Professor Rod Rainey, is a world expert on the subject of Tidal Power.
Prior to his retirement, he worked in this field for nearly 40 years at Atkins, the civil engineers. He will explain that the Government studies on the Severn barrage cover all the easy aspects in great detail, but are silent on a very important question: how to build it?
Two options that have been considered are the French tidal power barrage at La Rance, built in the 1960s, and the Thames barrier which was built in the 1980s.
La Rance is primarily bult of concrete, with foundations like a building, and a temporary coffer dam which was built to allow construction as if it was on dry land. It is a very nice barrage, but it was so expensive that the French have not built any more.
The Thames Barrier illustrates that it is cheaper to build in steel. The Thames Barrier has gates which rotate upwards from the seabed, like a gas valve.
A tidal power barrage could be built in a similar way, but with the gates replaced by “breast-shot” water wheels, which are much cheaper than the Kaplan turbines installed at La Rance, and also do not harm the fish.
Professor Rainey recently published, in the Proceedings of the Royal Society, some hydraulic and structural calculations for a steel barrage of this design, for the Severn estuary. He compared the weight of steel required with that in the Atkins-designed Beatrice offshore wind farm, in Scotland. Per unit of energy generated annually, it is about one third of the latter. Since steel fabrication costs are roughly proportional to steel weight, it looks economic.
For more information on Rod Rainey and on Tidal Power click here.
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