From the magazine – Now that the Dutch SH2IPDrive project exploring hydrogen as a maritime fuel is about halfway through its four-year duration, we can start to see the initial results and concrete actions. What do we know about the ships’ energy demand? What are alternative ways to carry hydrogen on board of ships? And how can we sail safely?
Since the IMO has updated its climate ambitions, research on alternative maritime fuels such as hydrogen is even more important. You might have heard of the Dutch SH2IPDrive project before, for example in one of the earlier articles published in SWZ|Maritime. This article gives an update on the project and was originally published in SWZ|Maritime’s November 2023 issue. It was written by Annabel Broer (pictured on the right), representative of SH2IPDRIVE and PhD student at the department Maritime and Transport Technology (MTT) at TU Delft, email@example.com, with input from Thijs Hasselaar (MARIN), Ana Carolina Alves (H2Cif), Fabian Benschop (Voyex). and Martijn Hoogeland (TNO).
To retrofit or design new hydrogen-fuelled vessels, maritime engineers need to get a clear picture of the vessels’ energy demand. Hydrogen ships should be optimised in a different way than their fossil-fuelled counterparts. Besides being new, hydrogen-based power, propulsion and energy (PPE) systems are overall more complex. For example, they require additional safety measures and have different cooling, heating and ventilation requirements.
To create efficient energy management systems and smart ship design, high fidelity load data is needed. The standard approach to getting the energy demand, is to estimate a load rating per consumer group and approximate the total energy needed. However, this provides only a crude picture of the propulsion power, auxiliary and part load. That is why MARIN conducts actual measurements on board ships for the SH2IPDrive project.
Measurements are performed on a number of coastal and inland vessels to derive a high fidelity database of operational power profiles. MARIN uses non-intrusive power analysers in the switchboards, strain gauges on the propeller shafts and energy meters on the boilers and a GPS. With these measurements, a database is filled with statistics and dynamic characteristics that describe typical large consumers and load groups.
Using this data, and a simulation model that predicts the propulsion power for future routes and missions under varying environmental conditions, a high fidelity operational power profile can be generated for any mission based on real-life measured data. This data can be used in several stages in the design process; to design a concept PPE system, to validate system performance and models, and to design energy and power management systems.
Carrying H2 on board
When ships have a high energy demand, the energy density of liquified or compressed H2 is not sufficient. Also, safety and practical concerns about the containment and handling of gaseous hydrogen on board remain. For these reasons, so called “hydrogen carriers” could pose solutions. Within SH2IPDrive, two of these are investigated – liquid organic hydrogen carriers (LOHCs, which could be easier to handle) and sodium borohydride (NaBH4, which has a higher energy density).
LOHCs store hydrogen within a chemical double bond, and can store up to 8 wt% of hydrogen . Within SH2IPDrive, Voyex works on three steps within the commercialisation of LOHCs. They produce the carrier (synthesis), work on the bonding of hydrogen to the carrier (hydrogenation) and try to make the release of hydrogen (dehydrogenation) from the carrier more efficient.
First of all, the carrier itself should be sustainable, otherwise there is no point in switching away from fossil fuels. The Voyex LOHC is composed from biomass waste streams and recycled plastics. For the carrier synthesis, Voyex succeeded in increasing the yield from 35 to 75 per cent. Now, they are working on scaling up the batch production process from 10 to 1000 grammes. Eventually, a pilot plant will be built for the production of 150 kg of LOHC liquid per day.
The next step is to add the hydrogen to the carrier. For this part of the process, a pilot plant will also be built. Voyex aims for a factory that binds 600 kg of hydrogen to LOHCs per day. With this factory in place, only the de-hydrogenation step is to be studied. With the current techniques, Voyex can obtain 60 kg of hydrogen per tonne of LOHC. More might be possible with optimisation of the catalyst.
To increase efficiency, the de-hydrogenation (which needs about 200-220°C) could be supplied with waste heat from other processes on board. That is why Voyex is building a plant that can be integrated with a 30 kW hydrogen engine. The de-hydrogenation system used there will serve as a blueprint for a subsequent series of ten to fifteen systems in different pilot projects.
The other promising maritime hydrogen carrier, NaBH4, is an inorganic salt that can theoretically store up to 10.7 wt% of hydrogen . To release the hydrogen, NaBH4 is fed into a hydrolysis reactor. Here, it is combined with ultra-pure water to form hydrogen and a spent fuel (NaBO2).
Right now, the H2CiF system can operate continuously, allowing a vessel to sail without gaseous hydrogen stored on board. This is because the hydrogen is stored as a solid within the NaBH4 and is only released on-demand in the reactor. This results in easier fuel bunkering and lower safety risks. Within SH2IPDrive, H2CiF is designing a low-temperature and low-pressure modular H2 extraction system. It should be able to extract 100 to 1000 kW of hydrogen gas.
What about safety?
Of course, the introduction of a new technology on ships calls for new equipment and results in different behaviour of materials and fuels. These changes will result in new hazardous scenarios that have to be mitigated in the overall design. In a previous SWZ article, TNO indicated how HAZID and risk analysis studies are set-up and equivalent safety compared to fossil-fuelled vessels is reached.
Various questions are still waiting for an answer. For example, what happens when containerised hydrogen storage systems drop from heights? How will a liquid hydrogen spill behave? And what is the best way to detect hydrogen leakage in a confined space? Finding the answer to these questions is done via simulations, experiments, and when possible with both.
To illustrate this approach, we can look at the hydrogen spilling risk. First, TNO and TU Delft simulate the process to predict the temperature drop of the steel and the probability that it will break once it is cooled down far below the normal design temperatures. They will follow up these simulations with an actual liquid hydrogen spill test.
To assess if the “equivalent safety” benchmark is reached, TNO will use modelling tools. They currently work with Hydrogen Plus Other Alternative Fuels Risk Assessment Models (HYRAM+) as it is known to work well for hydrogen processes. Nonetheless, it is not specific for maritime or offshore applications. Therefore, HYRAM+ results will be compared with Computational Fluid Dynamics (CFD) analysis to see why and how discrepancies between the two tools arise.
As you can see, the development of hydrogen shipping comes with many different facets. SH2IPDrive partners are gathering detailed load data to improve ship designs and explore the abilities of two promising hydrogen carriers while strictly monitoring all safety risks involved.
New challenges and questions arise relating to the smart integration of hydrogen storage on board vessels, reliable safety analysis tools and many more areas. Examples include how smart energy management systems can be programmed, how hydrogen carriers should be bunkered, and how the lifetime of hydrogen technologies can be prolonged within the harsh maritime environment.
This will therefore not be the final piece you read on the activities of the SH2IPDrive project, and we’re looking forward to updating you again in the future.
Picture: The Voyex R&D system with which the company is loading and releasing hydrogen daily from its liquid organic hydrogen carrier (LOHC) at kg-scale.
- Makepeace, J.W., He, T., Weidenthaler, C., Jensen, T.R., Chang, F., Vegge, T., Ngene, P., Kojima, Y., de Jongh, P.E., Chen, P., David, W.I., 2019, Reversible ammonia-based and liquid organic hydrogen carriers for high density hydrogen storage: Recent progress, International Journal of Hydrogen Energy 44, 7746-7767, doi:10.1016/j.ijhydene.2019.01.144
- Kojima, Y., 2019, Hydrogen storage materials for hydrogen and energy carriers, International Journal of Hydrogen Energy 44, 18179-18192, doi:10.1016/j.ijhydene.2019.05.119