Washington, May 21 : Fuel cells powered by hydrogen are going to help develop the next generation of harbour tugs, which would help to cut emissions.
According to a report by ENN (Environmental News Network), WorldWise Marine Engineering (WWM) is working in this direction to develop a 50 tonne bollard pull harbour tug that will have zero emissions when on standby and very low emissions in service.
Working with tug operators Ijmuiden-based Iskes and Rotterdam-based Smit, WWM has designed an electric propulsion system for the harbour tug that is powered by fuel cells running on hydrogen, thus achieving zero emission conditions.
The system would also run on a battery back-up during standby and mobilisation periods and would only fire up diesel generators when substantial bollard pull is required, according to Michiel Wijsmuller, managing director of WWM.
"We will also incorporate power regenerating features by way of the towing winch when paying out the towline and by one of the propeller units when the tug acts in the dynamic braking or steering mode," he said.
WWM's fully electric tug will be powered by 200 kW fuel cells during waiting time and mobilisation/demobilisation periods.
During berthing and assist operations, diesel generators can be brought on line to provide more power but with a generator bank of 2-4 units, the engine load can be closely matched to the electrical demand, ensuring the diesels operate at maximum efficiency and optimum load.
A retractable Voith in-line azimuthal thruster in the bow for mobilisation and demobilisation purposes is a major energy saver.
"The tug can move around safely on hydrogen power, said Wijsmuller. "Then, when we are using the main generator sets and electric motors in a ship-handling operation the thruster is tucked away, cutting drag," he added.
According to Wijsmuller, the main propulsion motors are mounted directly on top of the stern azimuthal propellers. The result is that the hull provides ample space and flexibility for installing tanks to store hydrogen under a pressure of 700 bar.
"Our studies show this tug will reduce the emission of NOx, SOx and particulate matter by 95%, while oil fuel consumption, and so CO2 emission, is reduced by 50% compared to a conventional harbour tug," said Wijsmuller.