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First hydrogen plane tested in US..

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Lifer
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The aircraft, called Global Observer, is a so-called high altitude - long endurance (Hale) aircraft.

It can operate at 65,000ft (20,000m) and be used for defence missions, weather and environmental monitoring, aerial mapping, and as a low-cost telecommunications infrastructure.

The plane, which looks like a glider, was first flown on 26 May at US Army's test range in Arizona. A second test flight took place on 2 June.

The company says it is confident it can be deployed for US government applications within two years.

"We are now ready to quickly satisfy an urgent national security need for an affordable, persistent Hale system for communications relay and intelligence, surveillance and reconnaissance missions," said Tim Conver, AeroVironment's...
 
Ohio State University was operating a modified Beechcraft airplane on hydrogen about twenty years ago. There is nothing new under the sun.
 
Liquid hydrogen might not be so energy-dense as other fuels. However, at 20 km altitude the temperature ahould be somewhere at -40, so its thermal protection (against boiling) can be reduced (the thermal protection can be reduced during lift off, letting the boiling hydrogen used as gas in the engine to cool off the rest of the tank).
They could use methanol as fuel for their fuel cells.
 
You mean liquid hydrogen? But you should add to that the mass/volume of the thermoisolation. As the hydrogen tanks gets bigger and bigger, the amount of thermoisolation needed gets smaller and smaller. Also, the loss of hydrogen (either used to cool the tank by evaporation or lost in other ways) gets lower and lower.
No wonder the rockets using liquid hydrogen and liquid oxygene are fueled all the time until the very last moment before the launch.
 
"Myth 4 ? Hydrogen has a higher energy density than gasoline or diesel

Hydrogen has more energy per unit mass than other fuels (61,100 BTUs per pound versus 20,900 BTUs per pound of gasoline). The problem with hydrogen is that it is much less dense (pounds per gallon) than other fuels. A gallon of gasoline has a mass of 6.0 pounds, the same gallon of liquid hydrogen only has a mass of 0.567 pounds or only 9.45% of the mass of gasoline. Therefore one gallon of gasoline yields 125,400 BTUs of energy while a gallon of liquid hydrogen yields only 34,643 BTUs or 27.6% of the energy in a gallon of gasoline. The Space Shuttle uses hydrogen as a fuel, because its mass is low, and the fuel is carried in an external fuel tank that is jettisoned during lift off. Automobiles can not have external fuel tanks that are discarded, and the energy per unit volume is used to determine a fuel?s energy density in automobiles. Compressed gaseous hydrogen is even less dense than liquid hydrogen. At 5,000 psi of pressure gaseous hydrogen only has a density of 0.25 pounds per gallon or one twenty fourth the density of gasoline. Gasoline and diesel are far superior fuels to hydrogen in this regard."

http://www.slspart.com/hydrogen_fm.html
 
Originally posted by: phaxmohdem
"Myth 4 ? Hydrogen has a higher energy density than gasoline or diesel

Hydrogen has more energy per unit mass than other fuels (61,100 BTUs per pound versus 20,900 BTUs per pound of gasoline). The problem with hydrogen is that it is much less dense (pounds per gallon) than other fuels. A gallon of gasoline has a mass of 6.0 pounds, the same gallon of liquid hydrogen only has a mass of 0.567 pounds or only 9.45% of the mass of gasoline. Therefore one gallon of gasoline yields 125,400 BTUs of energy while a gallon of liquid hydrogen yields only 34,643 BTUs or 27.6% of the energy in a gallon of gasoline. The Space Shuttle uses hydrogen as a fuel, because its mass is low, and the fuel is carried in an external fuel tank that is jettisoned during lift off. Automobiles can not have external fuel tanks that are discarded, and the energy per unit volume is used to determine a fuel?s energy density in automobiles. Compressed gaseous hydrogen is even less dense than liquid hydrogen. At 5,000 psi of pressure gaseous hydrogen only has a density of 0.25 pounds per gallon or one twenty fourth the density of gasoline. Gasoline and diesel are far superior fuels to hydrogen in this regard."

http://www.slspart.com/hydrogen_fm.html
Click to expand...
Simply put, oxidation of hydrogen has a very large free energy that can be converted at ~90% efficiency to electricity. Gasoline engines cannot, thermodynamically speaking, achieve greater than 50% efficiency, with most being about 13% efficient (IIRC). So, the harvestable energy density of hydrogen is much higher (depending on pressure and phase, of course) than that of gasoline. I'm not going to look up the densities of hydrogen at the moment, but I'm pretty confident that the overall energy density is also greater than that of gasoline.

