Safety with Liquid Hydrogen

Relative to conventional fuels, hydrogen has a wider flammability range in air (4–75%), higher permeability through some materials, and a lower ignition energy (0.02 mJ). These characteristics make it vital to provide adequate ventilation, prevent leaks, and eliminate ignition sources in any hydrogen system design and operation. System monitoring and detection is important to ensure that all safety precautions are active and operating as intended. 

The very rapid 20 m/s rise rate of gaseous hydrogen in air under ambient conditions greatly aids with ventilation and dilution. Hydrogen also has an auto-ignition temperature of 585°C, which is higher than most fuels. Hydrogen is colorless, odorless, and not toxic to breathe. However, low oxygen detection is needed anywhere hydrogen may accumulate near personnel since asphyxiation is possible if insufficient oxygen is available.

When combusted, hydrogen produces no smoke or soot, which eliminates associated inhalation risks common with fossil and other hydrocarbon fuels. The resulting flame also produces much less radiant energy compared to hydrocarbon fires, thereby reducing the zone of potential heat damage or burns. A hydrogen flame is nearly invisible under daylight conditions, requiring infrared sensors or cameras for detection. At night, the flame is pale blue in appearance. For all hydrogen systems, emergency and fire response planning and coordination is a critical consideration.

The use of LH2 introduces additional safety concerns beyond gaseous hydrogen due to the temperature extremes and phase change characteristics inherent in cryogenic fluid systems. Personnel training, appropriate protective clothing, human interface designs, and safe operations are key to mitigating frostbite and other physiological risks. Appropriate equipment design that eliminates the possibility of human contact with cryogenic surfaces is preferable whenever possible. Exclusion zones, caution and warning systems, safety sensors, and approved operational procedures further mitigate risks to personnel.

The large temperature ranges in cryogenic systems require careful materials selection and design to accommodate differences in thermal expansion and contraction. Phase change from liquid to vapor (and sometime the reverse) occurs throughout a LH2 system, resulting in potential rapid pressure changes in isolated volumes. This must be addressed with appropriate design, operations, and pressure relief devices. If maximum vent relief flow rates are high enough, flaring may be required.

Mitigation of ice buildup is necessary where it may cause key components to not operate properly or create other hazards. Likewise, prevention of oxygen condensing out of the air is addressed with proper insulation on any surfaces that may reach low enough cryogenic temperatures. Any LH2 spills will begin to immediately vaporize and rise as the vapor warms. However, the initially cold hydrogen vapor will be denser than air and can result in temporary regions of high concentration near the ground.

Material selection for hydrogen service must address the design and operational requirements for strength, ductility, fatigue, permeability, and other material properties. Approved cleaning processes must be followed to ensure that unacceptable contaminants are not introduced to the system from materials. Purity levels of the hydrogen are generally dictated by the fuel cell specifications or other feed requirements. Purging and inerting of the assembled system is required for various operations to prevent the introduction of air or other contaminant fluids.

Retrograde US Energy Policy

"The biggest story in the data is the dramatic growth of [US] solar energy, with a 30 percent increase in generation in a single year, which will allow solar and wind combined to overtake coal in 2024." [1]

This pie chart and quote may be one of the last bits of promising US energy news we'll get for the next few years. Many colleagues have asked my opinion about the prospects for hydrogen in the US under the new administration. Here's a breakdown of what we already know, and my guess about what's to come.

Federal Energy Policy

The new federal energy policy can be summarized as a huge step backwards that prioritizes oil and gas while demonizing intermittent renewables [2]. This ignores the fact that solar and wind are the lowest cost power generation sources to bring online and operate, which is the primary reason they have grown so rapidly in recent years.

Mitigation of greenhouse gases and pollution are existentially crucial additional benefits of renewables, making them the logical focus for growth from both an economics and environmental perspective. But propaganda trumps cost of electricity, public health, casualty losses, and the future quality of life for coming generations in the current administration.

The new secretary of energy has parroted this policy, with additional emphasis on liquefied natural gas (LNG) exports from the US. LNG is 85-95% methane, which is a 25 times more potent greenhouse gas than carbon dioxide over 100 years (85 times more over 20 years). Gas leaks and intentional venting are prevalent sources of methane emissions from production, transport, and end use of LNG.

What About Hydrogen?

