What's the holdup on green hydrogen?

Factual Questions
41

The question is really “what problem is hydrogen solving?”
As medium for energy transport it is pretty terrible. Volumetric inefficiency and hazard management are big problems. It is extremely hard to beat electricity for most needs. Domestic energy use can be totally electricity, and a huge number of households already are. One might feel suspicious that efforts to push hydrogen gas as a domestic energy component is more about existing industries desperately trying to find a role in the future.
One area we need hydrogen is in ammonia synthesis- not for energy transport but simply to replace the black ammonia used in fertiliser production. That gets you 1% of global GHG in one hit.
As a short term energy buffer it might have value. Pumped hydro is the poster child for this, but not everywhere has the geography to do this. Batteries are really expensive and there is no reasonable prospect they will be able to bridge the gap anytime soon.
So if the efficiency and capital costs can be sorted out hydrogen may become a player here. That might enable it to springboard into other areas, but given the advantages other technologies have in most of the big energy delivery markets those inroads will still probably be quite niche.

One amusing idea comes to me. There are industries where CO2 emission is intrinsic to operation. Carbon capture is all well and good but long term sequestration is fraught. Combining hydrogen and the CO2 can yield a green methane which would be useful for other industries. Running furnaces for a start. Capture that CO2, rinse and repeat. There is still net carbon coming into the system from steel manufacturing, but most others just need the heat. So using hydrogen as an energy transport medium as an adjunct to carbon capture could yield a closed carbon cycle. Volumetric efficiency would still favour moving the CO2 to the hydrogen, but if the CO2 is pretty hot exiting the industrial process that additional heat may swing the balance to on the spot conversion. Just me pulling random ideas out of the proverbial. I doubt I’m the first to think of this, I just haven’t heard it before.

42

Right. SMR > oxycombustion > coal > NG >> air as far as ease of capture goes. There is already commercial capture from SMR.

43

I think you meant, “that can’t be fixed”. And I agree with you. For the longest time there was sponsored research into adsorbents (like Metal Organic Frameworks) or other similar products - that never panned out commercially.

See above post, - the current fix for “less density” is ammonia - which will liquefy the hydrogen and make it dense. (But ammonia has its problems). Many are betting on Ammonia and it maybe a whole new thread to go over the pros and cos.

The biggest pro for Ammonia is that it is a fuel that is 100% Carbon free.

Or ammonia/hydrogen based gas turbines (aeroderivatives like the LM6000 - since they have operating history on High Hydrogen fuels. LM6000 is derived from GE’s CF6-80C2 high bypass turbofan aircraft engine .

Fuel Cells are used in Mining a lot, but I am not aware of fuel cells in the 10+ MW range which is what the Ships would need.

Methane does not work. The energy and capital investment in converting hydrogen to methane and removing the CO2 from the exhaust is overwhelming. For the levels of Carbon Capture needed to stabilize global warming, methane does not work.

44

@am77494 , are you up to speed on flame speeds? I recall some GE combustion guys talking about this for ammonia (slow), hydrogen (fast), and mixtures. But I don’t remember much beyond that it was important to consider.

45

Ruken - I was up to speed about 6 years back. GE itself has/was split into 2 groups - the Power generation group which makes the Frame gas Turbines (primarily Greenville, NC) and the Aircraft Engines/Aeroderivates group (although this is in the US - it is sort of run by the Italians who own Baker Hughes GE).

The Frame gas turbines are usually bulkier and less accommodating to variations in Wobbe Index (A dimensionless number - used by Chemical Engineers and Gas Turbine Mechanical Engineers to characterize flame speed)

Although some of the Frame gas turbines have operating experience on low Wobbe Index fuels (Hydrogen , Ammonia, etc.), its the Aero-derivatives that shine in this space.

And Nova12, a new gas turbine by Baker Hughes (Breakoff from GE) is competing with Caterpillar (former Solar Gas Turbines).

Hydrogen is the worst fuel for a gas turbine - because gas turbines are mass flow machines and Hydrogen has it the least. But 50+ years has gone by and people have not come up with a better fuel - so Hydrogen or Ammonia it is.

Or we can sit around and debate for another decade or two, when the problem will resolve by itself :slight_smile:

46

Chemical beats electrical for long distance transmission and long duration storage. This is why Japan wants to import chemical energy and isn’t looking to run power cables to other countries. This is why nobody is seriously looking to run a 23,000 TEU ship off of batteries, but wind-to-X projects are in the works. This is why farmers in the Midwest want to run electrolyzers off onsite intermittent generation. Use cases vary widely, and pithy statements in support of or against any one option have a high likelihood of being uninformed.

47

I can’t speak to the economics of the overall process, but the Sabatier reaction can be and is run to very high conversion. There’s a large proportion of water in the exhaust (a feature, if you’re on the ISS), but even then I would expect the costs of generating the starting hydrogen and CO2 streams to dominate.

