Energy Markets and Net Zero

[Mr Poppy]

Nov 1, 2022 20:22:16 GMT Mr Poppy said:

Nov 1, 2022 19:19:11 GMT leftieliberal said:

euanmearns.com/green-mythology-tidal-base-load-power-in-the-uk/ as a good place to start and then go to the academic research.

Thank you for the link (a repost I think?). From the link:

"10 GW*6 hours*0.4 = 24 GWh storage to fill the troughs and roughly half this amount if we use the peaks to fill the troughs.

12 GWh of storage turns out to not be an absurd amount"

That is not necessarily the optimal solution but I'd point out two things:

Quick follow up to explain why "That (ie 12GWh of short-term storage for 10GW of tidal lagoon capacity) is not necessarily the optimal solution"

The 'overall optimum' solution for the entire grid (incl interconnectors) will have a lot of 'sub-optimal' solutions for each of the component parts.

We see this already when there is 'too much' wind, or need to use 'peaking plants' to meet high demand, or the switching off of some nuclear plants for periods during the Summer - all those component parts are being used 'sub-optimally' at an individual level but that creates the overall optimal solution for the grid. In addition and related to the importance of the 'local' issue are 'constraint payments'*

Tidal lagoons + short-term storage can provide 'base load' but it doesn't have to be a 100% optimal use of the tide as that creates problems elsewhere (eg a lack of the required GWh of short-term storage)

Note some of the other Green 'base load' options have a bit of flex (ie their supply is adjusted during the day, depending on overall supply-demand). Bioenergy can certainly be flexed and even new nuclear can be flexed a bit. We will also very likely to be able to use Hydrogen for 'peaking plants' to help fill in the 'troughs' of the tidal supply. For the 'peaks' then sometimes, some of that potential (pun intended) energy will not be used to generate. Also interconnectors of course, although I personally wouldn't put too much emphasis in those and would highlight that for the periods when we have excess tidal generation then we'd already have a lot of excess wind generation and have filled up all available short-term storage. All those issues with relevant links to the tech are somewhere on this thread but I can repost if required.  

Note I'm specifically only talking about Supply Side. Within NG's future scenarios (notably 'Consumer Transformation (CT)' and 'Leading the Way (LW)') they also expect some demand side flex.

So, with some flexing within other aspects of supply-demand and some sub-optimal generation from tidal lagoons then the actual short-term storage required, specifically for adding in 10GW of tidal lagoons to the mix, would be less than 12GWh (which isn't an absurd amount anyway).

Exactly how much less would depend on a lot of assumptions about the rest of the grid but those can be simulated using the realistic costs for each component part. We don't have to state the final outcome today - we just need a plan to start us moving faster in the right direction. Changing that plan as required, as we go.

NB I'm also not forgetting or ignoring the other issues WRT to environmental impact, etc. I'm just purely looking at the numbers and (IMO) Tidal Lagoons need to reconsidered.

* We want to minimise those but as they say: "Managing future constraints

As more onshore and offshore zero carbon generation connects to the system in the north and east of Britain, constraint costs (particularly for the movement of power from north to south) are likely to increase "

www.nationalgrideso.com/electricity-explained/how-do-we-balance-grid/what-are-constraints-payments

[leftieliberal]

Alternatives to air conditioners: theconversation.com/these-air-conditioner-alternatives-are-cheaper-and-better-for-the-planet-187193

[c-a-r-f-r-e-w]

Nov 2, 2022 0:15:02 GMT lens said:

Nov 1, 2022 20:37:39 GMT c-a-r-f-r-e-w said:

Re: hydrogen, while storing energy as hydrogen gas H₂ (or liquifying it etc.) can have issues regarding storage requirements, leakage etc., you can also store the hydrogen in other forms with less onerous requirements, e.g. as ammonia or as hydrides.

For ammonia, it's extra complexity, and yet another stage of losing energy efficiency in a conversion process. And AFAIK you can't use ammonia directly as fuel in a fuel cell. (??) It's also pretty unpleasant stuff if it leaks.

For hydrides, they've been talked about for years (decades) and whilst they certainly exist, then come with a raft of problems of their own - typically needing a big temperature differential between absorption and release. They have certain specialist niches, but for mass storage - no. (Maybe someday - but don't hold your breath.)

Sure, but I didn’t suggest using ammonia in a fuel cell.* You can just burn it as fuel, which may not be as efficient as batteries, but useful in the case of shipping say, where your batteries or compressed air may not be very practical. (Also, while ammonia might be too unpleasant for consumer use it might be easier on some big container ship).

And I didn’t say hydrides had to be used for mass energy storage. But again, you may need different storage options for different use cases. Hydrides have been tested for use in submarines I think, and offer a form of compression that doesn’t need any moving parts. But anyway, they can provide a safer, easier way to store hydrogen for when you need it for all those non-energy uses. (Even if using it for energy uses when you can’t use batteries etc., you might at times prefer a hydride that has twice the density and doesn’t need compression or cooling like hydrogen gas or air).

* I think it’s possible you can use ammonia in a fuel cell, it’s just not very efficient yet.

Recent progress in ammonia fuel cells and their potential applications

pubs.rsc.org/en/content/articlelanding/2021/ta/d0ta08810b

“Herein, a comparative study based on the chosen design, working principles, advantages and disadvantages of direct ammonia fuel cells is summarised. This work aims to review the most recent advances in ammonia fuel cells and demonstrates how close this technology type is to integration with future applications. At present, several challenges such as material selection, NOx formation, CO2 tolerance, limited power densities and long term stability must still be overcome and are also addressed within the contents of this review.”

[c-a-r-f-r-e-w]

Nov 2, 2022 0:15:02 GMT lens said:

Nov 1, 2022 20:37:39 GMT c-a-r-f-r-e-w said:

Re: hydrogen, while storing energy as hydrogen gas H₂ (or liquifying it etc.) can have issues regarding storage requirements, leakage etc., you can also store the hydrogen in other forms with less onerous requirements, e.g. as ammonia or as hydrides.

