The Pentland Firth helps fills and drain the North Sea twice a day - water flows of up to 3 million tons a second.

Pentland Firth

One of the best sites anywhere in the world for tidal power generation from tidal turbines is the Pentland Firth, between the north of Scotland and Orkney. This is a deep (60-90m) channel that carries water from the Atlantic Ocean to help fill and drain the North Sea and the Baltic twice a day, with current flows at up to 16 knots.

Pentland Firth looking west

The attachment of secure mounting systems for tidal devices is limited by the operating environment found in the Firth. The  seabed is generally considered to be a scoured rock layer that would require either a gravity base or drilled anchor system. However, the overall depth and  high tidal flows preclude the use of divers and jack-up drilling. Gravity base designs are well understood and have been in use for many years in the marine sector. These are the most likely and lowest risk means of securing turbines in this environment. An alternative is to use dynamically-positioned drillships operating in neap tides at near to their limit of station-keeping ability.

The long-term effect on the environment from the operation of underwater turbines is not well understood though recent studies suggest that the rotating blades move too slowly to be a significant danger to marine animals.

One representation of this energy resource is shown in the hotspot chart alongside.

It can be seen that the best resource lies at the east end of the Firth, where the channel is narrowest, and especially between the islands of Stroma and Swona, the two islands straddling the main flow.

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