Question:

In the article on tidal-stream turbines (issue 6), I learned about a technology I was not aware of. The article indicated that the installation had a major drawback: masts breaking surface (…). But don’t the blades break surface before the supporting mast? Even if it does not break surface, the tidal-stream system as a whole must be a hazard for all boats, especially fishing boats. Do the regulations allow the creation of new invisible obstacles without the requirement to inform those who use the sea? Additionally, concerning Danish wind farms, the "True or False" box indicated that the use of speed-increasing gears on offshore wind turbines boosts their power output. What prevents the widespread application of such speed-increasing gears to land-based wind turbines?

Answer:

In the article on tidal-stream turbines, the author is not referring to the mast itself, but to the entire mast-blade assembly, the blades being higher when in the upper position.
This type of installation can indeed be a problem for fishing vessels, at least for trawlers. However, given the necessity to position tidal-stream turbines in high-current areas at the outlets of undersea valleys located, in this particular case, at the extremity of fjords, trawling areas are excluded by definition. Concerning Denmark, the widespread application of the speedincreasing mechanism to boost output by 10% is technically feasible, but is not planned. It is not considered desirable to have too high rotation speeds close to inhabited areas…