There is no mention of hydrogen whatsoever in any US energy policy documents released by the new administration. So what does that mean for federal policy regarding hydrogen? Let's connect some dots by enumerating a few key benefits of hydrogen in the energy sector:

1. Hydrogen produces no greenhouse gases and no pollution of any kind when used to produce electricity with fuel cells. If burned in a turbine or other combustion engine, it produces some NOx (as all combustion processes do) that can be minimized with various design and operational parameters.
2. Hydrogen can store energy at nearly unlimited scale from intermittent renewables when excess generation capacity is available, and be used to generate electricity when demand exceeds generation capacity.
3. Hydrogen's unparalleled specific energy relative to any other conventional fuel enables high performance sustainable solutions across multiple mobile and transportation sectors (e.g., aviation, rail, maritime, trucking, etc.)
4. Hydrogen provides unique energy resiliency and eliminates fuel logistics dependencies for remote or isolated regions.

Note that none of the above benefits are aligned with the new federal energy policies. Nor were they eight years ago when we saw this energy policy disaster unfold the first time around. Looking back at that timeframe may help make a clear-eyed assessment of what's to come.

The Path Ahead

Within this new reality, what is the future for hydrogen in the US? Regrettably, here are my predictions:

• Federal funding for hydrogen programs, including the hydrogen hubs, will be largely gutted. One potential exception is military applications where hydrogen addresses strategic defense and national security challenges that no other approach can match.
• States and local policies and funding will help in a few US regions. California will remain the hydrogen hotbed it has been for many years. Hawaii, New York, Pennsylvania, and parts of New England also have or may provide supportive policies for hydrogen. Texas will be a wildcard since there is much in place for hydrogen production, but may have fractured policies depending on the area (e.g., Gulf coast vs rural areas). However, many other states and locales already have policies that are hostile toward renewables and hydrogen, and will be emboldened to double down on derailing permitting and similar tactics with the new federal policies.
• Private sector funding for hydrogen systems and products has been extensive in some industry sectors and regions. Many of these hydrogen applications have demonstrated performance and economic viability at various commercial readiness levels. It's unlikely that private investors will walk away from sunk cost investments if there is an opportunity to get a reasonable return. The challenge is which global markets are the best targets if most of the US is off the table, which leads to my final prediction.
• Global regions will likely stay the course, or even accelerate hydrogen plans, as the US backs away. China will build on its lead as the largest producer and user of hydrogen and associated systems. The European Union, United Kingdom, India, South Korea, Japan, and Australia may find increased interest in new hydrogen projects in their regions with the drying up of US funds and incentives. The same for other countries and regions with established and emerging hydrogen programs such as Canada, South America, Middle East, Africa, and other countries in the Asia and Indo-Pacific regions.

[1] John Timmer, Ars Technica, Jan 27, 2025.

[2] Executive Order, Jan 20, 2025.

[3] Secretarial Order, Feb 5, 2025.

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 break-through 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 co-founder in seven technology startups; and provided R&D and engineering support to many organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management series. He also teaches courses, workshops, and webinars on liquid hydrogen systems.

Cryogenic Hydrogen Thermal Design Options

A key storage consideration for liquid hydrogen is the vaporization rate caused by environmental heat loads, often referred to as boil-off. The above graphic shows some of the established methods for mitigating or eliminating boil-off categorized by the input power required [1].

Passive techniques require no input power and include design and material selection for insulation, structural supports, piping, and other tank interfaces that minimize heat transfer to the inner tank wall. Hybrid methods require some input power for valve actuation, mixers, pumps, or other components to reduce the boil-off rate. 

Finally, active techniques require power input for cryo-refrigeration or densification processes. Depending on the concept of operation for the system, application of the appropriate combination of these methods can minimize or eliminate boil-off losses [2].

Hydrogen Storage Options

The most common commercially available storage options along with some of their key characteristics are shown above [1]. Each of these methods has advantages and disadvantages that are critical considerations for selecting the best storage method for a given system and use case.

Low-to-moderate pressure storage in salt caverns or other compatible underground locations enables large quantities of gaseous hydrogen to be stored for long periods of time. Electrical energy input is required for a blower or compressor to inject the hydrogen and buffer gas underground at the desired storage pressure. This approach relies on the necessary local geology as well as connection to a gaseous distribution system similar to natural gas infrastructures. A hydrogen liquefaction plant can also be sited nearby using the underground hydrogen storage as feedstock after removal of the buffer gas.

