Oscillating-water-column wave energy converters and air turbines: A review

The wave energy is having more and more interest and support as a promising renewable resource to replace part of the energy supply, although it is still immature compared to other renewable technologies. This work presents a complete analysis of the wave energy technology, starting with the characterisation of this global resource in which the most suitable places to be exploited are showed, and the classification of the different types of wave energy converters in according to several features. It is also described in detail each of the stages that are part in the energy conversion, that is, from the capture of the energy from the waves to the extraction of a proper electrical signal to be injected to the grid. Likewise, existing offshore energy transmission alternatives and possible layouts are described.

Review of wave energy technologies and the necessary power-equipment

Current status of self rectifying air turbines for wave energy conversion

A review of impulse turbines for wave energy conversion

The wave energy sector has made and is still doing a great effort in order to open up a niche in the energy market, working on several and diverse concepts and making advances in all aspects towards more efficient technologies However, economic viability has not been achieved yet, for which maximisation of power production over the full range of sea conditions is crucial Precise mathematical models are essential to accurately reproduce the behaviour, including nonlinear dynamics, and understand the performance of wave energy converters Therefore, nonlinear models must be considered, which are required for power absorption assessment, simulation of devices motion and model-based control systems Main sources of nonlinear dynamics within the entire chain of a wave energy converter - incoming wave trains, wave-structure interaction, power take-off systems or mooring lines- are identified, with especial attention to the wave-device hydrodynamic interaction, and their influence is studied in the present paper for different types of converters In addition, different approaches to model nonlinear wave-device interaction are presented, highlighting their advantages and drawbacks Besides the traditional Navier-Stokes equations or potential flow methods, ‘new’ methods such as system-identification models, smoothed particle hydrodynamics or nonlinear potential flow methods are analysed

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Mathematical modelling of wave energy converters: A review of nonlinear approaches

A twin unidirectional impulse turbine topology for OWC based wave energy plants

This paper describes the present status of the art on air turbines, which could be used for wave energy conversion. The air turbines included in the paper are as follows: Wells type turbines, impulse turbines, radial turbines, cross-flow turbine, and Savonius turbine. The overall performances of the turbines under irregular wave conditions, which typically occur in the sea, have been compared by numerical simulation and sea trial. As a result, under irregular wave conditions it is found that the running and starting characteristics of the impulse type turbines could be superior to those of the Wells turbine. Moreover, as the current challenge on turbine technology, the authors explain a twin-impulse turbine topology for wave energy conversion.

/pdf/air-turbines-for-wave-energy-conversion-1byeolr017.pdf

Air Turbines for Wave Energy Conversion

A twin unidirectional impulse turbine topology for OWC based wave energy plants – Experimental validation and scaling

In o r d e r to deve lop a h igh performance impulse turbine for wave power conversion with air flow rectification system, the impulse turbine has been designed and investigated e x p e r i m e n t a l l y by mode l tes t ing. T h e n , the r u n n i n g a n d s t a r t i ng characteristics in irregular ocean waves have been clarified by a computer simulation, taking account of energy conversion efficiency of oscillating water column ( O W C ) . As a resul t , a suitable choice of design factors has been suggested for the set t ing angle of guide vane a n d the r o t o r prof i le . K E Y WORDS" Ocean wave energy, guide vane, impulse turbine, wave power conversion, f low rectifying air turbine N O M E N C L A T U R E Ac A t b CA CT di dm do f h h* I K l in P Q FR t t* • air chamber cross-sect ional area • turbine f low passage area • blade height • input coefficient (Eq. 3) • torque coefficient (Eq. 2) • width of passage at entrance • width of passage at mid-chord • width of passage at exit • f requency of wave under s inusoidal f low condit ion • height of O W C non-d imens iona l height of O W C h/H1/3 • moment of inertia of rotor • non-d imens iona l per iod = rnm/H1/3 • chord length of rotor blade • air chamber area ratio At /Ac • output • f low rate • mean radius • t ime • non-d imens iona l t ime under sinusoidal f low condit ion = t / T t *

Impulse Turbine For Wave Power Conversion With Air Flow Rectification System

A twin unidirectional impulse turbine has been proposed in order to enhance the performance of wave energy plant. This turbine system uses two unidirectional impulse turbines and their flow direction is different from each other. However, the turbine characteristics have not been clarified to date. The performances of a unidirectional impulse turbine under steady flow conditions were investigated experimentally by using a wind tunnel with large piston/cylinder in this study. Then, efficiency of the twin impulse turbine have been estimated by a quasi-steady analysis using experimental results.

/pdf/a-twin-unidirectional-impulse-turbine-for-wave-energy-jelrx4toi6.pdf

T. Setoguchi

Papers

A twin unidirectional impulse turbine topology for OWC based wave energy plants

Air Turbines for Wave Energy Conversion

A twin unidirectional impulse turbine topology for OWC based wave energy plants – Experimental validation and scaling

Impulse Turbine For Wave Power Conversion With Air Flow Rectification System

A twin unidirectional impulse turbine for wave energy conversion