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Hydrogen

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Ian Dunn
607548.  Thu Sep 03, 2009 8:15 am Reply with quote

Hydrogen is most abundant element in the universe, but because it is so light there is hardly any hydrogen gas on Earth and it easily excepts the planet's gravity.

It is often said that hydrogen powered cars are the future and it is probably true, but there is two major problem with hydrogen power cars at the moment. One is that there are hardly any hydrogen fuelling stations in the country. The other is that because there are no sources of hydrogen on its own on Earth, we have to get it from other sources. At the moment, these are fossil fuels.

 
soup
607565.  Thu Sep 03, 2009 8:34 am Reply with quote

Ian Dunn wrote:
The other is that because there are no sources of hydrogen on its own on Earth, we have to get it from other sources. At the moment, these are fossil fuels.


So not from water then?

 
Posital
607569.  Thu Sep 03, 2009 8:39 am Reply with quote

Another problem is storage.

Can't be fun sitting on what might be a zepplin-full of explosive gas.

Electrolysis of water produces hydrogen and oxygen in abundance... although not very cost-effective.

 
Peregrine Arkwright
607574.  Thu Sep 03, 2009 8:54 am Reply with quote

.

The advantage of hydrogen fuel (I'll duck for a moment the deal-breaking question of where we might get it from) is that since the by-product of burning would just be water vapour, we would break out of the global-warming conundrum of fossil fuels and the carbon cycle.

I was once told by someone quite senior at Rolls-Royce that they estimated the RB211 family of aircraft engines had the potential for a further fifty years of development, and it would then be the last R-R engine fuelled by kerosene.

The next generation after the RB211 would be hydrogen-fuelled engines, using the skin friction of high speed aircraft to bring supercooled hydrogen fuel back up to a usable temperature. Strangely enough, it was way back in 1973 when I was told that. The assumption then was that environmentally-friendly nuclear fusion would be used to split water into hydrogen and oxygen in the first place.

Peregrine Arkwright

 
Ian Dunn
607587.  Thu Sep 03, 2009 9:52 am Reply with quote

soup wrote:
Ian Dunn wrote:
The other is that because there are no sources of hydrogen on its own on Earth, we have to get it from other sources. At the moment, these are fossil fuels.


So not from water then?


In hydrogen powered vechiles, water is the waste product. Hydrogen is mixed with oxygen in the air and water comes out of the exhaust.

 
soup
607598.  Thu Sep 03, 2009 10:01 am Reply with quote

Where does the Hydrogen come from initially?

May I suggest you re-read the last ten words of PA's post

 
Davini994
607627.  Thu Sep 03, 2009 10:40 am Reply with quote

It's not so much where the hydrogen physically comes from, it's where the energy to get it into pure hydrogen comes from.

If you are taking it from water, (2 atoms of hydrogen and one of oxygen), then you need to put in the same amount of energy to get hydrogen as what you use later, when you are reversing the process.

Hydrogen (H2) has a high energy level, much higher than more stable compounds like water (H2O). Which is why it goes boom, and why we can use it for fuel.

 
soup
607652.  Thu Sep 03, 2009 11:28 am Reply with quote

Davini994 wrote:
It's not so much where the hydrogen physically comes from, it's where the energy to get it into pure hydrogen comes from.



The energy can come from hydro, solar, wind, nuclear etc sources.
I can't see where fossil fuels are required.

Yes most energy (at the moment) is generated from fossil fuels but it is NOT the source of Hydrogen as ID stated in his OP rather it is the main source of the energy to split water into Hydrogen and Oxygen.

Apologies :- seems I was wrong, most Hydrogen is extracted from Fossil fuels, but I can see this (Hydrogen via electrolysis) becoming more of an issue when fossil fuels run out.


Last edited by soup on Thu Sep 03, 2009 12:35 pm; edited 2 times in total

 
Davini994
607658.  Thu Sep 03, 2009 11:46 am Reply with quote

Yes Soup, I agree, the energy can come from other sources. These industries aren't in place at the mo though, which is worth mentioning as it means if we can introduce hydrogen power we still need to do a load more stuff to get it to being a 'clean' energy.

One thing I didn't know until I looked it up (which I should I'm sure) is that most hydrogen production takes the H directly out of the fossil fuels, not from water.

Wiki wrote:
Most of today's hydrogen is produced using fossil energy resources... Hydrogen can also be produced from water by electrolysis or by chemical reduction using chemical hydrides or aluminum.

http://en.wikipedia.org/wiki/Hydrogen_vehicle#Production

So I've mislead you there a bit, apologies.

 
Posital
607839.  Thu Sep 03, 2009 2:50 pm Reply with quote

Davini994 wrote:
If you are taking it from water, (2 atoms of hydrogen and one of oxygen), then you need to put in the same amount of energy to get hydrogen as what you use later, when you are reversing the process.

Sadly, not true - especially if you're using electrolysis, then things become far more complex. The conversion also produces heat, which is potentially lost.

Check out wiki for a reasonable explanation.

If the production of hydrogen requires fossil fuels, it kinda defeats the point as the main by-products would be greenhouse gasses, IIRC.

 
Ion Zone
607844.  Thu Sep 03, 2009 3:12 pm Reply with quote

It's cheaper to charge a battery in an electric car than make hydrogen from electricity.

 
Davini994
607916.  Thu Sep 03, 2009 7:33 pm Reply with quote

Posital wrote:
Davini994 wrote:
If you are taking it from water, (2 atoms of hydrogen and one of oxygen), then you need to put in the same amount of energy to get hydrogen as what you use later, when you are reversing the process.

Sadly, not true - especially if you're using electrolysis, then things become far more complex. The conversion also produces heat, which is potentially lost.

If I understand you correctly, then you are talking about the industrial process not being 100% efficient. For that to be of any relevance, there would have to be a process - any process - that is 100% efficient. There isn't of course, from the 2nd law of thermodynamics.

If you'd like to review, you'll also see that I've written "energy put in" to the chemical process of breaking the H2O. Industrial inefficiencies don't go in.

The real question is, is it possible for me to write anything without you misunderstanding in order to drag the conversion into tedious waters?

 
soup
607938.  Fri Sep 04, 2009 12:38 am Reply with quote

Ion Zone wrote:
It's cheaper to charge a battery in an electric car than make hydrogen from electricity.


Yes, but it is much much quicker to fill a 'fuel' tank with liquefied Hydrogen than it is to charge any currently available battery. Battery technology would need to advance to the stage where you could fully recharge a car drive sized battery in 3~4 minutes (currently in the 5~13 hours range) to compete with filling a hydrogen tank.

 
Posital
607943.  Fri Sep 04, 2009 1:56 am Reply with quote

Davini994 wrote:
The real question is, is it possible for me to write anything without you misunderstanding in order to drag the conversion into tedious waters?
Sorry Dav - it's nothing personal. What you said before was clearly incorrect (as you stated and corrected above).

I can't see any misunderstanding.

There are other, more complex, reasons for energy to be lost. I didn't want to go on about it at length - so gave the wiki link instead.

I'm sorry to hear you find this tedious - I've got no axe to grind.

 
Ian Dunn
607951.  Fri Sep 04, 2009 2:34 am Reply with quote

Ion Zone wrote:
It's cheaper to charge a battery in an electric car than make hydrogen from electricity.


Yes, but the batteries weigh more so affect the quality of the car's ride. Also, at the moment, most of the power being used to recharge those batteries also comes from fossil fuels, because that's how most of the power in the country is generated.

 

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