Material-based or solid-state storage is a broad category that encompasses methods to store hydrogen in a matrix material via microscale adsorption or chemical absorption. Many materials and methods have been developed, with metal hydrides currently the most common type in commercial use. Thermal energy is generally required for the solid-state storage reaction to occur as adding hydrogen is exothermic requiring cooling, and removal is endothermic with heat addition. Metal hydride systems are generally better suited to stationary applications due to their low mass fraction and should be installed where low-cost process heat and cooling are available or low pressure is especially important. However, newer technologies using lightweight matrix materials such as aerogels may hold promise for some mobility applications.

Compressed gaseous hydrogen storage requires electrical energy to create the high pressures required. Cooling is also needed to bring the gas stream back down to ambient temperature due to the heat of compression. Composite overwrap pressure vessels (COPV) designed to withstand the high pressures are commercially available at 350 or 700 bar. Initial mobility demonstrations with hydrogen often use COPV storage, and for some applications this option is sufficient to meet the system goals. For many mobile applications, however, the volumetric energy density and mass fraction of compressed hydrogen storage is too low to meet performance requirements.

Cryogenic LH2 has nearly double the volumetric storage density of 700 bar compressed hydrogen at ambient temperature, and along with low-pressure storage conditions enables a much higher mass fraction. For this reason, many transportation applications transitioning to hydrogen are storing or planning to store in cryogenic liquid form. The primary electrical energy input required for LH2 storage is the liquefaction process. As previously mentioned, LH2 has been the primary storage and distribution method in the space industry for many decades.

In aviation, H2Fly demonstrated LH2 onboard storage during successful flight testing of their small demonstrator aircraft. ZeroAvia and Airbus have publicly shared their LH2 design plans for new aircraft. Nikola and Hyzon have demonstrated long-range truck routes with LH2, and First Mode has demonstrated hydrogen in a large mining truck. Operational mobility systems using LH2 include Hyundai Rotem trams and marine vessels from multiple companies.

Cryo-compressed hydrogen is another option that has intriguing advantages for some mobile applications. In this supercritical storage state, the hydrogen is compressed at cryogenic temperature resulting in higher potential volumetric density compared to LH2 storage. However, the mass fraction is generally less than LH2 storage systems due to the need for thicker walled vessels to withstand the higher pressures. The U.S. Department of Energy (DOE) has funded development of this technology over many years, and it is now being commercialized by Daimler Truck, Verne, and others. Daimler has also developed a ‘subcooled’ transfer process that can fuel a truck with 80 kilogram of hydrogen in 15 minutes or less without a return vent line resulting in onboard cryo-compressed storage. [2]

Focusing on a Hydrogen Future

You may recognize the above graphic as a slightly modified version of the Eisenhower decision matrix, a powerful tool for managing day-to-day activities. I've found it can also be useful for business or career strategy by re-labeling the axes "revenue" and "impact". The familiar resulting quadrants help identify priorities for executing, investing, delegating, and deleting.

In a recent talk, Thomas Friedman spoke about two unprecedented "supercycles" we are in the midst of: climate change and AI. The first is an existential threat; and the second could help us solve the first one, or become an existential threat itself, or both.

Within that sobering context, here's where my company is heading in 2025:

• Liquid hydrogen systems development (execute): In my previous post, I mentioned the hydrogen microgrid project, LH2 drones and automated fueling systems, and NASA lunar lander development activities my company supports. These are core company projects, and the first two will remain top business priorities in 2025 with the goal of full scale demonstrations.
• Knowledge transfer (invest): I've already invested a good deal of time into creating various resources and tools for developing liquid hydrogen systems, most of them freely accessible on my Training page. Have also contributed to LH2 related standards and guidelines development, and will continue those efforts. Next, I'll be creating, training, and fine-tuning a hydrogen AI agent called H2 Sage using: curated public domain data; my intellectual property data from 40 years of hydrogen technology and systems development; and the most powerful LLM APIs available (e.g., OpenAI o3 and future frontier models).
• Space projects (delegate): This is a very difficult pivot for me. I worked directly for NASA for 31 years, and continued supporting them on various contracts for another 9 years. Have also done space related work for DOD and multiple private sector organizations over that timeframe. But it's time to let my younger and more talented colleagues at NASA, its contractor teams, and commercial space to continue forward in this inspiring and important area without me.
• Talkers vs doers (delete): Not long ago, only chemistry teachers and professionals working in just a few industry sectors talked about hydrogen. Now almost everybody - especially on social media and from various news outlets - seems to have an opinion on the topic. On one end of the "talker" spectrum are hydrogen haters (see my old post), and on the other end are those pitching hydrogen concepts they cannot deliver. Both ends, and many talkers in between, often have little or no actual experience with hydrogen. And they are impeding our progress toward addressing climate change with misinformation and predictable failures. We need to support the hydrogen doers and ignore the hydrogen talkers.

