Yes, We Will Be Flying in Hydrogen-Powered Passenger Planes
A response to Michael Barnard’s CleanTechnica story “No, You Won’t Be Flying In Hydrogen-Powered Passenger Planes”
Background
Firstly some background — who am I, to be commenting on Mr Barnards supposedly expert view, expressed in CleanTechnica?
I’ve worked in Chartered Engineer capacity, for Airbus, Cobham, BAE Systems, GE Aviation, Finmechanica, NATS, naming a few amongst others, in Aerospace projects of all descriptions, contributing to the design of aircraft, airports, submarines, land vehicles, satellite systems, surface ships, air-to-air refuelling systems, again just a few amongst others over the past thirty years since starting on my career as a Systems Engineer.
My job roles have included Systems Engineer, Hardware Engineer, Systems Architect, Design Authority, System Modeling Engineer, & Research Engineer. I am a historical energy handling component patentee, inspired by working firstly in the electrical metering industry as a hardware Engineer, and have had several project venture companies of my own. My last for-profit research venture was PhD candidate work in virtual world and UAV technologies.
I’ve also had occasion to work consulting with PhD candidate researchers and PhD qualified researchers at University of Cranfield and other UK Universities, as well as fellow industrial researchers of the UK Aerospace companies mentioned earlier, and the UK Civil Aviation Authority, on the collaborative civilian ASTRAEA (“Autonomous Systems Technology Related Airborne Evaluation & Assessment”) program in UK.
I’ve been working self funded since 2017 on what I call the global energy problem, which is physically existential, and which examines the part played by profit itself, in the problem.
In that research I use my usual formal Model Based Systems Engineering (MBSE), including stakeholder analysis skills, coupled with PhD research training, to analyse the systems of nature and humanity, converting all money and energy flows of humanity to quantitative mathematically signed common units (KWhrs) enable the system to be audited, and to easily see what adjustments need to be made to the system of humanity, to make the latter fit with the system of nature (We currently don’t fit).
In this I maintain an offline System Model using the tools of my trade, underpinning everything published in Medium, which is more or less documentation of the system model, more than 400 stories to date, and more than 10,000 responses to the relevant stories of others in Medium to date.
My historical credentials to date, which I used to pretentiously boast after my name, before I moved beyond that, to working non profit, are:
BEng, MSc, CEng, MIET, MINCOSE.
Open Dialog
I am informed, rightly or wrongly that Mr Barnard writes in Medium, by folk commenting on my stories, quoting information apparently seen in Medium.
But I have no visibility of Mr Barnard, or his writings in Medium.
Either I am banned from seeing any of it, or it doesn’t exist.
But given so many folk now have quoted his writings as reference information, claiming to more or less prove impossibility of the hydrogen future which I say is the only solution, I guess its necessary for me to comment on his writings, per my usual method, in Medium, to show why he is wrong.
Besides, since the issue is existential. It’s really important we diagnose it correctly, to get the fix right, and Mr Barnard appears to have a large following, therefore significant influence. The misinformation he is generating is quite harmful in my view.
Cutting to the Chase
What matters most in aerospace (At least for everything that flies), is energy weight density.
This is more or less independent of battery size etc. The lower end figure is for battery including case, and the other is for just the contents of the battery, so we might as well say its 0.38KWhrs per kg for all practical purposes.
Note these are theoretical values, never yet achieved. Practically achieved values are less.
For hydrogen, the basic energy density is 33.33 kWh/kg. The higher heating value is 39.39 kWh/kg. The lower heating value is what is available if the hydrogen is consumed in a fuel cell, the higher value is what is available when combusted in an internal combustion engine (ICE). The energy content is set by chemistry, its a property of the chemical composition of the fundamental element, hydrogen, H2, in the periodic table, it does not vary.
So comparing like with like, disregarding storage containers, there is almost two orders of magnitude difference between the energy density of hydrogen, and the energy density of Lithium.
Raw hydrogen has almost 100x the maximum possible energy density of raw Lithium.
What does vary hugely with hydrogen, and this is what makes it so infuriatingly arguable, is its storability, which varies hugely. So this needs to be taken into account when comparing with lithium batteries.
In the case of practically contained Lithium, we saw 0.38kWhrs/kg
This is the maximum “Gravimetric Capacity”
Gravimetric Capacity is a metric conveniently used to compare different power capabilities in vehicles.
A development of Gravimetric Capacity is “Gravimetric efficiency”. This is a figure obtained by dividing the weight of fuel (or battery chemistry), by the combined weight of fuel (or chemistry) plus container.