48

Not sure - what you mean by this. Here is the Sabatier Reaction carried out at 400 C (752 F) and 30 bar (435 psia) (temp and pressure are per wikipedia because i cant disclose proprietary data) :

CO2 + 4H2 → CH4 + 2H2O

Assuming your preferred units are mass :

44 lbs of CO2 reacts with 8 lbs of H2, in the theoretical world of 100% conversion to make 16 lbs of methane and 36 lbs of water.

But thermodynamics (Gibbs reactor) limits this conversion to :
44 lbs of CO2 reacts with 8 lbs of H2, in the thermodynamic limit to make 7.1 lbs of Methane, 9.7 lbs of CO2 , 9.5 lbs of CO 3.8 lbs of Hydrogen and 22 lbs of Water

The thermodynamic limit is the best you can do. So, as you can see, Sebatier reaction involves quite a bit of capital investment in equipment and a quite a bit of energy lost in heating / cooling / pressurizing etc. etc.

Which is why Gas Turbines will need to adapt to Hydrogen as fuel rather than expecting it to be converted to methane.

49

Can’t you get an arbitrary yield efficiency, by throwing more input energy into the process? For instance, take all of those output products, liquefy them, distill them to separate them, and dump the excess CO2 and hydrogen back into the input end.

50

True, and you can get higher conversion (by putting in more energy) and more equipment, but the law of diminishing returns kicks in because of Entropy.

Hydrogen is indeed cryogenically distilled for use in the semiconductor manufacture - but that’s a niche market. Large scale processes for power production are not economic.

51

Oh, sure, I wasn’t saying it was practical. I was just questioning the apparent statement that it was impossible.

52

Of course it’s the best you can do, but that limit varies, as expected, with pressure and temperature, e.g. Fig. 6 from a recent paper :

Unlike something like Haber-Bosch, this is not a high-recycle process. Obviously there are tradeoffs, but you can output NG-grid-acceptable (once dried) gas from the methanator.

My objection is neither that SNG is cheap (it’s not) nor to

, despite that being sufficiently vague as to describe any number of perfectly viable processes, but to

Purification of the exhaust is not why this process is expensive. Hydrolysis and the initial carbon capture are why. There are dozens of process flows and economic analyses to choose from. The one I linked to above discusses how hydrolysis dominates the cost. Here’s the most recent one that’s come across my desk:

For cost structure with total plant output of 48 MWel, the total cost of electrolysis, methanation and related auxiliary equipment is 1,000 €/kWel, of which 86.3% is for electrolysis. The cost of methanation is thus 13.7% (137 €/kWel).

That’s just CAPEX (and they’re including electrolyzer, methanation, compression, power electronics, plumbing, construction, controls.) Operationally, the methanator is a net steam generator.

I’m still not convinced anyone should be pursuing it, although the Germans seem much more enthusiastic about it and AFAIK have the largest plant in operation. I agree with you that we’ll need more turbines that can run on hydrogen, and it seems the folks who make them are already on it. But I also wonder about the 62% of natural gas that doesn’t get used to generate grid power. But that’s a question for an “Electrify Everything?” GD thread that’s on the back burner.

53

So, please use your own figure and compare the conversions I reported above. Are they consistent with the chart ?

Whether it is Haber or Texaco or Ostwald or Sebatier Process - they always report / recommend a window of temperature/pressure for operation and a catalyst.

Thats the reason - the process gets patented (sometimes) to them.

54

Or, to fit with the theme of asking others to do our work for us (what an odd request), we can just see what other papers say [no preview, alas]:

That’s consistent with the other article.

If I run my own slapdash Gibbs minimization with your conditions, I get:

molecule pounds
CH4 15
CO2 2.3
CO 0.01
H2O 34
H2 0.4

Which is consistent with both papers.

For kids playing at home who don’t want to fuss with CHEMKIN or Excel, this handy dandy calculator returns:

molecule pounds
CH4 15
CO2 1.8
CO 0.01
H2O 35
H2 0.3

Also in agreement.

But perhaps there’s some rash of fugly miscalculations in the literature that needs to be stomped out.

55

I did my work and presented it. You want to dispute it- then post your own results, which you have done now - and it does not match the major simulators.

I stand by the results I posted in Post 48. They have been independently verified using Hysys and Aspen.

I have not used Chemkin for many years now, but I maybe able to find it. Before I do that - please check the temperature and pressure you are using.

Also, since you are using Chemkin, I am guessing you are flame speed / NOx prediction person - because Chemkin kinetics are done at Ambient pressures, because usual internal combustion engines or gas turbines have fairly low pressures.

56

Okay, I went back and checked your numbers. It seems you are assuming the reactor to run Isothermally. Running the reactor isothermally - produces the numbers you are showing, but please note that reactors at this scale are more close to adiabatic ( not isothermal).

The only commercial plant making Synthetic Methane, (in the US), in my knowledge is the Great Plains Synfuels Plant. Its designed by Lurgi - a German company.

Here is their block flow diagram : 7.5.1. Great Plains Synfuels Plant | netl.doe.gov

If you see the block flow diagram, the methane is adiabatically reacted in the reactor and subsequently cooled.

