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Economic harnessing of river and tidal energy

Published on 28 August 2013
Composite 'skin, muscle, bone' turbine blade
Composite 'skin, muscle, bone' turbine blade

TidalDesign, a TSB-funded collaborative project has developed two viable build options for Green Tide Turbines' innovative tidal stream turbine, potentially generating energy at approximately 50% of the cost of conventional tidal stream technologies.

Energy security and the need to reduce carbon emissions are creating a huge demand for renewable energy sources. River current and tidal stream are seen as two environmentally friendly energy sources with significant potential, both globally and within the UK due to its substantial coastline. However the technologies required to exploit these energy sources are still in their infancy and there is a need to increase efficiency to overcome the technical challenges presented by the aggressive environment in which these devices are installed.

Green Tide Turbine (GTT) had already conceived a novel water turbine for use in tidal stream or river currents prior to the TIdalDesign project, but required innovative manufacturing approaches and materials for their turbine stator and rotor blades. Using their expertise, the project team identified appropriate material combinations with the required physical properties and demonstrated these in terms of their suitability for manufacture and durability.

After evaluating a range of candidate turbine materials that included advanced steels, non-ferrous alloys and composites. The team manufactured two scaled prototypes using new approaches that were developed within the project alongside standard design and manufacturing procedures.

One of these concepts used a lightweight 'skin, muscle, bone' design in order to take advantage of recycled materials, such as Polyethylene Terephthalate (PET) that is resistant to the detrimental effects of water. The second model provided a low-cost solution tailored to the harsh marine environment, using a cast aluminium structure with an outer foaling release coating designed to have good durability in seawater and resilience to floating debris.

Following testing and computer modelling both options proved their viability and provided GTT with an added level of confidence for their cost model. The crucial 'cost of energy' for conventional tidal stream technologies is estimated to be between £190 and £227 per MWhr depending on the proximity of the farm to the shore and Offshore wind is reported to have a power cost of £117 per MWhr (DECC,2011). Exercises using the TidalDesign Technology however, resulted in an estimated power cost of £103 per MWhr, suggesting considerable market potential.

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