Solar Panels for Hydrogen?

[cjdelphi]

after seeing the solar plane land it made think back to the time I saw a hydrogen jet powered engine...

so how many watts of power would it take to feed 2 turbines? the idea being to use solar to produce enough gas to drive the turbines? and could energy produced go into making more hydrogen? or is that heading into over unity territory. ..

but with this method filling planes with water to power them sounds good to me.. but I don't think enough hydrogen could be produced from solar?

 

[duke37]

You will need to lubricate the turbines with snake oil.

 

[davenn]

so how many watts of power would it take to feed 2 turbines? the

who knows ... you haven't state any spec's on a particular turbine ?

or is that heading into over unity territory. ..

yes

but with this method filling planes with water to power them sounds good to me..

you do realise that water is really heavy > .... in all things aircraft related, the aim is to make the aircraft as light and as efficient as possible


Dave

 

[cjdelphi]

Hydrogen when burnt with oxygen = water which is fed back into the water tank...

regarding the hydrogen turbine, no clue I've never seen the specs it was a tv clip years ago...

 

[(*steve*)]

Why waste energy converting energy from electrical to chemical if you don't need to?

 

[cjdelphi]

Why waste energy converting energy from electrical to chemical if you don't need to?

So you prefer to continue to burn fossils? and when we run out of oil ... then what? electric is useless unless you wish to travel very slowly by a prop engine...

 

[hevans1944]

@cjdelphi: If you have enough solar power to make hydrogen in flight using electrolysis (an inefficient process), then you have enough solar power to run electric motors to turn propellers or ducted fans. Store any excess solar-generated electricity in supercapacitors while flying your solar-powered airplane. Or don't fly at night.

Photovoltaic solar panels produce high-quality electricity. There is no reason to downgrade this energy to something else except perhaps for storage and transportation to remote sites far away from the solar panels. Hydrogen is not a very high density means of energy storage, nor can commercially useful (for power) quantities be transported without significant costs. Better to use that expensive electricity from solar panels (or nuclear power) to form complex hydrocarbons from water and CO2 in the air and use those hydrocarbons for fuel. That would be an inefficient but closed-cycle system that does not add to or subtract from CO2 and water vapor already present in the atmosphere. It can power civilization for at least the next thousand years, or until a practical means of storing industrial quantities of electricity is developed.

Hydrocarbon synthesis, even if the energy cost were zero (which it isn't), is still not as efficient as digging hydrocarbons (oil, gas, coal) out of the ground, although those will eventually run out. The world is fortunate that the infrastructure and technology already exists for mass refining, distribution, and use of hydrocarbon fuel, so why reinvent that wheel for synthesizing inefficient hydrogen fuel?

 

[cjdelphi]

so how do you run the jet engine without fuel? hence the need the generate hydrogen from solar arrays...

 

[(*steve*)]

Interestingly enough, anything but the smallest modern prop aircraft is essentially "jet" powered. In addition all large modern jet aircraft are essentially propelled by large ducted fans.

And on to the other point, no I am certainly NOT suggesting the use of fossil fuels.

 

[(*steve*)]

well, you could achieve the same thermal efficiency by using the energy from the panels to heat a resistor.

It might be somewhat more efficient to use one of those newfangled electric motors though.

 

[davenn]

Hydrogen when burnt with oxygen = water which is fed back into the water tank...

You haven't really thought about this have you ?
You only get a tiny bit of water back. your tank water supply would need to be constantly replenished
I will remind you again .... water is very heavy. Kerosene isn't in comparison


Dave

 

[cjdelphi]

You haven't really thought about this have you ?
You only get a tiny bit of water back. your tank water supply would need to be constantly replenished
I will remind you again .... water is very heavy. Kerosene isn't in comparison


Dave

if I had of do you think I'd be here?

 

[hevans1944]

if I had of do you think I'd be here?

Hmmmm. Why not? Most of us here who propose ideas and/or attempt to solve problems have given it considerable thought. Else, this would be just another free-form blog.

I think (my opinion only) you may have bought in to the "hydrogen economy" nonsense, and now are looking at possible "solutions" that could be used to implement such. There aren't any. Hydrogen as a fuel is only efficient if "burned" in a nuclear fusion reactor, and there is exactly ONE of those working nearby: our Sun at 93,000,000 miles safe operating distance. Unless civilization progresses to the point where we can put little stars in a bottle and generate electricity from that, good ol' Sol remains our only renewable source of energy. So, the logical progression from that is to use PV arrays and perhaps wind turbines to "farm" sunlight. But then some bright bulb decided that solar electricity could be used to create hydrogen by electrolysis of water. Voila! The Hydrogen Economy is born! Like a lot of ideas, this one wasn't thought all the way through.

