Propulsion Considerations Following the Electrification of the Tug Industry
By Emil Cerdier, CTO, Berg Propulsion
The tug industry is undergoing a rapid transformation, driven by regulatory pressure, sustainability goals, and evolving operational expectations. At Berg Propulsion, we see this shift as an evolution that calls for rethinking propulsion—from product design to fleet operations.
From Diesel to Electric: The Changing Landscape
The industry is steadily transitioning from traditional diesel-mechanical tugs toward parallel hybrid and fully electric configurations. This shift introduces several key considerations:
- Emissions & Regulations: Stricter environmental rules require future-ready propulsion strategies.
- Operating Costs: While electric energy may be cheaper per unit, CAPEX for electric systems is higher—demanding a smarter balance of performance and investment.
- Infrastructure Gaps: Not all ports are ready with charging infrastructure, which significantly impacts the feasibility of electric tugs.
This is not a one-size-fits-all situation. Combustion engines, hybrid, and electric tugs all have roles to play, depending on operational profiles, port infrastructure, and regional energy availability.
Four Dimensions of Propulsion Efficiency
To navigate this complexity, we break propulsion efficiency into four layers:
- Product Efficiency
Optimizing individual components—propellers, nozzles, gears, motors—for best performance. - System Efficiency
Ensuring all parts of the propulsion system work together without sub-optimizing any single element. - Operational Efficiency
Helping crews operate vessels efficiently using smart tools like mode selectors, pre-set operating profiles, and intuitive bridge interfaces. - Life Cycle Efficiency
Maximizing uptime and minimizing downtime through better service, remote support, and long-term fleet planning.
Parallel Hybrids & Electric Tugs: Engineering Trade-offs
Hybrid propulsion offers flexibility—allowing vessels to alternate between mechanical and electrical power. But that flexibility introduces new challenges:
- Electric motors offer fast response and precision for safer close-quarters maneuvering.
- Mechanical drive offers range and high-load efficiency with minimal conversion losses.
- Parallel hybrids combine both, offering redundancy and operational agility.
Still, the higher equipment cost of electric setups (batteries, integration, controls) makes efficiency design-critical. Every kilowatt saved translates to smaller batteries, smaller motors, and lower investment.
Why Bigger Propellers Matter
At Berg, we advocate for larger-diameter propellers paired with high-torque gears. Why?
- Larger propellers running at a lower rpm increases efficiency.
- This allows for either better performance with the same installed power—or same performance with reduced installed power.
- This optimizes both CAPEX and OPEX, which is important especially in full-electric setups where installed power has a higher cost.
The Hidden Power of Operation Profiles
One of the most underestimated savings potentials is how the tug is operated.
A real-world hybrid tug project showed this clearly: during concept evaluation, studies showed an 8% fuel savings comparing a conventional diesel mechanic tug vs a parallel hybrid tug. But once in operation—using intelligent mode selection bridge interface the operational profile was optimized and actual fuel savings reached 48%.
That gain wasn’t just from technology. It was from operational awareness.
By giving crews clear information—load, fuel use, power status—and simple pre-programmed modes (standby, transit, full power), we help them make smarter decisions on the water, every day.
Final Thoughts
There is no universal propulsion solution. Each vessel and fleet requires a tailored approach. But one truth holds across all:
Operational behavior matters just as much as engineering design.
At Berg Propulsion, we’re here to support you with the tools, expertise, and insight to get it right.