Hydrogen really is not a very good way of storing energy. Much of the support in it's favour has come in the past from oil and gas companies who see it as a way of keeping core businesses alive (production from fossil fuels by reforming) whilst making out they now have green credentials. Even with carbon capture, gas production invariably leads to a certain level of methane leakage from the wells - and methane contributes to climate change worse kg for kg than CO2.

The same vested interests are very keen to greenwash by switching the dialogue to green hydrogen via electrolysis. Good in principle - but the first use of renewable electricity should be to displace "dirty" electricity from the grid at time of use, secondly to store in a more efficient form (such as a grid battery), and if any is left to run electrolysis, then that hydrogen should be used in the chemical industry where millions of tonnes (of dirty hydrogen) are currently used annually.

If you compare hydrogen with batteries, then sure, batteries are more efficient. But how long will it be until we can produce enough batteries for all requirements? Whether it’s having enough factories or indeed enough resources for the batteries.* Even for the grid, as we quickly ramp up renewables... if we can’t get enough batteries cheaply enough, we might prefer an inefficient alternative instead of just throwing the surplus energy away because we can’t get the batteries.

if we can’t get enough grid batteries quickly enough then we need to consider alternatives. If we compare hydrogen to your other suggestion, compressed air, then hydrogen can work out quite good, because you can keep the electrolysers running to make hydrogen for other uses when you don’t need them to deal with shortfalls in the grid.

(Came across a study a while back that suggested compressed air wins out over hydrogen short-term, but longer-term hydrogen wins out. I’ll post the link if I can find it).


With carbon capture, then as I indicated earlier, I am more interested in using it to extract existing carbon from the air, than I am in using it to burn more fossil fuels with the associated methane release.

* There is also the issue of energy security: if key resources for batteries get hoovered up, or there’s some crisis as with gas now, might be wise to have an alternative, 

[c-a-r-f-r-e-w]

Oct 26, 2022 12:56:30 GMT lens said:

Oct 25, 2022 14:55:09 GMT Mr Poppy said:

lens Let's agree to disagree on the broader opportunities for hydrogen and in case it wasn't clear with my mention of the Sinclair C5 then happy to agree that Riversimple have a sh!t product (I did clearly state that might as well use regenerative braking to charge a (relatively) small battery). We're probably a lot closer to agreeing on the bigger issues than it seems.

Oct 22, 2022 16:32:37 GMT Mr Poppy said:

9You didn't respond to the options of what to do once we'd fully charged grid batteries (add in pumped hydro and those with BEVs) and the market price for electricity exports was negative (see below options for a reminder)

Get into the surplus peak situation you describe and for energy storage it makes more sense to go with more liquid air/CO2 or compressed air storage, than more electrolysis if the latter is to spend most of its time idle. (The former, as with batteries, can go back to electricity much more easily and efficiently than with hydrogen - fuel cells are not an option for grid scale generation.)

No, you can keep them running. Posted on the old board I think about how Hydrogen demand is predicted to rise substantially. It’s used for fertiliser, electronics, rocket fuel etc.

So when you don’t need electrolysers to make hydrogen for the grid, you can then use them to make hydrogen for other purposes.

We may also use hydrogen to make synthetic biofuels for aircraft. It’s useful to try and consider all use cases, and issues with batteries, not just hydrogen, to get a fuller picture.

[Mr Poppy]

c-a-r-f-r-e-w Just a quick reminder of some other stuff posted back on the ol' UKPR

1. For massive (XXX or even XX TWh), long-term storage of hydrogen then repurpose existing nat.gas storage where possible (eg the plan for Rough and elsewhere in UK+rWorld) and make use of salt caverns (UK has massive capacity for that)

2. Hydrogen can be used for 'peaking plants' (direct replacement for nat.gas, see previous link for Briggs plant). Where possible we want to repurpose existing plants and infrastructure as that reduces the capital cost and hence makes them a/ more likely to happen, b/ happen quicker (if the 'will' to do so via sufficient 'carrot+sticks' is there). There is also 'embodied carbon' in the construction of new stuff and other environmental issues to consider (eg the lithium mining process, the challenge of getting approval for tidal lagoons and pumped/flexible hydro, etc)

3. Strategic reserve (and other reserves held in the supply chain). UK+rWorld holds stores of oil as well as gas for either strategic purposes and/or due to the risks of a pure JIT approach (we saw in the 'panic buying' crisis a while back how that can play out). With the unreliable and unpredictable nature of stuff like wind then we will likely need a larger TWh of 'reserve' in the future than we have now. IIRC I put that at 20TWh (minimum).

Of course if people put up their own numbers, or want to use NG's numbers (posted multiple times) and adjust (eg knock off say 50TWh of demand in the 2050 scenarios as in the future we will have a lot less people needing/using cars) then they can and should do so. Pretty simple to state your assumptions and show your numbers I'd have thought, non?

[c-a-r-f-r-e-w]

Nov 3, 2022 16:29:05 GMT Mr Poppy said:

c-a-r-f-r-e-w Just a quick reminder of some other stuff posted back on the ol' UKPR

1. For massive (XXX or even XX TWh), long-term storage of hydrogen then repurpose existing nat.gas storage where possible (eg the plan for Rough and elsewhere in UK+rWorld) and make use of salt caverns (UK has massive capacity for that)

2. Hydrogen can be used for 'peaking plants' (direct replacement for nat.gas, see previous link for Briggs plant). Where possible we want to repurpose existing plants and infrastructure as that reduces the capital cost and hence makes them a/ more likely to happen, b/ happen quicker (if the 'will' to do so via sufficient 'carrot+sticks' is there). There is also 'embodied carbon' in the construction of new stuff and other environmental issues to consider (eg the lithium mining process, the challenge of getting approval for tidal lagoons and pumped/flexible hydro, etc)

3. Strategic reserve (and other reserves held in the supply chain). UK+rWorld holds stores of oil as well as gas for either strategic purposes and/or due to the risks of a pure JIT approach (we saw in the 'panic buying' crisis a while back how that can play out). With the unreliable and unpredictable nature of stuff like wind then we will likely need a larger TWh of 'reserve' in the future than we have now. IIRC I put that at 20TWh (minimum).

