Abstract

The development of renewable energy is desired worldwide due to consideration for the environment. In this research, in order to realize Subsea Hydrogen Production and Storage Facility (SHPS) that produces compressed hydrogen by using the electric power obtained from ocean renewable energy, SLWR (Steel Lazy Wave Riser) is adopted for riser that sends hydrogen to the sea surface from a depth of 4000 m. In addition to understanding the characteristics of SLWR, we tried to understand the response characteristics by systematically calculating the dynamic behavior of the regular wave including the mooring device for small floats equipped with four SLWRs.

INTRODUCTION

Energy development by renewable energy is desired in world because of consideration for environment. However, its production is easily affected by natural situation, so stable energy supply is difficult. Therefore, we propose Subsea Hydrogen Production and Storage Facility (SHPS), which produces highly compressed hydrogen using electric power obtained from marine renewable energy, and conducted basic research on its economic efficiency (Eto, 2017). Since the surrounding area of hydrogen production by water electrolysis in deep sea is a high-pressure environment, hydrogen can be safely produced and stored, and compression cost can be expected to be reduced.

SHPS considers it one of the means to efficiently supply energy obtained from marine renewable energy. SHPS is a system that utilizes the electric power generated by marine renewable energy such as offshore wind power, sends electric power and alkaline water from on the surface of the sea to electrolysis equipment installed in deep sea to produce compressed hydrogen, and sends the compressed hydrogen on the surface of the sea by riser. Fig. 1 shows an overview of SHPS. Floating part of SHPS is determined to have the minimum necessary function to supply compressed hydrogen produced on the seabed to transport ship, which is small float shown in Fig. 2. In addition, by reducing the size of the floating body system, the influence of external forces can be suppressed, which is considered to be economically advantageous.

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