16 ms·

Seasonal energy storage in aluminium for 100% solar heat and electricity supply

118 points by NiceWayToDoIT 6y ago

tomas_kalisz 6y ago
Hallo everybody, Let me comment on several aspects which I see crucial, and apologize the length of this contribution which I have to split into several parts. This is the first part. 1) Aluminum as a high energy density storage medium The authors of the disputed article have the same point as many contributors herein – that a cheap, economically feasible energy storage may be the crucial „missing link“ between electricity from renewable energy sources and a more sustainable „carbon neutral“ economy. Indeed, with respect to energy density – which may be roughly taken as an estimate for the costs of energy storage in the chosen medium – aluminum looks pretty favourable. Please note that the volumetric energy density value given in the disputed article for hydrogen pertains to liquid hydrogen which is the most dense practically applicable form of elemental hydrogen at normal pressure. Obviously the vessels for reliable storage of cryogenic liquid hydrogen are more expensive than (pretty expensive) pressure vessels chosen as a more feasible technical solution by automobile manufacturers developing hydrogen cars. Therein, volumetric density slightly above 1 kWh/L is a current standard with hydrogen pressurized to 70 MPa (700 bars). 2) Energy losses from irreversibilities in energy storage and/or recovery High level of reversibility in the respective energy storage and recovery is the main advantage of batteries. Unfortunately, there is at least one fundamental reason for which critical disadvantage of batteries - high price for a unit capacity – is basically incurrable even with cheapest materials. This fundamental reason is the ratio between volume and mass of the electrochemically active materials which can be put into a reasonably operable battery on one hand and the overall volume and mass of all other parts necessary for this reasonable function. This unfavourable ratio can significantly, in several orders of magnitude, improve in „flow“ batteries, and even more if we split the function of the flow battery into a separate electrolyzer designed solely for „charging“ our storage system and a separate fuel cells designed solely for „discharging“ (electricity recovery from the storage system). Unfortunately, the only electrochemically active medium that is more-less applicable in such „ideal“ electricity storage systems (that enable both high capacity and high storage efficiency by combining the high efficiency of direct electrochemical energy conversion with high energy density of a neat „fuel“ used as the energy storage medium), is still hydrogen – which, however, suffers from the costly storage due to low volumetric energy density in comparison with conventional fuels. As soon as we try to improve hydrogen energy density by converting it chemically into a form which is more favourable form the viewpoint of the cheap storage and transport (e.g. into liquid ammonia having energy density above 4 kWh/L, or, by carbon dioxide reduction, into carbon-based synthetic fuels), we will necesarily lose a significant part of the energy originally conserved in hydrogen, as a Gibbs energy of the respective reaction dissipated on the expense of a thermodynamically „spontaneous“ chemical conversion. For example, by simple hydrogen conversion into ammonia by its reaction with atmospheric nitrogen that is achievable on an industrial scale by well-known Haber-Bosch process, you unavoidably lose about 30 % of the renewable electricity which you originally conserved in the „green“ hydrogen. Very similar numbers apply for carbon dioxide conversion into synthetic methane by well-known Sabbatier process, and you can take as a rule of thumb that the more complicated conversion, the more of the originally conserved energy you have to sacrifice. Even worse, none of the synthetic fuels currently considered for large scale energy storage can even approach hydrogen in technical maturity of its direct electrochemical re-conversion into electricity. For example, known ammonia fuel cells are still at least order of magitude worse in their performance than hydrogen fuel cells. And, to my best knowledge, reliable and highly efficient hydrogen fuel cells are - after decades of development - still impossible without use of precious and therefore pretty expensive platinum metals. Finally, as soon as you resort to simply burning your synthetic fuel in an internal combustion engine or any similar equipment, the efficiency of electricity recovery from the respective fuel drops to some 40 %. The second part will follow.
