Modelling the Bombora mWave

ARR Ltd provide close and detailed support to Bombora Wavepower Pty in the numerical modelling of mWave and the interpretation of their experimental results.

The mWave features a series of air-inflated rubber membranes mounted to a concrete structure on the sea floor, all arranged at an angle to the incoming waves. As waves pass over the mWave air inside the membranes is squeezed into a duct and through a turbine. The turbine spins a generator to produce electricity. The air is then recycled to reinflate the membranes ready for the next wave.

The efficient modelling of mWave is highly challenging as it requires coupling the hydrodynamics and aerodynamics of multiple flexible membranes. To support this ARR Ltd modelled the membrane deformations in a potential-flow solver that could be adjusted to match the expected deformations of the mWave membranes. The hydrodynamic coefficients from these membrane deformations were then used to produce, frequency-domain, spectral-domian and  non-linear time-domain models of the mWave, to estimate the expected response, power capture and annual energy production. Once verified the numerical models were handed over to Bombora, allowing them to use and modify them as they wished.

ARR Ltd also worked with Bombora to successfully validate the model against wave-tank data, including refinements of the model to better replicate the laboratory layout used in the testing.

ARR Ltd continues to work with Bombora providing on-going support for the models, including modifying the numerical models where novel configurations or further refinements are required.

IEC wave resource standards

Dr Folley, a director of ARR, is chair of the IEC committee responsible for the development of International Standards for wave energy resource assessment and characterisation since 2009, when it was first proposed. To achieve this Dr Folley has worked with international experts from academia and industry to produce an International Standard for the wave energy resource. The first Technical Specification for this standard was published in 2015 and is available through the IEC website.

The chair of this important committee was awarded to Dr Folley in recognition of the extensive work he has done in this area. Specifically, Dr Folley has looked at the representation of the wave climate in the context of extracting wave energy, which requires a different perspective to a traditional wave climate study that may be undertaken for a harbour or conventional offshore structure. Details of papers published by Dr Folley in this area are listed below and are available on request.

Do you need a wave resource assessment and characterisation that is tailored for wave energy converters? Contact ARR to discuss how we can help.

Papers on wave energy resource assessment

Folley, M. and Whittaker, T. [2009]. Analysis of the nearshore wave energy resource, Renewable Energy 34(7): 1709-1715

Folley, M., Elsaesser, B. and Whittaker, T. [2009]. Analysis of the wave energy resource at the European Marine Energy Centre, 9th International Breakwaters Conference, Edinburgh, UK

Folley, M., Cornett, A., Holmes, B., Lenee-Bluhm, P. & Liria, P. [2012]. Standardising resource assessment of wave energy converters, 4th International Conference on Ocean Energy. Dublin, Ireland

Folley, M. [2017] The Wave Energy Resource, in Handbook of ocean wave energy, Ed. Pecher, A and Kofoed, J.P., Springer International Publishing

Oyster concept development

Whilst at Queen’s University Belfast, Dr Folley, a director of ARR, completed the research that launched the development of Oyster by Aquamarine Power Ltd. Although flap-type wave energy converters had been considered for decades, it was the work of Dr Folley that resulted in an understanding of the hydrodynamics, which supported the design of Oyster. A number of Dr Folley’s peer-reviewed papers on this subject are listed below and can be obtained upon request. Many flap-type wave energy converters have and continue to be proposed, the work of Dr Folley enables these concepts to be optimised.

Dr Folley has gained the ability to develop fundamental understandings of wave energy converters through three decades of dedicated research in this area. Does your hydrodynamics team have this depth of experience? How could your wave energy converter project be enhanced with insight developed by working with Applied Renewables Research Ltd? Contact ARR to discuss how we could help.

Papers on flap-type wave energy converter hydrodynamics and design

Folley, M., Whittaker, T.J.T. and Osterried, M. [2004] The Oscillating Wave Surge Converter, 14th International Conference on Ocean and Polar Engineering, ISOPE 2004, Toulon, France

Folley, M., Whittaker, T.J.T. and Henry, A. [2007] The effect of water depth on the performance of a small surging wave energy converter, Ocean Engineering, 34 (8-9), 1265-1274

Folley, M., Whittaker, T.J.T. and van’t Hoff, J. [2007] The design of small seabed-mounted bottom-hinged wave energy converters, 7th European Wave and Tidal Energy Conference, Aporto, Portugal

Whittaker, T. and Folley, M. [2012]. Nearshore Oscillating Wave Surge Converters and the Development of Oyster. Philosophical Transactions of the Royal Society A 370: 345-364