I envisage ranks of these things, possibly looking like a regiment of airliner engines, mounted on pad footings across the current flow of whatever seaway is considered.
If two-way generators are uneconomic one-way ones could be mounted to swing into the direction of the prevailing current, like ships at anchor, or actuated to do the same.
It appears logical to me that any water generator would be a tiny fraction of the size of a wind generator of the same output.
If this idea is economic then only a suitable sea current would be required with no reference to any tidal range, avoiding use of the Severn Estuary.
What about the North Sea which must have millions if not billions of tonnes of water on the move at any time with a depth allowing siting of generators below shipping draught? Can this immense momentum be put to use for power generation in this way?
MARTIN HOOK (M), Dene Cottage, Church Lane, Challock, Ashford, Kent, TN25 4BS