The rotational moulding process offers a range of crucial benefits to WEC designers that could initiate a step-change impact in LCoE. This targeted project will assess the potential application of new and existing technologies to overcome these hurdles. We will investigate hybrid rotationally moulded structures with concrete ballast material that contributes to the strength of the structure and innovative new design concepts for accepting point loads and preventing buckling of the rotationally moulded structures.

The advantages of polymer-based design verses steel, particularly with fatigue and corrosion resistance, are becoming increasingly utilised in marine applications. Polyethylene products form the majority of low cost solutions, due to the low price and distinguishing plastic behaviour. Last year the world’s first all polyethylene WEC was successfully tested at full scale (50m long), acting as clear demonstration of the material’s capabilities and potential.

Rotational moulding is the cheapest form of polyethylene moulding and the one that can output the largest end products, making it an attractive option for WEC designers.

A few key engineering challenges are preventing rotational moulding from immediate application, namely with the typically thin wall thickness and low yield stress of the material. This means that metal parts are often still required to cope with the high point loads witnessed by wave energy devices, negating many of the advantages of the material. Also the large internal cavities, whilst posing a prime opportunity for active or passive ballasting, do not allow for internal bulkheads using standard techniques, preventing the easy creation of engineered internal spaces. Our advancements hope to overcome these challenges.