tomas_kalisz 6y ago
Hallo everybody, Apologies again for the length. This is the second part of my comment. 3) Consequences for the economical feasibility of renewables if supported by currently considered power-to-fuel concepts On the basis of previous considerations, we can conclude that should the electricity from renewable resources storage (using currently considered storage techniques as discussed above) become economically competitive with fossil fuels as a mere heat source, the primary energy from renewables should be at least three times, possibly rather four or five times cheaper than the electricity generated from fossil fuels in conventional coal- gas- or oil-fired power plants. Although the price of electricity from renewables has the decreasing tendency, expecting that it becomes competitive with heat from fossil fuels in a near future, especially if we will waste more than a half thereof during the energy storage and recovery, may not be realistic. Therefore, should we wish a “carbon neutral” economy, we may basically have two options: (i) either dispute if we should subsidize rather the renewable electricity in combination with costly hydrogen storage or with one of currently disputed, still highly inefficient power-to-fuel concepts, or, rather, comparably inefficient state-of-art nuclear technology (I am going to add a remark to nuclear technology below), (ii) or seek for an alternative electricity storage method which is so cheap and efficient that it could make, at least in the annual average, the electricity generated from renewables cheaper than the electricity generated from conventional sources. I personally prefer the option (ii). 4) Remarks regarding nuclear energy as a possible solution for “carbon neutral” future I do not like to discourage others, however, I am somewhat sceptical with respect to perspective of nuclear energy in view of the current state of nuclear industry. Please note that, basically, the single concept which they can currently offer are huge PWRs with poor adaptability to grid conditions and extremely poor efficiency of entire power plants about 25 %, on the level of 19th century steam engines. For the extreme regulatory hurdles, they can hardly offer anything significantly improved in a reasonable timeline. Everything is even more complicated by concerns about nuclear weapon proliferation, resulting in plans for burying the spent nuclear fuel forever instead of reprocessing it. In this respect, it appears that what we can currently afford is heavily subsidized, technically outdated wasting with valuable fissile natural nuclides which are definitely a consumable natural resource. 5) Open space for a quick development in metal-based power-to-fuel concepts towards reversibility / high efficiency Although just the concept of energy storage in metallic aluminium as presented in the disputed article currently suffers from the common disadvantage of all currently considered alternative fuels – namely, form the absence of a reliable, industrially scalable method for direct metal reconversion into electricity – there may exist other options, wherein this goal could be achievable within a reasonable time schedule. In 1970-ties, a visionary American inventor Stephen F. Skala filed a series of patent applications proposing cheap alkali metals sodium and potassium as media for a feasible energy storage and transport. Likely, he assumed nuclear energy as a cheap and clean electricity source then, however, this assumption obviously failed: https://1url.cz/AKtDH https://1url.cz/AKtDH https://1url.cz/zKtDR https://1url.cz/zKtDR https://1url.cz/7KtD8 https://1url.cz/7KtD8 https://1url.cz/lKtDy https://1url.cz/lKtDy https://1url.cz/OKthL https://1url.cz/OKthL https://1url.cz/UKtht https://1url.cz/UKtht https://1url.cz/sKthz https://1url.cz/sKthz In my opinion, his vision of Diesel engines fuelled with liquid Na-K alloy and water and producing sodium and potassium hydroxide from which the respective metals can be recovered by electrolysis (the well-known Castner process) may be still appealing, although some aspects like a possible wreckage of a re-build oil tanker full of the alloy explosively reacting with sea water shall be considered very carefully. Similarly, his idea of pipelines serving in parallel for the liquid Na-K alloy transport and as electricity transmission lines might perhaps still deserve an attention of those who consider various alternatives for economically feasible energy transport from sunny desert areas to densely populated regions with a high energy demand. Interestingly, although Skala obviously researched the relevant state of the art thoroughly and strived to address possible improvements in the efficiency of Castner process, he missed the document which may be crucial for feasibility of the sodium economy, because it possibly opens the doors towards direct reconversion of sodium into electricity. It is the Lockheed patent US 3 730 766 by Geisler, https://1url.cz/5KthN https://1url.cz/5KthN describing a membrane-free fuel cell, operating with a consumable alkali metal anode and aqueous solution of the respective alkali metal hydroxide as the electrolyte. If a rapidly flowing very thin electrolyte film may indeed tame the spontaneous sodium reaction with water the way that it may produce useful electricity as described in Geisler’s patent, I believe that this principle could be developed in reliable electricity generators having megawatt outputs within a few years, and reshape the entire landscape of electricity production, storage and transmission within 10-15 years. The third part will follow.