I am personally in favor of using fossil fuels to propel the engines of civilization, because we know that actually works. Unfortunately, so far we haven't done this in a very responsible way with respect to our environment. There may not be a responsible way as long as profit is the only motive, but I think that is not a topic for discussion in this forum. If you would abandon fossil fuels as the primary means of moving energy around the planet, you need to find something as equally effective to replace it. That could be supercapacitors, but much more R&D is required.

 

[BobK]

But, Mr. Fusion will be here soon won't it?

I was a physics major and had dreams of solving the nuclear fusion problem. Then I took a course in Magnetohydrodynamics. It was the first time the math became so disconnected from the intuition that I was lost, and I realized I was not likely to save the world after all. Switched to computer science after that, and it has served me well as a career.

Bob

 

[hevans1944]

after seeing the solar plane land it made think back to the time I saw a hydrogen jet powered engine...

You should have seen the hydrogen-jet nuclear powered rocket engine developed by NASA for a manned Mars mission back in the 1952 to 1972 period. Liquid hydrogen was stored on-board for use as reaction mass, not as fuel, and heated by a small nuclear reactor. The technology is well-developed and ready for flight test, but it has been in mothballs since the NERVA program was de-funded by our near-sighted Congress in 1972. This is the same body politic that refuses to fund fast breeder reactors to ensure the USA has a virtually inexhaustible source of nuclear energy. Fast breeder reactors, just in case you didn't know, manufacture more nuclear fuel than they consume.

 

[BGB]

reminds me of a random

You should have seen the hydrogen-jet nuclear powered rocket engine developed by NASA for a manned Mars mission back in the 1952 to 1972 period. Liquid hydrogen was stored on-board for use as reaction mass, not as fuel, and heated by a small nuclear reactor. The technology is well-developed and ready for flight test, but it has been in mothballs since the NERVA program was de-funded by our near-sighted Congress in 1972. This is the same body politic that refuses to fund fast breeder reactors to ensure the USA has a virtually inexhaustible source of nuclear energy. Fast breeder reactors, just in case you didn't know, manufacture more nuclear fuel than they consume.

some ideas I had had before, but thus far still purely speculative, would be ways of combining ducted-fan with ion-engine technology to allow for a possibly much smaller and more powerful electric thruster (for terrestrial use).

one possible variation could be using a turbine system vaguely similar to a jet-engine, potentially driven by an electric motor, with a secondary helicon coupler antenna (basically, using a special antenna to feed RF into the air-stream).

for low-speed / low-power operation, the motor basically spins the blades and it works more like a ducted fan. and, when high-speed / high thrust is needed, it can fire up the RF coupler and start ionizing the air into plasma (at this point, the mechanics shift closer to it being an electrically-driven jet engine).

drawbacks:
for most use cases, it likely offers little advantage over ducted fans or jet engines (less efficient, ...).

some other variations of the idea had used electric arcs instead of RF coupling, ...

 

[(*steve*)]

If you look at modern high bypass jet engines, ~80% (from memory) of the trust comes from the bypass airflow, i.e. that from the ducted fan. The "jet" provides relatively little thrust, most of the energy being used to turn the large fan at the front. The major difference between this and a turboprop is that in the turboprop the fan is not ducted.

 

[BGB]

reminds me of a random idea

If you look at modern high bypass jet engines, ~80% (from memory) of the trust comes from the bypass airflow, i.e. that from the ducted fan. The "jet" provides relatively little thrust, most of the energy being used to turn the large fan at the front. The major difference between this and a turboprop is that in the turboprop the fan is not ducted.

I was more thinking like a turbojet (IOW: more like the engine in a fighter jet), where the goal is to have high exhaust speed and high thrust from a comparably small engine.

for a turbofan (like in a typical commercial aircraft), one almost may as well just use a big ducted fan instead if going electric, since mostly the jet engine is just being used to spin the high-bypass fan anyways.

so, yeah, the idea is basically useless for subsonic commercial aircraft or similar...


it could possibly be useful for things like high-speed unmanned aircraft, or cases where the larger area needed for fans or propellers is undesirable, or similar.

however, in these cases, it would be left to compete against the use of turbojets.