Thread: hydrogen fuel

One of the arguments regarding the use of H2 is that it more than makes up for its production "cost" by enhancing the petrol/diesel burn.

Below are some calculations I did a while back whilst trying to explain the unreality of this line of thought.



To split 1 litre of water into oxygen and hydrogen requires 16,000 kilo Joules (kJ) of energy (0r 16,000,000 Joules).

The electricity required to do this is calculated by the formulae below

Time (seconds) = Joules/volts x amps

Now if our 12 volt car alternator is made to crank out a massive 100 amps we can work out how long it will take to convert our 1 litre of water to gas.

Time (sec) = 16,000,000/12 x 100
= 13,333 seconds
= 3 hours 42 min.

or 4.4 kWh of power.

There is no way around using this amount of energy. This energy is required to excite the electrons in the water molecule enough to raise them to the next quantum level. It is only by doing this that the Hydrogen and oxygen will split.
Any energy short cuts are pure fantasy.

So now that we have generated our "Browns Gas", what are we going to get for it in energy terms? The answer is 16,000 kJ, the same amount of energy it took us to create it.

However to get 16,000 kJ of work out of an internal combustion engine operating at 30% effeciency we will require 53,000 kJ of fuel.

So to convert our 1 litre of water to browns gas we are going to use 53,000 kJ but only get back 16,000 kJ for our troubles, ie we are going to have to burn 37,000 kJ of fuel for no advantage.

For interest, 1 litre of petrol contains about 34,000 kJ of energy.

Now this 1 litre of water (after we have pumped 4.4 kWh through it) will split into 110 grams of Hydrogen and 890 grams of oxygen with a combined gas volume at atmospheric pressure and 20 deg C of 2,000 litres, 2/3's of which is hydrogen.

So we are using a massive 100 amps from our alternator to deliver about 360 litres of hydrogen gas per hour or 30 grams of hydrogen per hour.

Lets assume our vehicle is burning a very economical 10 litres/100km at 100 km/hr.
So we need 10 litres of petrol or about 7 kg every hour.

So we are to believe that by adding 30 grams (4,400 kJ) of hydrogen to 7,000 grams (238,000 kJ) of petrol, we will get massive fuel savings.
Only 1.8% of our total fuel kJ value being burnt is hydrogen.
We add something like 25% LPG to get economy gains in a diesel.

This is an example of why this hydrogen generating stuff is not all its cracked up to be, and why commercial production of said devices has not commenced.


Now I believe that most of these H2 generators are based on a 10 amp cell. If you are using one of these cells then only 0.18% of your total fuel consumed is coming from the H2.

Please don't try and tell me it makes a difference.


Having said all that, I do actually believe that H2 can enhance fuel burn of petrol/diesel (having seen University experimental results), BUT the concentrations needed are similar to those using LPG, and as someone pointed out earlier - LPG is a hell of a lot cheaper.

Young people in universities (who love nothing more than to prove someone wrong), have not been able to make it work. Have a look at some of the work done by The University of Tasmania.

So why would I think some untrained nobody who knows how to set up a web page is more able than 100's of trained "smart arse" uni students.

Well I don't.

I am a sceptic of the use of hydrogen generated by a car and used in the combustion process - the energy numbers just do not add up.

However in high school chemistry where in some reactions catalysts were used, this resulted in outputs seemed to exceed inputs (not actually the case - catalysts just enabled more processes in the reaction).

Now added Hydrogen is unlikely to act directly as a catalyst in a petrol burning environment but putting aside how the hydrogen is generated has anyone (a scientist not a AULRO person) tested whether the energy produced when burning petrol under pressure with hydrogen fumigation does actually produce more energy than expected (yes I know energy cannot be created or destroyed) - in other works does the hydrogen release energy creation processes over and above just burning petrol or hydrogen individually, ie does the hydrogen actually work something like a catalyst.

Cheers

Garry

Gary, I think the question that should be asked is "Does the addition of Hydrogen in the burn increase the efficiency of the burn?"

Originally Posted by Mick_Marsh

Gary, I think the question that should be asked is "Does the addition of Hydrogen in the burn increase the efficiency of the burn?"

Thats what I said .

Originally Posted by garrycol

Thats what I said .

I thought so. I hoped I made it more succinct.

Hydrogen is not a catalyst, as a catalyst is not consumed in the reaction.

A catalyst basically reduces the amount of energy required to start a reaction, however no extra energy is emitted from that reaction.

Example, lets say that paper normally starts to burn at 500 C. If we used a catalyst we maybe able to start the paper burning at 400 C.

Does adding hydrogen increase the effeciency of the burn? The answer according to the scientific data I have read is yes, BUT the amount of hydrogen needed to make a difference is in the order of 30%, AND the timing of the engine must be advanced to take advantage of the faster burn.

I guess this makes the 0.2 - 2.0% H2, created by an on board hydrogen generator with no advanced timing, look pretty silly.

Originally Posted by Freightdog

Hydrogen is not a catalyst, as a catalyst is not consumed in the reaction.

I did not say hydrogen was a catalyst.

Originally Posted by garrycol

I did not say hydrogen was a catalyst.

No you didn't but I think someone else did.

I just don't like the idea of using hydrogen in an internal combustion engine. If I had copious quantities of hydrogen, I would use it in a fuel cell and use electric motors. One motor in each hub ought to do it. PLC controlled. I imagine that would make an awesome machine and you could power your house with it when you get home.