we take the total coastline of Britain (length: 3000 km), and put a strip of
turbines 4 km wide all the way round, that strip would have an area of
13 000 km2. That is the area we must fill with turbines to deliver 16 kWh/d
per person. To put it another way, consider the number of turbines re-
quired. 16 kWh/d per person would be delivered by 44 000 “3 MW” tur-
bines, which works out to 15 per kilometre of coastline, if they were evenly
spaced around 3000 km of coast.
Offshore wind is tough to pull off because of the corrosive effects of
sea water. At the big Danish wind farm, Horns Reef, all 80 turbines had to
be dismantled and repaired after only 18 months’ exposure to the sea air.
The Kentish Flats turbines seem to be having similar problems with their
gearboxes, one third needing replacement during the first 18 months.
The area with depths between 25 m and 50 m is about 80 000 km2 – the size
of Scotland. Assuming again a power per unit area of 3 W/m2, “deep” off-
shore wind farms could deliver another 240 GW, or 96 kWh/d per person,
if turbines completely filled this area. Again, we must make corridors for
shipping. I suggest as before that we assume we can use one third of the
area for wind farms; this area would then be about 30% bigger than Wales,