Pathetic performance of tidal power station lauded as "world record"

In a "record month" at the MeyGen tidal power project in the Pentland Firth... I'll just quote them:

A tidal power station in the Pentland Firth between mainland Scotland and Orkney has broken the world record for electricity generation....
In an update on the progress of the MeyGen project, by Atlantis Resources, the company said it had generated 700 megawatt-hours of electricity in August, a world record amount.

For those who are not so good at doing arithmetic in their heads, August has 31 days.  31 days is 744 hours.  700 MWh divided by 744 hours is less than 1 megawatt average output.

The MeyGen project appears to be in phase 1A, with only 3 MW of turbines installed.  Dividing 941 kW average generation by 3 MW yields a 31.3% capacity factor.  There are wind farms which do considerably better than this.  Comparing this to an 1150 MW(e) nuclear plant operating at 90% capacity factor, it would take 2200 MeyGen-scale turbines to equal the nuclear plant.  That is a lot of turbines.

The projected cost of this is staggering.  In phase 1C:

We will build an additional 49 (73.5 MW) turbines at MeyGen at an estimated cost of £420m

This would be 55 total turbines.  If phase 1C has the same per-unit capacity and cost as the first 6 units, the total cost would be £471m for 82.5 MW of nameplate generation.  At 31.3% capacity factor, that is £18.3 per average watt.  Only the ultra-wealthy could afford this.  It makes the Hinckley EPRs look positively cheap.

And what about the environment?  Tidal power works by blocking water flows and generating power from the difference in hydraulic head.  It reduces the difference between low and high tide wherever it's used, reducing the size of the intertidal zone which is home to a great many forms of life.  What are the economic losses from this?

Some things are obvious mistakes.  Tidal power needs to be left to drift away on the tide.
  ¶ 9/02/2017 01:42:00 PM