Clean power: fuel cells

How viable are fuel cells in maritime propulsion?

In preparation for the upcoming MARPOL regulations, the maritime industry is looking at cleaner methods of propulsion. LNG, methanol, renewable energies—many options for greener shipping are undergoing development in the industry. In this first post of a short series, we explore the outsider in the race: fuel cells.

The 2020 sulfur limit is directly aimed at reducing air pollutants emitted by ship exhausts. While many companies are employing scrubbers (exhaust gas cleaning systems) to clean gases emitted by combustion of diesel and heavy fuel oil, alternative propulsion methods are a more sustainable option. Research into renewable fuels like LNG, hydrogen, or methanol is underway, but there is another runner in the race. Fuel cells could be the clean alternative the shipping industry is searching for.

The environmental benefits are clear

Fuel cells are modular in design, meaning they can be stacked or, alternatively, distributed across a ship, which minimizes electricity loss due to transmission. Combining a fuel cell with a supercapacitor offers the opportunity to reduce the size of the fuel stack and thus save on weight and costs. Fuel cells are showing promise in the cruise sector: Viking Cruises is developing what it hopes to be the world’s first hydrogen fuel cell powered cruise liner, for example. In terms of durability, fuel cells have fewer mechanical parts than traditional power systems. This generally means increased reliability as fuel cells tend to degrade gradually rather than fail completely.

Fuel cells have a major environmental advantage over traditional fuel types, directly converting chemical energy into electrical energy and removing the environmentally damaging middle step of combustion. It is this burning of fuels to produce thermal energy where most harmful air pollutants are emitted. Eliminating the need for fuel combustion supports compliance with tightening MARPOL regulations, as virtually no sulfur oxide (SOx) or nitrous oxide (NOx) are emitted during power production. An additional benefit of no combustion is a reduction in noise and vibration.

What obstacles stand in the way?

A crucial drawback to the viability of fuel cells in maritime is power density. On ships, space is limited so a higher power density is desirable to generate enough power, while remaining stable, and without taking up too much area on board. As it stands, fuel cells are too low in power density to fuel ships for long journeys—a particular challenge for cargo ships or submarines. High temperature single oxide fuel cells in particular are lower in power density and high in cost and so are often disregarded as not a competitive alternative. Early adopters of fuel cell technology use it as a backup, often switching back to diesel when more power is needed.

Fuel cells using pure hydrogen display a much more competitive power density but present a challenge when it comes to storage. As hydrogen is also quite expensive and requires sophisticated storage, ship operators may opt for a diesel-to-hydrogen conversion system on board. There is also currently very little being invested into refueling infrastructures installed at ports. It is challenges such as these that create the general consensus that fuel cell technology is “a long way off”.

Market viability will require a unanimous effort

Despite its clear ecological advantage, fuel cell technology is currently usually installed as a backup in combination with traditional fuels like diesel—undermining its full green potential. Overall it seems that fuel cells will only become viable if a large section of the market takes part. Research and production of fuel cells in shipping is still small scale, so prices remain high. While projects in the niche market are driving innovation, government support programs will be vital in developing fuel cell technology into a cost and power-efficient alternative for the maritime industry.

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