Yes, we did cover quite a bit about it on the old board, considering relative inefficiencies, future hydrogen economy etc. IIRC (though I don’t recall talking about stuff like ammonia?) and good point about the strategic reserve. 

We can usually consider more stuff: I think a comparison of hydrogen vs compressed air is useful, here’s the study I mentioned earlier to lens

www.sciencedirect.com/science/article/abs/pii/S2352152X16301712

“In terms of long-term storage compressed air storage is the most favorable storage technology today, followed by hydrogen storage. For 2030, hydrogen storage technologies significantly reduce their LEC. This changes the picture dramatically for deployment as long-term storage. In this case, in 2030 for all storage-discharge paths hydrogen storage is clearly the most favorable technology.“

[lens]

Nov 3, 2022 16:09:44 GMT c-a-r-f-r-e-w said:

Oct 26, 2022 12:56:30 GMT lens said:

Get into the surplus peak situation you describe and for energy storage it makes more sense to go with more liquid air/CO2 or compressed air storage, than more electrolysis if the latter is to spend most of its time idle. (The former, as with batteries, can go back to electricity much more easily and efficiently than with hydrogen - fuel cells are not an option for grid scale generation.)

No, you can keep them running. Posted on the old board I think about how Hydrogen demand is predicted to rise substantially. It’s used for fertiliser, electronics, rocket fuel etc.

So when you don’t need electrolysers to make hydrogen for the grid, you can then use them to make hydrogen for other purposes.

Yes, you can keep electrolysis plant running - but then it's not using these peaks of generation! It just becomes part of base load. You can't have cake (using only peak generation) and eat it (keep the plant running). That's the whole point.

And yes - I'm all for electrolysis to make hydrogen for "other purposes" (eg chemical industry) where HUGE quantities are currently used. But what on earth would be the point of using green hydrogen to generate grid electricity when it means you have to make more "dirty" hydrogen to compensate for the former not being able to be used in the chemical industry!?

[c-a-r-f-r-e-w]

More on ammonia…

You can also use reverse fuel cells for making ammonia, it can be a greener way than using the traditional Haber-Bosch process. Aussies seem quite keen on developing it:

www.science.org/content/article/ammonia-renewable-fuel-made-sun-air-and-water-could-power-globe-without-carbon)

“Other projects are following suit. The state of South Australia announced plans in February to build a AU$180 million ammonia plant, again relying on electrolyzers powered by renewable energy. Slated to open in 2020, the plant would be a regional source of fertilizer and liquid ammonia, which can be burned in a turbine or run through a fuel cell to make electricity. The supply of liquid energy will help stabilize the grid in South Australia, which suffered a debilitating blackout in 2016.”


Also, you might use ammonia as a means of transporting hydrogen, getting the hydrogen back out of it later.

“Converting hydrogen into ammonia only to convert it back again might seem strange. But hydrogen is hard to ship: It has to be liquefied by chilling it to temperatures below −253°C, using up a third of its energy content. Ammonia, by contrast, liquefies at −10°C under a bit of pressure. The energy penalty of converting the hydrogen to ammonia and back is roughly the same as chilling hydrogen, Dolan says—and because far more infrastructure already exists for handling and transporting ammonia, he says, ammonia is the safer bet.

That last step—stripping hydrogen off ammonia molecules—is what Dolan and his colleagues are working on. In a cavernous metal warehouse on the CSIRO campus that has long been used to study coal combustion, two of Dolan's colleagues are assembling a 2-meter-tall reactor that is dwarfed by a nearby coal reactor. When switched on, the reactor will "crack" ammonia into its two constituents: H2, to be gathered up for sale, and N2, to waft back into the air.””

[c-a-r-f-r-e-w]

Nov 3, 2022 18:19:57 GMT lens said:

Nov 3, 2022 16:09:44 GMT c-a-r-f-r-e-w said:

No, you can keep them running. Posted on the old board I think about how Hydrogen demand is predicted to rise substantially. It’s used for fertiliser, electronics, rocket fuel etc.

So when you don’t need electrolysers to make hydrogen for the grid, you can then use them to make hydrogen for other purposes.

Yes, you can keep electrolysis plant running - but then it's not using these peaks of generation! It just becomes part of base load. You can't have cake (using only peak generation) and eat it (keep the plant running). That's the whole point.

As long as you have surplus leccy that doesn’t need to go into the grid, you can use it to keep the electrolyser running to produce hydrogen. As we keep adding renewable capacity quickly, we will have more surplus leccy. And we can use that to produce hydrogen, some of which can be saved and burned to make leccy for when the grid needs extra, and the rest for hydrogen for other uses. Adding more surplus leccy makes using electrolysers more economical as you can run them for more of the time. (Which may be part of why in the study I linked electrolysers become more economical than compressed air in the future).

[c-a-r-f-r-e-w]

Nov 3, 2022 18:19:57 GMT lens said:

Nov 3, 2022 16:09:44 GMT c-a-r-f-r-e-w said:

No, you can keep them running. Posted on the old board I think about how Hydrogen demand is predicted to rise substantially. It’s used for fertiliser, electronics, rocket fuel etc.

So when you don’t need electrolysers to make hydrogen for the grid, you can then use them to make hydrogen for other purposes.

