Clarifying hydrogen fuel discussions:

By Andrew D. Ravani – 22 Jun 2021

So what makes the conversation about hydrogen as a fuel so convoluted? Well, to start we are talking about at least two wildly different technologies. 

Hydrogen fuel cell electric vehicle technology (FCEV) , 

and Hydrogen internal combustion engine fuel (HyICE). 

Both technologies assume consumption of Hydrogen in a gaseous state, but one is used to make electricity directly (FCEV), and the other is used to make mechanical work force directly (HyICE). One way of feeding both of these technologies fuel is full volume storage (holding a full amount of fuel for full operation in a pressurized or chemically bonded state – like the 2021 Toyota Mirai – a FCEV – at 400 miles), and the other is short-storage. Let’s look at the technology gap in on-demand creation coupled with “short-storage.”

SHORT STORAGE

Short-storage is coupled with on-demand production of hydrogen fuel to provide safer long-distance use of hydrogen-fueled transportation systems. For the sake of argument, “short-storage” is assumed to be an accumulator type vessel for low-pressure storage (<250psi) of an amount of hydrogen fuel to run a load at max power for 15 minutes – for example, the 2021 Toyota Mirai can run for 15 minutes at peak power on .15 Kg of hydrogen gas with its 171 hp engine. That’s around 30 miles range. Why is “short storage” a focus? It’s a relative volume that allows for sufficiently strong and well-sealed accumulators to be manufactured cheaply and in volume enough to move us into a hydrogen fuel economy while also reducing inconvenience and risk to the consumer. 

The gap that short-storage and demand production from inert fuel precursors fills is likely to be achieved at scale with deionized water and a low voltage graphene hydrogen reactor powered by an onboard battery bank (~200Ah 12 volt LiFePO4) – itself recharged by power plugin or integrated solar roofing and power reclamation from braking and slowing. 

The limitation here is our exploitation of the chemistry and working out what the right weight to power ratios should be to maximize the range while minimizing driver involvement in refueling and maintenance. It should be noted that the temptation of some drivers to put plain ground water into the fuel tank and expect it to work cannot be overlooked and should be safeguarded against or worked around. FACT: People will do stupid things, and then blame the technology for not preventing them from being stupid. 

The other technology gaps are in alternative storage means. Currently, we require very high-pressure vessels to contain hydrogen gas or vessels with rare earth elements or salts that bind the hydrogen and can only release it at >400C. That seems feasible for aviation applications and possibly larger-scale marine vessels, but the containment vessel proximity and heat dispersion in an automotive environment seems (to me) to be a headache not worth having. I definitely see it being useful in submarine applications – even in combination with nuclear reactors in a submarine environment. Imagine using the nascent heat of a reactor’s secondary coolant loop to release hydrogen gas for a fuel cell electric drive backup system. It makes a lot of sense and has the added benefit of being quiet.

Once we fully embrace pursuit of low-temp low-cost readily available catalyst assisted electrolytic production and make it work at scale, the next gap will be …? 

What do you see as other technology gaps to overcome in switching to hydrogen fuel?  

https://www.nature.com/articles/srep36770

https://h2tools.org/hyarc/calculator-tools/hydrogen-conversions-calculator

https://www.asknumbers.com/PressureConversion.aspx

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