The Green Hydrogen Problem That No One Is Talking About

[Meredith Poor + 883]

"One industry source told Oilprice that the production of one ton of hydrogen through electrolysis required an average of nine tons of water." OK, just in case everyone forgot their high school chemistry... H2O is 2 hydrogens at an atomic weight of 1 each, or 2 in total, plus one oxygen at an atomic weight of 16. A molecular weight of 18 divided by 2 = 9. Duh!

"The process of water purification, for its part, is rather wasteful. According to the same source, water treatment systems typically require some two tons of impure water to produce one ton of purified water." This would be necessary, for example, to hydrolyze sea water. Various researchers have produced electrodes and voltage settings that can hydrolyze seawater directly, so that purification isn't necessary. This has to run below 1.3 volts, since at higher voltages seawater hydrolyzes into hydrochloric acid and sodium hydroxide.

There's no shortage of water around an offshore wind turbine, pretty much by definition.

[Dan Warnick + 6,100]

1 hour ago, Meredith Poor said:

"One industry source told Oilprice that the production of one ton of hydrogen through electrolysis required an average of nine tons of water." OK, just in case everyone forgot their high school chemistry... H2O is 2 hydrogens at an atomic weight of 1 each, or 2 in total, plus one oxygen at an atomic weight of 16. A molecular weight of 18 divided by 2 = 9. Duh!

"The process of water purification, for its part, is rather wasteful. According to the same source, water treatment systems typically require some two tons of impure water to produce one ton of purified water." This would be necessary, for example, to hydrolyze sea water. Various researchers have produced electrodes and voltage settings that can hydrolyze seawater directly, so that purification isn't necessary. This has to run below 1.3 volts, since at higher voltages seawater hydrolyzes into hydrochloric acid and sodium hydroxide.

There's no shortage of water around an offshore wind turbine, pretty much by definition.

Heh-heh.  And New York City needs all the help it can get, to get back above sea level!   

Edited October 28, 2020 by Dan Warnick
Oops

[Jay McKinsey + 1,489]

And huge solar imbued deserts conveniently exist next to the ocean in Australia, Middle East and N. Africa.

Also of note is that the emissions of converting H2 to electricity is purified H2O which can be captured and stored near the power plant for reuse. 

[frankfurter + 562]

Can we put aside our differences for a moment?

I appeal to anyone who has knowledge of chemistry, please.  I am interested in the exhaust of a hydrogen ICE for consumers.

At sea level, 'air' is comprised primarily of N2 75%, O2 20%, H2O 5% (humidity).  Thus the molecules/compounds feeding into H2 ICE are: H2 + N2 + O2 + H2O.

I can see how H2 can combine with O to produce H2O, but what occurs to the remaining O and N2?  Would this combustion not produce NO nitrous oxide?  And in greater quantity than by burning hydrocarbons?   Also, would not the exhaust H2O be in the form of steam, thus increasing both the ambient air temperature and humidity?  And would not the entire combination have environmental consequences?

 

[Jay McKinsey + 1,489]

28 minutes ago, frankfurter said:

Can we put aside our differences for a moment?

I appeal to anyone who has knowledge of chemistry, please.  I am interested in the exhaust of a hydrogen ICE for consumers.

At sea level, 'air' is comprised primarily of N2 75%, O2 20%, H2O 5% (humidity).  Thus the molecules/compounds feeding into H2 ICE are: H2 + N2 + O2 + H2O.

I can see how H2 can combine with O to produce H2O, but what occurs to the remaining O and N2?  Would this combustion not produce NO nitrous oxide?  And in greater quantity than by burning hydrocarbons?   Also, would not the exhaust H2O be in the form of steam, thus increasing both the ambient air temperature and humidity?  And would not the entire combination have environmental consequences?

 

That is one reason that hydrogen vehicles use fuel cells with no combustion.

Yes they waste clean pure water by expelling it. 

see section 3.8 of https://www1.eere.energy.gov/hydrogenandfuelcells/tech_validation/pdfs/fcm03r0.pdf

Edited October 29, 2020 by Jay McKinsey

[KeyboardWarrior + 527]

The primary "problem" I've recognized with green hydrogen is that its sale price needs to be equivalent to hydrogen generated from methane. That is, if we're to keep chemical commodity prices stable. This isn't really an issue, except for the producers who will effectively be selling their power for $0.01 per kWh. 

