Monash study on solar-driven electrolysis for green hydrogen production cautions on life-cycle emissions and EROI
23 August 2021
Researchers at Monash University in Australia have conducted a lifecycle analysis and net energy analysis (LCA/NEA) of a hypothetical large-scale solar-electrolysis plant for the production of green hydrogen. The open-access paper on the study is published in the RSC journal Energy & Environmental Science.
Process flow diagram and construction phase boundary. Palmer et al.
An important consideration of solar-electrolysis in the context of climate mitigation is the enormity of upscaling required—both at the global scale with respect to the investment, land area, materials, and embodied energy; and at the project scale with respect to the potential localised impacts of gigawatt scale plants. According to the IEA, less than 0.1% of hydrogen is currently produced via water electrolysis and only a fraction of this production is powered by renewable energy.
Taking IRENA’s REmap scenario as a reference, renewable hydrogen could deliver 5% of total final energy demand in 2050. Assuming that a half of this demand is met by solar-electrolysis, 3,100 GW of solar would need to be dedicated to hydrogen production in 2050, or around four-times the current world solar PV installed capacity (based on the current world capacity factor for solar PV of 14%). These projections would imply that perhaps hundreds of gigawatt-scale plants will need to be in operation by 2050. Targets for hydrogen demand beyond 2050 are much greater.
Along with hydrogen production and use, an energy transition will involve the synchronous upscaling of renewable electricity, batteries, and energy use technologies. The materials and metals demanded by a low-carbon economy are projected to be immense and create challenges along the full supply pathway. Some of the most critical materials include cobalt, lithium, nickel, indium, silver, and tellurium. For hydrogen, the platinum group metals used in PEM electrolysers and fuel cells are critical. There is no immediate concern for copper resources, but the average ore grade is declining as higher grade deposits become exhausted.
Energy extraction and processing costs increase super-linearly with declining ore grade, and therefore will tend to worsen EROI. In light of the sheer scale of the hydrogen challenge, several questions demand close consideration. For instance, what will the costs be for water electrolysis powered by solar PV, in energy and material terms; what are the trade-offs between hydrogen and electric transition pathways; and how will energetic, financial, social and other constraints determine or shape future hydrogen production pathways?
—Palmer et al.
They calculated hydrogen production as the ratio of annual solar farm electricity output (minus transmission losses =and balance-of-plant loads), and electrolyzer efficiency. Solar farm electricity generation was determined using average global horizontal irradiance (GHI) for Learmonth, Western Australia of 2,200 kWh m-2 yr-1. They assumed electrolyzer efficiency of 55 kWh kg-1 H2, with sensitivity of 50 and 60 kWh kg-1 H2.
They ran two baseline scenarios:
The solar-battery scenario assumed that on-site battery storage powers standby operation with no grid connection, and depending on electrolyzer turndown, maintains minimum electrolyzer operation during periods of low solar electricity.
The solar-grid scenario assumed that the hydrogen site is connected to the regional grid—the North West Interconnected System (NWIS) of Western Australia. The grid connection enables grid imports to support load balancing of variable solar supply; and grid exports during surplus solar generation (i.e. solar generation exceeding electrolyzer capacity). The NWIS comprises mostly gas-fired generation and has a GHG emission factor of 620 g CO2-e kWh-1. This is higher than the global average of 510 g CO2-e kWh-1.
Key results from the study were:
For both baseline scenarios, the GHG emission intensity is around a quarter that of H2 produced from SMR. However, under reasonably anticipated conditions with grid buffering, the GHG emissions may be comparable to SMR.
For both baseline scenarios, the EROI is less than comparable estimates for fossil fuels, and under some conditions, much less.
For the solar-battery scenario, the solar modules were the most significant component that influenced EROI and GHG emissions.
For the solar-grid scenario, the solar modules were important for EROI, but grid emissions were equally important for GHG emissions.
Electrolyzer turndown is a key sensitivity. The baseline turndown was set at 95%, but at 80 to 90% turndown, the EROI and GHG are adversely impacted. For the solar-battery configuration, a lower turndown (higher minimum electrolyzer load) may be infeasible due to impractically large battery capacity.
