Innovative multi-material connector showcased by university-led team
During early January, a research team based at Brunel University, UK, launched an innovative 'multi-material connector' that is predicted to help reduce the running costs associated with mooring a range of devices commonly deployed throughout the offshore renewable energy industry.
Connectors form a key part of many offshore renewable energy systems, and are commonly used to join moorings for floating devices - like tidal and wave energy converters or floating wind turbines - with their anchors. For example, many 'penguin' type wave energy converters float on the surface of the sea, using the movement of the waves to power an on board turbine - and harvest the electricity they generate via cables embedded in its mooring ropes, which are constantly exposed to the harsh marine environment, as well as its wildlife.
In light of their important function, connectors often have a pivotal, and quite costly, role to play in installed systems. In an effort to help in minimising these costs, a team of researchers based at the Brunel University Experimental Techniques Centre and the Brunel Centre for Advanced Solidification Technology has created a connector using a novel composite material known as Basaltium. The material, which forms the centre of the new connector, is made from a recycled aluminium matrix strengthened by tiny basalt fibres, offering a more sustainable and environmentally friendly solution. This core is then coated in another cutting edge material - a custom formulated, lightweight and low-friction nylon called Oilon - produced by Leicester based plastics manufacturers Nylacast, which helps to significantly reduce rope wear.
As Dr. Lorna Aguilano of the Experimental Techniques Centre, explains, the idea for the connector first originated during a discussion with the Ireland based wave energy converter developer Sea Energies, in which representatives of the company observed that the chafing of the rope at the connector point was a 'continuous limitation and cost' for their operations. Another company called Tension Technology International (TTI) - which possesses many years of experience in the field - also confirmed and stressed that this point was in fact 'a big challenge for the industry, hence a novel design and novel material solution was required.' These discussion culminated in the creation of the connector as a multi-partner effort that offers a novel solution for the mooring challenge.
"The novel design loads in a balanced compression and offers the opportunity for the use of lighter materials, hence offering a more deployable solution with easier maintenance. The novel multi-material solution proposed not only offers a weight reduction, but due to the anti-corrosion, anti-fouling and UV-resistant properties of both the core and the Nylacast outer shell, the life-span of the connector increases by 30%," says Aguilano.
According to Aguilano, the new connectors could show a 30% increase in life span, taking it from a 20 year to a possible 30 years life span. This is due to a combination of factors, including the low friction of the materials, a decrease in weight of 60% compared to the stainless steel material typically used for these types of devices, and 'an ease in deployability as a consequence of the weight reduction.'
"Together, these new materials, Basaltium and Oilon, make connectors lighter and tougher, and mean moorings can last longer and cost less to manufacture and maintain," she says.
The connector was first designed for floating wave energy converters as part of the multi-partner Engineering and Physical Sciences Research Council (EPSRC)- backed STORM (Specialised Thimbles for Offshore Renewable Marine energy) project by TTI (which completed the design of the novel connector), Brunel University, which undertook the material development and optimisation and the casting of the connector's core and Nylacast (which assumed responsibility for the material development and production of the polymer outer shell) - alongside the European Marine Energy Centre (EMEC), which is now taking charge of disseminating the project results.
"The STORM project was a feasibility study, with the final scope to produce five connectors that could be tested to 40 tonnes. This was successfully demonstrated when the prototypes were tested TTI Testings laboratory environment up to 40 tonnes break load, after fatigue cycling the connector," says Aguilano.
"The connectors each weigh 13kg, while its counterpart in stainless steel would have weighed 37kg. The connector withstood the testing successfully proving the viability of the concept," she adds.
Aguilano also reveals that, on 25th January, the STORM connector project was awarded the Innovate UK Rushlight Award 2018 for the responsible product category - and the next day, members of the project team showcased the connector to stakeholders from across the offshore renewable energy industry during a mooring masterclass workshop organised by EMEC at the Brunel University Uxbridge campus. Ultimately, the project team hopes that staging events like these will prompt a wide range of practitioners from the offshore energy industries - including the oil and gas sector - to 'swap notes' about their experiences of working with marine moorings.
"Ocean energy is a developing industry and the masterclass aims to identify gaps in the industry, and spark new partnerships and projects to advance this vital component. The team will now focus on raising funds to upscale the connector to 100 tonnes breaking loads, that can be used for wave energy devices and also small scale offshore wind floating devices," says Aguilano.
"The plan is to then further upscale the connector to up to 800 or 1000 tonnes within the next five years, in order to satisfy also full scale floating wind, end users," she adds.
By Andrew Williams
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