One of the key decisions in developing a hydrogen system is deciding how - and in what form - to store and deliver it. The most common approaches are ambient temperature compressed gas up to 700 bar, or low pressure cryogenic liquid near 20 K.
Other methods have been tried and are the subject of ongoing research and development. These include: materials that trap hydrogen by molecular or chemical means; cryo-compressed (transcritical); and hydrogen "carriers" that are converted prior to use (e.g. ammonia).
Any application should be evaluated to determine the best approach given the system objectives, requirements, constraints, and concept of operations. For large scale applications, and vehicles with onboard hydrogen storage (land, sea, air, or space), liquid hydrogen is often the best solution.
Liquid hydrogen has several critical advantages compared to other forms of hydrogen storage:
- Relatively high volumetric density at low operating pressures
- Long history of production, storage, transport, and usage
- Off-the-shelf subsystems and components available
- Many legacy stationary, over-the-road, train, barge, and launch systems
- Zero boil-off possible with proven cryo-refrigeration technology
- Low temperature provides ancillary system capabilities
The above advantages are partially offset by the unique design and operational considerations associated with liquid hydrogen. Some key considerations include: liquefaction (and re-liquefaction), material properties, fluid thermodynamics, phase change, and thermal management.
Although there are well established and validated methods to fully address these considerations, the requisite knowledge base is not widely disseminated yet. The primary motivation for this blog is to share that knowledge base with a wider audience to accelerate the safe and effective adoption of liquid hydrogen in new areas of application.
Below is a presentation I gave a few months ago at the Center for Hydrogen Safety Asia-Pacific Conference that addresses zero boil-off and densified liquid hydrogen systems. Future posts will provide more details on these and other related topics.
Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.