Techno-economic assessment of a fuel flexible free piston engine generator based energy system for cold ironing application

This study assesses the techno-economic viability of a fuel-flexible free piston engine generator (FPEG) for providing shore power to maritime vessels (cold ironing) within ports. In cold ironing applications a localised power generation is required when there is limited electrical supply within the port. The FPEG offers an advantage over conventional engines by eliminating rotational components, with linear piston reciprocation leading to a compact and efficient conversion of fuel to electrical power. The FPEGs enable the engine to run on various fuels, including future options like hydrogen, ammonia, and methanol. The sizing of the FPEG is matched to the power requirements of different classes of vessel. Underpinning the techno-economic model is an FPEG model which is validated against experimental data. The results show that hydrogen fuel is the most efficient, with 41.08 % efficiency and the lowest fuel consumption compared to ammonia and methanol. Lower hydrogen consumption results in less NOx, despite its higher emission factor per mass of fuel burned. Green hydrogen however has the highest levelised cost, of the fuels investigated, at 0.40 £/kWh, with methanol being the cheapest at 0.18 £/kWh. The study calculates the greenhouse gas potential of the different fuels, highlighting the advantage of green hydrogen with calculated emissions to be 0.01 kgCO2-e/kWh, significantly lower than ammonia at 0.086 kgCO2-e/kWh and methanol at 0.635 kgCO2-e/kWh. Overall, this study shows the FPEG as a viable option for cold ironing applications, offering notable advantages over other generator types, such as fuel flexibility and compact design.