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| Liquid hydrogen jet aircraft in 1955 and rocket upper stage in 1966 (Source: NASA) |
On the topic of hydrogen, there seems to be a great deal of misinformation being circulated. Liquid hydrogen systems in particular are sometimes characterized as being a far-off vision that will require years or decades to deploy. This is complete nonsense. There are no true technology gaps preventing the widespread application of hydrogen systems.
The answer to most questions about hydrogen can be summed up as "it's already been done". Below are some of the hydrogen myths that seem to keep getting regurgitated. I'll discuss more in subsequent myth busting episodes, and do a deeper dive into many of them in later posts.
Myth #1: Liquid Hydrogen Isn't Ready Yet
Large scale liquid hydrogen systems have been in continuous use for nearly sixty years in the space sector for launching spacecraft and vehicles to orbit and beyond. All the required technology and equipment for ground based systems is available off-the-shelf from multiple sources. New applications require good systems engineering not fundamental research.
Most people are very familiar with the large orange External Tank of the Space Shuttle that contained liquid hydrogen and oxygen for the main engines. The giant spherical storage tank at Kennedy Space Center is another familiar image that appears near the top of any liquid hydrogen internet search.
Anyone who watched a launch of the Space Shuttle on television, or any launches of the Ariane V or rockets with a Centaur upper stage, have seen the results of liquid hydrogen systems in action. Production, delivery, storage, fueling, and consumption. Successfully in operation for decades and continuing into the foreseeable future with existing and new launch vehicles.
But the legacy of hydrogen reaches back even further. Hydrogen was the first fuel used in the development of jet engine technology in the 1930s. A liquid hydrogen turbojet engine with afterburner was built and tested in the 1950s; and successful flights of a B-57 jet aircraft with liquid hydrogen were also performed in the 1950s. Myth busted.
Myth #2: Hydrogen Leaks Through Everything
This myth seems to come from people who found hydrogen on the periodic table, noticed that it's the first element and contains only one proton, and are now convinced that nothing can contain it. Variations on this theme include that it can "squeeze" between the molecules of any solid container.
Materials suitable for hydrogen service (compressed gas and liquid) are well known and routinely used. Stainless steel (300 series) and aluminum alloys for tanks, piping, and other components. Various seal materials for valves, ports, and fittings depending on the application. Newer composite and polymer formulations are being developed that do need to be tested, but these materials are not required nor used in existing conventional hydrogen systems.
As proof, compressed hydrogen containers at 700 bar (10,000 psi) have been in storage for over a decade with no measurable loss of pressure. And liquid hydrogen systems are intentionally designed to meet extremely low leakage requirements for safety reasons. Myth busted.
Myth #3: Hydrogen is Too Dangerous
This is a culturally ingrained myth partially based on an 85 year old film of a dirigible in flames. The fact that the outer skin was a highly flammable cotton canvas doped with cellulose acetate butyrate and aluminum powder rarely gets mentioned. A very bad material choice for an application where electrostatic discharges are possible (and even common).
Also not mentioned is that hydrogen burning in daylight is invisible to the eye and conventional cameras. It also produces not smoke or soot. And hydrogen rises at a rate of 20 m/s at ambient temperatures in air. So there is literally no hydrogen in the picture beyond the first two seconds after the skin is breached.
If the Hindenburg had used helium or hot air (or any other lifting gas instead of hydrogen) the result would have been unchanged. The same footage would exist of a dirigible crashing to the ground with visible flames and smoke from the burning skin. It's also interesting to note that there was no detonation or explosion even though the entire containment fabric became engulfed by the advancing flame front characteristic of solid combustion.
The unfortunate use of the term "hydrogen bomb" tied to the frightening images of mushroom clouds caused by thermonuclear weapons detonation is another factor. Nevermind that it's a nuclear fusion process at extremely high temperatures and pressures that has nothing to do with the flammability of hydrogen or its use as a fuel or for energy storage.
In contrast, we seem to have cultural amnesia regarding the millions of accidents and videos involving hydrocarbon explosions, fires, noxious smoke, toxic spills, and so on. Natural gas detonations leveling buildings and city blocks; jet fuel accidents on runways and after in-flight collisions; oil and diesel tanker fires and spills; gasoline fires in vehicles of all types; etc.
I sometimes ask a seemingly simple question when talking with someone who insists hydrogen is too dangerous. Would you rather stand next to a hydrogen storage tank, or one filled with a liquid or gaseous fuel of your choice, while both are being riddled with bullets?
In fairness this is a trick question; the military already tested the hydrogen scenario (sans the bystander) with live rounds and nothing happened. The hydrogen escaped into the atmosphere with no ignition and no environmental impact. Not so lucky if you choose a tank with jet fuel, diesel, kerosene, gasoline, natural gas, or propane.
Of course, there are legitimate safety issues associated with the wide flammability range of hydrogen in air and its low ignition energy. These hazards are addressed with properly designed systems based on well known standards and guidelines that have been developed over many decades.
The biggest safety risks are posed by systems developed by organizations without the appropriate experience that don't follow the proper standards and guidelines. This is a reasonable concern that must be guarded against. So except for unqualified practitioners, myth busted.
Myth #4: Hydrogen Produced from Water is Too Inefficient
The proponents of this myth have moved slightly beyond the periodic table and black and white movies. After pulling out their high school or undergrad introduction to chemistry textbook, they wax eloquently about the binding energy of water and other hand waving arguments.
If you start to inquire about their knowledge of how electrolyzers work, the conversation begins to wane. Alkaline vs proton exchange membrane electrolysis; electrode material options; electrolyte formulations; high pressure and high temperature operations. These topics aren't in their chemistry primer.
Modern electrolyzers have efficiencies in excess of 70% (defined as the higher heating value of the hydrogen produced divided by the electrical energy consumed). These are large scale units that have been commercially available for many years. And they can be operated in-situ at the point of use.
Compare this to the “well-to-wheel” energy efficiency of exploring, discovering, drilling/mining, extracting, refining, and distributing current fossil fuels to their point of use. Myth busted.
