The use of LH2 for powering electric aircraft, and automobiles is a
subject dear to my heart.
The energy density of liquid hydrogen (51,500 Btu/lb (119.93 kJ/g)
Lower Heating Value (at 25 C and 1 atm) ) is over two and half times
that of gasoline at 19,000 Btu/lb (44.5 kJ/g). [Source:
https://www.energy.gov/sites/prod/files/2014/03/f12/fcm01r0.pdf ]
Given that the energy efficiency of an internal combustion engine is
between 20% and 30%, the use of electric motors with an efficiency of
~90% could provide 9.7 times more duration or power. I was unable to
find any mention of this fuel-cell technology's efficiency, so my
figures will doubtless require some revision. Toyota's current
fuel-cell technology efficiency is ~60%.
The use of LH2 overcomes the issue of very highly pressurized H2, but introduces other challenges such as availability and longer term
storage. If a fleet of solar powered sea-water-electrolysis buoys
employing a cryo-cooler were put to work, the issue of liquid H2
availability might easily be solved (if the temperature could be
adequately controlled).
See:
https://www.researchgate.net/publication/268814011_Challenges_and_Benefits_offered_by_Liquid_Hydrogen_Fuels_in_Commercial_Aviation
https://www.theverge.com/2013/5/11/4320948/us-navy-drone-flies-two-days-straight-using-liquid-hydrogen-tank
https://www.nrl.navy.mil/lasr/sites/www.nrl.navy.mil.lasr/files/pdfs/AIAA liquid hydrogen paper 2013[12-1231-4608].pdf
=====================================================================
https://newatlas.com/aircraft/hypoint-turbo-air-cooled-fuel-cell-hydrogen-evtol-electric-aircraft/
HyPoint's "turbo fuel cells" promise huge range and power for eVTOLs
By Loz Blain
May 31, 2020
[Image]
Bartini's eVTOL design, with eight tilting, coaxial ducted rotors,
promises 550-km (342-mi) ranges and 300-km/h (186-mph) speeds thanks
to HyPoint's turbo air-cooled hydrogen fuel cell powertrainsBartini
VIEW 8 IMAGES
A California company says its new "turbo air-cooled" fuel cell design
can deliver three times the power and four times the lifespan of a
regular fuel cell, opening the door for high-speed, long-range, hydrogen-powered electric VTOL aircraft.
Weight is everything in aviation, and it's even more important when
you're talking about energy-intensive vertical takeoff and landing
like the coming eVTOL air taxi contenders are promising. Nearly every
company on that list is building its prototypes using lithium
batteries, but the simple fact is, lithium batteries have terrible
energy density.
Commercial air taxis will need to fly all day, not spend long hours
hooked up to charging stations, so every company that's planning
around lithium is praying for a magical new chemistry to emerge from a
test lab that doubles or triples the capacity of the best batteries
available today.
That may well happen, but hydrogen is beginning to look like an
excellent alternative. It's a pain in the butt when it comes to ground transport, but in electric aviation it might find a perfect use case.
It offers much higher energy density, promising excellent flight
endurance, and it lets you fill up with fuel in minutes, just like
topping up your car's gas tank.
The eVTOL market is threatening to begin commercial flights around
2025, but it's becoming very doubtful that lithium battery technology
will have the required energy density by that stage. Hydrogen offers a compelling alternative
The eVTOL market is threatening to begin commercial flights around
2025, but it's becoming very doubtful that lithium battery technology
will have the required energy density by that stage. Hydrogen offers a compelling alternativeBartini
Indeed, some businesses are starting to bet on it. US East Coast eVTOL
startup Skai is racing to be early to market with a six-rotor,
five-seat aircraft it says will be capable of four hours or 400 miles
(644 km) in the air before you'll need to top up the hydrogen tanks.
But an American startup says one piece of the puzzle is still missing
for the perfect eVTOL powertrain: a lightweight, high-power fuel cell
design.