[KeyboardWarrior + 527]

37 minutes ago, frankfurter said:

Can we put aside our differences for a moment?

I appeal to anyone who has knowledge of chemistry, please.  I am interested in the exhaust of a hydrogen ICE for consumers.

At sea level, 'air' is comprised primarily of N2 75%, O2 20%, H2O 5% (humidity).  Thus the molecules/compounds feeding into H2 ICE are: H2 + N2 + O2 + H2O.

I can see how H2 can combine with O to produce H2O, but what occurs to the remaining O and N2?  Would this combustion not produce NO nitrous oxide?  And in greater quantity than by burning hydrocarbons?   Also, would not the exhaust H2O be in the form of steam, thus increasing both the ambient air temperature and humidity?  And would not the entire combination have environmental consequences?

 

No sir. The second oxygen atom is accounted for in the balanced equation. Yes, a little bit of NOx is produced if we're burning it in a standard ICE, but in the case of fuel cells this doesn't happen.

[KeyboardWarrior + 527]

7 hours ago, Meredith Poor said:

"One industry source told Oilprice that the production of one ton of hydrogen through electrolysis required an average of nine tons of water." OK, just in case everyone forgot their high school chemistry... H2O is 2 hydrogens at an atomic weight of 1 each, or 2 in total, plus one oxygen at an atomic weight of 16. A molecular weight of 18 divided by 2 = 9. Duh!

Good luck trying to explain that to anyone. 

[KeyboardWarrior + 527]

7 hours ago, Meredith Poor said:

This has to run below 1.3 volts, since at higher voltages seawater hydrolyzes into hydrochloric acid and sodium hydroxide

Of course this by itself is rather useful. A solar and wind driven chloro-alkali industry seems to a more profitable use of power offtake. 

[Enthalpic + 1,496]

1 hour ago, frankfurter said:

 

I appeal to anyone who has knowledge of chemistry, please.  I am interested in the exhaust of a hydrogen ICE for consumers.

At sea level, 'air' is comprised primarily of N2 75%, O2 20%, H2O 5% (humidity).  Thus the molecules/compounds feeding into H2 ICE are: H2 + N2 + O2 + H2O.

I can see how H2 can combine with O to produce H2O, but what occurs to the remaining O and N2?  Would this combustion not produce NO nitrous oxide?  And in greater quantity than by burning hydrocarbons?   Also, would not the exhaust H2O be in the form of steam, thus increasing both the ambient air temperature and humidity?  And would not the entire combination have environmental consequences?

 

The catalytic converter cleans up the oxides.  You also control the fuel mixture (rich:lean).

All combustion engines produce steam (tailpipes drip water).

 

Edited October 29, 2020 by Enthalpic

[frankfurter + 562]

Interesting. Yes, I considered the possibility of a catalytic, but this continues to use expensive metals. The ideal result for an ICE would be to control the burn ultra-precisely to consume the fuel precisely to produce the precise exhaust. Perfection would be something like this...

H2 + O2 + N2 --> H2O + N2O

pure hydrogen + pure oxygen + pure nitrogen -> combusts -> water + nitrous oxide

no laughing matter.

 

[Wombat + 1,028]

10 hours ago, Jay McKinsey said:

And huge solar imbued deserts conveniently exist next to the ocean in Australia, Middle East and N. Africa.

Also of note is that the emissions of converting H2 to electricity is purified H2O which can be captured and stored near the power plant for reuse. 

I am not even sure that the proposed green H2 plant in Western Australia will even use desalination. I believe it will be fairly close to the Ord river irrigation scheme. Will try to find out.

[Wombat + 1,028]

15 minutes ago, Wombat said:

I am not even sure that the proposed green H2 plant in Western Australia will even use desalination. I believe it will be fairly close to the Ord river irrigation scheme. Will try to find out.

