Pentland Firth
| Pentland Firth | ||
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| Connects waters | North Sea | |
| with water | North Atlantic | |
| Separates land mass | Orkney | |
| of land mass | Scottish mainland | |
| Data | ||
| Geographical location | 58 ° 42 '49 " N , 3 ° 8' 55" W | |
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| Smallest width | 10 km | |
| Coastal towns | John o 'Groats | |
| Islands | Isle of Stroma , Swona , Muckle Skerry | |
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Pentland Firth (loosely translated: "the strait in the land of the Picts") refers to the strait / sound between the Scottish mainland and Orkney . It was created when the sea level rose in the post-ice age , sometime between 12,000 and 10,000 BC. u. Z. (Dates are available, but are controversial).
meaning
The Pentland Firth is one of the most difficult sea areas in the border area between the North Sea and the North Atlantic because of its extreme current and wind conditions . So has z. B. During the commissioning trip of MV St. Sunniva , a ferry of the shipping company P&O - Peninsular and Oriental Line - a cavalryman smashed the bridge deck in the 1980s , so that the ferry had to run back to Aberdeen under the protection of the Scottish coast .
Almost 100% of the failing crossings in the Ferry Lifeline Service between Orkney ( Stromness ) and the Scottish mainland ( Scrabster ) are not due to adverse weather conditions in the sea area around Orkney or off the Scottish north coast in general, but solely to the account of the conditions on the decisive ones four nautical miles between the south coast of Hoy and the mainland at Scrabster.
Tidal Races
The Firth is well known for the intensity of the tidal current, which is one of the most energetic in the world due to its high flow rate. The main stream between Duncansby Head and Muckle Skerry , which is only about 7 km wide , has an average of eight times as much water as the Amazon . This is why this area is also known as the “Saudi Arabia of the tidal force ”. Up to 16 knots (around 30 km / h) were measured west of the Pentland Skerries . Elsewhere, significantly higher top speeds are achieved, but due to the small cross-sections and the lower average speed, they only have a small total volume flow ( Saltstraumen 22 kn or Skookumchuck Narrows in British Columbia with 17 kn). These hydrological peculiarities offer great potential for energetic use.
In December 2014 it was announced that the MeyGen ocean current power plant with a capacity of approx. 400 MW is to be built in the Pentland Firth . According to the operator, this is the largest such power plant planned to date. Construction began in 2015, the first electricity was produced in 2016 with two 1.5 MW systems, and two more were installed in 2017. The trial run ran very successfully for a year until summer 2018. A total of 269 turbines are to be used, the annual standard working capacity of which should correspond to the consumption of around 175,000 households.
The force of the tidal currents creates electrical cables and tidal rapids that can occur at certain times of the tidal current. Some of the main rapids are:
- 'The Merry Men of Mey'. Southwest of Stroma ; from St John's point across the Firth towards Tor Ness on the Isle of Hoy . In particular, on a sandbank that is only 25 m flat, 5 km west of Stroma, with a westerly current (westerly current) and wind from the west (westerly wind), constant standing and permanently breaking waves of several meters in height form. The speed of the tidal current can exceed 10 knots (18.5 km / h).
- 'The Swelkie'. The north end of Stroma is evenly rounded and drops to a depth of 60 m, so that the current is locally very strongly accelerated both at low tide and at high tide, breaks off behind Swelkie Point and can form a huge vortex. According to a Viking legend, the vortex is caused by a sea witch who turned the millstones of the salt mill there to keep the sea salty. Swelkie is derived from the Old Norse word svalga and means devourer.
- The 'Duncansby Race' always flows in an easterly direction. It starts after low tide with the onset of the tidal current along the north-east side of the Boar of Duncansby , which is only 10 m deep and 2 km long , immediately before the Ness of Duncansby to the south-east. With increasing tide currents and increasing water depth over the Boar of Duncansby , more and more water flows faster and faster over the shoal, now to the east-northeast, over the next two and a half hours. This creates another race west of it parallel to the coast in front of the Ness of Huna . After high tide, the ebb tide going northwest creates a Nehrstrom counterclockwise, so that again a stream going northeast goes over the shoal. Also east of Duncansby Head , rapids with different but always dangerous characters form at different phases of the tide. It becomes particularly dangerous in stormy winds against the tidal current, as the vortices interrupt the energy transport within the storm waves, whereby their kinetic energy is converted into potential, the wave builds up to a wall of water and collapses under gravity the next moment.
- The 'Liddel Eddy' (Liddel-Nehrstrom) forms between the islands of South Ronaldsay and Muckle Skerry at high tide .
Web links
Individual evidence
- ^ Saudi Arabia of marine energy . BBC website December 29, 2013.
- ↑ Frank Binder: New technology in the sea for generating energy · Mega project off Scotland. Huge turbines have to withstand strong tidal currents. Forces like a hurricane on land with 350 km / h . Daily port report , October 25, 2017, pp. 1, 15. For the trial operation, see reference article "Ocean current power plant"
- ↑ Green light for world's largest planned tidal energy project in Scotland . In: The Guardian , December 19, 2014, accessed December 24, 2014.