Here is Haldor Topsoe A/S, who have supplied hundreds of Methanation reactors to Ammonia Plants worldwide’s design - https://cdn.intechopen.com/pdfs/11472/InTech-Synthetic_natural_gas_sng_from_coal_and_biomass_a_survey_of_existing_process_technologies_open_issues_and_perspectives.pdf

See Page 113, Figure 6, you will see it is an adiabatic reactor.

If you still doubt my numbers. we can reach out to @Stranger_On_A_Train to check, because from previous posts, it seems like he has good expertise on this.

57

I can’t speak to Great Plains, but HT’s TREMP involves multiple (yes as you wrote, isothermal) reactors with interstage cooling. Hence their stressing high quality steam generation and 85% heat recovery as a selling point. It’s not like they’re just shoving hot gas in a single pipe, letting it bake, and collecting the results. The PK-7R catalyst for the final reactor “can operate at temperatures as high as 450 C” (as opposed to 700 C for the first stage), and this paper models the final reactor at 300 C (although different starting composition from gasification, not electrolysis/CC.) Whether 300 or 450 C, the final output from the methanator has high conversion of CO2 and minimal CO and does not require expensive cleanup, just water removal. The previous cost models all assume multiple reactors, and the cost of the methanation is dwarfed by electrolysis and carbon capture.

58

Blue hydrogen isn’t looking so hot:

This feels like another place where properly charging for externalities would quickly lead to the right answer. Either natural gas companies would fix up their leaky infrastructure, or they’d conclude that it’s too expensive and that we just need to stop digging up fossil carbon. Blue hydrogen seems to be the new clean coal.

59

Well the debate over Hydrogen is hotting up in the UK.

The government has just released a strategy paper that evisages Blue Hydrogen as the key step towards decarbonisation and it is financing some signifcant projects.

https://www.gov.uk/government/publications/uk-hydrogen-strategy/uk-hydrogen-strategy-accessible-html-version

This is very apealing to the Oil and Gas lobby. The UK has a very big investment in its methane gas network which has drawn on the vast reserves under the North Sea. Contrast this with France which does not have a domestic gas network and invested instead in an Nuclear power based energy strategy.

The longer term goal is that electroytic Green Hydrogen technology will eventually become available at grid scale.

However, this Hydrogen policy is not without its critics who argue the Blue hydrogen created from methane and using carbon capture technology compares poorly to simply buring methane in Gas turbines as is done at the moment.

A report from Cornell has looked into this in some detail and has been picked up by several publications.

https://onlinelibrary.wiley.com/doi/full/10.1002/ese3.956

So here we have the making of a political row over what should be the industrial strategy. The political strategy is to invest in low carbone renewable technologies and sell this expertise to the world. We will see a great deal of this at the upcoming COP 26 meeting in Glasgow later this year.

Other countries are also developing industrial strategies and I guess will be publishing them in due course.

So to answer the orginal question, the holdup with Green Hydrogen is that the technology is not ready from grid scale application. Government are hedging their bets in their industrial stragies (if they have one.)

Blue Hydrogen looks easier to implement at scale, especially if it is confined to large scale industrial users. But there is a big question mark over whether it does really reduce carbon simply cause another problem with leaky hydrogen and especially methane which is another powerful global warming gas.

The issue of domestic gas supply, which is a big portion of the UK energy usage has several solutions and adding hydrogen to the mix has yet to be proved. It has to be compared to other solutions such as simply insulating homes better and air and ground source heat pumps. Again, with heat pumps, this is a technology that is new and improving. But it is still far too expensive to roll out on a mass scale. The question is when it will become viable to replace the twenty millon domestic gas boilers in the UK that currently provide hot water and central heating in this cool climate. Reduce the demand and you reduce the size of the problem. Use a technology that does not rely on burning gas for small scale heating and you reduce carbon emissions required.

The problem is that there is now a urgent political imperative to come up with a solution that addresses climate change by reducing CO2 and aside from progress in renewable electricity generation, the technical solutions storage and distribution are not looking very compelling. Hydrogen generation is just one of several grid scale technologies that might become viable. It will be easier to make it work for large scale industrial energy users, but that is not going to grab many headlines.

Energy policies have a lot of history and there have been some big, expensive mistakes in the past. The UK bet big on AGR Nuclear (ouch!), then the Dash for Gas from the NorthSea. Now Renewables and Inter-connects.

Next: Carbon Capture and Hydrogen for grid storage and distribution… I am not so sure.

Vehicle to Grid might be easier if everyone ends up with a ton of battery tech sitting in their driveway.

However, let not these mere technical considerations detract from the politics.

60

Some hydrogen hubs will rely on natural gas plus carbon capture and storage to produce hydrogen—the so-called blue hydrogen. The grants will also benefit large oil and gas producers that are partners in the hydrogen hubs in the Appalachia region and in the Gulf Coast in Texas.

ExxonMobil, Chevron, and EQT Corporation will be among the beneficiaries, and the climate justice warriors are having none of it.