Decoupling Power Generation from Consumer Demand – The FIHS Architecture for Marine Hybrid Power Systems

FIHS (Fully Integrated Hybrid System) is a patented marine hybrid power-system architecture developed by Trygve Johannes Økland. The architecture decouples electrical power generation from continuously varying vessel demand by using an energy storage system (ESS) as the active interface between generation and consumption. Instead of requiring generating sets to continuously follow vessel load, FIHS enables them to operate at predetermined efficient operating points while the ESS absorbs surplus generation or supplies the difference when vessel demand exceeds generator output. This technical paper describes the engineering background and development of FIHS, including the investigation of permanent-magnet propulsion efficiency, hybrid power-system studies, generator operating efficiency, energy storage, dynamic positioning (DP), redundancy, emissions and maintenance. It explains how these investigations led to the central FIHS principle: the operating condition of the generating plant should be determined by the characteristics of the generator set rather than by instantaneous consumer demand. The paper also discusses the potential application of FIHS with medium-speed, high-speed, diesel, dual-fuel and gas generating sets, and compares the architecture with conventional load-following and variable-speed power-generation concepts.