A fuel cell primer
Basic diagram showing the key components of a proton exchange membrane
fuel cell
Basic diagram showing the key components of a proton exchange membrane
fuel cellPublic Domain
To very quickly recap how a fuel cell works in the most basic terms,
hydrogen is fed in to the anode side, where a platinum catalyst splits
it from H2 into positively charged hydrogen ions, or protons, and
negatively charged electrons. A proton exchange membrane allows only
the protons through to the cathode side, creating an electrical
potential that pulls the electrons through to the other side along an
external path. This external path is where you place your electrical
load.
When the electrons arrive on the other side, they meet the protons in
the presence of oxygen and a second electrochemical reaction occurs to
create water. Pure water flows out of the fuel cell and is the only
"exhaust" from the process per se.
Hypoint's "turbo air-cooled" fuel cell design
Which brings us to HyPoint, a California-headquartered startup run by
three Sergeis and an Alex, the latter of which caught up with us for a
video call from his home, where he's waiting out the COVID lockdown.
Starting out in 2018, HyPoint set out to create low-temperature proton
exchange membrane (LTPEM) fuel cell systems for industrial-grade drone
systems. But since moving to Silicon Valley and being accepted into
the Alchemist Accelerator program, the company began looking at a
bigger target.
HyPoint started out working on hydrogen-powered drones in 2018
HyPoint started out working on hydrogen-powered drones in 2018HyPoint
"When we arrived in the United States we saw a huge potential market
in urban air mobility," says CEO Alex Ivanenko, PhD. "The main drivers
of this market are mobility, compactness and energy density. Now, the
main powertrains are built on lithium batteries, which have a
fundamental technical barrier. Existing lithium batteries have a low
energy density, while existing fuel cells have low specific power. The
air transport market requires both high specific power and high energy
density. There's no power source that can satisfy both requirements at
the same time. Not lithium, not fuel cells."
Forecasting that suitable lithium battery technology might be as much
as 15 years away, the HyPoint team began focusing its efforts on a
fuel cell design specifically targeted at eVTOLs. To keep things
lightweight, it would have to be an air-cooled design; liquid-cooled
fuel cells, says Ivanenko, work well in the automotive world, but the associated coolant tanks and pumps add parasitic mass that literally
isn't going to fly in the aviation world.
But today's available air-cooled fuel cells, he says, have limited
power capacity and lifespan, and they only work in temperatures
between -5 and 30 C (23 and 86 F). So the HyPoint team set out to
develop something faster and hardier, and came up with what they call
the "turbo air-cooled fuel cell."
"We boost the power of the fuel cell stack by placing it inside an air
duct, where pressurized, humidified and thermally stabilized air is
circulated by fans," says Ivanenko. "The compression of air is
maintained about 3 bars inside by a compression system, and the air
with reduced oxygen content is charged through a control valve, and
replaced with fresh compressed air with normal oxygen content."
Turbo air-cooled fuel cell advantages
The extra oxygen on the cathode side of the fuel cell stack, in
conjunction with a new High Temperature Proton Exchange Membrane
(HTPEM) technology HyPoint has developed, allows you to force three
times as much hydrogen through the fuel cell as a traditional design,
tripling its specific power output without adding any parasitic
cooling mass that might weigh a VTOL aircraft down.
With the entire system taken into account, the HyPoint system delivers
2,000 watts of power per kilogram (2.2 lb) of mass. The best of the liquid-cooled fuel cells deliver between 150-800 W/kg, and other
air-cooled fuel cells sit at about 800 W/kg.
Higher specific power than lithium, higher energy density than other
fuel cell systems
Higher specific power than lithium, higher energy density than other
fuel cell systemsHyPoint
The energy density of the full system comes in at around 960 Wh/kg,
where lithium batteries typically sit at about a third of that figure
and other air- and liquid-cooled fuel cell systems come in a little
over half all according to HyPoint's own figures.
The system has some other huge benefits as well, says Ivanenko; it
accepts "dirty" hydrogen that's only 99 percent pure, which is a
fraction of the cost of the 99.999 percent purified hydrogen you need
for an LPTEM system. "That's a huge decrease in a significant
operational parameter for a commercial eVTOL operation," he adds.
