Shanghai International Port Trials Hybrid Tugboat Propulsion System

Shanghai International Port has trialled a hybrid propulsion system on a newbuild harbour tug designed to cut fuel consumption and emissions while maintaining full ship-assist power. The vessel, Hai Gang 712, combines a battery energy storage system with three variable-speed mtu diesel engines from Rolls-Royce Power Systems in a hybrid configuration. Developed to address the variable load conditions that harbour tugs face, the system features fast charging and could be rolled out across further newbuild tugs following the successful demonstration.

 

The Challenge for Harbour Tugs

 

Harbour tugs operate under demanding and highly variable conditions. They need full throttle to tow and escort ships while also manoeuvring with precision. Yet they spend more than half their operating life on low engine loads. Much of this time is spent idling while waiting for the next ship-assist job. This uneven usage pattern creates particular challenges for conventional powertrains.

These operating characteristics call for innovative propulsion solutions. The core challenge is lowering fuel consumption and emissions during low-load periods. At the same time, the tug must retain sufficient power for demanding towage work. Balancing these competing needs is central to improving tug efficiency. The hybrid system installed on Hai Gang 712 represents one response to this challenge.

 

The Hybrid Propulsion Configuration

 

The vessel combines conventional engines with battery storage in a hybrid layout. Hai Gang 712 operates in the Port of Shanghai with an energy storage system and three mtu Series 4000 M64 engines. These 12-cylinder variable-speed diesel engines are supplied by Rolls-Royce Power Systems. Together they can generate 1,300 kilowatts of electrical power. This complements the onboard 1,960 kilowatt-hour battery pack.

Power is managed through an integrated distribution system. The engines and battery deliver sufficient power via a DC bus power distribution system. The batteries balance out peak loads and store energy when it is not needed. This creates a system that uses energy selectively rather than holding it constantly in reserve. The result is a more efficient use of available power across varying demands.

 

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Fast-Charging Capability

 

A key feature of the system is its ability to charge quickly. Hai Gang 712 has only short breaks between towage and manoeuvring work. Its power system was therefore designed for fast battery charging during these gaps. The batteries can charge from 30 percent to 90 percent during a typical layover. This layover lasts around 90 minutes between assignments.

This fast-charging capability was central to the propulsion concept. It was developed by the Shanghai International Port Group with Rolls-Royce Power Systems. The concept was implemented on the tug as a research project to test it in real conditions. Testing in an operational port environment allows the technology to be validated in practice. This real-world approach strengthens confidence in the system's viability.

 

Efficiency and Reliability Benefits

 

The variable-speed engines deliver notable efficiency gains. Rolls-Royce says its mtu variable-speed engines reduce fuel consumption by up to 20 percent. They also extend the time between overhauls by up to 20 percent compared with conventional constant-speed engines. These improvements lower both operating and maintenance costs over the vessel's life. The engines also help reduce emissions and noise during operation.

Reliability remains a critical consideration alongside efficiency. Company representatives stressed that the variable-speed engines ensure the tug is ready even if the batteries are not fully charged. This readiness is essential given the unpredictable timing of ship-assist calls. In tug operations, efficiency only counts if reliability accompanies it. The system is designed to keep the vessel prepared for the next job at all times.

 

Broader Rollout and Technology Development

 

The successful trial has prompted plans for wider adoption. Shanghai International Port intends to install these hybrid systems on more newbuild tugs. This follows the successful demonstration of the technology on Hai Gang 712. Expanding the system across the fleet could multiply the efficiency and emissions benefits. It signals confidence in the concept's performance under real conditions.

The collaboration extends beyond a single vessel or operator. Rolls-Royce is working with other shipyards and port authorities in China to develop these technologies further. The company has also developed and patented a Superior System Controller to optimise engine performance. This controller determines the best operating point in relation to electrical power demand. Such refinements aim to make the technology suitable for a wider range of real-world applications.