Development of the technology used in Ocean Flow’s tidal energy capture device, Evopod, reached an important milestone with the demonstration of grid connectivity during its 1:10th scale trials unit in Strangford Narrows Northern Ireland. The output from the Evopod can now be fed into the domestic mains circuit of the Queen’s University Marine Laboratory in County Down.
Developed by Tyne and Wear based Ocean Flow Energy, Evopod is a semi-submerged, floating, tethered device. It uses a simple but effective mooring system that allows the free floating device to maintain optimum heading into the tidal stream. Installed as an individual device or as a tidal farm, the technology offers clean, green energy.
The Evopod employs a fixed pitch turbine driving a permanent magnet generator through a gearbox. Power control and data capture are essential for reliable energy generation. For an effective sensing solution to measure the torque and rotational speed of the turbine, Ocean Flow Energy turned to Sensor Technology and its TorqSense strain transducer.
Torque is a critical measurement as it indicates the power that can be derived from the system as well as giving an indication of the stresses on the turbine. But the marine environment and the nature of the turbine’s operation places unique performance requirements on the sensing equipment.
Ocean Flow Energy design engineer Roger Cox says: “We had used TorqSense transducers before and had good experiences with them. We knew they were reliable in challenging applications, and would give us the quality data we needed as part of our proof of concept of the Evopod.”
“We used TorqSense devices on the first Evopod design to go into the sea, and they’ve been working reliably on our 1/10 scale test unit for five years,” he says. “They are now being considered for our larger scale mono-turbine and twin turbine units.”
It is believed the scale models of the innovative Evopod which demonstrate the viability of the oceans as an energy source could soon see dependable, affordable energy from tidal streams and ocean currents become a reality.
Evopod overcomes the key concerns that have been expressed for tidal stream turbine installations. As a floating tethered device it imposes minimal disturbance on sensitive seabed ecosystems and its single turbine rotates at such low speeds (10 – 20rpm) that they are likely to be a low threat to marine wildlife. Further, Evopod’s novel mooring solution employs a tight envelope to reduce the size of the exclusion zone for shipping. A seabed region of one square kilometre can support enough Evopods to supply all the energy needs of up to 40,000 homes. This would reduce carbon dioxide emissions by 110,000 tonnes per annum if replacing power from a coal-fired power station.