Actually, it will employ desalination, has just received "major project status" as well. Here are some of the details:

https://www.pv-magazine-australia.com/2020/10/25/50-billion-green-hydrogen-hub-gets-federal-government-guernsey/?utm_source=Bibblio&utm_campaign=Internal

[KeyboardWarrior + 527]

9 hours ago, frankfurter said:

Interesting. Yes, I considered the possibility of a catalytic, but this continues to use expensive metals. The ideal result for an ICE would be to control the burn ultra-precisely to consume the fuel precisely to produce the precise exhaust. Perfection would be something like this...

H2 + O2 + N2 --> H2O + N2O

pure hydrogen + pure oxygen + pure nitrogen -> combusts -> water + nitrous oxide

no laughing matter.

 

Try this:

2H2 + O2 --> 2H2O

That's the balanced equation. There is no NOx by default. 

[KeyboardWarrior + 527]

7 hours ago, Wombat said:

Actually, it will employ desalination, has just received "major project status" as well. Here are some of the details:

https://www.pv-magazine-australia.com/2020/10/25/50-billion-green-hydrogen-hub-gets-federal-government-guernsey/?utm_source=Bibblio&utm_campaign=Internal

I guess there's going to be some energy spent to perform that task. With current membrane technology it probably isn't too concerning. I'll go take a look. 

[Enthalpic + 1,496]

11 hours ago, frankfurter said:

Interesting. Yes, I considered the possibility of a catalytic, but this continues to use expensive metals. The ideal result for an ICE would be to control the burn ultra-precisely to consume the fuel precisely to produce the precise exhaust. Perfection would be something like this...

H2 + O2 + N2 --> H2O + N2O

pure hydrogen + pure oxygen + pure nitrogen -> combusts -> water + nitrous oxide

no laughing matter.

 

No, unless your goal is to make nitrous oxide / fix atmospheric nitrogen.   

Formation of NOx is undesirable. With typical hydrocarbons it is a balancing act. 

Run it rich, cool, low pressures and you are left with too many products from incomplete combustion (carbon monoxide, etc.)  Run it lean, hot, high pressure you get the undesirable nitrogen oxides. Modern fuel injectors, O2 sensors and catalytic converters can handle both problems very well.

 

You also get less useful energy from the fuel if you are making nitrogen oxides (compare the enthalpies of formation).

https://en.wikipedia.org/wiki/Hess's_law

 

 

Edited October 29, 2020 by Enthalpic

[Jan van Eck + 7,558]

On 10/29/2020 at 4:56 AM, frankfurter said:

Interesting. Yes, I considered the possibility of a catalytic, but this continues to use expensive metals. The ideal result for an ICE would be to control the burn ultra-precisely to consume the fuel precisely to produce the precise exhaust. Perfection would be something like this...

H2 + O2 + N2 --> H2O + N2O

pure hydrogen + pure oxygen + pure nitrogen -> combusts -> water + nitrous oxide

no laughing matter.

 

You are incorrect.  There are no measurable NOx outputs from a hydrogen engine.  Your "N2O" would be less than 1 ppm.  You need no catalytic converter because there is nothing to convert. 

On 10/29/2020 at 1:04 AM, frankfurter said:

Also, would not the exhaust H2O be in the form of steam, thus increasing both the ambient air temperature and humidity?

No.  YOu get water in vapor form, not as steam.  The addition of water vapor to the outside air (although probably not measurable) would lower outside temperatures by increasing the ability of the dry air to absorb heat.  Heat is absorbed into water vapor, a process known as "latent heat." The water vapor in turn will be extracted from the atmosphere in the form of rain or snow. It thus adds to the amount of clean, fresh water on the planet. 

23 hours ago, KeyboardWarrior said:

Try this:

2H2 + O2 --> 2H2O

That's the balanced equation. There is no NOx by default. 

You are correct. 

[Marcin2 + 724]

N2 does not react with H2 or O2 in combustion of H2. This is due to very strong tripple bond in N2 molecule, it is very difficult to break this bond.

[Jay McKinsey + 1,489]

Mazda seems to think that hydrogen combustion in air resluts in NOx

Lean burn and exhaust gas recirculation (EGR) are adopted to reduce nitrogen oxide (NOx) emissions. NOx is primarily reduced by lean burn at low engine speeds, and by EGR and a three-way catalyst at high engine speeds. The three-way catalyst is the same as that used in the base model. Optimal and appropriate use of lean burn and EGR satisfies both goals of high output and low emissions.

https://www.mazda.com/en/innovation/technology/env/hre/

[frankfurter + 562]

On 10/30/2020 at 2:07 AM, KeyboardWarrior said:

Try this:

2H2 + O2 --> 2H2O

That's the balanced equation. There is no NOx by default. 

great! 