That said, hydrogen is not the end-all, be-all of future fuels that people are looking for.
 
I thought I read that hydrogen was packing twice the energy as gas at the same wieght. The problem being, as mentioned above, that hydrogen is much lighter than gas so at best attainable pressure/mass these days hydrogen will provide only about half the driving range as gasoline. I still think hydrogen makes a whole lot of sense going forward, we just need to nail down the production, delivery and storage issues. Personaly I wouldnt mind filling up my car twice as often if the hydrogen was produced at home instead of overseas...
 
Specific Gravity, Gas (Air = 1) @ 68°F (20°C), 1 atm: 0.0696
Specific Gravity, Liquid @ B.P., 1 atm: 0.0710
Click to expand...
Source: http://www-safety.deas.harvard.edu/services/hydrogen.html

Though liquid hydrogen's density is apparently much lower at 1 atm, it's not stored at 1 atm. Pressure vessels designed specifically for storing hydrogen at extremely high pressures (and, therefore, higher densities) have been in the works for a very long time. Based on its linear molecular configuration and lack of polarity, I would have to assume that hydrogen is more compressible than water. To what degree? I'd have to dig out some of my books which are still buried from my recent move.
 
Originally posted by: Soldier
I thought I read that hydrogen was packing twice the energy as gas at the same wieght. The problem being, as mentioned above, that hydrogen is much lighter than gas so at best attainable pressure/mass these days hydrogen will provide only about half the driving range as gasoline. I still think hydrogen makes a whole lot of sense going forward, we just need to nail down the production, delivery and storage issues. Personaly I wouldnt mind filling up my car twice as often if the hydrogen was produced at home instead of overseas...
Click to expand...

How do you get liquid Hydrogen?
 
Originally posted by: CycloWizard
Originally posted by: phaxmohdem
"Myth 4 ? Hydrogen has a higher energy density than gasoline or diesel

Hydrogen has more energy per unit mass than other fuels (61,100 BTUs per pound versus 20,900 BTUs per pound of gasoline). The problem with hydrogen is that it is much less dense (pounds per gallon) than other fuels. A gallon of gasoline has a mass of 6.0 pounds, the same gallon of liquid hydrogen only has a mass of 0.567 pounds or only 9.45% of the mass of gasoline. Therefore one gallon of gasoline yields 125,400 BTUs of energy while a gallon of liquid hydrogen yields only 34,643 BTUs or 27.6% of the energy in a gallon of gasoline. The Space Shuttle uses hydrogen as a fuel, because its mass is low, and the fuel is carried in an external fuel tank that is jettisoned during lift off. Automobiles can not have external fuel tanks that are discarded, and the energy per unit volume is used to determine a fuel?s energy density in automobiles. Compressed gaseous hydrogen is even less dense than liquid hydrogen. At 5,000 psi of pressure gaseous hydrogen only has a density of 0.25 pounds per gallon or one twenty fourth the density of gasoline. Gasoline and diesel are far superior fuels to hydrogen in this regard."

http://www.slspart.com/hydrogen_fm.html
Click to expand...
Simply put, oxidation of hydrogen has a very large free energy that can be converted at ~90% efficiency to electricity. Gasoline engines cannot, thermodynamically speaking, achieve greater than 50% efficiency, with most being about 13% efficient (IIRC). So, the harvestable energy density of hydrogen is much higher (depending on pressure and phase, of course) than that of gasoline. I'm not going to look up the densities of hydrogen at the moment, but I'm pretty confident that the overall energy density is also greater than that of gasoline.

That said, hydrogen is not the end-all, be-all of future fuels that people are looking for.
Click to expand...