tomas_kalisz 6y ago
Hallo everybody This is the third and final part of my comments. 6) Broader context with a few illustrative examples I provided a scheme showing the requirements and possible consequences of econokmically feasible large-scale electricity storage in publicly available application OrgPad. The scheme is directly accessible under link https://orgpad.com/s/5BfLP-cxj-7 https://orgpad.com/s/5BfLP-cxj-7 A few technical instructions (which might be useful if you will use OrgPad for the first time): Mouse click-and-draw serves for moving the entire canvas, mouse wheel for zooming the entire picture, cells having a fine shadow have a hidden content which can be opened by mouse click on the respective cell. The application does work in modern web browsers like Chrome, Chromium, Mozilla, Opera, Safari, not (or only very poorly) in IE. 7) Conclusion The crucial question is why the relevant laboratory and technical records pertaining to this potentially game-changing invention quietly sleep in Lockheed archives. Myself, I have not a capacity to test a model device in laboratory, nor find out what Lockheed exactly tested and with which outcome. Should any of the readers, however, have such opportunity, I believe that clarifying the crucial question (whether or not Geisler’s device might have indeed worked) might be worth of the respective effort. Thank you very much for your patience.
Havoc 6y ago
I’d rather see them implement the European supergrid frankly. PV in the Sahara and high voltage lines up to Europe. Think that would be a win for everyone
- IfOnlyYouKnew 6y ago
  That’s sort of a brute force approach. And the Sahara is warm, but solar irradiation varies far less than temperatures. It’s going to be a lie mix of many of these promising ideas, blended in such a way that is, hopefully, not too expensive, not too insecure, not dirty in a new way, and not not at least a little bit fun.
  - ThomPete 6y ago
    the fact that you have to blend them is what makes them expensive and for what? Less than 20% of our energy need is electricity.
- bildung 6y ago
  Right at the beginning of the study it is stated why that is no alternative: The seasonal production/consumption patterns could lead to "excess PV production in summer on a local, national or even international scale". As Sahara PV is still on the northern hemisphere this would not solve the problem the study tries to tackle.
  - tda 6y ago
    I would like to see the numbers; how much overbuilding would be necessary. Even if you need to install say 50%-100% extra capacity to meet demand in winter, solar power would still be perfectly economically viable. And I'm sure a valid use for excess power in summer can be found, e.g. desalination. Fresh water demand is surely higher in summer in the Sahara, and otherwise fresh water is easily stored
    - stdbrouw 6y ago
      I looked up the numbers for Aswan in the south of Egypt. Roughly 360 hours of sunshine or a bit more in the summer, 290 hours in winter months [1], so about 80% of max. If we look at direct normal irradiance instead, a more appropriate metric, it varies between 7.93 kWh/m^2/day in June vs. 5.51 kWh/m^2/day in December [2], so about 70% of max. Hour-to-hour and day-to-day fluctuations are another thing altogether, and higher demand in winter (e.g. for heating) yet another consideration, but if we're purely interested in some sort of "seasonal correction" I guess you'd want to overbuild by 40% or a bit less if you set the angle of the panels in such a way as to optimize winter production at the expense of summer production, a common strategy. The closer you get to the equator, the less it matters whether you're in the northern hemisphere or the southern hemisphere. Aswan is at 24°N, a latitude at which you can still find a lot of smaller cities, but as you go to the south of that, infrastructure disappears and it might not be economical to build PV or solar thermal installations in the absolute middle of nowhere. Seems to be about the latitude to which DESERTEC proposes to lay HDVC connections. Not an expert though, just someone who can look up some numbers. [1] https://en.wikipedia.org/wiki/Aswan https://en.wikipedia.org/wiki/Aswan [2] https://www.researchgate.net/figure/Average-Direct-normal-irradiance-of-Aswan-Egypt_fig3_324538284 https://www.researchgate.net/figure/Average-Direct-normal-ir...
blueblisters 6y ago
> The efficiency of this process is approximately 50%, and it is estimated that it may be increased to almost 65% with non-consumable electrodes, wetted cathodes, lower temperature electrolysis cells, and reduction of heat losses That's not too terrible I suppose, plus aluminium is rather convenient to store.
harperlee 6y ago
Without knowing, 500kg per dwelling sounds like it would pose some supply scaling problems.
