The Nuts and Bolts of Tidal Flow Energy Generation
Date: 7th September 2018
If the principal drama at the European Marine Energy Centre (EMEC), in the Orkney Islands off the north coast of Scotland, centers around mammoth projects such as the submerged Microsoft Data Center or the giant 200-foot-long, 500-ton turbines that generate energy from tidal flow, one of the smallest contributors to this drama involves the nuts and bolts to hold these behemoths together and anchor them to the ocean floor. While small in size, these fasteners are not small in significance.
For decades, Whitford Ltd., based in Runcorn, Cheshire in the United Kingdom has been providing corrosion-resistant coatings for fasteners, which have been holding together oil rigs throughout the world, including those components that anchor the rigs to the ocean floor. That technology translates seamlessly to renewable energy projects. Whitford’s Xylan® coatings are an integral part of many renewable energy structures. Corrosion, both galvanic and red-rust, is a crucial concern with spiral, single or multi-blade devices on floating, surface or sub-surface piled foundation components. Xylan inhibits this corrosion. In addition, the stresses placed on turbine blades on a root fastener connection are significant. Xylan also delivers benefits in terms of torque-tension certainty.
Whitford Ltd.’s parent company, Whitford Worldwide, is the manufacturer of the largest, most complete line of fluoropolymer coatings for industrial purposes, with manufacturing facilities and sales offices throughout the world.
“EMEC is a leading global test site, providing developers with facilities to test devices from individual components up to full-scale equipment, with grid connection for power takeoff,” explains Gareth Berry, who is responsible for the specification of Whitford products in the Europe/Middle East/Africa region within the company’s Energy Sector. “We were first introduced to EMEC in 2011 and have developed a progressively closer relationship over the ensuing years. So much so that they are very much advocates for Whitford, having introduced us to several of the leading tidal energy developers.”
Whitford Coating Test Site Created
In August of 2011, when Atlantis Resources successfully connected its one-megawatt tidal turbine to the UK’s power grid, Whitford’s Xylan coating was utilized on several areas of the device. The tidal turbine uses Xylan 1424 on the heavy bolts and washers that secure the hatch covers. Xylan was chosen in preference to a multi-coat marine system since friction-resistant Xylan permits easy removal and refitting of the coated metal parts, while at the same time providing excellent resistance to the harsh elements to which the parts are continuously exposed.
The Atlantis turbine operates at a depth of about 50 meters (about half the length of a U.S. football field). The tides are strong in the North Atlantic — about four meters per second (equivalent to 7.8 knots, or 9 miles per hour). But there is also the severely corrosive salt water, so Whitford’s Xylan has been specified to resist the extreme environment.
To date, the results of using Xylan have been so promising, according to Berry, that EMEC was fully supportive when Whitford created its own test program in Orkney, launched in 2014, for further analysis of Whitford coatings in energy generation by tidal forces.
Panels, with a series of brightly colored Whitford-coated test strips and bolts affixed to them, can be seen on the side of the pier during low tide at EMEC’s Stromness Harbour test site in Orkney. They are part of a coatings test program taking place to analyze existing and developmental coating products under harsh environments.
“The pier provides a good representation of a splash zone,” Berry explained, “part of a structure that is intermittently exposed to air and immersed in the sea; subject to a range of wet and dry conditions as the test pieces are submerged and covered in line with the tidal ebb and flow. The pier provides an accessible location, which can be easily reached and regularly monitored, creating a standardized method in which to assess the performance of the coating. Since the surface and coating conditions remain the same, the only changeable factor is the time that the test pieces are exposed to the wet and dry conditions.”
Whitford’s aim is to be able to record high-quality live test data, according to Berry. The real environment perfectly depicts the conditions in which the coatings are used in service. Data received is key in determining the importance of Whitford coatings to multiple marine sectors including marine energy, offshore wind, as well as oil and gas. The company’s relationship with EMEC is open-ended, with Whitford expecting to keep the test panels and bolts in place for up to seven years.
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