An exciting renewable technology

Tidal Generator

Regular readers of this column will know that I am not impressed by the theory of anthropogenic global warming.  But I am very concerned about energy security, so I am in favour of renewables if they meet basic tests of environmental and economic sustainability.  Clearly wind turbines do not meet these criteria.  But under-sea tidal turbines just might.
 
A current of water has a much greater energy density than a current of air, so you can generate more power from a much smaller device.  Tidal power, like wind power, is intermittent, but critically, unlike wind power, it is totally and entirely predictable, which is a huge advantage.  The managers of the grid will know exactly how much power they can expect, and when.  And tidal turbines, which work both ways (on the flow and on the ebb) can produce power perhaps sixteen hours out of twenty-four.  Under-sea tidal turbines also avoid the huge environmental damage that on-shore wind farms do, despoiling landscapes, and blighting communities, and homes, and lives.  Moreover while wind turbines have to shut down for safety reasons in very high winds, it seems that there is no limit to the current speed in which a tidal turbine can generate power.
 
Of course the sea-bed presents a very corrosive and challenging environment, together with problems of cabling, and accessing the grid, but these problems are arguably no greater than those being addressed for off-shore wind.  After decades of North Sea drilling, British engineers are well experienced in creating durable structures for under-sea environments.  The turbines will be sufficiently deep to allow ships to pass over them, although of course trawlers and submarines will need to keep clear.
 
So I was delighted to be able to visit Rolls-Royce in Derby on Nov 20th to learn about their tidal turbine project.  Of course Rolls-Royce have unrivalled experience with turbines, and indeed with propeller systems, and are well-placed to take a leading role in this endeavour.  They have a pilot project, with a trial turbine due to be located in the Orkneys next year.  I saw the plans.  They start with a large tripod structure which can be anchored to the sea-bed using a ship and a remote-control submersible.  Then the turbine, looking for all the world like a torpedo with an out-size propeller, is attached at the top.  This can rotate around a vertical axis through 180 degrees to face the tidal current either way.  The blades can be feathered to present the most efficient angle of attack for the rate of flow at the time.
 
Britain has one of the best tidal environments for tidal power of any country in Europe — and a world-class engineering company capable of developing and exploiting the technology.  Rolls-Royce estimate that up to 5% of Britain’s electricity needs could be generated in this way — and the technology could be exported around the world.  I wish them every success, and I hope to be able to visit the Orkney site in due course.