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 break-through 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 co-founder in seven technology startups; and provided R&D and engineering support to many organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management series. He also teaches courses, workshops, and webinars on liquid hydrogen systems.

Liquid Hydrogen (LH2) Gifts from Santa in 2024

Image credit: Matt Moran, Moran Innovation LLC

It was a busy 2024 for my company, Moran Innovation, with implementation of all the capabilities shown above on Santa's list into new LH2 systems for NASA, DOD, and private sector customers. Also, lots of activities related to training, publications, and standards development. Here's a few highlights with hyperlinks to information that may be of interest to the hydrogen community:

 

• Decarbonizing mobility with liquid hydrogen. Published an SAE Edge™ report on this topic with contributors from multiple industry sectors and global regions. Discussed it at the WCX SAE Knowledge Bar and a SAE The Mobility Frontier webinar.
• Hydrogen-based microgrid. Completed the first phase of adding hydrogen capability to the PEARL microgrid in Honolulu. The expanded multifunctional operations will include production of hydrogen from solar-powered electrolysis, compressed storage, power generation from fuel cells, and in-tank liquefaction for unlimited LH2 storage time (dormancy) and offtake fueling.
• LH2 drones. Continued support of NEOEx Systems liquid hydrogen drone development with automated fueling and on-demand full lifecycle production and liquefaction. Their systems eliminate the need for LH2 distribution, transport, delivery, and ground support storage.
• Airport hydrogen fueling standards. Continued participation in the SAE AE-5CH Hydrogen Airport Taskgroup which published the first global guidelines for airport hydrogen refueling stations.
• Vacuum-jacket piping guideline. Began development of guidelines for vacuum insulated piping for cryogenic applications with a small group of fellow experts.
• NASA lunar landers. Completed the fourth year of providing cryogenic fluid management subject matter expertise to the NASA Human Landing System program and other contracts related to LH2 and other cryogens including zero boil-off systems.
• Courses, webinars, and workshops. Completed the first ever webinar series solely dedicated to LH2 resulting in 13 monthly webinar sessions during 2023-2024. Just released an online, on-demand LH2 systems course that will preview a new lecture every month in 2025 for free. Taught the hydrogen fundamentals portion of the AIAA/HYSKY Advanced Hydrogen Aerospace Technologies and Design course, and did other training and workshops at various conferences and venues. Details can be found on my website Training page.
• Global LH2 topics. Continued managing the Global LH2 Systems LinkedIn group that I started last year for sharing news and other topics relevant to the worldwide LH2 community.

The global momentum with LH2 systems development across many industry sectors and regions is very encouraging. Significant capital investments are accelerating the transition to hydrogen to meet our energy needs while eliminating the sources of damage to our environment and public health caused by burning fossil fuels. This transition also provides energy security, resiliency, and sustainability; all of which translates into a higher quality of life worldwide. And public policy has been moving in the right direction in most countries, albeit at a less than optimal pace.

Looking forward, there is some uncertainty regarding governmental support in some regions. Geopolitical shifts may stall some countries' progress on hydrogen allowing other countries to advance into global leadership positions (perhaps permanently). How do we keep the momentum going with hydrogen? I believe the answer lies in a quote I recently posted from the late Peter Drucker: "The best way to predict the future is to create it". So let's keep creating a better future together with hydrogen in 2025!

• 

  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 break-through 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 co-founder in seven technology startups; and provided R&D and engineering support to many organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management series. He also teaches courses, workshops, and webinars on liquid hydrogen systems.

Myth Busting (Episode 4): Hydrogen Haters

Image created using Bing AI

This episode of hydrogen myth busting is dedicated to the source of a great deal of misinformation on the topic: hydrogen haters. And with the recent announcement of the US hydrogen hub awards, they are in full blast mode in the news, social media, and many other available venues that provide a soapbox.

It's a curiosity of human behavior that we are willing to accept the assertions of people who have no expertise in some areas, but openly challenge them in others. If our friend who has never set foot in a kitchen (except to eat) started giving us a lecture about cooking a gourmet meal, we would laugh at them. Many of us would have a similar reaction if someone who doesn't know a wrench from a hammer started giving us advice on car repair.