And yes - I'm all for electrolysis to make hydrogen for "other purposes" (eg chemical industry) where HUGE quantities are currently used. But what on earth would be the point of using green hydrogen to generate grid electricity when it means you have to make more "dirty" hydrogen to compensate for the former not being able to be used in the chemical industry!?

Well obviously if you want to green both the grid and the hydrogen industry using leccy then you need to keep adding renewable leccy so you can produce enough hydrogen for both. You might also eventually want more green leccy to make green hydrogen to make ammonia for shipping, and green hydrogen to make synthetic biofuels for long haul aircraft etc. etc.

[lens]

Nov 3, 2022 18:38:41 GMT c-a-r-f-r-e-w said:

Nov 3, 2022 18:19:57 GMT lens said:

Yes, you can keep electrolysis plant running - but then it's not using these peaks of generation! It just becomes part of base load. You can't have cake (using only peak generation) and eat it (keep the plant running). That's the whole point.

As long as you have surplus leccy that doesn’t need to go into the grid, you can use it to keep the electrolyser running to produce hydrogen. As we keep adding renewable capacity quickly, we will have more surplus leccy. And we can use that to produce hydrogen, ........

No! Because using "surplus electricity" means having electrolysis equipment standing by idle, ready for such periods of surplus.

Whilst "keeping the electrolyser running" must by definition mean using electricity that is not "surplus".

You can't have your cake and eat it, I don't know why it seems so difficult to get this across. You must EITHER have inefficient usage of plant (but use cheap electricity) OR good plant utilisation - but pay the going rate for the electricity. 

If you build more renewable capacity, ("to get more surplus leccy") - then why spend that capital to just increase a surplus!? It doesn't make economic sense. A different argument supposes that you build extra capacity dedicated to hydrogen production. Which is fair enough. But it's then not "surplus" - it's effectively base load. (So no longer "cheap surplus".)

But assuming you do down the route of dedicated generation to make hydrogen, what then? Surely it makes most sense to use that directly in industry, rather than burnt in a thermal generation plant? If you do the latter, you then need to steam reform more gas for the industrial use - why not more efficiently just that gas to directly produce the electricity, and use the green hydrogen industrially? A much more efficient route?

And if you argue for a level of renewable generation which provides for direct grid usage, hydrogen for industry, *AND* hydrogen for some electricity generation, then great in principle - but likely *DECADES* away, even at an enhanced rollout rate. And assuming we don't run out of suitable sites. The amount of "dirty" hydrogen currently used by industry is massive - let's worry about starting to replace that for now. And for years to come.

[c-a-r-f-r-e-w]

Nov 3, 2022 23:12:15 GMT lens said:

Nov 3, 2022 18:38:41 GMT c-a-r-f-r-e-w said:

As long as you have surplus leccy that doesn’t need to go into the grid, you can use it to keep the electrolyser running to produce hydrogen. As we keep adding renewable capacity quickly, we will have more surplus leccy. And we can use that to produce hydrogen, ........

No! Because using "surplus electricity" means having electrolysis equipment standing by idle, ready for such periods of surplus.

Whilst "keeping the electrolyser running" must by definition mean using electricity that is not "surplus".
.

By surplus, it means surplus to the grid requirements. As we keep adding renewable energy we can get to a situation where we much of the time we have more than we need for the grid, so we can keep the electrolysers running using what’s left over making hydrogen for other things.

[c-a-r-f-r-e-w]

Nov 3, 2022 23:12:15 GMT lens said:

Nov 3, 2022 18:38:41 GMT c-a-r-f-r-e-w said:

As long as you have surplus leccy that doesn’t need to go into the grid, you can use it to keep the electrolyser running to produce hydrogen. As we keep adding renewable capacity quickly, we will have more surplus leccy. And we can use that to produce hydrogen, ........

If you build more renewable capacity, ("to get more surplus leccy") - then why spend that capital to just increase a surplus!?

So you can make sure you always have enough leccy for the grid and can use what’s left over to take advantage of the hydrgien economy.

[c-a-r-f-r-e-w]

Nov 3, 2022 23:12:15 GMT lens said:

Nov 3, 2022 18:38:41 GMT c-a-r-f-r-e-w said:

As long as you have surplus leccy that doesn’t need to go into the grid, you can use it to keep the electrolyser running to produce hydrogen. As we keep adding renewable capacity quickly, we will have more surplus leccy. And we can use that to produce hydrogen, ........

But assuming you do down the route of dedicated generation to make hydrogen, what then? Surely it makes most sense to use that directly in industry, rather than burnt in a thermal generation plant? If you do the latter, you then need to steam reform more gas for the industrial use - why not more efficiently just that gas to directly produce the electricity, and use the green hydrogen industrially? A much more efficient route?
.

No, if you have enough green hydrogen you don’t have to steam reform it. Your argument keeps resting on the idea that we will have to make a choice. 

Anyway, it’s not necessarily a choice between using green hydrogen for one thing rather than another. If you don’t have enough batteries, then it’s a choice between throwing the energy away or having the green hydrogen to use for one of the two things. Under your scenario, we wouldn’t even have cake, never mind eating it.

[c-a-r-f-r-e-w]

Nov 3, 2022 23:12:15 GMT lens said:

Nov 3, 2022 18:38:41 GMT c-a-r-f-r-e-w said:

As long as you have surplus leccy that doesn’t need to go into the grid, you can use it to keep the electrolyser running to produce hydrogen. As we keep adding renewable capacity quickly, we will have more surplus leccy. And we can use that to produce hydrogen, ........

And if you argue for a level of renewable generation which provides for direct grid usage, hydrogen for industry, *AND* hydrogen for some electricity generation, then great in principle - but likely *DECADES* away, even at an enhanced rollout rate. And assuming we don't run out of suitable sites. The amount of "dirty" hydrogen currently used by industry is massive - let's worry about starting to replace that for now. And for years to come.