So in the case of lithium, the Gravimetric efficiency is 380/460 = 0.82
For hydrogen using standard “Type 4” tanks (Containing Compressed hydrogen at 700 Bar), as used in cars, the Gravimetric Capacity is 1.8kWhrs/kg (Assumes 5.6kg of useable H2 per tank).
Compressed gas containers are the least gravimetrically efficient forms of hydrogen storage, but already we see the compressed hydrogen scenario provides 4.7x higher energy density than the best case lithium gravimetric efficiency.
This is the base comparison that matters, for comparing distances that can be travelled in the two scenarios, hydrogen fuel vs lithium batteries, because 4.7 times more energy gravimetric capacity means 4.7 times more flying time, and thus at least 4.7 times further travelled, for the same weight of system.
Adding more batteries doesn’t change this, because to be fair, if more batteries can be added, so also can more hydrogen be added, and adding more hydrogen will always have this advantage.
We can say “At least”, because as fuel is consumed, the onboard mass of fuel decreases, thus the distance that can be traveled per kg of fuel still remaining, increases.
We can’t say this about a battery system, the weight of the battery system does not change during flight, it stays at the same mass as the when the flight took off.
So it’s at least 4.7 times longer flown, by a class 4 bottled hydrogen system, than can be achieved by the same weight Lithium battery system.
But Gravimetric efficiency is stated to be between 0.3 and 0.85 for liquid hydrogen tank systems. This is again massive variation, and doesn’t reveal much by itself.
Liquid hydrogen density is indicated to be just over 70kg/m³ at 1 atm, and 80kg/m³ at 300 Bar (See PDF page 33, figure 1).
So we have to do a little maths, to deduce the gravimetric energy capacity of tanked liquid hydrogen systems, like the ones being developed by Airbus, and no doubt also US and Chinese efforts, which will all be aimed at the higher value of 80kg/m³ achieved by 300 bar liquid hydrogen storage. It seems reasonable to assume at least 75kg/m³ will be achieved.
The cryogenic tank holding 75kg hydrogen will have around 75 x 33kWhrs energy available = 2475 kWhrs.
The tank weight in that case, using worst case gravimetric efficiency of 0.3 implies that fuel weight divided by (Tank weight + fuel weight) is 0.3.
So the tank weight is around 175kg worst case, and 18.75kg best case.
So gravimetric energy efficiency is 2475 / 175 = 14.4 worst case, and 2475 / 18.75 = 132 best case.
In other words, recalling the highest possible lithium gravimetric energy density, the flight time of an equivalent weight practical liquid hydrogen system is at least 14.4 times that of the lithium battery maximum gravimetric energy capacity, but feasibly could be up to 132 times more.
I think that is pretty damning evidence, against the efforts currently being spent on electric flight efforts.
Anyone with any sense can see this is a dead-end for the possibilities of electric passenger flight.
The danger, it seems to me, is we have a certain capacity of extractable energy left, which can / will be extracted, pushing up planetary temperature still further, before all companies go bankrupt.
It this is spent on the right effort, by incentivising domestic and communty based solar, including with hydrogen production by all, by issue of solar indexed stimulus, which would be the highest quality investment that could be made with the remaining practically extractable energy, then we will achieve 100+ percent success, in only a few years, with even all the fuel requirements of aerospace met.
But if its spent on the wrong effort, as it is, sustaining the fossil fueled, extracted energy scenario for long enough, the economy will catastrophically collapse, with also deteriorating environmental effects.
How far do we want to push it? How long will we keep flogging the dead horse?
Given all the tradional arguments over hydrogen are about cost, and efficiency, I’ve explained many times why those concerns are obsolete, given what has to happen next.
Here’s the thing; energy extraction is finished, its winding down, and this is impacting all profit margins, progressively making all companies and businesses for profit bankrupt, whilst the only increasing source of energy, solar, continues to wind up, unmonetised.
As such all businesses will go into public ownership, at least the ones that are rescued when the solar indexed stimulus necessary to restore the energy value in money, is issued, to the public, and the public will use this to bail out the companies they want to keep.
We saw how this would work during the stimulus issued during covid.
Of course aerospace will be bailed out, everybody wants to have the convenience of flying.
We just confirmed another solid reason for why hydrogen fits in the new clean economy.
Thanks Michael Barnard, for prompting me to write this piece.
I hope this might help you to move, from appearing to uphold the interests of the traditonal fossil fuels and financial industries, to something more in line with what nature is actually forcing on us, much sooner than either of those industries seems to think.
For more information, see below.
