Wave Treader

Wave Treader is a unique wave energy device which attaches to the transition piece of an offshore wind turbine. Combining Wave Treader to an offshore wind farm shares the offshore infrastructure and also increases the yield from the sea area. Wave Treader also assists in power smoothing in the offshore wind farm and offers improved personnel access to the turbine, both of which are major benefits to site developers.

How it Works

Wave Treader concept utilises a fore and and aft arm and sponson which react through an interface structure onto the foundation of an offshore wind turbine. Between the arms and the interface structure hydraulic cylinders are mounted and as the wave passes the machine first the forward Sponson will lift and fall and then the aft sponson will lift and fall each stroking their hydraulic cylinder in turn. This pressurises hydraulic fluid which is then smoothed by hydraulic accumulators before driving a hydraulic motor which in turn drives an electricity generator. The electricity is then exported through the cable shared with the Wind Turbine.

Periodically the interface structure moves vertically to allow for the effects of tidal range, and it also can rotate to ensure that the sponsons are optimally aligned with the wave direction.

An initial study commissioned by us indicates that the additional loads placed on the foundation of an Offshore Wind Turbine from Wave Treader are relatively small, and therefore Wave Treader will not adversely affect the stability of the Wind Turbine.

Design

The structure comprises of steel load bearing members with the floating bodies moulded from GRP (Glass Reinforced Plastic). This allows standard offshore manufacturing techniques to be used, and importantly a wide range of fabrication yards across the world.

Reliability

Due to the machine’s remote locations where access will not always be possible, reliability has to be one of the key features. To maximise reliability, all the hydraulic and electrical equipment will be to standard, industry proven marine specifications, with the systems designed and assembled by experienced and skilled personnel. Additionally in the design of the machine care will be taken to minimize the possibility of single point failure modes. Typically this will be done by having duplication of the equipment, so that in the event of a failure in one item, the remaining items will continue producing electricity. The failed set can then be left shutdown until a weather window allows for it to be changed out for a replacement unit. The experience of the design team in handling heavy objects offshore and sub-sea will ensure that the mechanisms are in place to allow this to happen smoothly and safely. The machine is designed for an overall design life of 25 years, with refits every 5 years.

Market

Wave Treader is primarily aimed at the UK Round 3 and Scottish Territorial Water offshore wind farm sites

It is estimated that between 2015 and 2023 that between 7,500 and 8,300 offshore wind turbines will be installed in the UK waters

Wave Treader can also be retro-fitted to existing Round 1 & 2 sites.

Timescales

The company is building a full scale prototype in 2010 for deployment at a UK test centre in 2011. The device will be commercially available in time for deployment in Scottish Territorial Water and UK Round 3 offshore wind farm sites.