Hydrogen fuel powered boats

A container ship capable of 65 knots is slowly taking shape on the drawing boards at Southampton's Ship Science Department. Powered by hydrogen, it's a brave new apporach to an established industry.

'SMALLER and faster' is probably the mantra most closely associated with car manfuacturers, and perhaps those in the consumer electronics industry. But its probably not the first thing you think of when designing container ships, let along those travelling thousands of nautical miles laden with cargo. In the world of seaborne freight bigger is better. Or is it?

Ivo Veldhuis and Howard Stone, together with Dr Neil Richardson and Dr Steve Turnock, are researchers at the University of Southampton's School of Engineering Sciences. Their view differs slightly from the conventional wisdom, and it ties in closely with socio-economic factors such as worldwide fuel shortages and the increasing demand of manufacturers to deliver their products to the consumers faster.

For Ivo, the future of sea freight could lie in a new breed of container vessels which travel two and half times the speed of their traditional counterparts but carry less containers, allowing for more sailings between busy ports and therefore delivering cargo within a smaller time frame. 'My research started in the late nineties and was sparked by a conversation I had with a colleague' he recalls. 'We gave each other the challenge of improving the trans-Pacific route between Yokohama, Japan and Long Beach (part of Los Angeles). Normal container ships take between one and two weeks to deliver their cargo along the route and so we wanted to make this process more efficient'.

At 8,5000TEU (one TEU equates to one 20ft container), current container ships are leviathans of the ocean at 335m long. Ivo proposes to cut this size down to just 600TEU per ship and increase the present maximum speed of 25 knots (46.3 kph) to a whopping 65 knots (120.4 kph).

Ship Design

Hydrogen Oceanjet 600As blue-sky as Ivo's approach first appears, it can be qualified by achievable engineering. To prove the concept, Ivo has been busy working on a new ship design capable of completing the 18,000km roundtrip from Yokohama to L.A in half the time, thus allowing for double the amount of sailings per week. Hydrogen Oceanjet 600 - the present title for his new design - is a work in progress. Fuelled exclusively by liquid hydrogen and powered by four gas turbine engines, the Oceanjet represents an ambitious new set of thinking, but Ivo is confident such a ship offers real solutions to an industry always smart to new business improvements.

He explains that 65 knots requires an extremely high level of propulsion power for the size of the craft proposed (175m/600TEU). With this in mind, Oceanjet utilises gas turbine engines derived from similar turbine engines as those found on a Boeing 747, each capable of 49.2 megawatts of propulsive power when fuelled by hydrogen. This propulsive power has to be translated into forward speed, and Oceanjet utilises waterjets, which have a high propulsive efficiency at this high speed.

'The design that I am proposing allows for four such 2.5m-wide waterjets, two inside each demi-hull transoms of each cataman hull,' he explains. 'This type of propulsion system is actually capable of rotating the outgoing waterjet flow and so utilises the entire propulsion force to steer the ship at 65 knots. This makes for very direct control.'

The schematic layout of the ship design, is a catamaran with long and thin hulls known as a 'semi SWATH' (Small Water plane Area Twin Hull), an ideal shape to avoid unwanted wave resistance. 'A significant part of the vessel's buoyancy is located beneath the waterline,' says Ivo. 'As a result there is limited wave interaction and this translates into reduced wave resistance.'

Crucially, Oceanjet's design calls for large hydrofoils that create an aerofoil-shaped air cavity for running the ship with minimal foil friction. The hydrofoils create a vertical lift force that reduces the draught of the catamaran and consequently reduces the ship's surface area exposed to seawater. At such high-speeds frictional resistance between seawater and the ship's hull surface is the biggest resistance component. 'By reducing the draught via the hydrofoils, you reduce the frictional resistance', Ivo explains. An additional advantage from using the hydrofoils is damping of the ships motions.

Another benefit of the catamaran layout lies in the speed of loading and unloading it creates. Whereas conventional mono-hulled container ships require cargo to be loaded vertically, via cranes, Oceanjet allows for horizontal 'drive on and drop' container delivery, making the process a lot swifter.

Fuel system

For Oceanjet to function at such high speed it requires a high-octane fuel, and lots of it. Ivo explains that he considered a number of different fuel types for his design, but settled in liquid hydrogen. 'If you wanted to maintain such a speed for a long time using diesel fuel you would be looking at having to carry about 3,000 tonnes - that's about the same weight as the cargo', says Ivo. 'Methanol and ethanol are also too heavy. Liquid nitrogen is much lighter and more efficient. It releases a lot more energy per kilogram than conventional fuels, and the fuel delivery system I have devised can use both liquid and gaseous hydrogen, so no fuel is wasted.'

Ivo has calculated that the turbines require 0.86kg of liquid hydrogen per second in order to operate at 64 knots. That's 176m³of hydrogen every hour. For a ship to travel the distances required, it would therefore require a fuel storage capability of 14,500 m³. The design of the Oceanjet allows for ten separate but interconnected fuel tanks, with a total storage capacity of 1,001 tonnes of liquid hydrogen.

Safety first

Naturally, the use of liquid hydrogen raises a number of key safety questions, not least how volatile a liquid fuel can be inside a ship travelling in excess of 60 knots. Ivo admits that because hydrogen behaves differently to more conventional fuels it requires a different approach altogether. Current shipbuilding regulations do not allow for the use of liquid hydrogen as a fuel source, but this had not stopped Ivo scoping its potential.

'I have looked at how best to store the hydrogen and make it as safe as possible,' he details. 'For gas to become liquid it must be kept at -253°C. I have designed a safety system which vents the hydrogen quickly in the event of an accident. Liquid hydrogen turns to gas instantaneously when in contact with the air and doesn't linger and burn longer like other fuels such a kerosene.'

Oceanjet's catamaran design also improves the survivability of the craft should it strike a large underwater object. 'It can survive whether foilborne or non foilborne,' says Ivo. 'Say if one or more of the foils gets damaged, this particular vessel design can still function as a ship and make its way to safety'. What's more, even if the foil lift no longer operates then the static buoyancy of the vessel should keep it afloat. The hull will have normal watertight subdivisions, so the ship should survive, even if there is a hull breach.'

Further development

A project as bold as Oceanjet requires an equally bold infrastructure to support it, something that Ivo is quick to point out. 'It would require constant monitoring of the weather and sea states and will have to use state-of-the-art satellite tracking technology in order to operate efficiently,' he states. 'It would also need to operate outside established shipping lanes, perhaps in newly formed 'shipping motorways', specially designed areas of the ocean where high speed shipping can operate without the danger or hitting other vessels.'

There are also the environmental considerations of such an audacious move into hydrogen power. Although the fuel itself is relatively green when it is used, it is the production of such high volumes of the gas in liquid form that would cause the greatest impact. Current production processes are not refined enough to avoid the production of such high volumes of carbon dioxide a by-product. In fact, for every 1kg of liquid hydrogen produced, 12.8kg of CO2 is produced. But Ivo points out that this CO2 problem from hydrogen production equally applied for everyone in the hydrogen economy.

'We didn't go from horse and cart to automobile overnight', says Ivo. 'We got there gradually as the need for faster, more efficient transport became apparent. It's the same with hydrogen power. With global oil reserves vanishing, we are all looking at alternative methods to fuel future transport and with that will come more investment in greener fuel production and safer fuel storage an operation'

'When you start using liquid hydrogen, it creates new opportunities, both economic and in ship design. You wouldn't use diesel to lift a spaceship into orbit', he concludes.

For more information contact: Ivo Veldhuis (link on the right)

Published in New Boundaries, April 2006, Issue 4