Hydrogen powered combustion

[MartinJG]

This is interesting.

No mention of the high cost of producing hydrogen via hydrolysis. Crack that and it is game on.

[JimSh]

This is interesting.



No mention of the high cost of producing hydrogen via hydrolysis. Crack that and it is game on.

That's the easy bit. All you need is electricity.
They're already doing it in Orkney and Shetland.

https://www.bbc.com/future/article/20190327-the-tiny-islands-leading-the-way-in-hydrogen-power
https://www.shetland.org/blog/green-hydrogen-potential

[ColinB]

Hydrogen's a great idea and I really hope it takes off, well done Scotland for pioneering it.

But there're a lot of hurdles yet in scaling it up. Only 5% of the world's H2 production comes from electrolysis at present, the rest comes from fossil fuels. The most common process (steam reforming of methane) creates around 9-12 tons of CO2 for every ton of H2.
https://en.wikipedia.org/wiki/Hydrogen_production

So you either have to massively increase the amount of generating capacity even to meet the current demand, never mind any future demand as H2 usage increases, or you have to keep extracting the fossil fuels and have very large scale carbon capture and storage (CCS). At least the CCS problem is easier if it's captured at source rather than pumped out of the tailpipes of vehicles.

[MartinJG]

My simplistic understanding of converting Hydrogen through hydrolysis is that it has been traditionally hampered by the fact that it uses almost as much energy to convert. However, it seems to me the key here is untapped solar energy. Plenty of that for now subject to the usual constraints/braindead politics and power games. This effectively bridges the problem of storage with existing battery technology. There is the issue of storage under pressure which is potentially dangerous, however, even there, I believe the faster rate of dispersion of hydrogen into the atmosphere is less of a risk than petroleum gas (LPG) etc.

[JimSh]

Hydrogen's a great idea and I really hope it takes off, well done Scotland for pioneering it.

But there're a lot of hurdles yet in scaling it up. Only 5% of the world's H2 production comes from electrolysis at present, the rest comes from fossil fuels. The most common process (steam reforming of methane) creates around 9-12 tons of CO2 for every ton of H2.
https://en.wikipedia.org/wiki/Hydrogen_production

So you either have to massively increase the amount of generating capacity even to meet the current demand, never mind any future demand as H2 usage increases, or you have to keep extracting the fossil fuels and have very large scale carbon capture and storage (CCS). At least the CCS problem is easier if it's captured at source rather than pumped out of the tailpipes of vehicles.

Spot on. It needs an excess of electrical energy.
Generating hydrogen by electrolysis requires a lot of energy to break hydrogen-oxygen bonds.
Generating hydrogen from hydrocarbons requires slightly less energy to break carbon to hydrogen bonds which is partially offset by the energy obtained by making carbon to oxygen bonds but results in the formation of carbon dioxide.

[culzean]

Hydrogen's a great idea and I really hope it takes off, well done Scotland for pioneering it.

Hydrogen will take off if you fill a big balloon with it   

Hydrogen is not a fuel per se, it is an energy carrier,  it takes a lot more energy input to make it than you get back.  looking at USA a bloke from MIT says he gets 65 flat highway miles per 1 Kg of hydrogen from his Toyota Mirai ( hydrogen fuel cell ),  but to make 1kg of hydrogen takes about 48kw/ hours of electricity.  the average range of a battery EV is about 25kw/ h per 100 miles ( under ideal conditions in summer on flat road - 24kw Nissan leaf did about 70 miles in real world ).   So already hydrogen fuel cell requires much more primary energy than a normal battery car.   The fuel cell requires about 80Kw/h of primary energy input to cover 100 miles., and that is without the energy required to compress and transport it.

Solar power not really reliable in UK ( very little October to March ) so would we become reliant on sunny middle east for our energy once again ?

https://www.toyota.co.uk/new-cars/new-mirai/meet-mirai#1

[MartinJG]

Hydrogen's a great idea and I really hope it takes off, well done Scotland for pioneering it.

Hydrogen will take off if you fill a big balloon with it   

Hydrogen is not a fuel per se, it is an energy carrier,  it takes a lot more energy input to make it than you get back.  looking at USA a bloke from MIT says he gets 65 flat highway miles per 1 Kg of hydrogen from his Toyota Mirai ( hydrogen fuel cell ),  but to make 1kg of hydrogen takes about 48kw/ hours of electricity.  the average range of a battery EV is about 25kw/ h per 100 miles ( under ideal conditions in summer on flat road - 24kw Nissan leaf did about 70 miles in real world ).   So already hydrogen fuel cell requires much more primary energy than a normal battery car.   The fuel cell requires about 80Kw/h of primary energy input to cover 100 miles., and that is without the energy required to compress and transport it.

Solar power not really reliable in UK ( very little October to March ) so would we become reliant on sunny middle east for our energy once again ?

https://www.toyota.co.uk/new-cars/new-mirai/meet-mirai#1

Indeed, hence my caveat regarding politics/power games and storage for transport around the world etc. I know there is also one small fly in the ointment. Nox is a by product of hydrogen combustion which of course is the nemesis of heavy oil.

PS - The law of conservation of energy springs to mind regarding your point on H being a carrier. 'The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another'. Despite all the bull surrounding energy, some things never change .