In contrast, it seems that anyone with a mouth or keyboard can make absurd and unsubstantiated pronouncements about hydrogen that get blindly accepted as true by some. This misinformation often gets re-posted and amplified by a bandwagon of equally unqualified sources until suddenly it becomes the assumed 'conventional wisdom'.

Types of Haters

In my experience, hydrogen haters can be categorized into five main types (or combinations thereof) depending on their viewpoint. You might be a hydrogen hater if:

1. It threatens your business or expertise. This may seem obvious, but it's surprising how many people don't take this into account when they listen to someone's opinion on the subject. Clearly, if the use of hydrogen represents a threat to your business model, or a better alternative to your product, you are highly incentivized to trash talk it. Some cynical types might call this marketing 101. Similarly, if it has the potential to make the expertise you've developed over a career less relevant, you might be looking for any opportunity to derail its implementation.

2. It competes with your preferred solution. Closely related to the previous type, this category often includes proponents of other solutions to decarbonization. Sadly, this is analogous to picking a fight with someone on your own team, and can sometimes take on the heated tenor usually reserved for brawls (e.g., batteries vs hydrogen). We need a portfolio of solutions to the problem... attacking other legitimate options causes confusion and is counter-productive to the overall goal.

3. You think it's an oil and gas industry conspiracy. I admit to being taken off guard by this one having spent nearly four decades developing hydrogen systems, none of them associated with the oil & gas industry. The fact that this industry has recently begun investing in hydrogen projects as a path to transition away from legacy fossil fuels seems like a positive trend to me. Of course, any of these efforts must be assessed in terms of their lifecycle environmental and public health impacts to be certain we are heading in the right direction and not supporting 'greenwashing' projects. That said, the workforce skill sets in the oil & gas industry overlap very closely with those needed for large scale hydrogen infrastructure. Let's not throw out the baby with the dirty bathwater.

4. It makes you feel relevant. A tried and true method of getting attention when your actual achievements can't draw the limelight you crave is to attack a highly visible target. If you make your remarks inflammatory and play to a mob of people equally ignorant on the topic, all the better. In fact, you can even create a business model (or political career) using this tactic while disguising your lack of competence.

5. You are a victim of misinformation. The previous categories are largely responsible for creating this type of hydrogen hater. A primary challenge for this category is separating the signal from the noise on the topic, and then being open to changing one's mind based on facts, data, and evidence. The remainder of this post will address this challenge with some guidance on how to assess the misinformation overload when it comes to hydrogen.

Red Flags and Filters

There are a few red flags to watch for when you're reading or hearing opinions about hydrogen:

• "I ran some calculations...". Some people seem to think if they start with a preconceived (and often self-serving) conclusion, pull together some unverified assumptions that support it, and then reverse engineer simplistic equations full of errors and omissions, they can 'prove' their case. If it hasn't been published, or at least vetted by an independent third party, be very skeptical of anything claimed by these hand wavers.
• When someone challenges another's hydrogen claims with data and evidence, the best response is to engage in an objective discussion with the willingness to adjust both of your perspectives based on what you each learn. Compare this to bad behavior responses such as egotistical rants, personal attacks, trolling, empty sarcasm, ghosting, or continuing to repeat the same claims ad nauseum after being proven wrong. Be extremely skeptical of any information from individuals exhibiting these bad behaviors
• Claims that any given solution is always right or always wrong. This is an easy flag. Anyone who is forever beating the same dead horse at every opportunity and refuses to acknowledge that their preferred solution isn't universally the best in all applications - or that their hated solution will never work - can safely be ignored.

    

Once you've checked for the red flags, here's a quick set of questions you can ask to assess the source of the information:

How long has this individual worked with the relevant hydrogen systems being discussed? (points: 3-decades, 2-years, 1-studied it, 0-none)

What data and evidence is being provided to support the claims made? (points: 3-operational or test data, 2-technical publication, 1-validated model, 0-personal opinions)

Is the individual's income, status, business, ego, or religio-political beliefs threatened by increased use of hydrogen? (points: 3-definitely not, 2-maybe, 1-probably, 0-oh hell yes)

Now add up the points. Scoring:

    6 or higher: Information from this source is worth consideration

    3 to 5: Take information from this source with a grain of salt

    Below 3: Why are you reading/listening to this person?

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 break-through 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 co-founder in seven technology startups; and provided R&D and engineering support to many organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management series. He also teaches courses, workshops, and webinars on liquid hydrogen systems.