Mid-century NZF target less than a generation of ships away

People talk about 2050 as though it’s a lifetime away. It’s definitely not, says Berg Propulsion’s David Sakandelidze, Business Manager for Energy Efficiency. The IMO’s Net-Zero Framework (NZF) is now only 24 years away, he declares, less than the average life of a merchant vessel today.

He emphasises his point with some key statistics. Today’s 112,000 active ships emit approximately 1.05 billion tonnes of combined annual emissions. If the IMO’s NZF is adopted, it will require shipping to cuts its emissions by almost 44m tonnes every year between now and mid-century.

Berg has identified one specific shipping segment where significant fuel savings can be made. It consists of ships built for high speed but which, owing to market demand, are operating at least 20% below their design speed. Although this results in fuel and emissions savings, Sakandelidze explains, it means that propulsion systems are operating at less than their optimal level. The reduced engine and propulsion efficiency means that ships’ shaft generators cannot produce stable electric power.  

This sector of the fleet is significant, comprising about 11,000 vessels which account for 83m tonnes of emissions a year. And Berg, he says, has now successfully carried out retrofits to 70 vessels, 38 of which took place between May 2025 and May 2026. The upgrades have cut verified annual emissions by 114,000 tonnes.

Sakandlidze reveals that in one recent project, a Berg controllable pitch propeller (CPP) was modified. In a conventional CPP setup, he explains that the propellers controls thrust and vessel speed by adjusting the blade angle (pitch) while maintaining a constant engine rotation speed and direction, even when going astern. This allows the shaft generator to produce stable power but does lead to less efficiency when a vessel slows down.

So the company has developed new propeller blades, optimised for lower design speeds. This, combined with a 10-15% reduction in engine revs, restored propulsion efficiency at the reduced speeds. Furthermore, by adding a net frequency stabiliser, the shaft generator continues to produce stable electrical power despite the lower shaft speed.

The new propeller blades offer one hydrodynamic upgrade. Other steps could involve the addition or removal of nozzles around the propeller to improve thrust and efficiency, of the installation of hub fairing cones to reduce turbulence and drag at the propeller hub. Battery packs can be used for peak shaving or shore-based charging, generating further fuel savings.

Meanwhile, control system upgrades are also beneficial. Adding a ‘combinatory mode’, for example, optimises coordination between engine power and propeller pitch. And connecting the system to remote monitoring sensors and software facilitates real-time performance tracking and diagnostics. The company also provides software such as Berg Propulsion’s Dynamic Drive fuel optimisation system for intelligent power management. And its Engine Power Limiter ensures efficient power usage.

Berg Propulsion at SMM: Hall A4 / Stand 316