“Abstract

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.”

 

The full report is accessible via: https://doi.org/10.1016/j.energy.2025.136954

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

To meet the future EU emissions targets, this work presents the first of its kind experimental results from an engine representing the expansion cylinder of a recuperated split cycle engine (RSCE), operating with direct injection diesel and port injected hydrogen. The separate valve and cylinder geometry optimization of the compression and expansion cylinders, with quasi-isothermal compression and internal waste heat recovery in the RSCE, offers greater opportunities to optimize efficiency. The partial hydrogen substitution increases the calorific value and reduces overall carbon content. Results are examined at new test conditions, using the validated Ansys Chemkin-Pro numerical simulation. The results suggest that selected hydrogen content substantially reduces C02 to the 2030 targets. While this may come with NOx penalties, when liquid nitrogen is used in the process of quasi-isothermal compression, the dilution of the charge air with this species was found to reduce these emissions to approaching Euro 7 limits when coupled with the current NOx after-treatment system.”

 

The full report is accessible via: https://doi.org/10.1109/IREC64614.2025.10926793

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

The Joule cycle Linear Engine Generator (LEG) is a promising power generation technology with the potential to achieve zero carbon emissions. However, the LEG expander valve actuation system presents unique challenges due to its lack of a traditional crankshaft, the need for swift valve lift and reversal, and variable lift. This paper presents a Linear Variable Valve Actuation (LVVA) system for a LEG prototype. The LVVA system is powered by voice coil motors. Rigorous experimental investigations were conducted to analyze crucial performance factors, including energy consumption, force balance, energy flow distribution, and the relationship between valve lift duration and energy consumption. The results show that the LVVA system can achieve the desired valve lift and timing, as well as very small variations in LEG performance compared to the model using an ideal lift curve. The LVVA accounts for approximately 3.59 % of the LEG power output. The energy consumption of 1.607 J per valve stroke provides a slight advantage over traditional actuation systems. The obtained optimal lift curves were used to refine the LEG model. The influence of valve lift curves on LEG performance was evaluated which reveals rapid valve openings and relatively short duration contributing to improved LEG performance.”

 

Li M., Ngwaka U., Wu D., Wang Z., Korbekandi R.M., Baker N., Tsolakis A. Performance evaluation of linear variable valve actuation for a linear engine generator (2024) Energy, 298, art. no. 131361. DOI: 10.1016/j.energy.2024.131361

The full report is accessible via: https://doi.org/10.1016/j.energy.2024.131361