Tidal turbines

Grader A: partial

MeyGen began commercial operation in April 2018 with 6 MW and sells power to the GB grid, but it is the largest tidal-stream project in the world and expansion to 28 MW is only planned for 2027. Real but limited availability, as the poster's own 'small scale' note already described.

Test: D37 Horizons: tidal-stream electricity or turbines sold to ordinary customers outside pilots by 2020; a few small arrays count as limited availability.

• MeyGen (Wikipedia) (2018-04): Phase 1 commercial operation April 2018, 6 MW; claimed world's largest tidal stream project; Phase 2 planned 2027.

Grader B: partial

Tidal turbines produce grid power only in small arrays: MeyGen's 6 MW demonstration array entered operations in April 2018; global tidal-stream capacity stays tens of MW. Real but limited.

Test: Tidal-turbine power or units could be bought outside pilots by 2020; partial if limited/demonstration.

• MeyGen Phase 1A enters 25-year operations phase (2018-04): 6 MW, four-turbine demonstration array exporting to the grid.
• MeyGen (2024): Largest tidal-stream project still small scale.