- sideshowb 6y ago
  Most cars weigh more than that, yet here we are
  - harperlee 6y ago
    Yeah and if a home has 1.x cars, and let's say that means 500ks aluminum, we're talking about doubling demand. So perhaps that has impact in price?
  - w0utert 6y ago
    Most cars are mostly plastic and steel, and only a few percent aluminum, but I see your point
- CaptainJustin 6y ago
  With over 38M [1] households just in Germany that would come to: 19 million metric tons of Al. Each year the people of this planet mine 160 million metric tons of Bauxite [2]. Not sure how the Bauxite ore related in weight to the final product. Maybe this could be a viable option for some energy storage? [1] https://www.statista.com/statistics/464187/households-by-size-germany/ https://www.statista.com/statistics/464187/households-by-siz... [2] https://www.aluminum.org/industries/production/bauxite#:~:text=More%20than%20160%20million%20metric%20tons%20of%20bauxite%20are%20mined%20each%20year https://www.aluminum.org/industries/production/bauxite#:~:te....
  - harperlee 6y ago
    Thanks for the data, I think that makes my comment moot :)
  - magicalhippo 6y ago
    Wikipedia says[1] global production is roughly 64 million metric tons per year. [1]: https://en.wikipedia.org/wiki/List_of_countries_by_primary_aluminium_production https://en.wikipedia.org/wiki/List_of_countries_by_primary_a...
VBprogrammer 6y ago
The use of non-combustable electrodes only gets a passing mention here but it seems a key part of making this system less carbon intensive. Also, if I remember correctly aluminium smelters use some pretty nasty cover gasses in the process to avoid creating a giant firework, I didn't find a reference to these in the paper.
- albrewer 6y ago
  I worked in an iron foundry and not an aluminum one, but I was under the impression it was just a nitrogen blanket.
  - lylecheatham 6y ago
    Aluminum Nitride actually has a favorable formation so they have to use much less friendly gasses like Sulfur Hexaflouride.
    - VBprogrammer 6y ago
      Thanks, I had Sulfur Hexafluoride in the back of my head but I wasn't sure if I was misremembering that because I've been reading about circuit breakers where it is used as an insulator.
IfOnlyYouKnew 6y ago
Al processing already consumes vast amounts of energy, and the plants are already being used for intraday load balancing. There was a story recently about an incident in Germany where due to weather and strange market mechanisms, the grid was in danger or collapsing. The operator’s third line of defense (after gas peakers and hydroelectric storage, IIRC), was to remotely turn off the Al plant 600 km away, something they can contractually (and technically) do up to four times per day and six times per week for an hour each. That plant uses 1 % of Germany’s electricity. It’s not the only such plant, and Hermany generally frowns on frivolous uses of Aluminum: cans are far less popular, for example, and will earn you dirty looks. The Audis may make up for it I part, but in the US it should be possible to shift some non-trivial fraction of the electricity consumption by, say, doubling processing capabilities and running them seasonally. Al isn’t too expensive, and the plant is a small part of the costs anyway, with energy making up the bulk. Of course there are countless opportunities to optimize consumption patterns once consuming devices all have data connections: heat and cooling, washing machines, dryers, dishwashers, roombas, notebooks... all these devices could shift their consumption on the hours-to-one-day scale and easily cushion even large variability in production. Once electric cars are ubiquitous, they‘ll make up the bulk of consumer electricity usage and they could even feed power back into the grid. The only real problem with Al is, obviously, that we keep misreading it as AI. The confusion will drive some lesser Al insane, and either that or the singularity will cause a bloodbath, henceforth known as Al Gore.
- blauditore 6y ago
  >cans are far less popular, for example, and will earn you dirty looks I never heard nor experienced this myself in Germany. After all, almost all of they get recycled because their price includes a deposit you get back upon recycling.
  - Tade0 6y ago
    I believe it may have more to do with the stigma of drinking your Bier from a can, as opposed to a glass.
