This special interest group is for professionals to connect and discuss all types of carbon-free power alternatives, including nuclear, renewable, tidal and more.

Post

Green hydrogen and unicorns

image credit: credit: iStock

Question: what do green hydrogen and unicorns have in common?

Answer: they are both mythical.

Well, OK. Not entirely. Green hydrogen, as defined by proponents, does have at least the theoretical potential to be a real thing. Unicorns (as in magical creatures, not high-valued private startups), not so much.

The thing is, nearly all the hydrogen that’s currently labelled as “green”, isn’t. It’s a dark olive drab, shading toward black. AKA dirty.

Don’t get me wrong, I’m not dissing the concept of green hydrogen. Electrolytic hydrogen produced using electricity from resources with zero atmospheric carbon emissions would be great! Stored fuel to replace natural gas for generating power on demand; chemical reducing agent to replace coked coal in steel production; chemical feedstock to produce clean ammonia for fertilizer and long term energy storage, … the list goes on.

Your access to Member Features is limited.

Please or apply for membership to continue reading this post.

Unfortunately, the conditions required to produce truly green hydrogen are currently rare. It wouldn’t be far wrong to say nonexistent. Nor is that situation likely to change anytime soon.

To be truly green, it’s not sufficient for electrolytic hydrogen to be produced using electricity from zero-emissions energy resources. It must be electricity that would otherwise be wasted. If there is any competing use for the electricity consumed by electrolytic hydrogen production, then the hydrogen produced takes on the footprint of the added generation needed to satisfy the competing use. 

That may sound contrived, but it’s not. It’s basic accounting. Say a given amount of clean energy is available; it can be used to produce some amount of hydrogen, or it can be used to satisfy a competing demand. Option A: use it for the competing demand instead of producing hydrogen. Option B: use it to produce hydrogen, leaving the competing demand to find its supply elsewhere. Choosing option B requires a marginal increase in generation somewhere on the grid. Marginal increases in generation almost always translate to increased output from fossil-fueled power plants.

Unless they’re in curtailment, wind and solar resources have no ability to increase output on demand. But if they’re in curtailment, there’s presumably no competing use for the electricity that electrolysis would be using. The conditions for truly green hydrogen production would be satisfied.

More often, renewables will already be delivering everything their nameplate capacity and current weather conditions allow. Any marginal increase in supply to the grid will have to come from elsewhere. “Elsewhere” is at present almost always a fossil-fueled power plant. Hence, option B incurs the carbon footprint of fossil-fueled generation in an amount matching the electricity consumed for hydrogen production.

In the best case, the power plant would be a natural gas combined cycle plant with a net thermal efficiency of 60%. It would then take 5.4 kg of natural gas to produce the 50 kWh of electricity for one kg of electrolytic hydrogen. The carbon footprint would be 14.8 kg CO2. In the worst case, the plant would be coal-fired, net thermal efficiency 40%. Then it would take ~13.7 kg of coal for the electricity to make one kg of hydrogen. The footprint would be 50 kg of CO2 per kg H2.

By comparison, it only takes ~2.86 kg of natural gas to produce one kg of H2 by conventional steam methane reforming (no CCS). The carbon footprint would be 7.86 kg CO2. Clearly, there’s a stiff penalty for violating the “no competing use” condition for green hydrogen production.

Why did I say earlier that the situation for production of green hydrogen won’t be changing any time soon? It’s because the cost for grid-scale battery storage is dropping. Installed capacity will be increasing rapidly, and charging all that capacity will be a higher-value competing use for otherwise excess wind and solar production. That situation will hold for at least the next decade.

I conclude that if you’re expecting to see (truly) green hydrogen taking off in a big way anytime soon, you might think about taking up unicorn spotting. I think you’ll have a better chance of success.
 

Roger Arnold's picture
Thank Roger for the Post!
Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.
More posts from this member

Discussions

Spell checking: Press the CTRL or COMMAND key then click on the underlined misspelled word.
Bob Meinetz's picture
Bob Meinetz on Feb 27, 2021

"I conclude that if you’re expecting to see (truly) green hydrogen taking off in a big way anytime soon, you might think about taking up unicorn spotting. I think you’ll have a better chance of success."

There used to be a feature of online discussion boards called the "kick": when someone commented on a thread, it would "kick" the topic back to the top of the list of threads on the board's homepage. That way, contributors would be constantly exposed to the topics of most interest to all. If a topic wasn't that interesting, it would be off the homepage in a matter of minutes (all new topics started at the top of the homepage).

The most interesting topics would get a disproportionately large share of attention (or contention), even to the point where moderators had to close it (I recall one thread that had over 700 responses).
Occasionally commenters would reply with just the word "kick" to move the thread back to the top of the homepage so more people would see it - an obvious technique that was permitted. When it was abused, moderators would occasionally have to step in and delete multiple kicks.

No thread on EnergyCentral this morning deserves to be kicked more than this from Roger Arnold. His threads and comments typically present cogent perspective, backed by analysis. Not hype, but facts. I would kick it if I could - I really have nothing to add to it - but typically (and unfortunately) for EnergyCentral, threads like this quickly move off the homepage and don't get the attention they deserve, buried by advertising for contributors' special interests.

Maybe Audra and Matt would consider instituting the kick, or even a side column named "Today's Top Topics", with titles linked to the threads which have most recently received a comment?
 

Matt Chester's picture
Matt Chester on Mar 1, 2021

If there is any competing use for the electricity consumed by electrolytic hydrogen production, then the hydrogen produced takes on the footprint of the added generation needed to satisfy the competing use. 

 

Interesting way to frame it, Roger. Definitely helpful in accounting to draw hard lines like this. Would taking this thinking a step further then suggest that there can be no such thing as green hydrogen unless the grid is already decarbonized completely? What about on-site use of hydrogen that's produced in industrial facilities? 

Appreciate the thought experiment! 

Roger Arnold's picture
Roger Arnold on Mar 1, 2021

When one is aiming to understand the consequences of available options, the rule is that you have to consider the system as whole -- to the extent possible -- and the full suite of consequences -- as far as you're able to determine them. But real world systems are always complex, and no analysis of a complex system is going to be perfect.

Plus, if one wants to communicate the results of an analysis to the general community, shortcuts and simplifications are unavoidable. E.g., that phrase "no competing uses". What exactly did I mean by that? 

To answer your question, Matt, no, it would be going too far to say that there can be no such thing as green hydrogen unless the grid is already decarbonized completely. In regions heavily supplied with variable renewables, there will be intervals when there is a temporary surplus of RE. The wholesale price of electricity in those intervals will be zero or negative. Any electrolytic hydrogen produced in those intervals will be truly green. But until the grid has gotten pretty close to being completely decarbonized, those intervals will be too short and infrequent to support electrolytic production of hydrogen at scale. 

It is possible to produce green hydrogen from dedicated renewables at installations too remote for connection to the grid. On an island in the ocean, say, or the middle of the Sahara. But if the dedicated resources being used could reasonably have been connected to the grid, withholding that connection in order to produce hydrogen will result in higher consumption of fossil fuels and higher carbon emissions than if the resources had been connected. The hydrogen produced may be sold as green, but it will be false labeling. 

Matt Chester's picture
Matt Chester on Mar 1, 2021

Appreciate the thoughtful reply and the food for thought, Roger!

Get Published - Build a Following

The Energy Central Power Industry Network is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »