Transportation and Installation (T&I) Recommendation for a Semi-Submersible Floating Offshore HVAC Substation

GE has worked with Genesis to develop a semi-submersible Floating Offshore Substation (FOSS) solution (810MW, HVAC) for USA west coast with 1100-mter water depth. This concept design is based on the metocean data in Morro Bay Area, California (CA). The 1100-meter water depth and swell metocean (long period wave) give rise to extra technical challenges for floating OSS design, especially for the dynamic cable design. The developed semi-submersible Floating Offshore Substation (FOSS) solution (810MW, HVAC) has been further validated and confirmed by one wave basin test performed at Oceanide (South-France) during July 2023. As one part of one complete FOSS solution, how to transport and install (T&I) FOSS at California west coast site has been investigated. This California site condition brings special challenges for the T&I, such as the port infrastructure limitation, etc. The main purpose of this paper is to discuss the recommended transportation and installation (T&I) methodology for the FOSS, which includes the load-out, dry transport, discharge, mooring preset, wet tow, mooring hookup and dynamic cable installation. The recommended T&I methodology is mainly based on the fabrication base case, that the FOSS topside has been integrated onto the hull at the fabrication yard. Based on the recommended T&I methodology presented in this paper, it can be concluded that the GE FOSS (810MW, HVAC) can be transported from Asian fabrication yard to California west coast, and installed.