  - arbitrage 6y ago
alecmg 6y ago
I remember reading Donald Sadoway got inspiration for developing liquid metal batteries [1] from watching how aluminum smelting is basically a battery already. These batteries are more efficient than aluminum energy storage, and were also aimed at large scale with cheap abundant materials (initially at least). But high temperatures involved make it not very convenient. [1] https://en.wikipedia.org/wiki/Molten-salt_battery#Liquid-metal_batteries https://en.wikipedia.org/wiki/Molten-salt_battery#Liquid-met...
- audunw 6y ago
  Donald Sadoways battery startup Ambri seems to finally be breaking through commercially, so I'm quite optimistic about them. It was quiet for a while but now there seems to be commercial progress: https://ambri.com/news/ https://ambri.com/news/
  - baking 6y ago
    They had a partnership with NEC Energy Solutions which then left the integration business about 9 months later, so that was probably a business setback. I'm still hopeful that they get a chance to scale with projects like data centers and municipal electric utilities. https://www.greentechmedia.com/articles/read/storage-integrator-nec-es-halts-new-business-begins-winding-down https://www.greentechmedia.com/articles/read/storage-integra... Edit: This recent Real Engineering piece updates their current business situation: https://www.youtube.com/watch?v=-PL32ea0MqM https://www.youtube.com/watch?v=-PL32ea0MqM https://teitimes.com/teaser/2021-02/#pf7 https://teitimes.com/teaser/2021-02/#pf7 The first systems will go into the field as 40 kWh trial systems to demonstrate their effectiveness and operation. The pilot battery for Terra-Scale, which will be one of these trial systems, will be installed late 2021. A larger 1 MWh commercial-scale trial system will be installed in late 2022. Volume production will then start in 2023, at which time Ambri will build battery systems that are available in 1 MWh blocks and have discharge rates of 4 hours or longer.
tim333 6y ago
It's also potentially an energy source for space launches - the space shuttle boosters burnt aluminium.
IXxXI 6y ago
Elon Musk deployed a grid tied multi megawatt hr battery in australia that is far superior. https://www.popularmechanics.com/science/a31350880/elon-musk-battery-farm/ https://www.popularmechanics.com/science/a31350880/elon-musk...
TruthWillHurt 6y ago
This is a very stupid proposition made by looking at energy-capacity figures without taking real-world application hurdles into account. Aluminum fuel cells have a slow energy discharge rate, largely due to the Oxigen-Reduction Rate (ORR) limit, even when the air Cathode is doped in exotic catalysts such as Platinum. Furthermore, fuel-cell Electrodes, be it an Aluminum-air or Hydrogen-air fuel-cell, suffer from "CO2 Poisoning", which makes their efficiency drop in open air. Not commercialy viable.
- ed25519FUUU 6y ago
  The unfortunate reality is energy/battery tech headlines like these are one of the reasons we haven’t been able to garner widespread support for nuclear. Everyone thinks we’re on the cusp of having a big enough or strong enough battery to power industrialized cities but in reality we’re impossibly far from that.
  - Robotbeat 6y ago
    No. The reason nuclear has a hard time isn’t because of technology. It’s because of paranoia and poor scicomm. And because no one really cares about climate change enough to make it a priority. People won’t say out loud “climate change is less of a priority than phasing out nuclear (or removing hydro dams or saving a few bucks on upfront cost of postal trucks, etc),” but that’s what they’re implying. In that sense, Greta Thunberg is right that leaders just don’t care that much about climate change. Storage technology is capable of powering cities. Heck, the largest grid storage sites in the US are for backing up nuclear power plants on the East Coast (matching day/night loads with baseload supply). This silly infighting between different clean energy technologies (storage, nuclear, renewables) needs to stop.
    - whizzter 6y ago
      Imo it's a rather cruel irony that the green parties (in Europe at least) were in big part getting their growth from and membership dedication from the Harrisburg and Chernobyl accidents. So when we really need a "green" party they're filled with zealots who're unable see the harm reduction tradeoffs that needs to be done.
giantg2 6y ago
So from a residential perspective, they're just using this to produce hydrogen for a hydrogen fuel cell. The reactions that require the higher temperatures would need to be industrial (and don't seem to be more beneficial than other methods). So what are the benefits?
