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Last Updated: Friday, 5 October 2007, 15:16 GMT 16:16 UK
A Viking past and 'green' future
Up Helly Aa Viking fire festival on Shetland
Up Helly Aa on Shetland, but the Vikings also had ties with the firth
Feared by sailors for centuries, the fast-flowing tides of the Pentland Firth could make it a powerhouse in terms of "green" energy.

Influential government advisory body, the Sustainable Development Commission (SDC), highlighted its potential in a report released last week.

Here, the BBC Scotland website takes a look at some of the facts, figures and history of the firth.

LENGTH AND BREADTH

Orkney seen from across the Pentland Firth on the Scottish mainland
The firth stretches for about 17 miles (27km), while the gap between the mainland and Orkney is between six miles (9km) and eight miles (12km).

The histories of the coastlines along the channel are littered with shipwrecks.

FAST-FLOWING

The North Sea
The tide flows through from the Atlantic to the North Sea and back twice a day.

The currents are estimated to reach speeds of up to 12 knots.

VIKING MYTH

Alistair Carmichael MP at Up Helly Aa
The firth is mentioned in the Norse Sagas and said to be the site of a great battle.

The Vikings had a strong influence on place names on the northern mainland and on Orkney.

TIDAL STREAM

Tidal turbine technology designed by E.ON and Lunar Energy
Tidal stream technology could be deployed on the firth.

This uses the energy contained in fast-flowing tidal currents generally found in constrained channels.

POWER POTENTIAL

Light bulb
According to the Sustainable Development Commission, 5% of the UK's electricity could be generated using tidal stream.

Almost 60% of that power could be sourced around the Pentland Firth.

SEE ALSO
Firth could be key to tidal power
01 Oct 07 |  Highlands and Islands
Advisers endorse tidal power plan
01 Oct 07 |  Science/Nature
Orkney tidal power plans unveiled
28 Sep 07 |  North East/N Isles
Swinging wave device to be tested
13 Jun 07 |  Highlands and Islands
Wave energy set to turn the tide
15 Mar 07 |  Business
Orkney to get 'biggest' wave farm
20 Feb 07 |  Scotland

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