The emissions factor of electricity for the solar module supply chain is a critical sensitivity. Production in a lower emission region would significantly decrease the GHG emission intensity.
Operational lifetime is important for both EROI and GHG intensity. Early decommissioning due to obsolescence, accelerated degradation, or premature failure would worsen both metrics.
We found that EROI was lower than the reference EROI for fossil fuels under baseline scenarios, and under some 20 conditions with multiple sensitivities, much lower. Ongoing efficiency improvements in solar module manufacturing will drive improvements in EROI, while resource constraints will worsen EROI.
Further work needs to be undertaken to ascertain turndown and ramp rates of electrolysers and post-electrolysis processes at scale, the impact on control, safety, degradation and performance, and integration with hydrogen liquefaction or ammonia plants. Design for sustainability implies that life cycle parameters need to be treated as objective functions in plant optimisation. We recommend that LCA and NEA are integrated with project planning to inform decision making to ensure that hydrogen meets the goals of sustainable production.
—Palmer et al.
Resources
Graham Palmer, Ashl (2021) ey Roberts, Andrew Hoadley, Roger Dargaville and Damon Honner “Life-cycle greenhouse gas emissions and net energy assessment of large-scale hydrogen production via electrolysis and solar PV” Energy Environ. Sci., doi: 10.1039/D1EE01288F
They certainly knew the results they wanted to show, and went all out to get them.
14% solar capacity based on world averages?
That would include every rooftop installation in sunny old Hamburg and so on.
Funnily enough, the mass production of hydrogen will be from ground based arrays where it is exceptionally sunny.
Knock that up to 20% as a realistic figure, which is an error of a third right there.
55KWh/kg of hydrogen?
No progress from worst current day practice there, then
We can hit 48KWh/kg right now, and there are other alternatives aside from electrolysis.
There are other electrolysis methods available which do not use PEM and precious metals.
GIGO
Posted by: Davemart | 23 August 2021 at 06:48 AM
Here are the capacity factors for utility solar in the US monthly:
https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_6_07_b
As can be seen, the lowest in any month was in a January at 15.2% and the highest 32.9%.
Most solar arrays for hydrogen are to be installed in far more consistently sunny areas than the continental US, yet somehow these guys manage to magic up an average figure of 14%
Agenda, much?
Posted by: Davemart | 23 August 2021 at 07:17 AM
I think they key number is Electrolyzer turndown which they are setting at 95%.
Thus, if there is no sun, you still have to run the system at 5%, so you need a grid connection or batteries - or wind which they do not seem to mention.
Why does this have to be as high as 5% - could you not make systems that can be idled to 0% or 0.5% ?
In that case, you don't need any of anyone else's electricity or any storage.
My view is that H2 should be the use of last resort for renewables, rather than the main purpose.
You should set things up so that you can use as much as possible and turn the excess into H2.
And don't try to get to zero carbon or you will end up like New Zealand trying to keep it at zero Covid - if you allow a reasonable amount of carbon (i.e. use gas for load balancing and kerosene or jetA for aircraft), it all goes into the "possible" basket from the "crazy" basket.
Posted by: mahonj | 23 August 2021 at 07:57 AM
Note also their talk of horizontal irradiance, ie they are assuming that you can't even set fixed panels are the best angle for the latitude, let alone move them.
Of course, motors might be too expensive and not worth the bother, but the increase for angled panels is much smaller, and in any case this paper is about efficiencies, not economics, and they have simply picked the most lousy figures they could dig up.
Its a hatchet job, and a poor one.
Posted by: Davemart | 23 August 2021 at 09:01 AM
Cost of H2 production is the central issue. If it cannot be made cheaply, it can not be competitive.
