximize the mean wave energy conversion from seas for floating oscillating water column (OWC) devices. For this purpose, the linear air turbine PTOs are first analytically optimized to maximize the mean energy conversion for regular waves, based on which a simple...

The paper presents an investigation of fix-referenced and self-referenced wave energy converters and a comparison of their corresponding wave energy conversion capacities from real seas. For conducting the comparisons, two popular wave energy converters, point absorber and oscillating water column, and their power conversion capacities in the fixed...

In this work, a simple methodology of shipbuilding associated with wave energy aims to investigate the development and feasibility of a floating reinforced concrete structure for the offshore renewable energy generation system known as Oscillating Water Column. By proving the irreversible damage that burning fossil fuels can cause to the environmen...

This paper presents an investigation on air compressibility in the air chamber and its effects on the power conversion of oscillating water column (OWC) devices. As it is well known that for practical OWC plants, their air chambers may be large enough for accommodating significant air compressibility, the “spring effect,” an effect that is frequent...

This paper offers a holistic approach to the evaluation of an ocean renewable energy (ORE) technology type or specific project in order to provide a comprehensive assessment of both narrow economic and broader socioeconomic performance. This assessment incorporates methods from three pillars areas: Economic - financial returns and efficient use of...

Interconnected floaters could use relative rotations around connection joints to drive a power take-off (PTO) system, such that the ocean wave energy can be converted into a useful energy. In this paper, our attention is on the PTO optimization for the interconnected floaters. A fully linear dynamic system, including the linear hydrodynamics of the...

This paper presents a fundamental investigation on optimizing the power takeoff (PTO) for maximizing wave energy conversion of the wave-activated bodies (WABs) wave energy converters. In this research, two relative heave motions are taken for capture power, and a linear PTO is considered in the primary analysis. For such a linear dynamic system, th...

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Gu´erinel, and W Sheng. Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex. 11th European Wave and Tidal Energy Conference (EWTEC), Nantes, France. 6-11 Sept.,2015.

MA Bhinder, M Karimirad, S Weller, Y Debruyne, M Gu´erinel, and W Sheng. Modelling mooring line non-linearities (material and geometric effects) for a wave energy converter using AQWA, SIMA and Orcaflex. 11th European Wave and Tidal Energy Conference (EWTEC), Nantes, France. 6-11 Sept.,2015.

The increased demand for clean renewable sources of electricity has fostered strong growth in wave energy development in recent years. This led to greater understanding of the various systems involved in the conversion of wave energy to electrical energy, which in turn led to more accurate and sophisticated models of each system. Mathematical model...

This paper presents a dynamic analysis of a two-raft wave energy conversion device based on the three-dimensional wave radiation-diffraction method. The device consists of two hinged cylindrical rafts of elliptical cross section and a power take-off system at the joint. The effect of raft length, linear damping and spring coefficient in the power t...

In this paper, a novel two-raft wave energy absorption device is proposed and investigated with a numerical method. The novel device consists of two hinged cylindrical rafts of elliptical cross section with spring-damping-mass oscillators system inside and a Power TakeOff (PTO) system at the joint. During the rotation of the rafts driven by ocean w...

Marine renewable energy (MRE) devices (e.g. floating point absorbers) are designed to maximise energy absorption, however the non-linear dynamics of the mooring lines can have a significant impact on the resulting response of the device. A comprehensive design approach is required because the mooring system not only represents a considerable part o...

Abstract The performance of wave energy converters and other offshore renewable energy platforms, non-linear effects is frequently assessed in time domain, especially when the nonlinear forces from the large amplitude motions, mooring forces, power take-off or the energy conversion control system are considered. One popular approach in the time-dom...

The performance of wave energy converters and other offshore renewable energy platforms,non-linear effects is frequently assessed in time domain, specially when the nonlinear forces from the large amplitude motions, mooring forces, power take-off or the energy conversion control system are considered. One popular approach in the time-domain analysi...

In the development of wave energy converters, the mooring system is a key component for a safe station-keeping and an important factor in the cost of the wave energy production. Generally, when designing a mooring system for a wave energy converter, two important conditions must be considered: (i) that the mooring system must be strong enough to li...

This work deals with the numerical studies on hydrodynamics of oscillating water column (OWC) wave ener-gy converters and its damping optimization on maximizing wave energy conversion by the OWC device. As a fundamental step, the hydrodynamic problems have been systematically studied by considering the interac-tions of the wave-structure and of the...

Wave measurement is of vital importance for assessing the wave power resources and for developing wave energy devices, especially for the wave energy production and the survivability of the wave energy device. Wave buoys are one of the most popular measuring technologies developed and used for long-term wave measurements. In order to figure out whe...

Extracting wave energy from seas has been proven to be very difficult although various technologies have been developed since 1970s. Among the proposed technologies, only few of them have been actually progressed to the advanced stages such as sea trials or pre-commercial sea trial and engineering. One critical question may be how we can design an...

