October 16th, 2012

(For those of you looking for something as far as possible from the campaign)

Duc Guillaume was, you may recall, deeply interested in the management of his English conquest, and commissioned the totally unromantic Domesday Book, basically a survey of land taxpayers. The successors to his diligent curia regis are still at it, managing Crown property: now distinguished from the private assets of the Queen like Sandringham, these include the foreshore and the seabed out to 10 miles. The Crown Estate have therefore carried out a survey of the tidal and wave resources of the UK – out to the 200-mile edge of the exclusive economic zone, where the Crown doesn’t SFIK have any property rights, but maybe they know something about the Statute of Westminster (1275) I don’t.

On the basis of pure technical feasibility – ignoring the economic issues for now as the technology is immature – they estimate total theoretical UK resources at:

  • Wave: 69 TWh/year (27 GW);
  • Tidal stream: 95 TWh/year (32 GW);
  • Tidal range (barrage schemes): 96 TWh/year (45 GW);
  • Tidal range (lagoon schemes): 25 TWh/year (14 GW).

The last two are to a considerable extent alternative uses of the same estuaries.

For comparison, total UK electricity production in 2011 was 374 TW/h and capacity 89 GW. So wave and tidal power could in theory meet up to 70% of UK electricity demand if they were continuous, which they won’t be. But even on the more limited scale that will be imposed by economics, this isn’t chickenfeed.

There’s a nice map on page 9 showing where the resources are:

The accessible high-quality wave energy is off the Hebrides and similar remote places, implying large transmission costs. Nobody will be mad enough to place wave farms in the shipping lanes of the Western Approaches, or in the storm-tossed fishing grounds between Scotland and Iceland. The good tidal range sites are in estuaries close to centres of population, but there are big potential conflicts with other environmental uses (such as bird wetland habitats). The least-hassle technology is tidal stream, which in many places doesn’t SFIK interfere much with anything else.

The Crown Estate leave out the Alderney Race in the Channel Isles, which can support a 3GW tidal stream array. The currents are ferocious there: the Casquets rocks west of Alderney have a fine collection of 300 seabed wrecks.

The reason may be that Alderney isn’t part of the Crown of Great Britain and Northern Ireland, but held by the Queen as Duke of Normandy and therefore vassal of the King of France, as laid down in the Treaty of Paris, 1258-9. Does the Grand Coutumier Normand have anything to say about underwater tidal turbines and DC cables?

William would have liked this. Canute only used the tides to make an elegant moral point. But William’s successor can make them pay real dues and service. Book it, clerk!

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