Experimental Study of a Scaled Flexible Riser for Hydrogen Transport from a Floating Wind Turbine Platform to the Seabed

Dolphyn Hydrogen aims to support the UK Government’s 2030 hydrogen targets by deploying a 10-15 MW Commercial Scale Demonstrator that produces hydrogen offshore using wind energy. To achieve this, hydrodynamic studies are required to optimise the flexible pipeline transporting hydrogen from a floating wind turbine to the seabed, as well as the buoyancy modules that create the riser’s lazy wave shape. A key parameter is ensuring the riser never bends below its minimum allowable radius. The hydrodynamic behaviour of a 6-inch NOV flexible pipe is tested at 1:62 scale in the University of Plymouth’s COAST Laboratory Ocean Basin. The riser is connected to a semi submersible platform with heave plates, and both operational and storm conditions representative of the Celtic Sea are examined. Design waves that maximise platform surge or mooring loads are also identified and tested. Underwater Qualisys cameras track ten markers along the riser, enabling reconstruction of its shape at each time step and calculation of the minimum bending radius. Comparing full sea-state results with those from Design waves helps assess whether Design waves can reliably predict minimum radii for flexible risers.