Denmark aims for new benchmark in green shipping

Denmark’s Green Ship of the Future project has been set up to develop technologies that could improve the environmental performance of cargo vessels. Stuart Nathan reports

Centuries ago a Danish ship was a source of terror but little pollution. Modern Denmark has kept up the seafaring tradition of its Viking ancestors and has ambitious plans to become a world leader in reducing emissions from shipping, which, by some estimates, accounts for almost five per cent of global CO2.

The Green Ship of the Future project aims to improve the environmental performance of cargo ships of all types and sizes. ‘Emissions from ships have been in the media for some time now in Denmark,’ Søren Jensen, R&D chief of marine-engine builder MAN Diesel, told The Engineer. ‘Shipping is much more efficient than air freight, rail or trucks, but there’s still a need to reduce emissions because… the [high] volume of shipping means that the actual emissions are quite large.’

Last year, the Danish government set up the ‘Green Ship of the Future’ project to develop technologies to reduce CO2 emissions from shipping and also to tackle emissions of oxides of sulphur and nitrogen. These, Jensen explained, are a particular problem in the ports and terminals where the ships operate. Looking at the areas of machinery, propulsion, operation and logistics, the project brought together ship owners such as AP Møller-Maersk and DFDS, shipbuilders such as the Odense Lindø Shipyard, equipment suppliers such as ABB and MAN Diesel, and Danish research institutions and universities. The project was timed so that it could present demonstration models to the United Nations Climate Change Conference, COP15, which will take place in Copenhagen later this year. The goals are ambitious — a 30 per cent cut in CO2 emissions, compared with 2007 levels, and a 90 per cent reduction in NOx and SOx.

‘At the beginning of the programme we started with 10 projects, but others have been suggested over the year,’ said Jensen. ‘The originals are now well ahead and the new ones which were started subsequently are all up and running.’

The level of development varies between projects. In some cases the technology being studied was already fairly well developed and the Green Ship project has added impetus to get prototype technologies up and running in test ships. In others, the technologies are new and the aim is to have a theoretical study produced by the end of the year for COP15, Jensen said.

Marine engines are a major focus of the project, and MAN Diesel is involved in several of these. ‘One of the things we’re looking at is waste heat recovery,’ said Jensen. ‘The two-stroke diesel engines we use on big ships are actually pretty efficient — about 45-50 per cent — but a proportion of the energy is lost through the heat of the exhaust gas. We’re aiming to harness that so that we can use it to boost overall efficiency.’

To do this, an extra boiler is installed in the system, which is heated by the exhaust gases. The steam raised in this boiler is routed through a steam turbine, while the exhaust gases also drive a turbine. ‘The power these generate is free because it’s coming from a waste product,’ said Jensen. ‘You can design it according to your needs; you can use it as extra propulsion power and to generate electricity. Overall, it increases the efficiency of the engine by 10 per cent.’

Further along in development is an exhaust-gas recirculation (EGR) technology, which is aimed at reducing NOx generation. Originally developed in the 1970s, EGR involves sending a proportion of the exhaust gas back into the engine’s cylinders. This has the effect of reducing the temperature of the combustion mixture — as there is more matter inside the cylinder, the energy of the fuel/air explosion can’t raise the temperature as much. As NOx forms when the combustion mixture burns at a high temperature, the cooler combustion mixture slows down NOx formation and reduces the final emissions.

‘There is legislation coming up which says we should reduce NOx by 80 per cent on ships built after 2016,’ said Jensen. ‘We’d done some work on exhaust-gas recirculation, but we hadn’t reached the field-test stage before we started up the Green Ships. We didn’t have the service experience: what was the durability of the system, and what was the effect on the engine, in terms of endurance? So with AP Møller-Maersk, we have a project where we are making a field test, and we’ve just finalised the installation, retrofitted onto a vessel called Alexander Maersk. In a few months, we’ll be ready to run.’

Another project is looking at methods to reduce the SOx emissions, using a wet scrubber to remove the SOx post-combustion. ‘One way of reducing SOx is… to use fuels without sulphur, and this is a problem for the oil companies,’ Jensen said. ‘But heavier oils that contain sulphur are half the price of lighter sulphur-free distillates, so there’s a lot of money for investment. If we install scrubbing technology and treat the residue, the cost of that is still cheaper than using the more expensive fuel; there’s a relatively short payback on the investment. We’re working on this with DFDS, and we’ve retrofitted a system. This should also come to fruition before COP15.’

Monitoring technologies are also represented, with the project looking at automated engine monitoring, where the operating parameters of the engine are continuously recorded and used to ensure that the engine is always set for optimal fuel consumption.

The project isn’t confined to engine technologies, however. One strand is looking at a method to reduce the friction of the ship’s hull moving through the water, by injecting air under the hull. Led by DK, this part of the project has also progressed to trials, with a fast ferry equipped with the air lubrication system. According to DK, the air-lubricated ship is more efficient at higher speeds, with efficiency increasing as speed rises above 36.5 knots.

DK is also testing air lubrication with an 83m tanker and believes the system could achieve savings of 15 per cent in fuel efficiency, and therefore in CO2 emissions.

Another project is centred around developing a double-bladed propellor. Co-ordinated by Injector, a company that specialises in producing hydrodynamic trawldoors for fishing boats, the propellor is designed so that its blades produce thrust over their entire area, rather than solely at the tips. Jensen believes that Green Ship will help Denmark maintain its position as a world centre for environmental technologies. ‘We still want to be the most advanced nation for these technologies,’ he said.

With a few months still to go before COP15, Jensen sees the project as a success already. ‘We’ll continue the collaboration long after COP15. We’ve never been able to sit together, with representatives from so many companies associated with the shipping industry and discuss such subjects openly.’