he problem with exploiting tidal power has, rather, been finding places where it can be done efficiently: bays, estuaries or straits with a suitable tidal reach and a topography that permits a system to be constructed. Only then, with established designs, can turbines be installed through which the tide can ebb and flow. That would change, though, if turbines could simply be attached to the sea floor. And several firms
Since a turbine is not much use if its blades stick above the surface, they need to be located in reasonably deep water
words | John Clifford, Director at Cocoon Renewable Energy Consultants Ltd, and Elaine Prescott
The ebb & flow of tidal power generation One problem with renewable energy is that neither the wind nor the sun is reliable. That cannot, however, be said of the tides. The Newtonian clockwork of sun and moon can always be relied on. 32
are trying to make it so. Some, such as Andritz Hydro Hammerfest, in Norway, and Marine Current Turbines from Bristol, in Britain, take the relatively simple approach of sticking what are little more than strengthened wind turbines onto the seabed. In the case of such turbines, though, bigger is better. And, since a turbine is not much use if its blades stick above the surface, they need to be located in reasonably deep water. This is a shame, because a lot of otherwise-suitable sites are too shallow. Not all wind turbines work this way, though. Some smaller ones are skeletal cylindrical structures whose axis of rotation are at right-angles to the direction of the wind, rather than aligned with it. And that, with the important modification that this axis is horizontal rather than vertical, is the basis for several novel designs for tidal-power generators which can operate in shallow water too. Engineers at Ocean Renewable Power Company, in Portland, Maine, and Kepler Energy, in London, both use this approach. And Ocean Renewable is starting to commercialise it. In September 2012 its TidGen generator was deployed in the Gulf of Maine. It thus became the first plant to deliver offshore-generated power of any kind (wind, wave or tidal) to an
GIBRALTAR MAGAZINE â€˘ MARCH 2014
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