DYNAMIC BEHAVIOR OF FLOATING SYSTEM WITH SLWRS

Abstract

 Subsea Hydrogen Production and Storage Facility (SHPS) has been proposed by us that uses ocean renewable energy to produce compressed hydrogen. SHPS consists of subsea production facilities that produce and store compressed hydrogen, a small floating body that sends electricity and alkaline water from the sea to the seabed, and risers that connect the floats to the subsea facilities. And SHPS aims to produce compressed hydrogen of about 40MPa, so its submarine production facilities are expected to be installed in the sea area at a depth of 4000m. As a riser system used in ocean development, there are Flexible Riser and Steel Catenary Riser (SCR) among other things. However, flexible riser is expensive, and SCR has problems with fatigue at touchdown zone (TDZ). Therefore, Steel Lazy Wave Riser (SLWR) with buoyant materials attached to SCR was developed. Due to the effect of buoyant materials, SLWR reduces breakage due to the riser's own weight and fatigue in TDZ, and realizes miniaturization of the floating part of SHPS. And SLWR is cheaper than other riser systems. However, SLWR is mainly analyzed for FPSO, and the response characteristics of small floating body with SLWR are not fully understood. In addition, since the small floating body is permanently installed in the installation sea area, it is not possible to evacuate even in stormy weather, so it is necessary to confirm the safety in the ultimate limit state. Therefore, in this study, the characteristics of SLWR were first grasped, and a parametric study on dynamic behavior in a regular wave including a mooring device for a small floating body with four SLWRs was conducted, and efforts were made to understand the response characteristics.