In the first part of the investigation, a new latching control technology is proposed, and it has been shown that the new latching control technique is capable of greatly improving wave energy conversion in regular waves. In this part of the research, a new analysis technique is developed for studying the latching control technology. A ‘time-out’ m...

This is an investigation on the development of a numerical assessment method for the hydrodynamic performance of an oscillating water column (OWC) wave energy converter. In the research work, a systematic study has been carried out on how the hydrodynamic problem can be solved and represented reliably, focusing on the phenomena of the interactions...

This is the second part of the assessment of primary energy conversions of oscillating water columns (OWCs) wave energy converters. In the first part of the research work, the hydrodynamic performance of OWC wave energy converter has been extensively examined, targeting on a reliable numerical assessment method. In this part of the research work, t...

In guiding the progression and implementation of wave energy converters in a more effective and solid way, stepwise protocols have been recommended for assessing and validating their performance, feasibility, reliability and survivability during the devices׳ progression stages from the concepts to full-scale commercial devices. One important aspect...

Oscillating water column (OWC) wave energy converters (WECs) are probably the simplest and most promising wave energy converters due to their good feasibility, reliability and survivability in practical wave energy conversions and also regarded as the most studied and developed when compared to other types of the wave energy converters. This resear...

NREL airfoils have been specially developed for wind turbine applications, and projected to yield about 30% more annual energy without increasing the maximum power level. These airfoils are designed to have a limited maximum lift and insensitivity to the leading-edge roughness. As a result, these airfoils have quite different leading-edge profiles...

Control technologies have been proposed and widely studied for improving wave energy conversion efficiency since 1970s (see Falnes [1] and Salter et al. [2]), and it has been proven that control technologies could significantly improve the wave energy conversion efficiency if a phase optimum or an amplitude optimum or both can be implemented. Among...

It has been suggested that for full scale oscillating water column (OWC) devices, the pressure in and the volume of the air chambers can be large to create air compressibility in the air chamber. Due to compressibility, its density and temperature are different from those in atmosphere. When in exhalation, the pressurized air is driven out of the a...

The paper presents an investigation to the thermodynamics of the air flow in the air chamber for the oscillating water column wave energy converters, in which the oscillating water surface in the water column pressurizes or de-pressurises the air in the chamber. To study the thermodynamics and the compressibility of the air in the chamber, a method...

In developing a wave energy converter (WEC), assessing and rating the device is a difficult, but important issue. Conventionally, a large scaled device (maybe large enough for accommodating a power takeoff (PTO) system) or prototype device is needed to be tested in wave tanks or in seas in different wave conditions so that a power matrix for the de...

Oscillating water column (OWC) wave energy converters (WECs) are a popular type of wave energy devices. Generally, the OWC WECs have a simple structure and working principle, but with a high conversion efficiency, and a high reliability in power take-off due to a small torque and a high rotation speed for a certain power extraction. The OWC devices...

Oscillating water column (OWC) wave energy converters (WECs) are a popular type of wave energy devices, due to their advantages over many other WECs. For example, OWC WECs normally have no moving components in sea water, and have a small torque and a high rotational speed for a certain power take-off. Practically, some foundation-type pioneer plant...

Dynamic stall is a complex process encountered by an aerofoil in the unsteady flow environment such as a helicopter rotor in forward flight as well as a fixed wing aircraft in manoeuvres and in other unsteady situations. The onset of dynamic stall effectively determines the flight envelope of the helicopter. Significant effort are being made to dev...

An Oscillating Water Column (OWC) is a promising wave energy device due to its obvious advantages over many other wave energy converters: There are no moving components in the sea water. Though the bottom-fixed OWC have been quite successful in several practical applications, the projection of a massive wave energy production and the availability o...

The GOAHEAD (Generation of an Advanced Helicopter Experimental Aerodynamic Database for CFD code validation) consortium was created in the frame of an EU-project in order to create an experimental database for the validation of 3D-CFD and comprehensive aeromechanics methods for the prediction of unsteady viscous flows. This included the rotor dynam...

The oscillating water column (OWC) is one of the more successful wave energy converters so far due to its mechanical and structural simplicity; there are no components for power take-off in seawater. Though there are some successful practical developments in bottom-fixed OWCs, floating OWCs are still in different stages of development. A specific o...

Oscillating Water Column (OWC) is one type of promising wave energy devices due to its obvious advantage over many other wave energy converters: no moving component in sea water. Two types of OWCs (bottom-fixed and floating) have been widely investigated, and the bottom-fixed OWCs have been very successful in several practical applications. Recentl...

National Renewable Energy Laboratory, USA (NREL) airfoils have been specially developed for wind turbine applications, and projected to yield more annual energy without increasing the maximum power level. These airfoils are designed to have a limited maximum lift and relatively low sensitivity to leading-edge roughness. As a result, these airfoils...