The challenge of building effective storage and delivery infrastructure may have dampened the industry’s enthusiasm for fuel cells, but the technology may yet help achieve the GHG mandate
“Fuel cells were the talk of 2018, not so much this year,” says Jan-Erik Räsänen, head of new technology at Foreship, the design and engineering firm based in Helsinki, Finland, that caters almost exclusively to passenger ships. “After exploring the technology, the industry realised that fuel cells are further into the future than originally expected,” he adds.
That said, Foreship still sees fuel cells as playing a significant role in shipping as it moves away from fossil fuels. The problem is not with fuel cells, but with the fuel. There is, as yet, no pathway towards the mass, renewable production of hydrogen that is commercially viable.
Transporting and storing the fuel onboard ships remains a daunting challenge and technological breakthroughs will be needed in this regard. The basic technology of fuel cells, however, is in place, but the products need to mature and fall in cost.
Presently, fuel cells are being deployed in passenger ships, where environmentally friendly technology can have an immediate impact on ticket sales. Such fuel cells typically handle hotel loads, leaving main propulsion and an element of shipboard power to be handled by diesel engines. Fuel cells need time to start up and shut down and are tuned to take up constant loads; they need batteries for peak shaving.
Mr Räsänen believes both the proton exchange membrane (PEM) fuel cell and the solid oxide fuel cell (SOFC) have potential in marine conditions. PEMs, which have lower operating temperatures, are currently the more mature, having become widely used in the automotive industry, says Mr Räsänen. He adds that this could be the reason PEMs are preferred over SOFCs for ships. But eventually the higher energy conversion efficiency of SOFCs – 75% – may tip the balance, he says.
There are pros and cons to each approach: SOFCs operate at temperatures upward of 750 degree Celsius, but are more tolerant of impurities in hydrogen, whereas PEMs are cheaper, at least for the time being.
The show stopper however, is that hydrogen is not currently available as a bunker fuel. This means ships need a steam reforming process onboard and this requires space-consuming, expensive infrastructure. The largest fuel cell being developed by ABB as a test case for marine applications is 3 MW and cruise ship loads are in the range of 60 MW, according to Mr Räsänen.
Another bottleneck is the nature of hydrogen, which has a bearing on storage. If the cryogenic LNG fuel tank onboard requires twice as much space as marine gas oil (MGO), the hydrogen tank, with its pressurised containment system and insulation, needs to be four times as big as the MGO tank.
There could be incremental gains to this method of hydrogen storage, but alternative technologies may be needed to shift the equation, says Mr Räsänen, pointing to the recent collaboration between a hydrogen storage technology company and MAN Energy Solutions.
The agreement between MAN, Hydrogeneous LOHC Technologies and Frames Group seeks to leverage Hydrogeneous’ technology, which uses heat transfer oil to store hydrogen at room temperature. The goal is to build large storage systems for the fuel.