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Shanghai International Port trials tugboat hybrid propulsion
China’s Hai Gang 712 demonstrates how a propulsion concept addresses power and energy challenges that affect harbour tugs operating in variable conditions
Harbour tugs need to go full throttle to tow and escort ships and need to manoeuvre with precision, but they operate more than half their life on low engine loads, idling while waiting for their next ship-assist work.
This brings challenges to powertrains that need innovative solutions for lowering fuel consumption and emissions while ensuring tugboats have sufficient power to assist ships in and around ports.
One such solution has been installed on a newbuild harbour tug in China. Hai Gang 712, operating in the Port of Shanghai, has an energy storage system and three mtu Series 4000 M64 engines from Rolls-Royce Power Systems in a hybrid propulsion configuration.
These 12-cylinder variable-speed mtu diesel engines can generate 1,300 kWe of electrical power to complement the onboard 1,960 kWh battery pack, delivering sufficient power via the DC bus power distribution system.
Hai Gang 712 has short breaks between ship towage and manoeuvring work, so its power system was designed for fast battery charging, from 30% to 90% during its regular layover of around 90 minutes.
This fast-charging capability was part of a new propulsion concept developed by the Shanghai International Port Group in collaboration with Rolls-Royce Power Systems and implemented on this tug as a research project to test it in real port conditions.
Rolls-Royce Solutions senior sales manager for commercial marine and offshore, Andreas Müller-Hirlinger, said the variable-speed engines were an important part of the hybrid propulsion as they ensure Hai Gang 712 is ready even if the batteries are not fully charged, while lowering fuel consumption, emissions and noise.
“Harbour tugs work under constantly changing load conditions,” he explained. “One moment they need maximum power, and the next, precise manoeuvring. Any propulsion concept must perform across that entire range.”
The batteries balance out peak loads and store energy when it is not currently needed. This creates a system that uses energy selectively, rather than constantly holding it in reserve.
Rolls-Royce said mtu variable-speed engines reduce fuel consumption by up to 20% and extend the time between overhauls by up to 20% when compared with conventional engines of equivalent power working at constant speed.
“A hybrid system with variable-speed engines is valuable if it helps operators reduce fuel consumption and maintenance while keeping the vessel ready for the next job,” said Mr Müller-Hirlinger.
“For an operator, the real benchmark is simple: when the next call comes in, the tug has to be ready,” he said.
In port operations, tugboat efficiency is determined across several areas simultaneously: fuel consumption, emissions, fleet availability, safety, reliability, manoeuvrability, bollard pull and towline forces.
Variable-speed engines need to continuously adapt to actual power requirements and ensure tugs operate within the optimum range in every situation.
“In tug operations, efficiency only counts if reliability comes with it,” said Mr Müller-Hirlinger.
Shanghai International Port intends to install mtu variable-speed hybrid systems on more newbuild tugs after the successful demonstration of the technology on Hai Gang 712.
Rolls-Royce is working with other shipyards and port authorities in China to further develop these technologies and make them suitable for use in more real-world conditions.
The power group has developed and patented its Superior System Controller to determine the best operating point in a variable speed mtu genset engine’s performance in relation to electrical power demand.
Its mtu diesel generators range from 720 kWe to 3,100 kWe for auxiliary and emergency power generation and diesel-electric propulsion. They come with options and accessories such as sound shields, control panels and power take out for firefighting pump drives. Their time between overhauls can be as high as 42,000 hours, reducing maintenance costs.
Riviera will host TUGTECHNOLOGY ‘27 in Rotterdam, the Netherlands, 19-20 May 2027. Use this link for more information and to register.
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