Tidal Energy Limited (TEL) is a UK company that makes tidal power devices. TEL recently received funding that it will use for a feasibility study of its “DeltaStream” technology and assess a potential deployment site for its device in West Wales.
The DeltaStream device has three horizontal axis turbines mounted on a common triangular frame. This configuration provides a low center of gravity and structural stability so the device can sit on the seabed without the need for an anchoring system.Â
TEL owns at least two international patent applications directed to its tidal power technology. International Publication Nos. WO 2009/081162 (‘162 Application) and WO 2010/007342 (‘342 Application) are directed to the tidal power device’s framework and node structure and turbine assembly, respectively.
Figure 1 of each application is essentially the same and is reproduced below. Both applications describe a freestanding structural frame assembly comprising steel tubes (2) and welded corner modules (3) interconnected by the tubes (2).Â
Angled tube limbs (7, 8) extend from the corner modules (3), with each limb fixed to a respective nacelle tower (9). Turbines (19) are mounted to each corner module (3) via a support shaft (20).
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The frame assembly, which may have a triangular footprint, is held in position by its own mass and lack of buoyancy due to water flooding the tubes (2) and corner modules (3). The tubes’ (2) proximity to the sea bed and the structure’s large base area relative to height provide additional stability.
According to the ‘342 Application, the turbine blade stagger angle and the choice of blade profiles are optimized so that the axial load on the turbine is kept in check, even at high rotational speeds.Â
Other advantages TEL touts are the DeltaStream’s lightweight foundation, its lower cost of manufacture using many off the shelf components and the ease of maintenance, in particular because of quick replacement of the three nacelle modules.
Interestingly, the DeltaStream device marries two types of technologies: Â according to TEL’s web site, it “uses the same concept as a wind turbine together with ship propeller technology.”
