Stormy Seas in Shetland
Monday, February 18, 2013
A large storm bringing gale force winds and high seas swept across the Atlantic at the beginning of February, hitting Scotland and bringing waves to some areas in excess of 20m height, even taller than a five storey building.
The wave buoy deployed by Aegir Wave Power off the coast of St. Ninian's Isle remained on site throughout the storm, measuring a peak significant wave height of 11.2m on Monday 4th February. Individual waves were approaching 17m height from the trough of the wave to its crest; the same height as the tower of Sumburgh Head Lighthouse. At the peak of the storm, the instantaneous energy in the seas off the southwest of Shetland measured ~930MW/km of coastline.
Maurice Henderson captured some impressive images of the waves hitting Eshaness on the North West coast of Shetland.
Measuring the Sea
Good knowledge of the wave climate at a potential wave project site is critical for machine design and forecasting the potential energy yield. We assess the climate through a combination of satellite measurements, which are generally available for the past 20 years, and recordings taken from onsite wave measurement buoys. The measurement buoys are around 70cm in diameter and float on the sea surface. Accelerometers housed inside each buoy record its motion and this information is transmitted back to shore through a radio transmission. In this way we can collect live information on wave heights, directions and periods as well as building up a longer term record to allow us to compare with satellite measurements.
Take a look at the waves near you
If you live on the coast there’s a good chance there will be a measurement buoy deployed not too far from you. If you live in the UK or Ireland check out this website for an overview of some of what’s out there. We also hope to add a live feed from the Aegir buoy, located around 4km off the coast of St. Ninian's Isle, onto this website in future.
How to cope with big waves
Waves as high as the ones measured on 4th February are rare, even in the seas off Scotland, but despite occurring only once every year or so a wave energy converter must be able to withstand them. This is the key challenge for wave energy design – how to survive the ferocity of ocean storms whilst remaining a cost efficient generator in the small seas which occur most of the time.
Read how Pelamis machines are designed to survive the stormiest wave conditions here.
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