Development of a novel wave energy converter based on hydrodynamic lift forces

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Development of a novel wave energy converter based on hydrodynamic lift forces
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The LiftWEC project involves the development of a novel wave energy converter whose primary coupling with the waves is through the generation of hydrodynamic lift on a rotating hydrofoil. That is, the wave energy converter consists of a hydrofoil that is driven by the waves to rotate around an axis orthogonal to the principle wave direction. Useful energy can then be extracted from the system through some form of generating element which acts to resist the motion of the hydrofoil. Thus, the LiftWEC concept has many similarities to wind turbines, which in recent years have shown that renewable energy can be readily generated both practically and economically. However, whilst significant commercialisation has taken place in wind and solar energy technologies, wave energy remains an untapped source of renewable energy; although it has the potential to make a significant contribution to the future energy system and thus help to reduce climate change.

Literature studies and patent searches indicate that of the many hundreds of wave energy converter concepts that have been developed, only a few are based on hydrodynamic lift whilst the vast majority of devices seek to exploit either the buoyancy or diffraction force regimes. However, using hydrodynamic lift in a wave energy converter has a number of significant advantages including; (1) the reduction of extreme loads through reducing the circulation, also like a wind turbine, which improves survivability, and (2) unidirectional rotation, which significantly simplifies power extraction over traditional wave energy converters which typically involve reciprocating motions and thus reduce power quality. Unfortunately, none of the currently existing lift-based wave energy converter concepts have a high efficiency in all sea-states due to difficulties in maintaining a good lift-to-drag ratio. It is envisaged that novel solutions will be developed in the LiftWEC project to overcome these difficulties and thus enable the commercial development of wave energy.

The objective of the LiftWEC project is to determine the potential for using lift in wave energy converters to produce renewable energy at a commercially competitive price whilst ensuring a minimal environmental/social impact. This will be achieved by a combination of numerical/physical modelling and desk-based studies of the structural design, the operational & maintenance requirements and the environmental/social impacts of the technology. The numerical/physical modelling will demonstrate the concept’s performance in the laboratory, thereby taking the concept to Technology Readiness Level (TRL) 3, whilst the desk-based studies will allow the socially-acceptable commercial potential to be determined. A holistic, whole system design and development approach is being taken by the project in an attempt to overcome many of the issues that have previously challenged the wave energy industry. Where available, pre-existing knowledge and experience will be used in the project to ensure that the resultant LiftWEC system is designed to build on current knowledge in wave energy technologies.