It works at more or less any real-world temperature, from -50 to +50
C (-58 to 122 F) and beyond. And while it's still in the lab at this
stage, the team projects these fuel cells will last some 20,000 hours
without maintenance, where LTPEM systems typically last around 5,000
hours another very significant factor for a commercial operator.
The next steps
HyPoint has been in contact with a number of major players in the
emerging eVTOL market in the US, Europe and Australia, says Ivanenko,
but NDAs restrict him from mentioning them by name just yet, with the
exception of ZeroAvia and Bartini.
"We're seeing big interest from many companies," he says. "We believe
we've found a solution for them. Many of them are asking for us to
validate our technology with a prototype, because we've only validated
it in the lab so far. We agree with that. So our development plan for
this year is to build a 15- to 20-kW prototype, to validate the
technology. Then a full scale, say 150-200-kW system in 2022."
HyPoint's turbo air-cooled fuel cells are only at the laboratory stage
right now
HyPoint's turbo air-cooled fuel cells are only at the laboratory stage
right nowHyPoint
Moving from a lithium-powered prototype to a hydrogen powertrain, he
says, shouldn't require a total redesign of most eVTOL airframes, so
the opportunity to achieve long-range flights with fast refueling is
open to more or less any of the contenders if they're willing to move
some things around inside the aircraft design.
What about safety? Will hydrogen eVTOLs be an explosion risk?
Mindful of our ever-alert commenters, some of whom vocally believe
hydrogen has no place in aviation, we put the question of safety to
Ivanenko, who immediately rolls his eyes, grins and mimes shooting
himself in the head.
"That's a common question from consumers," he says. "And that's OK,
because I think most consumer technology will be too difficult to
switch over to hydrogen technology anyway. That's one of the reasons
why we're focused on B2B with large companies that care about
efficiency.
"But yes, 'it's a hydrogen bomb! Remember the Hindenburg!' That was in
1938. Almost a hundred years ago. What people need to understand is
that hydrogen, oxygen, propane and natural gas are all in the same
group of dangerous flammable gases. The propane bottle you use on your
BBQ has the same warning certificate, it's in the same class as
hydrogen.
"There's no special hazard class for hydrogen. Moreover, hydrogen is
the lightest gas in the universe, and it can't be concentrated in the
field to achieve the kinds of dangerous concentrations that might
cause a big boom. Of course, you should follow special safety rules,
but you shouldn't be afraid of hydrogen gas. Oxygen is much more
dangerous."
HyPoint's hydrogen powertrains are compact, lightweight and very
powerful
HyPoint's hydrogen powertrains are compact, lightweight and very powerfulHyPoint
He goes on to point out that he drives a Toyota Mirai hydrogen-powered
car. "It's been thoroughly crash-tested for safety. Any manufacturer
of hydrogen powertrains understands what steps to take to get an
appropriate safety certificate for a given application, and we'll be
no different."
It's possible that lithium battery technology will make a quantum leap
in energy density in the next five years, which is roughly when most
eVTOL companies are projecting they'll be ready to start commercial
air taxi flights. Maybe the batteries of 2025 will have huge
capacities, light weight, ultra-fast charging and they'll meet all the
right safety criteria. But it's very possible they won't, and if
that's the case, hydrogen innovators like HyPoint could well find
themselves in a highly advantageous position. Certainly a company to
watch.
Source: HyPoint with thanks to David Mayman
TAGS
AIRCRAFTFUEL CELLEVTOLAIR TAXISHYDROGEN-POWERED
Loz Blain
Loz Blain
Loz has been one of our most versatile contributors since 2007.
Joining the team as a motorcycle specialist, he has since covered
everything from medical technology to aeronautics, music gear and
historical artefacts. Since 2010 he's branched out into photography,
video and audio production.
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christopher MAY 31, 2020 06:43 PM
A PhD, but no brains: "we saw a huge potential market in urban air
mobility," says CEO Alex Ivanenko, PhD. Nobody is going to let air
taxis fly over people anytime soon, if ever, and if they accidentally
did anyhow, it's only going to take one crash and a pile of dead
people below, before everyone else realizes how stupid that idea was
and they never get permission to fly over people ever again. No taxi
will ever be viable when it's not allowed to operate near customers...