In related news:
“Hydrogen lobbyist quits, slams oil companies’ “false claims” about blue hydrogen”
Chris Jackson stepped down this week as chair of the UK Hydrogen and Fuel Cell Association. Jackson, who founded a green hydrogen company two years ago, was head of the industry group for a little over a year. “The energy transition cannot be achieved by one silver bullet, and green hydrogen alone cannot solve all the world’s challenges,” he wrote in a LinkedIn post announcing his resignation. “But while there might not be a single ‘right’ answer, there are answers that are wrong.”
Jackson continues by saying that blue hydrogen is “at best an expensive distraction, and at worst a lock-in for continued fossil fuel use” which would derail goals that the country and the world have set for decarbonizing the economy. He takes particular issue with the fact that oil and gas companies have asked the UK government for decades of subsidies while also claiming that blue hydrogen will be inexpensive to produce. “If the false claims made by oil companies about the cost of blue hydrogen were true, their projects would make a profit by 2030,” he told The Guardian.
“Instead, they’re asking taxpayers for billions in subsidies for the next 25 years. They should tell the government they don’t need it. The fact that they don’t tells you everything you need to know.”
https://arstechnica.com/tech-policy/2021/08/ex-lobbyist-slams-blue-hydrogen-says-it-would-lock-in-fossil-fuel-dependence/
Posted by: electric-car-insider.com | 23 August 2021 at 09:04 AM
Beginning to figure out why I've been calling it "hypedrogen"?
Posted by: Engineer-Poet | 23 August 2021 at 09:34 AM
@electric car insider:
What has any of that got to do with that the 'study' is plainly claptrap with tendentious and selective figures?
The same goes for EP's comment
you surely can't maintain that these figures are in any way sensible.
Posted by: Davemart | 23 August 2021 at 10:05 AM
@EP:
With the use of hydrogen as coolant for turbines the nuclear industry is already meshed to some degree with hydrogen.
Initial moves are now being made to ingrate hydrogen production:
https://www.greencarcongress.com/2021/08/20210816-nel.html
This has the potential to be transformative for the nuclear industry, as it represents a market for otherwise surplus power so increasing the profitable hours per year.
Posted by: Davemart | 23 August 2021 at 10:34 AM
Oh, I've been talking up dump loads for years and years. Electrolysis is not high on my list; we have a host of better things to do with off-peak electric power. Plasma gasification of sewage sludge and MSW should be looked at much more seriously, because getting rid of both a waste problem and a methane source if landfilled ought to push them towards the top priorities.
Posted by: Engineer-Poet | 23 August 2021 at 12:04 PM
Ray Charles could have seen this coming
Posted by: dursun | 23 August 2021 at 04:39 PM
I always appreciate the links you post, Davemart.
I’m not in a position to argue whether the OP’s estimation of capacity factor is fair or too pessimistic.
I think it is fair to point out that the promised “cheap H2” has not materialized, is not on the same downslope as batteries and solar, and that the H2 subsidies requested are enormous.
I don’t believe that lithium is “the” answer, but millions of parked cars could be a viable virtual power plant for peak shifting and that could get us a long way to where we need to go with intermittent renewables that have already proven to be economically competitive.
I believe that Ambri or another cheap scalable stationary battery chemistry (e.g. iron) is more likely to hit the necessary price point than solar+electrolyzer.
I’d be delighted if stationary H2 became cost competitive as storage. I just don’t see it beating the competition without market distortions.
Posted by: electric-car-insider.com | 23 August 2021 at 10:40 PM
@electric car insider
' I’m not in a position to argue whether the OP’s estimation of capacity factor is fair or too pessimistic. '
Unless you are entirely unable to understand what is plainly stated, then of course you are.
You just don't want to admit it.
' I think it is fair to point out that the promised “cheap H2” has not materialized, is not on the same downslope as batteries and solar, and that the H2 subsidies requested are enormous. '
Promised by whom, for what, and in what time frame?
Stop inventing straw men.
' I don’t believe that lithium is “the” answer, but millions of parked cars could be a viable virtual power plant for peak shifting'
Batteries are fine for peak shifting, but do nothing at all to address the things that hydrogen is essential for.
There is much justified criticism of AGW deniers.
But greenies get strangely selective in their interpretation of what bodies like the IPCC reckon we have to do to keep AGW within bounds.
