The electric ferry Ellen sails on 100 per cent electricity between Ærø and Als. But even though smaller electric ferries have seen the light of day and green solutions are being developed for container ships, virtually all large ships in the maritime sector sail on fossil fuels. This makes the sector a major CO2 emitter.
According to the European Environment Agency, emissions account for around 3 to 4 per cent of the EU’s total emissions. If no solution is found, emissions will increase significantly as the sector grows. The OECD predicts that the need for shipping will triple by 2050.
In DTU’s laboratories, researchers are developing a fuel cell system that will generate CO2-free power for large ships such as container ships. Electricity will replace fossil fuels.
A fuel cell can produce electricity by means of an electrochemical reaction between oxygen and several types of gases, including hydrogen and ammonia.
One of the solutions is to use a so-called SOFC system (solid oxide fuel cell), which is a high-temperature fuel cell system, and add ammonia to the system. The system can, among other things, use green ammonia to produce CO2-free power, and will be an integral part of the ships, replacing the current engines running on fossil fuels.
“The SOFC system will probably cost twice as much as a standard marine engine. This should also be seen in relation to the need for more efficient solutions for ships . So fuel cells will take some years to become financially competitive, but our planet has limited resources, which means that saving a large amount of resources has great value despite the higher initial costs. These initial costs will ultimately benefit our planet,” says Henrik Lund Frandsen, Professor at DTU Energy. He is working on several projects integrating SOFC systems.
Must be refuelled with green ammonia
In order for the SOFC system to produce CO2-free power, the ammonia production must also be green—and this may present a challenge. Right now, ammonia is predominantly produced with fossil fuels, making it the most greenhouse gas-intensive chemical to produce worldwide, with production accounting for about 1.5 per cent of the total global CO2 emissions. But with the help of Power-to-X, it will be possible to produce green ammonia that does not emit CO2, and this is the method that must be expanded if SOFC systems on ships are to be launched at scale.
“Right now, the production of green ammonia is virtually non-existing. If we don’t get any green ammonia, the system is worth nothing. But green ammonia will be a reality—most likely before the end of this decade. Whether it ultimately will be used through a fuel cell system is more uncertain,” says Henrik Lund Frandsen.
However, if green ammonia production truly gets off the ground, there are several aspects that speak in favour of an integrated SOFC system.
“The efficiency of converting energy from ammonia via a fuel cell is very high, which means that you can save a lot of fuel compared to the amount required by an internal combustion engine. In addition, large amounts of toxic nitrogen oxides are released when burning ammonia. In SOFC fuel cells—under our system conditions—these gases are not produced. So you save significantly on the gas cleaning system compared to if the ship were to sail on ammonia and a combustion engine,” says Anke Hagen, Professor at DTU Energy who has headed the Aegir project, which among other things worked with SOFC in the maritime sector.
Testing the technology
One of the projects Henrik Lund Frandsen is working on is about replacing the ships’ auxiliary engine with a fuel cell system. Large ships have both a main engine that drives the ship forward and an auxiliary engine that, using fuel, generates power for the actual ship operation—such as lighting and cooling systems. The project is run in collaboration with the company Alfa Laval.
“Right now, the first prototype of the auxiliary motor is being tested. This is currently the best case, as you can double the efficiency with an SOFC system as an auxiliary engine. So you only need half as much fuel as with an auxiliary combustion engine, resulting in significant fuel savings. For the very large main engines, the efficiency is around 50 per cent, which is almost where it could be financially viable to replace with fuel cells. But with an auxiliary motor, we can boost efficiency to 60-70 per cent, which will be a huge gain, considering that green ammonia is also more expensive to produce," says Henrik Lund Frandsen.
The industry must invest in fuel cells
Despite the large climate benefit, the researchers point out that the system must also be financially viable before we will see results.
“The costs increase if you produce the fuel yourself rather than extracting it from the ground ‘for free’. On the other hand, savings are achieved by the high efficiency, but economics is often a driver for development. So the goal is to make the technology cheaper so the roll-out happens faster,” says Henrik Lund Frandsen.
If you ask the researchers, we may some day see container ships running on electricity using fuel cells. The question is whether the industry will look to fuel cells or other solutions.
“We have the technology. It can always be improved in terms of cost and service life in order to become competitive in the long term. It is first and foremost a question of whether we dare to invest in the technology commercially before we can see it integrated. Green solutions are attracting a lot of attention from the major stakeholders in the sector. I believe that once you build ships that can use ammonia as fuel in a combustion engine, it will be easier to switch to an SOFC system,” says Anke Hagen.
