Evopod™ is a device for generating electricity from coastal tidal streams, tidal estuaries, rivers and ocean currents. It is a unique floating solution drawing upon proven technologies used in the offshore oil and gas and marine industries.

A key obstacle to the economic potential of tidal stream turbines is the high cost of intervention to recover bottom mounted devices in the event of component failure. Oceanflow™ recognises that component failure is inevitable in a multi-device farm installation and that intervention must be simple, cheap and fast. Floating solutions overcome the disadvantages of bottom mounted devices in that they are more accessible for first line maintenance and, with the Evopod™ disconnectable mooring and power export solution, easily recoverable to sheltered water for servicing or repair activities.

It is important that the floating platform supporting the turbines does not pick up motions from passing waves and that the turbine can be kept away from wave action in average sea conditions. The Evopod™ small waterplane area struts and deeply submerged nacelle ensure low motion characteristics and optimal alignment with the flow. In addition the streamline struts avoid wake interference with the turbine.

Evopod™ is tethered to the seabed using a catenary spread mooring system with simple pin-pile or gravity anchors. Mono and twin turbine Evopod™ units for deployment at coastal sites exposed to harsh wave climates employ a swivel mooring connection that allows the free floating device to maintain optimum heading into the direction of flow.

The multi-turbine support platform for more sheltered estuarine conditions is moored fore and aft and allows access and removal of individual turbines for maintenance. The semi-submerged platform can also provide a stable platform for mounting of wind turbines. The mooring and ballasting arrangement can cope with large changes in tidal elevation and can provide a more environmentally acceptable solution than barrages for exploiting tidal estuaries.

Novel Features

• Patented low motion hull form (UK Patent No. GB 2422878, USA Patent No. 7,541,688 and South Africa Patent No. 2007/3743)
• High efficiency large diameter turbine
• Simple but effective mooring system that allows the device to maintain an optimum heading to the tidal stream (UK Patent Application GB 0809127.4)
• Power train solution that makes maximum use of standard power generation components
• Marine aspects (shaft, seals, stern bearing, power export swivel) all employ standard marine components

Evopod’s key discriminators are:

• Designed for efficient operation in exposed sea areas where waves coexist with tidal current.
• Can be easily disconnected from its mooring system and removed off-site for essential maintenance in safe sheltered non-tidal areas. Without easy recovery for maintenance the power generating performance of the turbine would fall off due to biofouling.
• Does not require long duration, expensive and risky installation operations as required for fixed seabed mounted devices.
• Overall improved economics of power production compared to bottom mounted devices through lower installation costs and greater annual generating uptime through better access for repair in the event of component failure.