A vessel off the coast of Bilbao is now operating with an on-board ammonia cracker making pure hydrogen fuel to power its auxiliary services, in what the company behind the scheme claims is a “world first”.
The 4.4m-long Bertha B supply vessel was fitted with the on-board ammonia cracker by Spanish start-up H2Site, with the resulting hydrogen used in a 30kW proton exchange membrane (PEM) fuel cell, which in turn provides electricity to the ship.
Both components are integrated within a single container located on the ship’s deck, while the 30kW fuel cell currently uses around 120kg of ammonia per day, stored in large bottles.
“It is the first time that such a solution is installed and operated onboard," H2Site chief executive Andrés Galnares told Hydrogen Insight. “The special feature of our cracker is that it generates very high purity hydrogen without using additional gas separation technology, and this maximises the fuel cell efficiency. Existing solutions generate a blend of hydrogen and nitrogen.”
However, as the Bertha B is a near-shore vessel, sailing time is limited to a few hours.
H2Site told Hydrogen Insight today that it is currently building units with the same technology in the MW range, which could allow the fuel cells to power larger vessels.
The installation was carried out as part of H2Site’s validation of its “integrated membrane reactor” which ensures that no traces of ammonia are left in the hydrogen after cracking, and will eventually be removed from the Bertha B vessel.
PEM fuel cells require a high purity of hydrogen in order to operate efficiently. In fact, trace amounts of ammonia in a PEM fuel cell would cause irreversible damage, according to scientists at Australian research agency CSIRO.
“Our innovative membrane reactor technology not only brings an improvement in system efficiency but also reduces the footprint of the installation,” said Jose Medrano, Technical Director at H2Site. “This is especially important in applications where space is limited, such as onboard a vessel.”
However, the process of cracking expensive ammonia back into hydrogen and then using it in a fuel cell brings about significant energy losses.
H2Site said its cracker operates at 90% efficiency, while the fuel cell has an efficiency of around 50-55%, resulting in a round trip efficiency of around 35%, comparable to an internal combustion engine.
But according to CSIRO’s more generalised report on general ammonia-to-hydrogen fuel cell technology, the well-to-wake efficiency of operating a fuel cell powered by hydrogen cracked from renewably-sourced ammonia would result in an overall round trip efficiency of 11%-19%, based on 24% energy losses in the cracker and a further 40-60% in the fuel cell.
This is because the production of ammonia would require significant amounts of renewable energy to make green hydrogen and even more to power the Haber-Bosch process that synthesises hydrogen and nitrogen, resulting in significant expense.
Medrano added: “We have focused our design efforts on minimising the ammonia consumption, which will be key for the scale up to suit higher power output units.”
H2Site is sourcing the ammonia from a local gas supplier, indicating that it is grey NH3 made from polluting fossil gas.
The Haber-Bosch process used to synthetise hydrogen and nitrogen into grey ammonia from fossil gas has a carbon intensity of around 1.5 tonnes of carbon dioxide-equivalent per tonne of NH3, currently accounting for around 1.2% of global carbon emissions.
Green ammonia made with renewable hydrogen remains scarce for the time being. But the northern region surrounding Bilbao is hoping to host a major green hydrogen hub — an ambition that was recently dealt a blow by developer Repsol’s decision to freeze investment in its Basque country hydrogen programme — as part of Spain’s plan to develop a series of Hydrogen Corridors of H2 supply and demand.
UPDATED: to add detail on the installation