14 replies to this topic

[mariner]

I ahd never heard of " natural hydrogen" before but this light level post on UK's BBC explains some of it 

 

https://www.bbc.co.u...siness-67541581

 

It sems a very long shot and " too good to be true" etc. but it suggests that mfrs. keeping a hydrogen engine option open might be smart 

[ensign14]

Wasn't that by The Real Thing?

[Magoo]

Wow, if this were to prove out, hydrogen becomes viable. 

[cbo]

I ahd never heard of " natural hydrogen" before but this light level post on UK's BBC explains some of it

https://www.bbc.co.u...siness-67541581

It sems a very long shot and " too good to be true" etc. but it suggests that mfrs. keeping a hydrogen engine option open might be smart

Largest known deposit can meet current demand for two years.....

If the automotive industry converted all its products (cars) to hydrogen-electric cars, that deposit of 250 million tonnes would likely meet future demand for a couple of days.....

The total expected deposits world wide of 100.000 million tons would allegedly meet current demand for 800 years. But future demand would be much, much higher (think cars, trucks, planes, ships).

By all means exploit it, but as with all hydrogen ventures, it is largely hot air and fantasy as an alternative to BEVs.

[desmo]

Would it make more sense to combust H2 in ICEs or use it to fuel EVs via fuel cells?

[cbo]

Would it make more sense to combust H2 in ICEs or use it to fuel EVs via fuel cells?

Efficiency is about the same, IIRC.

But fuel cell emit only water while there will always be pollutants from a combustion proces and a bit of co2 emission from lubricating oil being consumed by the engine. So hydrogen combustion is not Zero Emission.

[Magoo]

H2 ICE is horrible for passenger cars.

 

The most practical way to create a 200 HP H2 ICE is to start with a 400 HP gasoline ICE. Then try to deal with the NOx emissions. 

 

It is sort of cool to stand next to an H2 ICE on the dyno, tho. There is far less noise, heat, smoke, and drama than a gasoline ICE. it's like a disgruntled air compressor. 

[gruntguru]

Fuel cell is way ahead on efficiency - 40% - 60% ATM. (ICE is 20% - 30%.)

 

In addition, the fuel cell - electric vehicle already has most of the hardware for regen braking. Only need to add a small battery-pack or supercapacitor.

Edited by gruntguru, 13 December 2023 - 22:16.

[cbo]

Fuel cell is way ahead on efficiency - 40% - 60% ATM. (ICE is 20% - 30%.)

In addition, the fuel cell - electric vehicle already has most of the hardware for regen braking. Only need to add a small battery-pack or supercapacitor.

I've seen figures suggesting tank-to-wheel efficiency for fuelcell of about 50% and about 40-45% for hydrogen ICE. Well-to-wheel efficiency for fuelcell of about 35% and 30% for hydrogen ICE. The figures may be for heavy vehicles, though.

Fossil ICE is said to be about 20% and BEV 75-85% measured as well-to-wheel.

Edited by cbo, 14 December 2023 - 11:11.

[Greg Locock]

And what thermodynamic reason is behind the 20% for ICEV vs 45 for H2IC? You are being lied to, there isn't one (in fact H2 would be worse thermodynamically, due to pumping losses). There's 17% gone in well to pump for FF, but if you think H2 is not going to run a similar figure for that step I've got a bridge to sell you. I suspect your 'source' is comparing max efficiency of an H2IC engine to the 20% that is generally quoted for real life usage profiles for FFIC.

[gruntguru]

I've seen figures suggesting tank-to-wheel efficiency for fuelcell of about 50% and about 40-45% for hydrogen ICE. Well-to-wheel efficiency for fuelcell of about 35% and 30% for hydrogen ICE. The figures may be for heavy vehicles, though.

Fossil ICE is said to be about 20% and BEV 75-85% measured as well-to-wheel.

 

At best, H2 ICE will approach Petrol ICE for efficiency. Which means a peak efficiency of perhaps 37% (eg Prius) and an average efficiency across a drive cycle of perhaps 25% with a conventional transmission. If you are going to add a hybrid transmission (electric motors) you are better off with a fuel cell.

[mariner]

My chemistry knowledge is terrible - I know the "correct" air/fuel ratio for petrol engines is 14.7:1 weight of air vs weight of fuel - but is different for  pure hydrogen fuel?

 

I sort of  assume so as carbon atoms are heavier than hydrogen ones but if the hydrogen is injected as gas how does the ratio work please?

[cbo]

At best, H2 ICE will approach Petrol ICE for efficiency. Which means a peak efficiency of perhaps 37% (eg Prius) and an average efficiency across a drive cycle of perhaps 25% with a conventional transmission. If you are going to add a hybrid transmission (electric motors) you are better off with a fuel cell.

Are we takling tank-to-wheel or well-to-wheel?

[Greg Locock]

37% is on the dyno, 25% is tank to wheel, less 17% for well to tank, giving 20%, roughly

 

@mariner Stoke air fuel ratio for H2 is 2H2+O2=2H20, so 4 g of Hydrogen, 32 g of oxygen, and roughly 120g of N2, so by weight 39:1, , by volume 3.5:1, which is why you get a big hit in VE. Quick check for a generic long chain hydrocarbon CH2+1.5O2=CO2+H20 14g of fuel, 48g of O2, 180g of N2, so by weight 16:1, close enough.

 

The upper limit to efficiency is usually NOx/exhaust valve temp in a production FF engine, but I'm very rusty on engines. 

[gruntguru]

JCB have had a fairly serious crack at building a small efficient hydrogen ICE. Turbocharging fixes the VE problem. https://www.youtube....eature=emb_logo

Lightweight technical stuff from 14:40.