With the marine industry working towards IMO 2050 emissions targets, and sustainability a hot topic across all industries, the need for cleaner alternative fuels has never been more critical. We’ve already looked at what LNG and methanol have to offer, and now it’s time for hydrogen. So, what are the benefits and challenges of replacing traditional fossil fuels with hydrogen?
Along with LNG and methanol, hydrogen has the potential to play a huge part in the future of the shipping industry. It can be used to create hydrogen-based fuels, such as ammonia, and it can also be used as a fuel in itself.
The benefits of hydrogen
At first glance, hydrogen looks like a compelling option for shipping, not least because it’s considerably cleaner than diesel. It’s currently made using natural gas, but the goal is to introduce sustainable zero-emission ways for how hydrogen is produced.
“The most obvious solution is that we use electricity from renewables like solar, hydro and wind power, using electrolysis to produce green hydrogen,” Raphael Ryser, Senior Expert Turbocharging and Engine Technology at Accelleron explains.
Hydrogen is already being used in specific applications, such as short-haul shipping, where there’s no need to store huge amounts of fuel. We’ve seen ferries in both Norway and America running on hydrogen, and this is made possible by the fact they’re only travelling for a few kilometres at a time, and the amount of fuel required each day is limited.
“It’s also considerably easier for countries such as Norway to produce green hydrogen, as it has greater access to renewable energy sources such as hydro power, enabling hydrogen to be produced locally,” Raphael adds.
This makes a lot more sense than producing hydrogen and transporting it to different locations, as there are several challenges that come into play, not least the density of the fuel itself.
While there is plenty of potential for using hydrogen in short-haul shipping, there are bigger challenges when it comes to long-haul shipping.
The challenges facing hydrogen
Hydrogen has a low volumetric energy density, Raphael, explains, which means it requires a larger tank volume for storage. In fact, hydrogen is less dense than ammonia, methanol and LNG, which also lag behind traditional fossil fuels. This makes storage a specific issue, with a considerable amount of space required to store large quantities of hydrogen. In its densest liquified form, hydrogen is comparable to Styrofoam when it comes to weight – it really is incredibly light.
There are other big challenges when it comes to storage as well. If liquified, the fuel needs to be kept at 20 Kelvin (-423.67 Fahrenheit / -253.15 Celsius), which is problematic as it’s very energy-intensive to get down to such incredibly low temperatures. It can be pressurized as an alternative, but needs to be stored at up to 700 bar pressure, which introduces additional concerns about the design and materials used for storage.
The type of materials used to store hydrogen need to be considered carefully, as hydrogen can affect the material it’s in contact with. It can attack steel, for example, leading to the material becoming more brittle. “There are some specific grades of steel that can cope with hydrogen, but the design and materials also need to take the very high pressures required into account,” adds Raphael.
Hydrogen is difficult to store when it comes to a safety point of view, too. “The explosion limits of mixtures with air are extremely wide,” Raphael explains, “and the minimum ignition energy is very low. This is a particular issue when stored in confined spaces, where even a very small spark can lead to explosions.
“This isn’t necessarily such an issue when it comes to the actual vessels, as hydrogen also disperses quickly in less confined conditions, so it shouldn’t be a problem if the ship is designed properly.”
A solution for short-haul shipping
It’s clear there are plenty of challenges to overcome, but many of the biggest barriers to the adoption of hydrogen are not applicable or as impactful to short-haul shipping, especially where hydrogen can be produced locally and doesn’t need to be transported or stored in large quantities. “This is where hydrogen works best,” says Raphael.
And for long-haul shipping? Going that next step, and turning hydrogen into ammonia may remain a more practical solution, along with other alternative fuels such as methanol. Check back soon, as we look at what ammonia has to offer the shipping industry in the next instalment.