I already argued and cited some data to indicate that indeed, compressed air might work better in the near term. Whether it’s decades I don’t know: though the study says it swaps over around 2030. We are supposedly adding quite a lot of renewables but I won’t really believe it till it’s happening. These things can ramp up quite quickly though. 

[lens]

Nov 3, 2022 16:01:52 GMT c-a-r-f-r-e-w said:

Nov 2, 2022 0:15:02 GMT lens said:

Hydrogen really is not a very good way of storing energy. Much of the support in it's favour has come in the past from oil and gas companies who see it as a way of keeping core businesses alive (production from fossil fuels by reforming) whilst making out they now have green credentials. Even with carbon capture, gas production invariably leads to a certain level of methane leakage from the wells - and methane contributes to climate change worse kg for kg than CO2.

The same vested interests are very keen to greenwash by switching the dialogue to green hydrogen via electrolysis. Good in principle - but the first use of renewable electricity should be to displace "dirty" electricity from the grid at time of use, secondly to store in a more efficient form (such as a grid battery), and if any is left to run electrolysis, then that hydrogen should be used in the chemical industry where millions of tonnes (of dirty hydrogen) are currently used annually.

If you compare hydrogen with batteries, then sure, batteries are more efficient. But how long will it be until we can produce enough batteries for all requirements? Whether it’s having enough factories or indeed enough resources for the batteries.* Even for the grid, as we quickly ramp up renewables... if we can’t get enough batteries cheaply enough, we might prefer an inefficient alternative instead of just throwing the surplus energy away because we can’t get the batteries.

if we can’t get enough grid batteries quickly enough then we need to consider alternatives. If we compare hydrogen to your other suggestion, compressed air, then hydrogen can work out quite good, ............

But there are batteries and batteries - don't just think of lithium-ion. Work is going on with such as sodium based. Not as likely to be as suitable for uses such as cars, but as sodium is so common, may be more suitable for grid storage, where weight is largely irrelevant. Such conventional batteries are ideal for usage from a grid point of view as the same device gives input and output, and can quickly switch between charge/discharge. (Whereas hydrogen storage would mean separate electrolysis equipment for "charging" and a power station for "discharging".) Such flexibility is why users are prepared to pay a premium per kWh for a certain amount of such storage.

But it's not a simple two way choice between such batteries and hydrogen. Compressed air has been mentioned, but it's not alone, and carbon dioxide liquefaction (in a closed loop) offers one way of getting a "battery" that is cheaper than such as Li-Ion, but much more efficient in a round trip than hydrogen, whilst being easily scaleable. See energydome.com/our-technology/

That "charges" by compressing and liquefying carbon dioxide and "discharges" by allowing it to turn back into a gas at normal pressure, driving a simple turbine as it does so. It's beauty (compared to air storage) is working at ambient temperature, and CO2 being a liquid at the 70 bar used means the store for holding such is relatively small. Compared to hydrogen, the advantage is that compression equipment, and a simple turbine driven by expanding gas are relatively straightforward, and give much better round trip efficiency. And the use of CO2 means far greater inherent safety compared to hydrogen or ammonia.

Yes, a good point about strategic matters and energy security. But if such a supply got cut off tomorrow, it wouldn't affect batteries already in use - just future production. It's not like the oil shocks of the 70's, or gas with the war in Ukraine. It wouldn't be a sudden cut to the energy supply itself - rather manufacturing of future product. But isn't that a potential issue with raw materials used in all manner of industries?

[c-a-r-f-r-e-w]

Nov 3, 2022 23:47:33 GMT lens said:

Nov 3, 2022 16:01:52 GMT c-a-r-f-r-e-w said:

If you compare hydrogen with batteries, then sure, batteries are more efficient. But how long will it be until we can produce enough batteries for all requirements? Whether it’s having enough factories or indeed enough resources for the batteries.* Even for the grid, as we quickly ramp up renewables... if we can’t get enough batteries cheaply enough, we might prefer an inefficient alternative instead of just throwing the surplus energy away because we can’t get the batteries.

if we can’t get enough grid batteries quickly enough then we need to consider alternatives. If we compare hydrogen to your other suggestion, compressed air, then hydrogen can work out quite good, ............

But there are batteries and batteries - don't just think of lithium-ion. Work is going on with such as sodium based. Not as likely to be as suitable for uses such as cars, but as sodium is so common, may be more suitable for grid storage, where weight is largely irrelevant. Such conventional batteries are ideal for usage from a grid point of view as the same device gives input and output, and can quickly switch between charge/discharge. (Whereas hydrogen storage would mean separate electrolysis equipment for "charging" and a power station for "discharging".) Such flexibility is why users are prepared to pay a premium per kWh for a certain amount of such storage.

But it's not a simple two way choice between such batteries and hydrogen. Compressed air has been mentioned, but it's not alone, and carbon dioxide liquefaction (in a closed loop) offers one way of getting a "battery" that is cheaper than such as Li-Ion, but much more efficient in a round trip than hydrogen, whilst being easily scaleable. See energydome.com/our-technology/

That "charges" by compressing and liquefying carbon dioxide and "discharges" by allowing it to turn back into a gas at normal pressure, driving a simple turbine as it does so. It's beauty (compared to air storage) is working at ambient temperature, and CO2 being a liquid at the 70 bar used means the store for holding such is relatively small. Compared to hydrogen, the advantage is that compression equipment, and a simple turbine driven by expanding gas are relatively straightforward, and give much better round trip efficiency. And the use of CO2 means far greater inherent safety compared to hydrogen or ammonia.

Yes, a good point about strategic matters and energy security. But if such a supply got cut off tomorrow, it wouldn't affect batteries already in use - just future production. It's not like the oil shocks of the 70's, or gas with the war in Ukraine. It wouldn't be a sudden cut to the energy supply itself - rather manufacturing of future product. But isn't that a potential issue with raw materials used in all manner of industries?

