[aquavivarium]

Originally Posted by V.Narayan

ELECTRIC POWERED AIRCRAFT

Commercial air travel results in 915 million tonnes of carbon emissions a year. This is about 2% of the 46,000 million tonnes of carbon put out into the atmosphere each year by all sources. Air travel accounts for 12% of all carbon emissions created by the transportation - road transportation weighs in at 74% with rail and sea accounting for the balance. Just as with automobiles so with aircraft, the clamour for reduction of the carbon footprints is alive and loud. A single passenger flying say London-New York emits as much carbon as a typical American surburban home does in a whole year on heating! The aviation industry is coming under pressure to cut emissions. More efficient engines and aircraft is one way. Better and faster trains is another way. And electric aircraft for regional traffic is a third way. For the foreseeable future all three will be needed.
.
.
.
Here are some of the more recent electric aircraft that are under development as experimental machines and precursors of the real thing.

Very informative. We shall see private light a/c go electric in 5-10 years mainly for recreation. I doubt same will happen for commercial airliners, reason as pointed is energy density, making a battery efficient is packing the same power in less volume but it will lead to weight gain thus bigger motors as engines thus again weight increase.

Only a revolution in battery technology or alternate fuels like Hydrogen etc can replace carbon based fuels.

Also commercial aviation has multiple layers of regulation, protocol and a very very costly type certification process. I guess conversation of land transportation to electric is more relevant.

[V.Narayan]

Hydrogen-powered electric plane makes first flight between two commercial airports


https://www.rechargenews.com/energy-...ts/2-1-1202977

A prototype fuel-cell plane has made the first ever trip between two commercial airports by a hydrogen-powered electric aircraft, according to German technology developer H2FLY.

The Stuttgart-based company has announced that its HY4 demonstrator plane flew 124km from Stuttgart to Freidrichshafen airport on 12th April 2022, with the four-seat aircraft then reaching a record high altitude for 7,230ft the following day. The Germans lead in this area. They flew the first hydrogen powered aircraft in recent times* - the HY4 in 2016 and now this.

Hydrogen alone amongst clean fuels has energy density to be a viable aviation fuel. I consider this to be a more significant development than the experimental pure electric aircrafts that have flown thus far. Liquid hydrogen has a energy density of 120 Mega Joules/ kg versus 43 for jet aviation fuel. That works in favour of hydrogen. But when you measure by volume cyrogenic hydrogen stored at minus 253 degrees centigrade has an energy density one-fourth that of jet fuel. This is the problem aeronautical designers are grappling with. You could carry hydrogen in its gaseous form but for the energy density to come close to that of jet fuel it needs to be stored at 700 atmospheres!

*The Soviets had flown a modified Tupolev Tu-154 in circa 1989 but that project ended with the collapse of the USSR.

[V.Narayan]

Rolls Royce tests aircraft engine running on hydrogen as the fuel

https://www.bbc.com/news/business-63758937

https://www.bloomberg.com/news/artic...-hydrogen-fuel


Rolls-Royce announced it used hydrogen fuel to successfully power a modern aircraft engine. BBC & Rolls Royce claim, incorrectly, that it is a first in the world of aviation.

The test was conducted with a converted Rolls-Royce AE 2100-A regional aircraft engine using hydrogen created by wind and tidal power. The design originally powered Saab 2000 turboprops. Given British inventiveness I am watching Rolls Royce's progress with interest.

The immediate aim is a simple one - to show that it is possible to run and control a jet engine using hydrogen fuel, rather than conventional aviation fuels. Sensible. Hydrogen being a lot more volatile than aviation fuel needs different handling. They used liquid hydrogen cryogenically stored {as will be the case with a real airliner} and then released it as gaseous hydrogen into the combustion chamber.

Given Rolls Royce's pedigree this might go somewhere. Though the start might be with regional turboprop powered airliners the real value is with the large airliners as they have the volumes to accommodate hydrogen fuel. Watch this space.


The Rolls Royce test bed at Boscombe Down

As mentioned earlier in these pages liquid hydrogen has a energy density of 120 Mega Joules/ kg versus 43 for jet aviation fuel. That works in favour of hydrogen. But when you measure by volume cryogenic hydrogen stored as a liquid at minus 253 degrees centigrade has an energy density one-fourth that of jet fuel. This is the problem aeronautical designers are grappling with - how to build a cryogenic fuel tank large enough to hold the requisite weight of fuel. Very roughly to carry the same amount of stored energy in its fuel tanks an aircraft will need tanks a little over 1.6X the size of current ones without even counting the weight and space needed for the cooling machinery and insulation.

BBC writes this is a first for the world of aviation. That's an incorrect statement like many others I observe with the BBC and some other Western media. The first liquid hydrogen powered airliner was the Tuploev Tu-155, a modified Tu-154M airliner that flew experimental flights in the old USSR in the late 1980s.


The hydrogen powered Tu-155 in flight. One of the three, the starboard one, Kuznetzov turbofan engines was modified for hydrogen. The other two, centre & port continued with normal fuel.


The interior arrangements of the Tu-155. While it might have worked in an experimental machine where weights could be managed in a real life airliner having all the fuel at the rear sounds like a centre of gravity nightmare!!

[srini1785]

Originally Posted by V.Narayan

They used liquid hydrogen cryogenically stored {as will be the case with a real airliner} and then released it as gaseous hydrogen into the combustion chamber.

Its interesting to note that hydrogen is being considered as jet fuel. While it was no secret that Hydrogen could provide energy, it was quiet difficult to harness it. Storing things cryogenically for extended periods of flight also requires energy. While in flight, the turbo fan can be used as an prime mover for a Generator, there may be a requirement of a battery pack during halts.

My take would be to just dump the Jet engine all together and launch the plane as a horizontal rocket using cryogenic hydrogen and oxygen. The result of the combination is water which can be used to produce artificial rain.

[V.Narayan]

Originally Posted by srini1785

My take would be to just dump the Jet engine all together and launch the plane as a horizontal rocket using cryogenic hydrogen and oxygen. The result of the combination is water which can be used to produce artificial rain.

The acceleration of Rocket will knock the dentures off a lot of passengers, not to mention the breakfast popping out

[SKC-auto]

From what I understand, testing an engine is a small part in the larger issue. Storing liquid hydrogen at -253°C will be the biggest issue, also the hydrogen tanks required will be huge leaving almost no space for passengers.

[SKC-auto]

This is the study done for liquid Hydrogen.

we estimate that evolutionary LH2-powered narrow-body aircraft could transport 165 passengers up to 3,400 km and LH2-powered turboprop aircraft could transport 70 passengers up to 1,400 km. Together, they could service about one-third (31 to 38%) of all passenger aviation traffic

https://theicct.org/publication/avia...ircraft-jan22/

[Ravi Parwan]

Storing cryogenic hydrogen will always use an auxiliary engine to burn the small percentage evaporating from the tank to cool the rest. This is the principle they use in LNG carriers, to use the vapors as fuel to cool the rest.

Instead of using heavier than air aircrafts, what is the progress being made on lighter than air aircrafts? using helium instead of hydrogen, can't the hot air balloon kind of aircrafts make a comeback?

Here are links to some of the different efforts being made in this direction.

https://edition.cnn.com/travel/artic...ntl/index.html

https://edition.cnn.com/travel/artic...ntl/index.html

[V.Narayan]

First hydrogen fuel cell powered aircraft takes to the air

https://www.msn.com/en-in/travel/air...5dd9ce24&ei=10


Universal Hydrogen Co. flew a 40-passenger regional airliner using hydrogen fuel cell propulsion - a world first for an aircraft of this type - on 2 March 2023.The plane, nicknamed Lightning McClean, took off from Grant County International Airport in Washington State and flew for 15 minutes, reaching an altitude of 3,500 Mean Sea Level.

The flight, conducted under an FAA Special Airworthiness Certificate, was the first in a two-year flight test campaign expected to culminate in 2025. In this first test flight, one of the airplane’s turbine engines was replaced with Universal Hydrogen’s fuel cell-electric, megawatt-class powertrain. The other remained a conventional engine for safety reasons.

Hydrogen fuel cells as opposed to burning hydrogen as a conventional fuel could open numerous possibilities of making hydrogen power practical from a volume of fuel to be carried point of view. I don't understand enough of the detailed workings of a fuel cell but this is what seems to me a simpler solution.

We live in interesting times where some of the fundamental energy sources and the manner in which they are harnessed is undergoing seismic changes. The last time our current civilization experienced this was about 120 years ago. At the time the motor car & motorized trucks and busses were making petroleum important and then in 1910 the British Royal Navy decided to convert its coal fired steam warships to oil fired and in one sweep revolutionized the use of oil across all Navies and then the merchant fleets.

[SKC-auto]

Another Hydrogen dream crashed.

Airbus postpones hydrogen aircraft by a decade atleast, so Hydrogen enthusiasts have to wait until 2045.

https://www.reuters.com/business/aer...ft-2025-02-07/