Thanks for some good info on the decommissioning of their old unit, and the comparative newness of the O2. I had thought they only had one prototype operating. It is interesting to compare their statements of HOW MUCH energy they put to the grid over time, as contrasted with Minesto’s far weaker and less specific claims.
I’m not sure where you get the idea that pitch control is “necessary” to handle a variance in stream velocity, unless you think they are powering an induction generator directly coupled to the 50 Hz grid over there. Even then, pitch control would not be strictly necessary. Look up “The Danish Concept” of wind turbine design from the 1980’s. The blades were just bolted to the hub - no pitch control whatsoever, in varying windspeeds, yet within a tight rpm range. Your assertion that pitch control is needed for varying current speeds sounds like stuff armchair-inventors come up with when they are not up to speed on a technology.
With variable RPM to match the variable current speed, as we see in wind turbines, pitch control is not needed for that purpose, but is instead used for overspeed protection and sometimes fine-tuning torque as each blade transitions the gradient from high winds at high heights, to lower-speed winds nearer to the ground. Small wind turbines almost never have pitch control. When they do, it’s usually a problem and breaks down, because it involves maintenance that nobody wants to, or bothers to, perform.
I was going from their renderings, and from the renderings, you see no twist or camber, indicating that the blades likely always rotate the same direction, with a less-than-180-degree pitch range, but rather a more restricted range of +/- whatever the working pitch is. Maybe their new model moves past this early design. There must be some reason they stopped running it. Maybe they wore it out already!
As to what you say “my idea” is that “would be more hassle anyway”, well, I haven’t stated “my idea”, I just said what I had originally thought “their idea” was, which was to take the time of lull between tidal flows to allow the “ship” to re-orient itself to the new current direction. And I’m not seeing how allowing it to passively reorient itself 180 degrees is “more hassle” than including a pitch-control system. Remember, when working with steel machinery, immersed in a salt-water environment, keeping everything as simple as possible, with the fewest wear points and lowest parts count possible, is advantageous. A pitch-control system on a rotor of that size and strength is no trivial undertaking, would add cost and complexity, and of course would require maintenance.