Sure. We have discussed battery alternatives in the past, I think alec was interested in flow batteries a while back and they are one of the things being compared with hydrides in one of the studies I mentioned. Someone posted a link on the old board to about nine different battery techs in contention: I find solid state quite interesting.

Hard to keep up with all the tech, that’s why it’s good to share: don’t recall the CO₂ variant being mentioned before so thanks for that.

Yes, raw material shortages can afflict a variety of industries and indeed energy technologies hence the value in some diversity. And a bit of diversity can give more chance for some spin-off gains. 



.

[lens]

Nov 3, 2022 23:32:07 GMT c-a-r-f-r-e-w said:

By surplus, it means surplus to the grid requirements. As we keep adding renewable energy we can get to a situation where we much of the time we have more than we need for the grid, so we can keep the electrolysers running using what’s left over making hydrogen for other things.

?? But if you've built out enough renewable to satisfy the grid requirement, then why build out more? Why spend the money on an unnecessary surplus?

If you're doing such build out to specifically make hydrogen, then fair enough - but it's no longer then a "surplus" in the way I understand the word. Hydrogen proponents talk about generation from "surpluses" in terms of the electricity being cheap. If you're building green generation capacity SPECIFICALLY for the hydrogen production, that goes out the window.

A separate issue is grid balancing - matching demand and supply to even out. But using electrolysis to just smooth the peaks brings us back to the plant laying idle when such peaks aren't happening. And nowadays there is the scope for far better ways of load balancing, especially with smart metering. Controlling when cars charge at home is an obvious one, as well as grid storage batteries (be they Li-Ion, flow, CO2 liquefaction, conventional hydroelectric or whatever), but thermal inertia could play a big part. (I'm old enough to remember electric storage heaters.) It's been in the news today about swimming pools having to close in the winter due to energy costs - what about using what would otherwise be peaks of power to heat such, if it would otherwise be electricity that wouldn't be able to be used?

[c-a-r-f-r-e-w]

Nov 4, 2022 0:07:21 GMT lens said:

Nov 3, 2022 23:32:07 GMT c-a-r-f-r-e-w said:

By surplus, it means surplus to the grid requirements. As we keep adding renewable energy we can get to a situation where we much of the time we have more than we need for the grid, so we can keep the electrolysers running using what’s left over making hydrogen for other things.

?? But if you've built out enough renewable to satisfy the grid requirement, then why build out more? Why spend the money on an unnecessary surplus?

Yeah, I already explained why. Electrolysers stay in use more of the time and we can use the spare energy to serve other needs besides the grid and make some dosh. It’s like you’re really against using green hydrogen to make more fertiliser or summat. Here’s a projection for the increase in hydrogen demand we could cater to:

[c-a-r-f-r-e-w]

Nov 4, 2022 0:07:21 GMT lens said:

Nov 3, 2022 23:32:07 GMT c-a-r-f-r-e-w said:

By surplus, it means surplus to the grid requirements. As we keep adding renewable energy we can get to a situation where we much of the time we have more than we need for the grid, so we can keep the electrolysers running using what’s left over making hydrogen for other things.

?? But if you've built out enough renewable to satisfy the grid requirement, then why build out more? Why spend the money on an unnecessary surplus?

If you're doing such build out to specifically make hydrogen, then fair enough - but it's no longer then a "surplus" in the way I understand the word. Hydrogen proponents talk about generation from "surpluses" in terms of the electricity being cheap. If you're building green generation capacity SPECIFICALLY for the hydrogen production, that goes out the window.

Feel free to use the word “surplus” any way you like, though it won’t change the utility of using spare leccy to make hydrogen. 

[c-a-r-f-r-e-w]

Nov 4, 2022 0:07:21 GMT lens said:

Nov 3, 2022 23:32:07 GMT c-a-r-f-r-e-w said:

By surplus, it means surplus to the grid requirements. As we keep adding renewable energy we can get to a situation where we much of the time we have more than we need for the grid, so we can keep the electrolysers running using what’s left over making hydrogen for other things.

A separate issue is grid balancing - matching demand and supply to even out. But using electrolysis to just smooth the peaks brings us back to the plant laying idle when such peaks aren't happening. And nowadays there is the scope for far better ways of load balancing, especially with smart metering. Controlling when cars charge at home is an obvious one, as well as grid storage batteries (be they Li-Ion, flow, CO2 liquefaction, conventional hydroelectric or whatever), but thermal inertia could play a big part. (I'm old enough to remember electric storage heaters.) It's been in the news today about swimming pools having to close in the winter due to energy costs - what about using what would otherwise be peaks of power to heat such, if it would otherwise be electricity that wouldn't be able to be used?

Sure, alec is big on demand management etc. , it can save leccy, and we can store some in car batteries, but it’s not the same as making money from lots of extra leccy, while decarbonising other processes using more green hydrogen etc.

[Mr Poppy]

Nov 3, 2022 23:12:15 GMT lens said:

Nov 3, 2022 18:38:41 GMT c-a-r-f-r-e-w said:

You must EITHER have both an inefficient usage of plant (but use cheap electricity) OR AND good economically viable plant utilisation.

Some minor corrections but by Jove old chap, I think the penny hath finally dropped 

Perhaps consider how 'inefficient' (aka 'optimal for the whole current grid is very suboptimal for many of the component parts) the current system is with regards to 'peaking plants' (only used for a few hours per day, not every day) and 'constraint payments'* for when there is 'surplus'** wind power. 

* www.nationalgrideso.com/electricity-explained/how-do-we-balance-grid/what-are-constraints-payments

** I'm aware you don't like that word. It is very context dependent. The 'surplus' needs to be 'economically viable' for electrolysers to be well... 'economically viable'. If at some point you and the other chap work out the inter-seasonal issue then.. well.... another 'penny drop' moment perhaps. 

