Page 31: of Maritime Reporter Magazine (February 2026)

PROPULSION ing IMO NOx requirements without an SCR. The combustor

Emissions Performance & is slightly longer than the standard DLE variant but can be

Hydrogen Operation

Fuel ? exibility and low emissions were two of the main retro? tted with minimal changes to the gas turbine core.

drivers behind Gotlandbolaget’s decision to use SGT-400 gas

Tech to Decarbonize Ocean-going Vessels turbines on Horizon X.

Long-haul shipping currently accounts for the majority of

As standard, the SGT-400 comes equipped with a Dry Low

Emissions (DLE) combustion system. The units for Gotland the maritime sector’s emissions footprint. As these vessels are required to travel long distances and remain away from

Horizon X will be dual-fuel and capable of operating on LNG and diesel, while demonstrating compliance with IMO’s Tier ports for extended periods, hybrid propulsion designs with alternative fuel capabilities represent the most practical op-

III NOx emission requirements (<2g/kWh) for the E2 and E3 tion for decarbonization. duty cycles without the need for a selective catalytic reduction

The primary challenge of applying hybrid technologies to (SCR) system. these vessels is the need to conserve space to maximize the

The gas turbines operate with a continuous ? ame and rela- carrying capacity of goods and fuel (due to the lower fuel den- tively long residence time within the combustor. Methane slip is negligible, with levels expected to be below 0.014g/kWh sities of low-carbon fuels compared to HFO and other marine when the gas turbine is operating between 50% and 100% of diesels). While the business case for installing a diesel- or gas- electric system, power conditioning equipment, and batteries its maximum continuous rating (MCR).

Recent combustion rig testing has demonstrated that, with remains dif? cult, the economics are improving.

Particularly on LNG carriers, the Ocean Green concept, using a modi? ed fuel injector, the combustion system can operate a hybrid combined-cycle with electric propulsion (like the sys- on methanol.

The long-term goal is for Gotland Horizon X to operate on tem that will be installed on Gotland Horizon X), is highly ap- plicable. The compact engine room layout and reduced weight 100% hydrogen fuel.

Hydrogen combustion characteristics differ from those of allow for a 7-11% increase in cargo carrying capacity, resulting natural gas, with wider ? ammability limits and higher ? ame in up to a 17% decrease in unit freight costs compared to a con- ventional 2-stroke 174,000 m3 LNG carrier or a smaller tanker.

speeds, which exacerbate the risk of ? ashback. Without sig-

The use of hydrogen fuel cells in hybrid systems is also gain- ni? cant modi? cations, standard DLE combustion systems on ing traction as a decarbonization pathway over the longer term. gas turbines are typically limited to 20-50% hydrogen by vol-

Siemens Energy is currently working with partners to apply hy- ume blended with natural gas. drogen fuel cells on marine vessels of various types and sizes.

Siemens Energy’s work to develop a 100% hydrogen-ca-

Using the inherent fuel ? exibility and ef? ciency of a gas tur- pable combustion system started over a decade ago. In 2023, bine, Gotland Horizon X is a true multi-fuel-capable fast ferry, the 100% target was achieved on the SGT-400 during the EU- funded HYFLEXPOWER demonstration project in France. offering both low CO2 and NOx emissions without sacri? c-

Additional testing will take place over the next few years as ing crossing speed or passenger and cargo capacity. The vessel provides a scalable blueprint for high-performance, sustainable part of the follow-on HyCoFlex project at the same location.

vessel design. It paves the way for zero-emission, ocean-going

The new combustor will be capable of operating not only on ships – accelerating the industry’s transition to a low-carbon 100% hydrogen, but also 100% natural gas (or LNG) and any future. blend of hydrogen and gas/LNG in between, while still meet-

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