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A Closer Look at Hydrogen Fuel Cells

Earlier this year, we wrote an article about hydrogen as a ship’s fuel. That was a general introduction to the subject, discussing the broad topics of production, propulsion, storage and supply. Now it’s time to take a closer look at one of the issues raised in that article: fuel cells. And more specifically, hydrogen-fuelled proton exchange membrane (PEM) fuel cells.

It is quite a complex subject; that is why we approached Jogchum Bruinsma to help us answer our questions. Besides being application manager maritime systems with PEM fuel cell producer Nedstack Fuel Cell Technology, Jogchum is also a board member of the Zero Emissions Ship Technology Association (ZESTAs).

What is a PEM fuel cell?

A PEM fuel cell combines hydrogen and oxygen to produce electricity, heat and water. This takes place in an electrochemical energy conversion process that not only produces zero NOx, SOx or CO2 emissions, a hydrogen fuel cell is also silent and free from vibrations.

How do they work?

PEM FC Reactions
A PEM fuel cell combines hydrogen and oxygen to produce electricity, heat and water.

There is a lot of electro-chemistry involved, but in summary: a hydrogen fuel cell consists of a catalyst membrane in between two cell plates. Hydrogen is on one side of the membrane, air is on the other. The fuel cell utilises the physical tension between hydrogen and oxygen to create a voltage difference – producing electricity with pure water as a by-product.

How much electricity can a hydrogen fuel cell produce?

A single Nedstack fuel cell up to around 250 amps. By stacking the fuel cells in series, you can create up to 14 kW in a single stack. The stacks are modular – and this is what we do at Nedstack – we connect these units to produce systems that deliver the amount of power required. We have 40kW, 100kW and 500kW output systems, for instance.

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PEM FC Stacking concept
Nedstack fuel cell stacks are modular; they can be installed in series to deliver the amount of power required.

We have read about new inland shipping vessels like the Maas being powered by hydrogen fuel cells. How much space does a fuel cell actually need?

It depends on what type of PEM technology you’re working with. The ones used in the automotive industry operate under high pressure so they are very dense and small. Our maritime systems operate at almost ambient pressure so the stacks are a bit bigger. A maritime hydrogen fuel cell system is almost the same size as a diesel engine. The fuel cell itself doesn’t take up the space – fuel storage is often the bigger issue. That’s because – in terms of volume – hydrogen is much less energy dense than natural gas or any other carbon-based fuel.

We have also read about other types of fuel cell. The SOFC, Solid Oxide Fuel Cell, for example. What is the difference with a PEM fuel cell?

Indeed, there are several types of fuel cell, one of which is the SOFC. PEM fuel cells stand out because they produce the most power per volume of fuel cell. This high power-density combined with a cold-start capability make them suitable for marine applications. An SOFC operates between 600 to 900 degrees Celsius, but a PEM fuel works at just 60 degrees. This means that a PEM fuel cell takes about two minutes or less to start up.

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Jogchum Bruinsma

For the maritime industry considering the various options for achieving the transition away from fossil fuels, what position do you see PEM fuel cells in this future market?

There is a strong argument for PEM fuel cells in all applications, where you can use electric propulsion and/or hotel load. In certain applications, using compressed hydrogen would provide enough fuel for three of four days of operations. With liquefied hydrogen, you can store up to three times more hydrogen in the same volume than with compressed hydrogen – giving you up to two weeks of autonomy. And then if you start to think out of the box and combine PEM fuel cells with other things like wind-assisted propulsion, then transatlantic crossings are definitely possible. Maybe the trip takes two days longer, but it will be without emissions.

I think that this will be combined with a cultural change. If you build a new vessel now, you want to do it as cheap as possible and with a fast return on investment and to generate the highest revenue. I think that this question will change to: I need to transport goods from A to B, how can I do this as cleanly and as sustainably as possible. This change is also accelerated by what consumers think. At some point in the future, consumers will start to choose products based on how sustainably they have been transported.

So you think hybridisation will be a big part of the future?

Absolutely. In inland shipping we are already seeing zero emissions using fuel cell and battery hybrids. Maybe in the short-term we will see fuel cell and diesel hybrid propulsion in short sea shipping. Crew transfer and other service vessels in the offshore wind sector is another good example. If they use fuel cells for in-field operations, and then diesel for shore-to-field operations, this would reduce their CO2 emissions by about 80%.

Are PEM fuel cells relevant for the breakbulk sector?

The technology is there, but change has to come from the sector itself. For example, at Nedstack we don’t want to change the shipping industry. Instead, we want to be available to help the shipping industry change itself; starting with short sea and intra-continental shipping before looking at intercontinental shipping, which requires a worldwide hydrogen supply chain.

Hydrogen fuel cells are obviously going to play an important part in the future of a sustainable maritime industry. What are the major obstacles slowing down the progress?

Policy is a major obstacle, but this is starting to change. What I hear from the industry is that they want to have the risks to investment reduced. This calls for stable government policies that determine the direction that we going in for the next 10 or 20 years. Regulations also need to get in order so that hydrogen production can work on a bigger scale, which is required if you want to bring the costs down.

And the next big thing is creating infrastructure to make hydrogen available at seaports. This will involve building an international network where you can bunker hydrogen at different locations. This will probably take a few years but I think this will become a competitive issue for ports.

It is a similar dilemma to what the industry faced with LNG. But it is more difficult because of the nature of hydrogen and of all the new technologies involved. We are not just changing from one fossil fuel to another. We are changing the ecosystem. You can almost call it a hydrogen revolution. Almost no one was talking about hydrogen three years ago, and now it is snowballing, which makes it more likely that people will start investing. It is becoming big business.

The hydrogen rainbow. A quick recap.

When you start learning about hydrogen’s role as a future fuel, you will notice pretty quickly that there are several different colours of hydrogen that correspond to the method of production. This can be a little confusing (especially as hydrogen is actually a colourless gas). That’s why we made this brief explanation below.

Grey hydrogen is produced from ‘cracking’ natural gas in a process called steam-methane reforming. Because this process is based on fossil fuels and produces CO2, grey hydrogen is not part of a clean energy supply. Possibly even less sustainable is brown hydrogen, which is produced from coal.

Blue hydrogen is a ‘cleaned up’ version of grey hydrogen. The CO2 emitted during the production process is stored with CCS (Carbon Capture and Storage), thus removing it from the atmosphere.

Pink hydrogen is produced by electrolysis using nuclear energy as a power source. White hydrogen is produced as a by-product from industrial processes, such as the production of chlorine.

In terms of a sustainable future, green hydrogen is the most significant. This is made by electrolysis that uses renewable energy such as wind or solar power as an energy source. Therefore, green hydrogen is a truly zero-emission fuel. A crucial point here is that green hydrogen production is a highly suitable way of using the peaks of production that go hand in hand with renewable energy.

The Zero Emissions Ship Technology Association (ZESTAs), is holding a virtual/face-to-face event coinciding with COP26 in Glasgow, Scotland on 1, 2 & 3 November. More info here: https://zestas.org/ship-zero/

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