Concrete 3D Printed Marine Wind, Solar and Energy Storage Support Structures

3DCP (3D Concrete Printing) can help solve logistical and sup-ply chain challenges for fabricating anchors and platforms for floating offshore wind (FOW) and other marine renewable energy structures (solar and wave). Offshore structures allow the harnessing of stronger and more consistent resources in expansive offshore areas, providing energy security with predictable energy sources, and boost-ing local economies. Sperra (formally RCAM Technologies) is a US company devel-oping a portfolio of 3DCP marine renewable energy support structures (Fig. 1). Sper-ra's portfolio has potential to reduce CAPEX 30% to 80% compared to steel compo-nents, increases manufacturing throughput, and reduces manufacturing footprint in space-constrained ports. 3DCP offers greater design flexibility, utilizing local material, and faster construction times. 3DCP is well suited to fabricating large structures and can be performed quayside, semisubmersible barges, or in a dry dock where can be towed out and submerged in deeper water to launch large platforms.
Fig. 1. Sperra’s product portfolio
Sperra established R&D printing facilities on the US east and west coasts (Los Ange-les and New York City). The Los Angeles facility is the only known a portside R&D 3DCP lab facility (550 m2). It has 1200 m of linear dock space which is available for marine testing and transport of prototypes.
Two key Sperra 3DCP case studies are presented for FOW. 1, a Cylindrical 3DCP suction anchor, 2, 3DCP energy storage spheres (Fig. 2).
Case study one is a trial print, and compression testing assessment of the effects of 3DCP indoor and outdoor printing of 0.8 m internal diameter cylinders (representing
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the structural basis of Sperra Suction anchors). The cylinders consisted of 2 x 50 mm side by side layers at 20 mm layer heights. A rebar ring was placed every 300 mm height interval. A 2 m cylinder was printed indoors as the initial trial, with a 3 m print-ed outdoors. The 3 m print was completed in one go in 2.5 hours of print time. No visible signs of shrinkage/drying cracking were noticed on the cylinder and is still in possession today. 50 mm x 100 mm cores were taken and tested in compression show-ing the effects of the interface bond, compared to cast concrete cylinders of the same mixture due to visible voids.
Case study two saw 4 x 400 mm diameter spheres printed with a print integrated structural base support. A 30 mm print layer at 10 mm layer heights was used. A key challenge was printing the extreme overhang and under hangs of the spheres mitigated by the integrated supports. The spheres were connected to a valve and pump/turbine system, resembling a prototype subscale marine pumped hydroelectric storage vessel. The prototype was fitted with cast in lifting anchors and submerged in 10 m of water depth in the Sperra facility testing channel for an hour long operational test. The spheres withstood 10 m water depth pressure without any leakage.