tricky to build on.

Admitting all these uncertainties, I arrive at an estimated total power
of 9 kWh/d per person from tidal stream-farms. This corresponds to 9% of
the raw incoming power mentioned on p83, 100 kWh per day per person.
(The extraction of 1.1 kWh/d/p in the Bristol channel, region 2, might
conflict with power generation by the Severn barrage; it would depend
on whether the tide farm significantly adds to the existing natural friction
created by the channel, or replaces it.)

Region U power area average raw power
  (knots) density   power d ω N S
  N S (W/m2) (km2) (kWh/d/p) (m) (km) (kWh/d/p)
1 1.7 3.1 7 400 1.1 30 30 2.3 7.8
2 1.8 3.2 8 350 1.1 30 17 1.5 4.7
3 1.3 2.3 2.9 1000 1.2 50 30 3.0 9.3
4 1.7 3.4 9 400 1.4 30 20 1.5 6.3
5 1.7 3.1 7 300 0.8 40 10 1.2 4.0
6 5.0 9.0 170 50 3.5 70 10 24 78
Total 9

(a)(b)

Figure G.7. Regions around the British Isles where peak
tidal flows exceed 1 m/s. The six darkly-coloured
regions are included in table G.8:
  1. the English channel (south of the Isle of Wight);
  2. the Bristol channel;
  3. to the north of Anglesey;
  4. to the north of the Isle of Man;
  5. between Northern Ireland, the Mull of Kintyre,
    and Islay; and
  6. the Pentland Firth (between Orkney and mainland
    Scotland), and within the Orkneys.
There are also enormous currents around the Channel
Islands, but they are not governed by the UK.
Runner-up regions include the North Sea, from the
Thames (London) to the Wash (Kings Lynn).
The contours show water depths greater than 100 m.
Tidal data are from Reed’s Nautical Almanac and DTI
Atlas of UK Marine Renewable Energy Resources (2004).
Table G.8. (a) Tidal power estimates assuming that stream farms are like wind farms. The power density is the average power per unit area of sea floor. The six regions are indicated in figure G.7. N = Neaps. S = Springs. (b) For comparison, this table shows the raw incoming power estimated using equation (G.1) (p312).