To keep things within copable boundaries not only hydrogen in huge volume from renewables, but sequestration and nuclear are integral.
' I believe that Ambri or another cheap scalable stationary battery chemistry (e.g. iron) is more likely to hit the necessary price point than solar+electrolyzer.'
You really love to develop 'beliefs' with little or no research.
Unfortunately for batteries, what is not stated in the press releases and often in the accompanying technical data, if they don't hide that entirely on the grounds of 'commercial confidentiality' so trying to sell a complete pig in a poke, are what the problem areas are whilst they big up the advantages.
I had a look into the iron batteries which are the current hype project.
They talk about storage for days, not months.
Why?
Because they leak energy, and would not have any energy left for long term,
The round trip efficiency is pretty ropy too.
They are cheap and should be fine for realistic applications of shifting load for a few days, although at high energy loss, certainly compared to lithium ion batteries.
For long term storage hydrogen and other chemicals are what is needed.
I would suggest you put your 'beliefs' on hold and actually find out something about the various technologies.
Posted by: Davemart | 24 August 2021 at 03:32 AM
Davemart, your ad hominem attacks simply detract from your arguments.
I agree we need better baseline generation and long term storage solutions that account for seasonal variation of solar and wind. Whether H2 can compete is unproven, and the asked for subsidies undercut the argument that they can.
For transportation, H2 is a shimmering mirage. It has never been competitive, and with Li-metal at 400-500 wH/kg today, and 1kWh/kg on the horizon, the argument for H2 as a fuel for anything on the road collapses.
Maybe there is an application for ocean transport, although I expect a renewable liquid fuel to be more practical there.
You’ve been championing H2 on these pages for a decade. I’m glad you do, otherwise there would be no debate at all and it would be quiet and boring with everyone else agreeing that H2 in transportation is a fuel’s errand.
There are some in industry still making those investments, so there still an active competition. But the sales numbers tell the score.
Posted by: electric-car-insider.com | 24 August 2021 at 09:06 AM
electric car insider:
You complain of ad hominem. but expect some level of respect for your judgement and honesty when you refuse to acknowledge that arguments make no sense, as they are beyond your powers of judgement
Get honest with yourself.
' I expect a renewable liquid fuel to be more practical there.'
!! which is usually renewable hydrogen plus whatever.
You have absolutely no idea about the technologies you pontificate on.
That is because you have 'beliefs' just like any other idealogue.
Posted by: Davemart | 24 August 2021 at 04:29 PM
Go ahead and be as nasty as you need to be to completely discredit yourself, Davemart.
Posted by: electric-car-insider.com | 24 August 2021 at 06:08 PM
MEEE-OW!
Posted by: Engineer-Poet | 24 August 2021 at 06:29 PM
“Enel chief executive Francesco Starace recently told Recharge, each kilogram of green hydrogen requires about 50kWh of electricity. “That’s about 500TWh of energy just to displace the existing grey hydrogen,” he said. “So can we then afford to lose money and time to dream about hydrogen being used to cook meals or drive cars? No, that’s stupid. It will not happen.”
He added that one kilogram of hydrogen — produced from 50kWh — would enable a fuel-cell car to travel 80-90km. “Now I take the 50kWh and I put them in an electric car, that car would drive 250km. It’s even worse with heating.
“So why should I do this stupid thing and put this stuff into hydrogen just because someone wants to use some [gas] pipes to move it? Forget it.”
- Recharge
Posted by: electric-car-insider.com | 26 August 2021 at 08:08 AM
Common sense like that is a rare and precious thing these days. Romantic nonsense reigns almost unchecked.
Hypedrogen has always been the stalking horse of the fossil fuel interests. It's much cheaper to make it from natural gas or even coal than from "renewable energy", and once it's in the system nobody can tell the difference. Emissions-free nuclear energy is most easily used to make electricity, which fits very well with EVs. The dichotomy between the two choices is stark, and it's obvious which one is the right one.
Posted by: Engineer-Poet | 26 August 2021 at 11:55 AM