Quote:
Originally Posted by tantragna @vina, as you claim about the industrial production of H2 is from methane, ...
Also note that I am not trying to make electricity by this process, I am trying to make an alternate fuel or better put as an fuel enhancer, so it may work or at worse it may not! So the energy used to release or split water is not recovered by chemical reaction to make electricity, but from mechanical energy using it as fuel in an ICE. Anyways I have already set a positive mood to give it a try atleast! Its better to do something constructive in the free-time, than the time (and money) we spend to do useless loafing around at many times.  Just trying my bit to conserve whatever we have in a better ways. As I am also into & interested in motorsports, I know the amount of dirty spill we cause on the environment. I had initially thought to make an electric bike or vehicle, but after some careful thinking & research found out that the battery units make the most of the damage on environment. So the water to water theory (atleast in theory sounds good) was a safe bet, so am working on it. Right now only on rigorous research, will find funds to materialize it to give it a try! Amen!
In the same wikipedia page, I found this too..
I am re-thinking now  |
Thanks first of all for taking it in the right spirit. Regarding the qikipedia entry I guess you reached this page:
Hydrogen production - Wikipedia, the free encyclopedia
As you can see, the very first entry is regarding Fertilisers - Urea production is by far the largest industrial Hydrogen consumer in the world - they use ammonia as feedstack which requires Hydrogen as its feedstock which then requires Natural Gas.
If you see Govt. of India policy regarding Natural gas - Fertiliser industry falls under the highest priority sector.
(BTW - Carbon black is produced as a by product and is then used by one major automotive component -
can you guess which one?)
I understood what you were trying to do after going to HHO pages on the internet. The thing is producing electricity from H2 gives you a far higher efficiency (80+ %) than ICE will ever give (less than 50% under best of circumstances) - bear in mind that Hydrogen is not like petrol or diesel - unlike petroleum
Hydrogen is not a source of energy - it can be a fuel, but energy to generate this fuel has to come from somewhere else.
Most of the Times-of-India kind of press (including HT, IE, ...) has journalists who were no good at Science to begin with and easily overlook such simple facts (and then accuse everyone else to be in the pockets of oil industry) - then they get impressed by spoonfeeding from people who are still wedded to Hydrogen.
If you read pure tech journals (and by tech I don't mean IT - there is hardly any science in what is generally known as information science) people have been cold about Hydrogen for decades now - even so research goes on by several commendably dedicated people and they do get due credit (minus the hype generated by idiot CEOs in gullible and stupid generic media)
I'm assuming you know enough about Carnot cycle (the fundamental thermodynamic cycle for heat-mechanical energy conversion -> this is the most optimal cycle possible and real engines try to approximate it as much as possible). And analysis shows that max thermal efficieny possible, assuming there are no other limits, depends on the initial and final temperatures of the working fluid. In ICE final temperature can be no lower than ambient (And usually far higher) while initial temperature can not be increased beyond a limit (otherwise engine's internal surfaces will sustain damage in no time) - hence the limitations (apart from the fact that you do not use ideal gases as working fluid).
Coming to batteries (this includes eletrolysis) the reason you lose energy is that even in what are known as "reversible reactions" the electro-chemical potential needed to go in one direction of the equation (this is usually the direction where battery gives out power) is less than in the other direction (this is the charging part). This is due to vagaries of activation energy barriers encoutered in the reaction AFAIK. The ratio of the two electro-chemical potentials is the max efficiency that you can achieve in theory.
For Li-ion batteries used in cellphones, the first voltage is about 3.7V (it falls considerably when battery is discharged, but that is not due to chemical properties, that is due to other limitations like internal resistance of battery) while the second voltage is about 4.1V.
So theoretically charge/discharge cycle can give back about 100*3.7/4.1 = 90% of the energy used up in charging the battery. For lead acid battery this falls to about 85%. In both cases actually efficiency achieved is 5% to 10% lower due to engineering decisions taken.
For electrolysis of water - AFAIK (and remember from my first semester chemistry lectures) the ratio falls quite a bit below 40% - hence there is no way you can recover more than 30% of the energy that goes into "charging" the battery (where charging the battery means generating H2+O2 by electrolysis of water, and discharging means creating water by reacting the two). Keep in mind that even if the second part of this "battery" is done by buring H2 and running ICE with that - you'll be dealing with Carnot cycle (rather than Gibbs Free energy) and the efficiency will be worse.
Regarding the urine part well
But seriously - if you are up to it, then it makes more sense to use urine directly as a fertiliser (rather than going on to produce urea in the first place) - that way you'll save far more energy. This sort of usage is called organic farming.