'First' natural fibre nacelle built for offshore wind turbines

Engineers Greenboats aims to test what it claims is the world's first natural fibre composite nacelle for offshore wind turbines later this year

Infusion of panels on the nacelle (pic: Sicomin)

Engineering firm Greenboats and bio-epoxy resin company Sicomin have produced a nacelle made from natural fibres that they aim to test in the harbour of Rotterdam this spring.

They claim the structure is one of the world's largest natural fibre composite (NFC) structures and marks the first use of such materials for an offshore wind turbine nacelle. Steel, aluminium, and polyester-based and epoxy-based glass-fibre reinforced composites have been used to date.

Product developer and manufacturer Greenboats was commissioned by an as-yet-unnamed wind energy technology developer, to design and produce a sustainable NFC nacelle.

The 7.3-metre-long structure has a surface area of about 100m2 and was engineered to satisfy all DNV-GL load cases that are needed for an offshore turbine nacelle. These include 55m/s max wind loads and 2KN loads on the guard rails.

Sicomin has also worked with German distributor Time Out Composites to make bio-based resins, intumescent fire-retardent gelcoats and ultraviolet-resistant (UV-resistent) clear coatings for the new nacelle.

Greenboats launched to show how large-scale NFC structures in wind energy can lower energy consumption in manufacturing by improving sustainability by using composite materials in turbines.

Friedrich Deimann, Greenboats founder and managing director, said: “For a structure like the nacelle, it was critical that we selected materials that process consistently and perform well in large-scale components, and that is where Sicomin are so strong.

“Their resins, gelcoats and clear coats meet our sustainability targets, and match our NFC ethos, with no compromise on performance.  And when we need to scale up, they can really supply on an industrial level."

More than 2.5 million tonnes of composite materials are in use across the wind industry around the world, while there remain few well-established recycling options, Sicomin stated.

To this end, the Sicomin GreenPoxy Resins were chosen by Greenboats for the NFC nacelle.

Sicomin's GreenPoxy range met challenging engineering requirements while matching manufacturing capability with the potential supply volumes needed by wind turbine manufacturers, the firm stated.

The bio-based epoxy was used to infuse BComp flax fibre reinforcements and balsa cores, with an intumescent weatherproof gelcoat applied on the outer surface, Sicomin said.

The intumescent gelcoat is a protective layer that will char and swell when exposed to fire, as opposed to spreading.

The manufacturing process sees cured panels cut to shape and then formed over a male plug and bonded together.

Then flax reinforcement plies are hand laminated with GreenPoxy resins and vacuum bagged and then added along all the panel joints lines. 

Highly UV resistant clear coating products are then used to protect and enhance the finish of the flax fibre.