[lens]

Nov 5, 2022 17:37:44 GMT Mr Poppy said:

Perhaps consider how 'inefficient' (aka 'optimal for the whole current grid is very suboptimal for many of the component parts) the current system is with regards to 'peaking plants' (only used for a few hours per day, not every day)

Oh, absolutely! Peaker plants are very inefficient (in terms of capital spent) - but (currently) necessary to ensure the lights stay on.

Which reminds me of the lectures about Redundancy Theory, many years ago at university. Basic premise was that in engineering terms a system with near 100% efficiency should not (contrary to what is "obvious") be normally regarded as desirable - a high degree of efficiency in a system often goes hand in hand with the risk of a small problem leading to catastrophic failure. I seem to remember a classic example given was such as a transport system. Best economy may be got from a railway line running near peak theoretical capacity - best utilisation of capital - but such is very non-resiliant in the event of even a small problem.

Which is different from efficiency of an individual device. A tungsten light bulb is quite inefficient at turning electricity into light - a LED bulb far, far better. No one should argue against LED in that case. (You'd still want the circuit to be fused a given percent higher than the expected current draw of the relevant bulb, though.) There are "good efficiencies" and "bad efficiencies" - when the latter lead to lack of resilience.

And it's hoped new technologies may mean peaker plants will be much less necessary in the future. Especially grid batteries, which have been having quite a lot of success in the last few years - especially in Australia. www.energy-storage.news/batteries-are-number-one-at-maintaining-australias-grid-frequency/ Note the same installation Try to do the same via hydrogen and you need not just the elctrolysis equipment - but a (little used) gas peaker station as well. The grid battery performs functions of electicity absorption AND delivery - at far higher efficiency.

But a lot of grid stabilisation is possible far easier through smart demand handling - adjusting tariffs to encourage usage during what would otherwise by a trough.

Note I am *NOT* saying that we should not make hydrogen via electrolysis. But such should go to industry and replace dirty hydrogen already used there. Even optimistically, it will take *DECADES* to build out sufficient green generation to satisfy all that demand. Until then, it's ridiculous to propose burning it in a power station - it would just mean using more gas to produce the hydrogen via reforming that you'd diverted green hydrogen away from  in the first place.......

[alec]

lens - you might be interested in this paper - www.sciencedirect.com/science/article/pii/S0306261920307091

It models power to hydrogen systems (PtH2) in the energy mix, and analyses various different scenarios using Monte Carlo simulations. They conclude that PtH2 use for seasonal storage would be needed for "the last mile" if total decarbonisation was needed, but that this wouldn't be the most cost effective option if some carbon emissions could be tolerated. In energy systems where the Thermal to Electricity Ratio (TEr, defined as the ratio of annual electricity demand to annual thermal demand) was high, hydrogen would be more useful, and looking at the UK energy demand, I've calculated that we would have a mid range TEr in their terms if we assumed 100% of gas demand was replaced by electricity. (In reality we would be less, as a proportion of our gas usage is for industrial purposes as gas, rather than as heat).

Given the UK's rather limited seasonal variation in renewable energy production (see previous post) we wouldn't be so troubled by the seasonal imbalances if we upscaled renewables in the same technology proportions as we have now, and this study indicates that most of the supply/demand imbalances can be offset by short term storage systems (batteries and heat storage) with a limited role for hydrogen, possibly 5% or less of annual demand. So pretty much in line with what you are saying, I think. But it's clear that we would need over capacity.

What is also notable is that they highlight the need for some form of carbon pricing and/or FITs style payments, and I personally think this is the key issue. We need oversupply of capacity, whether generation or storage, as you say in your post, and that won't happen within a market system unless there are payments made to compensate for idle capacity. That's a pretty basic concept to grasp, I think. Hydrogen will be a small part of the mix, probably for those rare 'emergency' periods of prolonged cold, still winter periods, which we might see only rarely, but which still need covering within the system. But as hydrogen is so expensive, we can't get that cover unless we have a system that pays for capacity, as hydrogen won't be able to deliver that service in a cost effective manner when it's up against other technologies.

I guess this goes to the heart of a planned energy system.

[lens]

Nov 6, 2022 23:00:41 GMT alec said:

lens - you might be interested in this paper - www.sciencedirect.com/science/article/pii/S0306261920307091

Yes, thank you Alec, though I can't pretend to have read it in depth! As one element, I'm a little surprised to read early on: "A PtH2 system can produce renewable ‘green’ H2 gas by using electricity to split de-ionized water through an electrolyzer (EC), then storing the H2 and subsequently reconverting it into electricity and heat through a fuel cell (FC). " ?

Technically quite true, but my understanding was that for grid electricity it was most likely the hydrogen would be burnt in a conventional gas power station? Not as efficient as a fuel cell, but the cost of a suitably large fuel cell to supply grid quantities on a "peaker" basis would likely rule such out?

The problem with such in depth reports is that they can be out of date almost before they are written as technologies evolve (and change in price), quite apart from new technologies emerging. Sometimes it may be better to consider a "ball park" approach.......?

Nov 6, 2022 23:00:41 GMT alec said:

Given the UK's rather limited seasonal variation in renewable energy production (see previous post) we wouldn't be so troubled by the seasonal imbalances if we upscaled renewables in the same technology proportions as we have now, and this study indicates that most of the supply/demand imbalances can be offset by short term storage systems (batteries and heat storage) with a limited role for hydrogen, possibly 5% or less of annual demand. So pretty much in line with what you are saying, I think. But it's clear that we would need over capacity.

It all raises the question of how much energy generation really does need to be carbon free. Shocking to purists - but isn't that what "nett-zero" really means anyway? You allow some use of fossil fuels - as long as offset by carbon negative processes elsewhere?

