Harvesting the Power of Ocean & Tidal Energy

The Osprey turbine is a vertical axis free flow device which produces power independently or as part of a larger system. Power output is expected to be from 1 kW up to 5 MW in a multiple system. It is the brainchild of Fowey-based FreeFlow 69 Ltd., research and development consultants in renewable energy, which is headed up by Pat Cooke. 

The team conceived the unique turbine concept while working on design and development for their offshore Ocean Hydro Electricity Generator (OHEG), a concept using tidal energy to create electricity 24 hours a day. Following successful testing of a model rotor, a reduced-scale model prototype has been developed to assist in the design of a full-scale prototype.

"There is still some way to go before the Osprey is fully commissioned and starts to generate electricity for the national grid," said Cooke. "But if, as we envisage it will, the Osprey performs successfully, it could play a key role in providing a simple 24-7 green power system—possibly in conjunction with a simplified version of our original OHEG concept."

With the advantage of having the gearbox and generator above the water level, the technology operates effectively in variable depths to maximize the efficiency of the power available through the tidal cycle, or in differing river heights.

It is also environmentally friendly and will not interfere with marine or river life, can be mounted on the sea bed or suspended on pontoons, is bi-directional and will turn the same way in a flooding or ebbing tide. Due to its modular design, a bank of Osprey turbines can be built up and added to in order to generate more power.

"We already have a patent application in place and plan to build a full size prototype by the Autumn," said Cooke. "If this is successful, as we are confident it will be, we intend to manufacture a range of small units for river applications, followed by a range of cross flow turbines for conventional micro hydro plants."

A prototype for an Archimedes screw type version turbine will also be produced for rivers where a weir or leat is available, such as old mill sites. Able Engineering will manufacture the river turbines and take on the project management of the larger river systems, while FreeFlow 69 will act as developer for the larger offshore systems.

Cooke, who is Chairman of Able Engineering as well as leading the FreeFlow 69 team, believes that exploiting tidal power from the sea and rivers can play a significant role in achieving the UK government's targets for renewable energy.

"It is estimated by the Carbon Trust that wave and tidal power can provide a fifth of the UK's electricity needs," he said. "The benefits of ramping up investment in tidal power generation would be considerable, providing not only a reliable source of energy, but the opportunity for Britain to be at the forefront of the global market in the same way that Danish companies took an early lead in the wind turbine industry."