Spud Murphy MAY 31, 2020 08:28 PM
The problem with hydrogen is that all it takes is one small leak and ker-friggin-boom, you're toast. Hydrogen becomes flammable at just 4%
in air, and explosive at 18.3%. In the closed structure of an
aircraft, there would have to be some serious safety measures, ie H2
sensors everywhere, and some form of emergency venting. Having seen
hydrogen explosions, I'm petty sure you wouldn't get me in any
aircraft (or other vehicle) using it.
vince MAY 31, 2020 10:00 PM
Vaporware until put into a working demonstration full size.
George Kafantaris MAY 31, 2020 10:15 PM
[S]uitable lithium battery technology might be as much as 15 years
away. Actually, it might not be that long. But the situation would
not be better. Why? Because even if the ideal battery was here today,
it would still need to be charged. This would require a grid capacity
that we do not have -- and time to charge it that we also do not have. Meanwhile, a fuel cell can refuel in minutes and be ready to go --
perhaps around the clock since there is so little to wear out. Hidden
in this is a national security component. Inevitably, future wars (and peace-keeping) will be carried out by flying drones that are
independent of the terrain and can move in unison in all directions --
under central control. Like a swarm of bees, they could be deployed
into an area of conflict and effect destruction (or protection) the
likes we have never seen -- or have imagined. It is wise, therefore,
for every country to develop its own fuel cell technology early. This
proved prudent in the case of the internal combustion engine. The
countries that had the most experience with this engine were able to
use it to their advantage in all sorts of things during WWII.
MarkGatti JUNE 1, 2020 02:34 AM
finally a decent looking design , have to ask are they missing the
simple fact that hydrogen is the best heat transfer fluid known , a
hydrogen car radiator would be 1/10 the size of water filled ones. For
doubters , BMW have tried setting fire to their liqified tanks of
hydrogen , nothing exciting happened , try holding a beach ball under
water , imagine something 10 times as buoyant, but unconstrained ,you
have to get hydrogen in a sealed container to get any kind of bang ,
as the man said O2 is more dangerous
Towerman JUNE 1, 2020 06:03 AM
""HyPoint's "turbo fuel cells" promise huge range and power for
eVTOLs"" Excellent write up Loz, complimenting exactly my points in
the last 5 articles. Electrics is going to blow the competition to
oblivion ! !
Kpar JUNE 1, 2020 08:47 AM
Wow, so many comments with opinions that need challenging.
Christopher, if man had been meant to fly, God would have given him
wings. Spud, you didn't read the article- it completely refutes your
claim of "ker-friggin-boom". George, the power still has to come
(mostly) from the existing power grid- H2 is not freely available in
nature, it must be freed from the chemical compounds in which it
resides- H2 is an energy storage system, not an energy source. Mark,
mostly correct, but the hydrogen must be mixed with an oxidizer first,
and then contained before ignition to get a BOOM. Vince, completely
correct. Now fo my comment- this article would make a lot more sense
if a schematic of the device were included.
ljaques JUNE 1, 2020 09:02 AM
Well, air taxis may have just been given a workable power source.
Permitting's gonna be a beeyotch, tho. Best of luck to the Alchemists
in question, three Sergeis and an Alex. LOL They have a marketable
buzz phrase and a potentially exciting new power density to work with.
I still don't see a consumer market, except perhaps in-town urgent
deliveries between businesses, which may be enough for them to succeed
when they get this to market. More power to ya, dudes! (groan)
Username JUNE 1, 2020 09:31 AM
Swap-able battery packs. Ultra capacitor charging station so you don't
"drain" the grid. Simple solutions.
guzmanchinky JUNE 1, 2020 10:50 AM
People are so worried about the safety of these things, they don't
realize that they will be far safer (yes, even with Hydrogen on board)
than a current helicopter, which has a DISMAL safety record compared
to commercial airliners and about double the failure rate of private
planes. Aviation will always have SOME amount of risk, but this
technology is inevitable one way or another. Now let's just hope it's
not too noisy if it becomes really popular (helicopters and jets are
annoying enough as is!)...
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