Berg Propulsion: How Retrofits Can Contribute to Decarbonization Goals
Rather than pinning its decarbonization hopes on future tonnage, shipping can pursue its goals today by retrofitting available technology to existing, conventionally fueled vessels, explains David Sakandelidze, Business Manager for Energy and Efficiency, Berg Propulsion.
The International Maritime Organization's (IMO) target for net-zero emissions from ships by around 2050 is now only 24 years away—less than the average lifetime of a commercial ship. Today, 112,000 active vessels emit approximately 1.05 billion metric tons of combined annual emissions. To understand how fast the intervening years to 2050 will pass, it is worth considering that meeting IMO's goal will require global shipping to cut its emissions by about 43.75 million tons every year.
To support and meaningfully contribute to our common goal, Berg Propulsion defined its own shipping segment to achieve fuel savings. This segment consists of ships built for high speed but due to market demand are operating at least 20% slower than design speed.
Such operating, while offering economical (and environmental) benefits in form of reduced fuel consumption, exposes inefficiencies of the propulsion power plant system which were designed for a different optimal operation point. The trade-off lies in reduced engine and propulsion efficiency, in turn causing a ship's shaft generator to lose its ability to produce stable electrical power.
Between 2022 and 2026, Berg Propulsion retrofitted 70 vessels—38 of these between May 2025 and May 2026—and the upgrades are already delivering verified annual emissions savings of 114,000 metric tons.
Modification, technology and innovation
For one recent vessel retrofit project, modifications to the design of Berg's controllable-pitch propellers (CPPs) brought measurable efficiency gains that we have subsequently verified with the owner.
In conventional set-ups, a CPP controls thrust and vessel speed by adjusting the blade angle (pitch) while maintaining a constant engine rotation speed and direction, even when moving astern. While this allows the shaft generator to produce stable power, efficiency losses occur when the vessel slows down.
To counter these losses, we developed new propeller blades, specifically optimized for lower design speeds. By combining the blades with a 10-15% reduction in engine RPM, we restored propulsion efficiency at these reduced speeds. Additionally, a net frequency stabiliser was installed to ensure that the shaft generator continued to produce stable electrical power despite the slower shaft speed.
The refined propeller blade design is just one hydrodynamic upgrade; vessel owners can add or remove nozzles around the propeller to improve thrust and efficiency, or fit hub fairing cones to reduce turbulence and drag at the propeller hub. In addition, existing technologies can be added to the mix: for example, battery packs can help reduce fuel consumption through peak shaving or shore-based charging, and hybrid fuel arrangements can similarly cut traditional fuel use.
Control system upgrades can also be used to great effect in retrofit projects. These can involve the inclusion of an enabling 'combinatory mode,' to optimize coordination between engine power and propeller pitch, while also connecting the system to remote-monitoring sensors and software to provide real-time performance tracking and diagnostics. On the software side, we also implement advanced control system features such as Berg Propulsion's Dynamic Drive fuel optimisation package for intelligent power management, plus our Engine Power Limiter (EPL) for efficient power usage.
Verified outcomes include highly efficient and versatile propulsion systems that perform well across a wide range of speeds, with existing ships delivering significantly lower fuel consumption per nautical mile and reducing their CO2, NOx and other emissions to align with regulatory requirements ahead.
