Tidal power isn’t new: the barrage on the Rance near Saint-Malo in Brittany has been generating useful power since 1966. But estuary dams have drawbacks: you sacrifice other uses, you get silting, and each project is bespoke. But a project in Northern Ireland now seems to have moved tidal power from the pigeon-hole “useful, niche, experimental” to “large-scale, replicable, near-commercial”.
It’s significant that the company, Marine Current Turbines, set up in 1999, is now a fully-owned subsidiary of the unsentimental giant Siemens, with no time for lost causes.
There are no really helpful photos on the company website, but here’s a CAD drawing that gives the idea:
Siemens/MCT seem to have solved the reliability issues that plague wave power; tidal environments tend to be somewhat sheltered, and the vulnerable rotors are safely below the surface. The Rance barrage has a decent capacity factor of 40%, higher than wind and solar but lower than geothermal or conventional. The availability shifts round the clock like the tides, which isn’t ideal for matching demand. But as the tides are 100% predictable, and generation varies smoothly along a sinusoidal curve, the problem must be very much easier to manage than the noisier intermittency of wind and solar, and makes a mixed system more resilient.
The important point for the economics is that the design is a standardised piece of kit, largely manufactured off-site, which can therefore benefit from economies of scale and learning. Which we will only get provided that a critical number of governments provide infant-industry subsidies (FITs or tax credits) to take us along the curve. Nova Scotia can’t do it by itself.
Japan, currently planning its own huge Energiewende away from oil and nuclear, is nibbling at tidal as a component of the new energy mix with another vendor. My guess is that it will scale up rapidly assuming the demonstration works.
Jerriais – the sadly extinct Jersey dialect of Norman-French – had a specific word for the difference between high and low water: le puognant, if I recall rightly. This matters in Jersey where the range can be 10 or 30 feet. I commend the word to tidal engineers.