Large internal combustion engines (like the diesel engines in ships) has about 34% efficiency. However, as you decrease the size of the engine (and increase its speed and rpm) you loose efficiency. Also, diesel engines run at a higher "hot" temperature than gasoline ones, and are more efficient.
Considering all the losses in small cars, I wouldn't bet on car's engines with better than 20% efficiency
 
Originally posted by: Genx87
Originally posted by: Soldier
I thought I read that hydrogen was packing twice the energy as gas at the same wieght. The problem being, as mentioned above, that hydrogen is much lighter than gas so at best attainable pressure/mass these days hydrogen will provide only about half the driving range as gasoline. I still think hydrogen makes a whole lot of sense going forward, we just need to nail down the production, delivery and storage issues. Personaly I wouldnt mind filling up my car twice as often if the hydrogen was produced at home instead of overseas...
Click to expand...

How do you get liquid Hydrogen?
Click to expand...

You can get gaseous hydrogen by water electrolysis. You then start to compress and cool the hydrogen (it will become hot as you compress it).
Let's say that you have now lots and lots of gaseous hydrogen at very high pressure. Let some of it to vent to atmosphere. Surprise surprise, it became very cold.
And this way you use mechanic work (increase of pressure) and you get cold hydrogen. Once you reach some very cold temperature (like -200 Celsius) your hydrogen will condense and become liquid.

(the actual technology might differ)
 
You can get gaseous hydrogen by water electrolysis. You then start to compress and cool the hydrogen (it will become hot as you compress it).
Let's say that you have now lots and lots of gaseous hydrogen at very high pressure. Let some of it to vent to atmosphere. Surprise surprise, it became very cold.
And this way you use mechanic work (increase of pressure) and you get cold hydrogen. Once you reach some very cold temperature (like -200 Celsius) your hydrogen will condense and become liquid.
Click to expand...

And I think that's what Genx was getting to - the most common method of producing hydrogen requires a lot of electricity. How do we get that? Coal, oil and nuclear are most common. So first, we'd need huge investments in renewable power sources. Otherwise, we'd be burning more oil in order to reduce our dependency on oil. :shocked:🙂

Hydrogen sucks in one other respect - trying to get the most energy-per-volume, while working with the least dense element in existence.

Be nice if we could figure out how to get a significant net energy gain from fusion. Sure they've already managed fusion of hydrogen, but it still doesn't provide enough of a net gain to make it worthwhile. At least, not yet.
 
Other ways to obtain hydrogen (but it contains also CO ) is to spray very hot coal with water. Voila, H2 and CO (gases) flow out.
 
Originally posted by: Calin
Large internal combustion engines (like the diesel engines in ships) has about 34% efficiency. However, as you decrease the size of the engine (and increase its speed and rpm) you loose efficiency. Also, diesel engines run at a higher "hot" temperature than gasoline ones, and are more efficient.
Considering all the losses in small cars, I wouldn't bet on car's engines with better than 20% efficiency
Click to expand...
You're right. I would bet on it being... ~13%, which is what I said before.
 
Hmm... the energy required to make Hydrogen a Liquid kills the point.
For a "Green" view, this is no achievement, as Toyota have stated, not only is Hydrogen the next Fuel, but it must be fuel cells, which split the hydrogen from oxygen when its needed, and using platinum this can be done very efficiently
 
Originally posted by: Siddy
Hmm... the energy required to make Hydrogen a Liquid kills the point.
For a "Green" view, this is no achievement, as Toyota have stated, not only is Hydrogen the next Fuel, but it must be fuel cells, which split the hydrogen from oxygen when its needed, and using platinum this can be done very efficiently
Click to expand...
Not to nitpick, but the job of the fuel cell is to recombine hydrogen gas and oxygen gas. The separation process can also be achieved by the fuel cell, but only when you input electricity, which still has to be produced by other means. You regain about 90% of the input energy when the gases recombine, but you still net a loss in power. Thus, the key is to find a way to generate and store hydrogen gas cheaply and safely. It can be stored very safely now at pretty high pressures (safer than your existing gas tank), but it still isn't cheap and the best way to get it is from crude oil refinement.
 
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