 

Edited November 1, 2020 by frankfurter

[Jay McKinsey + 1,489]

5 minutes ago, frankfurter said:

great!  but what happens to the N in 'air' when H2 is used in an ICE?  would the N not react with either H or O in some way during combustion?

 

"The combustion of hydrogen with air however can also produce oxides of nitrogen (NOx): H2 + O2 + N2 = H2O + N2 + NOx The oxides of nitrogen are created due to the high temperatures generated within the combustion chamber during combustion. This high temperature causes some of the nitrogen in the air to combine with the oxygen in the air. The amount of NOx formed depends on: • the air/fuel ratio • the engine compression ratio • the engine speed • the ignition timing • whether thermal dilution is utilized"

https://www1.eere.energy.gov/hydrogenandfuelcells/tech_validation/pdfs/fcm03r0.pdf

Edited November 1, 2020 by Jay McKinsey

[frankfurter + 562]

2 minutes ago, Jay McKinsey said:

The combustion of hydrogen with air however can also produce oxides of nitrogen (NOx): H2 + O2 + N2 = H2O + N2 + NOx The oxides of nitrogen are created due to the high temperatures generated within the combustion chamber during combustion. This high temperature causes some of the nitrogen in the air to combine with the oxygen in the air. The amount of NOx formed depends on: • the air/fuel ratio • the engine compression ratio • the engine speed • the ignition timing • whether thermal dilution is utilized

https://www1.eere.energy.gov/hydrogenandfuelcells/tech_validation/pdfs/fcm03r0.pdf

thanks for link. presumably the NOx is very minimal and can be managed.  [don't know what occurred with my original post].

[Jay McKinsey + 1,489]

1 minute ago, frankfurter said:

thanks for link. presumably the NOx is very minimal and can be managed.  [don't know what occurred with my original post].

You may have missed the other link I just posted. I think Mazda is the only company working on this.

Lean burn and exhaust gas recirculation (EGR) are adopted to reduce nitrogen oxide (NOx) emissions. NOx is primarily reduced by lean burn at low engine speeds, and by EGR and a three-way catalyst at high engine speeds. The three-way catalyst is the same as that used in the base model. Optimal and appropriate use of lean burn and EGR satisfies both goals of high output and low emissions.

https://www.mazda.com/en/innovation/technology/env/hre/

[Jan van Eck + 7,558]

9 minutes ago, Jay McKinsey said:

Mazda seems to think that hydrogen combustion in air results in NOx

that is when you use a stock engine block and retrofit the air intake to inject H2 gas.  You need to get the air:fuel ratio down to 180:1 in order to wrest the maximum benefit from the engine.  To do that, the engine needs to be purpose-built, a new design, which at least two companies are doing right now.  Then the NOx drops to below 1 ppm.  

Do remember that the auto-ignition temperature of  Hydrogen gas is 500 C. Octane, or C8H18, is somewhere around 1980 C.  When you use a spark ignition and you run below 500 C you are running a cool engine, one that will need supplemental heat in order to heat the cabin with the circulating fluid. With a cool engine and a low flow rate of the H2, the N2 gas in the atmosphere will flow through the engine unaffected by the combustion of the H2. 

If you have a high capital investment in the machinery to build a conventional engine and you want to change the fuel, then adding on some bolt-on features to inject the H2 into the inflow air stream is the low-cost way to go.  A lot cheaper than building a fresh engine from scratch.  And no, the production requirements are just not there to mandate investment in a new engine and block. So it does not get done, at least not by Mazda. 

[Jan van Eck + 7,558]

3 minutes ago, Jay McKinsey said:

You may have missed the other link I just posted. I think Mazda is the only company working on this.

Two {non-auto] companies new are working out the kinks on advanced H2 engines, for commercial vehicles.  They have results of N2 below 1 ppm, basically negligible.