Posted on 07/31/2019 3:57:54 PM PDT by amorphous
While the vision of whisking passengers between rooftops in aircraft capable of vertical takeoff has largely solidified in the general shape of multiple rotors, some with airfoils and others without, the question of how to power this new kind of aircraft is less so. Some envision pure electric with lots of high-capacity batteries; others believe batteries alone will never be ready to produce the power required, and pitch hybrid designs—with a fossil-fueled engine producing electricity to assist the motors during some or all phases of flight.
However, one recent entrant in the field of some 150 such aircraft being developed stays out of that fray: The Skai eVTOL by Alakai Technologies promises to use a hydrogen fuel cell to generate electricity on the fly to power the six-rotor, five-place aircraft.
A tank of liquid hydrogen in the aircraft could propel it up to about 100 knots for up to 400 miles or four hours, carrying up to 1,000 pounds, according to Bruce Holmes, Ph.D., a director at Alakai. The electricity is produced via a hydrogen fuel cell—similar to the technology used to propel spacecraft like the Apollo ships that took the first men to the moon back in 1969.
A fuel cell is relatively simple: A fan propels gaseous hydrogen from the top of the liquid tank and mixes the elemental gas with ambient air through the fuel cell. The hydrogen passes through a platinum screen and in doing so loses an electron and produces electricity. The only emissions are water and heat. Holmes said because the hydrogen boils in typical ambient conditions, about 1 percent per day is lost—even with the best tankage technology available.
The resulting heat can be used for warming the vehicle. The cold liquid hydrogen can be used for cooling the cabin and is pumped beneath the six motors to help cool them.
Skai will use fuel cells from Hydrogenics, which is being acquired by a subsidiary of diesel-engine manufacturer Cummins.
The liquid hydrogen is stored on the aircraft at about 150 psi. Fueling infrastructure is not in place at airports, yet. However, Holmes envisions it being much like hydrogen fueling stations for cars cropping up in California and five other states as well as nine other countries, all of which are participating in a coordinated international effort to expand the use of hydrogen-powered electric propulsion. Refueling times will be as little as 10 minutes.
In addition to the six redundant rotor systems, Skai is slated to include an airframe parachute and will be designed to be piloted from the ground, piloted from the aircraft, and capable of autonomous operation. The company is proposing an aggressive certification plan that calls for a type certificate, perhaps as soon as the fourth quarter of 2020. Holmes expects military versions will be flying soon, and that experience, he believes, will help the FAA get comfortable with the vehicle’s simple design features—especially since, other than the rotors, about the only moving part is the fan in the fuel cell. Three conforming prototypes will be built for the certification process.
With hydrogen sourced through renewable resources such as hydropower, wind, and solar, and with the fuel cell 95 percent reusable and 99 percent recyclable, Holmes said the aircraft will be much more environmentally friendly than aircraft using batteries or fossil fuels. A fuel cell has a 20,000-hour life-cycle, he said.
Worked awesome then right?! Oh the yuge manatee.
It’s not the 30’s.
Currently Toyota sells Mirai, a hydrogen fuel cell car.
Expansion from liquid to gas only about, what, 800 to 1. Pffftttt. Or BOOM!
There is also the Honda Clarity.
Much prefer fuel cells via hydrogen to batteries.
The “we love batteries” folks never consider where and how is all the electricity for recharging the batteries coming from. It’s not going to be wind and solar.
Thanks. I didn’t know Honda had one on the market today.
I knew they’d had one a number of years ago.
About the same that can go wrong using gasoline.
Liquid hydrogen under a constant 150 psi in a consumer environment will make an overcharged Tesla seem like a child’s 4th of July sparkler.
Is this a passenger transport or a personal transport vehicle?
If it's a passenger transport, I seem to recall an existing craft called a helicopter.
If it's a personal transport, this is just the most recent flavor of the decade.
I have lived with 6 decades of flavors/promises. Hasn't happened. The biggest problem isn't the equipment. It's the nut behind the wheel.
As seen all the time on our roads and highways, most people can barely operate an automobile in 2 dimensions. Vanishingly few are capable of operating a craft in 3 dimensions, let alone the necessary 4th dimension of time.
The human problem is the major problem to be solved to make personal aircraft viable. The rest has been in our grasp for some time.
You first...
Wouldn’t a turbojet engine burning hydrogen instead of petroleum be more efficient. Lockheed tested an L-1011 with hydrogen fuel decades ago.
The answer to the problem between the seat and steering wheel is a computer. Of course they also fail from time to time as the numerous fatalities in the news, involving autonomous vehicles, attest.
Here in the Coachella Valley (Palm Springs area), the local bus company has been using several hydrogen fuel cell buses for the last several years. All the other buses have run on natural gas for well over 15 years now.
The solution will be an autopilot and a robot copilot — who will slap the hand of any human who reaches for the controls.
400 nautical miles range - big whoop! Barely enough for Chicago to Toronto.
Completely agree that the reason we don't have flying cars is because most people aren't capable of flying.
Two Aggies are flying in an airplane and the engine dies.
One of them says, "Oh no! We're out of gas!"
How high up are we?
10,000 feet!
Nobody's ever gonna find us up here!
Aside from most people not being able to fly, the problem of not maintaining vehicles would be a disaster.
Generating the hydrogen via water electrolysis takes a large amount of electrical energy as well. In fact the overall cycle for hydrogen fuel cell energy storage is considerably less efficient than that of modern lithium-ion batteries, so that for a given energy output it takes more energy to "recharge" a hydrogen fuel cell.
The advantage of the fuel cell is that the active material (hydrogen) that your vehicle has to carry is very lightweight compared to that of batteries, and one of the materials (oxygen) that you need you can just grab from ambient air, so you don't have to carry it at all. And the conversion unit, the actual fuel cell itself, is quite compact and doesn't weigh anywhere near as much as batteries with equivalent power.
The most successful use of hydrogen fuel in history, as far as I know, would be when used to power the Space Shuttle's three main engines.
IIRC, heavy lift rocket motors are now are being designed to burn liquid methane. But carbon atoms in the molecule gums up fuel cells.
I’m curious as to the economics regarding cars and small aircraft, hydrogen v good ole fossil fuels?
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