Alex Salmond's fantasy of a tidal-powered Scotland washed away

Opinion One of Alex Salmond's ambitious dreams for an independent Scotland - that it would soon become rich by exporting clean green electricity pouring from tidal powerplants in the Pentland Firth - has been destroyed this week by new research showing that the Firth's potential output is far less than Salmond had thought.

The Scots politico, announcing early efforts in the Firth in 2008, went so far as to suggest that not only could Scotland power itself on Pentland 'leccy, but that it would be selling electricity in substantial amounts to less fortunate nations.

"The sort of power that potentially could come from this area is not some hundreds of megawatts, it's not just like one conventional power station, its 20 gigawatts and more than that, that's like 20 conventional power stations," he enthused back in 2008.

"We have to get in a position where we have a supergrid, not just to England but across to Europe to sell that energy to people who need it," added the would-be premier of an independent Scotland.

A steady twenty or even thirty gigawatts as envisioned by Mr Salmond would indeed be more than sufficient to meet all of Scotland's energy needs, not just that much smaller amount supplied today in electric form. At the moment (pdf page 4) Scotland consumes around 13,301 kilotons-of-oil-equivalent of energy in all forms (electricity, coal, oil, gas, all of it). Even in a future with fully electric transport, industry, heating etc, such a level of demand would equate to steady production of well under the Pentland's supposed 20 gigawatts, leaving a sizeable surplus for export to energy-starved England and the Continent.

There's just one problem with that: it's a load of rubbish, according to a new study published by a group of engineers based at Oxford uni and in Ireland and Australia. They write in the Proceedings of the Royal Society A:

It is found that three rows of turbines extending across the entire width of the Pentland Firth and blocking a large fraction of the channel can theoretically generate 1.9 GW, averaged ... generation of significantly more power than this is unlikely to be feasible as the available power per additional swept area of turbine is too small to be viable.

"We are happy our number is very robust," lead author Thomas Adcock tells the Guardian, describing the adviser who had given Salmond his figures as being "in a minority of one" among subject-matter experts.

Tellingly, the Scottish government webpage "Energy in Scotland: Get the facts" has now been amended to remove claims of 14GW tidal potential, though the foolish figure can still be seen in the Google cache for the moment.

So in fact the Pentland Firth, described as "the world's best site for tidal power" by Grauniad enviromation correspondent Damian Carrington today*, could at the outside maximum supply about 10 per cent of Scotland's energy needs (that is, less than a single percentage point of Britain's as a whole). The figure would almost certainly be a lot less in the real world, as the Firth is a busy shipping route and full exploitation would mean closing it completely.

The cost of doing this would be massive compared to that of simply building a nuclear power station with the same output (in the Severn estuary the proposed barrages were costed at six to ten times as much as equivalent nuclear plants). The price difference would have to be made up by government action to force electricity prices up much higher than they would otherwise be - and such government action has already been responsible for the bulk of the electricity price rises of the past decade. The scope for even more gouging is probably limited.

Comment

Carbon emissions may perhaps be a terrible and immediate menace. But the allied idea that the carbon-driven power sources of today can really be replaced in any meaningful or affordable fashion by renewables looks madder and madder every day. ®