[Jocko]

Orkney is having to produce Hydrogen as they have so much tidal generated electricity they cannot use it. The cables to mainland Scotland are too feeble to export it.

[JimSh]

Hydrogen's a great idea and I really hope it takes off, well done Scotland for pioneering it.

Hydrogen will take off if you fill a big balloon with it   

Hydrogen is not a fuel per se, it is an energy carrier,

Correct. Hydrogen can be regarded as an energy storage system[

  it takes a lot more energy input to make it than you get back. 

Not so. A conventional ICE engine has an efficiency of the order of 20%. Using hydrogen as a fuel in a fuel cell is approximately twice as efficient.

https://afdc.energy.gov/fuels/hydrogen_basics.html

https://www.viessmann.co.uk/heating-advice/how-efficient-are-hydrogen-fuel-cells#:~:text=According%20to%20the%20US%20Department%20of%20Energy%20Hydrogen,as%20the%20kinds%20of%20roads%20being%20driven%20on.

[JimSh]

'The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another'. Despite all the bull surrounding energy, some things never change .

Thermodynamics has nothing to do with politics.
Ye cannae change the laws o' thermodynamics cap'n

[culzean]

Modern petrol engines about 35% efficiency, modern diesels about 45%. 

[richardfrost]

The near term future for Hydrogen is less likely t be in vehicles and more likely to be in domestic heating and cooking. Hydrogen produced by renewable energy (e.g. wave and wind in the Orkneys) can be used as a means of storing this renewable energy for future use. Here in the UK there are several things going on looking at hydrogen. I could have sworn I saw on the BBC a story about the Northern Gas Networks trial in the North East. Can't find the story but here is a link to NGN's own item on it...

https://www.northerngasnetworks.co.uk/2021/07/23/green-light-for-first-hydrogen-blending-on-a-public-gas-network/

...and here is link to a BBC story on a plan to produce hydrogen from solar in Dorset...

https://www.bbc.co.uk/news/uk-england-dorset-57986600

Some people will find a 100 reasons why something can't be done but never propose an alternative other than keep doing what we have always done and hope for the best. Thankfully, there are people, scientists and engineers, who strive for a better way.

[embee]

The efficiencies being offered for IC engines is the maximum, however it varies enormously with different speed and load. At idle (doing no useful work) the efficiency is by definition zero. The real downside of an ICE is that it typically spends a lot of time running at very low efficiency. Engineering of an ICE system can make it work at more efficient regions for more of the time (downsizing, high gear ratios, different operating cycles to reduce pumping losses for example). A best BSFC of 250g/kWhr equates to around 34% thermal efficiency for a petrol engine, but off the optimum speed/load point a BSFC of 350g/kWhr is only 24%. In the attached image, running at 1500rpm and 1.5Bar BMEP (around 20Nm in that engine) it's more like 450g/kWhr and 18%.



A fuel cell or battery motor system doesn't suffer this very poor efficiency at light load/low speed which is typical of a ICE.

Storing energy in any form takes more input than you get back out again (entropy increases - law of thermodynamics - can't be avoided), think of it as thermodynamic friction. Doing it in some forms means a much bigger entropy increase (lower efficiency) than for other forms. Charging a battery produces heat and thus losses, you don't get out as many kWhrs as you put in. Producing free hydrogen from a compound takes energy. The trick is to use a storage and recovery system which is reasonably efficient and practically executable in the real world. Stored energy density, kWhr/kg and kWhr/litre volume, are both significant for any mobile (vehicle) system, but might not be as important for a static system (generating mains electricity etc). $/kWhr is the final deciding factor.

[John Ratsey]

The efficiencies being offered for IC engines is the maximum, however it varies enormously with different speed and load. At idle (doing no useful work) the efficiency is by definition zero.

Which is why one of the objectives of Honda's eHEV system is to keep the engine running in the most efficient zone

and not idle doing nothing useful (unfortunately, the vehicle designers didn't address the problem of the engine running to provide cabin heating during cold weather).

[JimSh]

Modern petrol engines about 35% efficiency, modern diesels about 45%.

I suppose it was an American site and comparing it to gas guzzler ICEs
I was being conservative (with a small c) in using the double figure.
 "The interest in hydrogen as an alternative transportation fuel stems from its ability to power fuel cells in zero-emission FCEVs, its potential for domestic production, its fast filling time, and the fuel cell's high efficiency. In fact, a fuel cell coupled with an electric motor is two to three times more efficient than an internal combustion engine running on gasoline."

"According to the US Department of Energy Hydrogen Program, a standard fuel car with a combustion engine runs at around 20 per cent efficiency, whereas vehicles that run using hydrogen fuel cells are around 40 to 60 per cent efficient. This number could vary depending on the size and weight of the car, as well as the kinds of roads being driven on.
https://afdc.energy.gov/fuels/hydrogen_basics.html

"The department goes on to state that the maximum efficiency that a combustion engine could achieve is around 58 per cent, however fuel cells have a theoretical maximum efficiency of 85 to 90 per cent. This depends on how the fuel cell is being used and is usually unachievable in real world applications. "
https://www.viessmann.co.uk/heating-advice/how-efficient-are-hydrogen-fuel-cells#:~:text=According%20to%20the%20US%20Department%20of%20Energy%20Hydrogen,as%20the%20kinds%20of%20roads%20being%20driven%20on