Performance evaluation of a direct drive wave energy converter using CFD

MA Zullah Y Lee – Renewable Energy, February 2012

Abstract
This paper presents a numerical study of the savonius type direct drive turbine incorporated in the rear bottom of typical chamber geometry of an oscillating water column chamber (OWC) for wave energy conversion. The paper deals with a numerical modelling devoted to investigate the effect of wave on the performance and internal flow of the savonius turbine in the components of an oscillating water column (OWC) system used for the wave energy capture. In the present paper, the flow behaviour is modelled by using the commercial code ANSYS CFX. The numerical flow models have been elaborated and simulated independently with different inlet geometries of a water chamber. Constant periodic wave flow calculations were performed to investigate the flow distribution at the turbines inlet section, as well as the properties of the savonius type turbine. The flow is assumed to be two-dimensional (2D), viscous, turbulent and unsteady. The commercial CFD code is used with a solver of the coupled conservation equations of mass, momentum and energy, with an implicit time scheme. Turbulence is modelled with the k–e model. Simulation result shows that the water velocity, differential pressure, and the best efficiency vary considerably depending on the savonius rotor angle. The obtained results also indicate that the developed models are well suitable to analyze the water flows both in the chamber and around the savonius rotor.

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Fatigue Behaviour of Glass Fibre Reinforced Composites for Ocean Energy Conversion Systems

A Boisseau, P Davies F Thiebaud – Applied Composite Materials, February 2012

Abstract
The development of ocean energy conversion systems places more severe requirements on materials than similar land-based structures such as wind turbines. Intervention and maintenance at sea are very costly, so for ocean energy supply to become economically viable long term durability must be guaranteed. Cyclic loading is a common feature of most energy conversion devices and composites are widely used, but few data are available concerning the fatigue behaviour in sea water of composite materials. This paper presents the results from an experimental study to fill this gap. The fatigue behavior of composite materials reinforced with different types of glass fibre is characterized in air and in sea water; the influence of testing in sea water rather than air is shown to be small. However, sea water ageing is shown to reduce the fatigue lifetime significantly and strongly depends on matrix formulation.

 

A novel design of composite water turbine using CFD

J Wang, J Piechna, N Muller – Journal of Hydrodynamics, Ser. B, February 2012

Abstract
This paper presents computational investigation of a novel design of composite material axial water turbine using Computational Fluid Dynamics (CFD). Based on three-dimensional numerical flow analysis, the flow characteristics through the water turbine with nozzle, wheel and diffuser are predicted. The extract power and torque of a composite water turbine at different rotating speeds were calculated and analyzed for a specific flow speed. The simulation results show that using nozzle and diffuser can increase the pressure drop across the turbine and extract more power from available water energy. These results provide a fundamental understanding of the composite water turbine, and this design and analysis method is used in the design process.

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Assessment of array shape of tidal stream turbines on hydro-environmental impacts and power output

R. Ahmadian, R.A. Falconer- Renewable Energy, August 2012

Abstract

This study investigates the significance of the layout of an array of tidal stream turbines on the power output and the hydro-environmental impacts of the array using the Research Centre’s widely used open-source hydro-environmental model, namely DIVAST (Depth Integrated Velocities And Solute Transport), which was modified by the authors to include turbines as momentum sinks, to simulate the impact of an array of turbines in a coastal environment. For this purpose, three various layouts of an array of turbines, having the same number of turbines and located in the Severn Estuary and Bristol Channel, were modelled and compared. The estuary, including the Bristol Channel, is approximately 200 km long and with a typical spring tidal range of over 14 m has the third highest rise and fall of tide in the world, with the spring tidal currents in the estuary being well in excess of 2 m/s.

Effect of non-standard operating frequencies on the economic cost of offshore AC networks

JL Domínguez-García, DJ Rogers, CE Ugalde-Loo, J Liang, O Gomis-Bellmunt- Renewable Energy, August 2012

Highlights
► Cost of offshore AC networks at non-standard operating frequencies is analysed. ► The network considered is similar to the European SuperGrid SuperNode. ► The focus is on frequency-cost scaling of electrical and infrastructure elements. ► A case study based upon Dogger Bank shows a minimum total at 93 Hz.

 

Quantifying the global wave power resource

K Gunn, C Stock-Williams- Renewable Energy, August 2012

Highlights
► NOAA WW3 data are used to calculate the global distribution of wave energy resource. ► The resource incident on the world’s coastlines is quantified: 2.11TW globally. ► The extractable resource is quantified using an illustrative wave energy converter. ► Confidence limits for presented results are derived and examined.