Project Portugal 2030

Summary

The number of offshore platforms, substations, subsea electrical interconnectors and cables is increasing significantly with the development of the MRE sector. Nevertheless, most nearshore and offshore locations of interest have a sandy and potentially mobile seabed. Hence, those technologies will experience additional challenges related to sediment mobility, in particular as the water depth decreases. The complex soil-flow-structure interactions further enhance scour development, especially in exposed locations. These challenges add to the need to mitigate the negative effects of offshore parks on the marine environment and the ambition to enhance biodiversity. Scour is a common problem in bottom-fixed subsea structures. Unsurprisingly, some research studies have been dedicated to better predict scour development and optimize the protections to reduce costs in offshore foundations [9]. However, such studies have not analyzed thoroughly subsea electric cables and manifolds, whose geometry and bed-shear stress amplification patterns can be considerably more complex. Therefore, there are knowledge gaps when it comes to the design of cost-effective and reliable scour protections for those components. On top of this, the industry stakeholders still remain highly dependent on heavy rubble-mound solutions that present considerable uncertainty in what concerns their scour-induced damage and installation accuracy [10]. In addition, often the alternatives to these protections imply using environmentally harmful materials. Recent studies show that modular solutions developed to promote biodiversity are a rising topic of research [11]. Available studies focus on the development and optimization of shapes, roughness and porosities to enhance biodiversity, but they lack a proper assessment of their stability at exposed locations and for typical installation conditions at the Portuguese coast, as well as proper hydrodynamic assessment of their influence on the scour development and scour protection [12]. In this sense, existing studies are limited and have considerable focus on the biological benefits, while lacking the extensive analysis of the solution’s viability from an engineering perspective. Within this context, SEACARE investigates 3 technical challenges that are crucial for the optimization of scour protections for subsea electrical cables and manifolds. The first one is the analysis and optimized design of scour protections in a non-horizontal seabed since most studies available focus on a horizontal seabed, while the Atlantic coast has several locations with considerably steep slopes. Secondly, it analyzes the performance of scour protection for cables laid side-by-side, which in offshore MRE farms may correspond to corridors of cables with a wide-cross section. Finally, nature-inclusive materials and shapes will be used to develop and demonstrate hydrodynamically optimized configurations that also contribute to cost-effective solutions. By overcoming these knowledge gaps, SEACARE achieves 4 goals that stand as practical contributions to the MRE industry: • New insights on seabed disturbances and scour characterization for non-standard and complex cases; • Innovative patented armor blocks to enhance sustainability and biodiversity of subsea infrastructures; • Reduction of overall costs (LCoE) of electrical subsea cables and related infrastructures; • New design guidelines of cables and manifolds scour protections for climate resilient MRE.