In which case, concentrate primarily on building renewable generation plant (via suitable incentives) and expect the rest to follow? So primarily usage being demand at time of production, secondly short term storage via battery, hydro and upcoming technologies, and last hydrogen production. Building electrolyser capacity as generation increases enough to make it viable. Then using such hydrogen industrially. Then using gas to feed a few remaining peaker plants? Not totally carbon free - but hugely better than at present. It is relatively cheap to decarbonise the first x% - far more difficult the last y%. But does it really matter? Better for the world to reduce greenhouse gas emissions by 50% fairly quickly, than worrying about when we'll be 100% down in the distant future?

[alec]

lens - valid points. I was also a bit surprised at the FC inclusion, but I think the other key point is that this wasn't a comparative study looking at lots of different energy storage options. So, for example, if we really are looking at no more than 5% of annual demand required as seasonal storage, your point about compressed CO2 would be worth looking at, alongside the LAES systems, as these appear to be easier to bring to market and less expensive that hydrogen.

I also agree about the idea of stripping every carbon based fuel out. Some minor gas usage only at the short term periods in winter when demand is high and the wind is flat would be very cheap, and if we got tree planting and land management practices sorted out, that's how we remove the carbon - way cheaper and more efficient than CCAS.

I have long felt that we are walking past the simple options here, in favour of the shiny new tech ideas, which big corporations want someone else to pay for.

[Mr Poppy]

Nov 4, 2022 0:11:10 GMT c-a-r-f-r-e-w said:

Nov 4, 2022 0:07:21 GMT lens said:

?? But if you've built out enough renewable to satisfy the grid requirement, then why build out more? Why spend the money on an unnecessary surplus?

Yeah, I already explained why. Electrolysers stay in use more of the time and we can use the spare energy to serve other needs besides the grid and make some dosh. It’s like you’re really against using green hydrogen to make more fertiliser or summat. Here’s a projection for the increase in hydrogen demand we could cater to:

Thank you for the graph, might I ask who the original source is?

Obviously a range of projections depending on the extent of hydrogen uptake by different demand categories (eg 'building heat and power' is probably the most uncertain category). The 'exponential' (ish) increase can also be seen in PWC's analysis (graph1). Of note in that graph is that low uptake of hydrogen ('weak policies') will very likely cause higher rises in global temperatures (via more 'climate delay') - hopefully fairly obvious why although I'm aware some people think 'vested interests' are behind any mention of the need for a significant role for hydrogen in meeting net zero by 2050.

www.pwc.com/gx/en/industries/energy-utilities-resources/future-energy/green-hydrogen-cost.html

Go down further in the above and you'll see a World map with timescale slider. Overall the price is likely to drop massively (obviously depends on many factors and is simply a 'projection' based on various assumptions). Within regions then UK is fairly well placed for domestic use and local exports due to lots of 'cheap wind' with Spain and Portugal are well placed due to lots of 'cheap sun' (some might go as far to say that is different countries making use of 'natural comparative advantage'). Transport costs and various other factors (eg Energy security and who you wish to trade with) are not considered but how dependent does Europe wish to be on Middle East/Africa?

[lens]

Nov 8, 2022 8:51:55 GMT Mr Poppy said:

Nov 4, 2022 0:11:10 GMT c-a-r-f-r-e-w said:

Yeah, I already explained why. Electrolysers stay in use more of the time and we can use the spare energy to serve other needs besides the grid and make some dosh. It’s like you’re really against using green hydrogen to make more fertiliser or summat. Here’s a projection for the increase in hydrogen demand we could cater to:

Of note in that graph is that low uptake of hydrogen ('weak policies') will very likely cause higher rises in global temperatures (via more 'climate delay') - hopefully fairly obvious why although I'm aware some people think 'vested interests' are behind any mention of the need for a significant role for hydrogen in meeting net zero by 2050.

Lower uptake of hydrogen will not necessarily cause more "climate delay" - possibily quite the opposite!

To take just one example from that graph - transportation.

That sector is responsible for a lot of CO2 and pollutants such as NOx currently. Such may be theoretically solved by a move to hydrogen, or a move to battery (and more direct electrification of rail). The latter is likely to need only about a third of the renewable generation build out that would be needed for battery and consequently may cause LESS climate delay than a higher uptake of hydrogen. Same may be true for such as "building heat and power". Here's a novel idea - why not just use the electricity directly for the purpose, rather than go the hydrogen middle man?

But that idea doesn't go down too well with those with existing interests in gas and hydrogen infrastructure, strangely enough. It's obviously in their business interests if all transportation relied on hydrogen.

Carfrew said I seem to be "really against using green hydrogen to make more fertiliser or summat" - and nothing could be further from the truth! That to me is a very *GOOD* use of green hydrogen - where you need hydrogen for it's chemical properties, and not just as a energy store. But it has to (viably) come from a specific build out of green generation - not magically appear cheaply from some supposed "surplus" capacity.

[lens]

I've previously mentioned Riversimple as a company which is committed to the idea of making a hydrogen car (even if they've barely managed a prototype after well over 20 years) and thought I'd check back to see if there was any more real news from them. (There isn't.)

But on their latest blog entry ( www.riversimple.com/about-blog/ ), I came across this:

"Converting methane into hydrogen is 75% efficient while converting it into electricity is only 49% efficient. So there is less energy wasted in using bio methane to make hydrogen than electricity."

Errrr, I suppose true in itself - but hugely misleading in the electric car context!? What gets glossed over is that both a BEV and a fuel cell car are driven by electricity. They gloss over that the fuel cell is only about 50% efficient - so comparing like with like the 75% figure becomes more like 37% versus 49%.

But of course, it's worse. Most truly green comparisons start off with assuming green electricity as the starting point, and producing the hydrogen by electrolysis. So there is no "only 49% efficiency in making electricity from gas" - whilst you have to add in electrolyser inefficiencies to those of the fuel cell.

Unfortunately, greenwashing is too commonplace amongst firms involved with the hydrogen business. Together with figures and comparisons cherry picked to give a misleading impression.