- esperen 6y ago
  Energy storage in the form of aluminum.
  - Robotbeat 6y ago
    Kind of irrelevant if we don’t have carbonfree electrodes for smelting aluminum.
    - esperen 6y ago
      If it brings the net carbon footprint down, it could be relevant. Progress is typically iterative
      - Robotbeat 6y ago
        But that hasn’t been established here. The aluminum produces hydrogen (at some level of inefficiency) which then produces electricity in a fuel cell (more inefficiency). Consumable electrodes are actually doing chemical work in the aluminum. It’s not just wear from use. To produce 78 grams of Aluminum directly requires 48 grams of Carbon electrodes (using made by graphitizing some tar or coke) which oxidizes to 176 grams of CO2. Aluminum is 31MJ/kg specific energy. Assuming 70% efficiency conversion from aluminum to hydrogen and 70% from hydrogen to electricity (both fairly optimistic figures), you’re talking about 535 grams of emitted CO2 for each kWh of electricity out. Ignoring the electricity input, inefficiencies and losses in making the aluminum, and assuming perfect conversion of the tar to electrodes. Worse than a good, advanced combined cycle natural gas plant (which can get as good as roughly 350 grams per kWh for record efficiency plants). I just don’t see how this is gonna be a net win without carbonfree electrodes. It seems just about impossible here. Storing hydrogen directly looks to make way more sense.
dominojab 6y ago
That's what ambri is developing , instead they use another transition metals that have the properties described in the paper.
acvny 6y ago
350–530 kg Al would be needed per apartment. One question left unanswered is - how many cycles does this system support before it becomes substantially inefficient?
Gravityloss 6y ago
There are zinc batteries as well, that you can buy today by https://redflow.com/ https://redflow.com/ . It looks relatively simple to me, during charging it's just electroplating zinc. (I'm not a chemist.)
at_a_remove 6y ago
I know their energy densities are crap, as are their discharge rates, but boy would I love to see nickel-iron batteries take off for large projects. HN is already about scale, scale, scale, and wow would nickel-iron benefit from that. Not exactly environmentally unfriendly, either. Another reason I think about this for infrastructure projects is, well, America is terrible about maintaining its infrastructure. It's a bit like code -- don't be surprised if that thing you banged out has to be viable for a decade more than you anticipated. And no battery tech stands up to decades of wear and tear like nickel-iron. I just know that any fancy battery stack we want to offset wind or solar will suffer from neglect as the people writing the budgets turn their eyes to shiny new things. Might as well plan for it.
specialist 6y ago
Meta: I LOVE this article's "Highlights" pullout at the top. +1 For respecting the audience. This should be the norm. "Pullout" might not be the right name. Preamble? Sidebar (up top)? The bullet list is not quite an Abstract. Maybe just Bullet List?
nwah1 6y ago
95% of worldwide grid energy storage comes from pumped storage hydro. Yet almost nobody mentions this, or suggests building more.

118 points by NiceWayToDoIT 6y ago

Hallo everybody, Let me comment on several aspects which I see crucial, and apologize the length of this contribution which I have to split into several parts. This is the first part. 1) Aluminum as a high energy density storage medium The authors of the disputed article have the same point as many contributors herein – that a cheap, economically feasible energy storage may be the crucial „missing link“ between electricity from renewable energy sources and a more sustainable „carbon neutral“ economy. Indeed, with respect to energy density – which may be roughly taken as an estimate for the costs of energy storage in the chosen medium – aluminum looks pretty favourable. Please note that the volumetric energy density value given in the disputed article for hydrogen pertains to liquid hydrogen which is the most dense practically applicable form of elemental hydrogen at normal pressure. Obviously the vessels for reliable storage of cryogenic liquid hydrogen are more expensive than (pretty expensive) pressure vessels chosen as a more feasible technical solution by automobile manufacturers developing hydrogen cars. Therein, volumetric density slightly above 1 kWh/L is a current standard with hydrogen pressurized to 70 MPa (700 bars). 2) Energy losses from irreversibilities in energy storage and/or recovery High level of reversibility in the respective energy storage and recovery is the main advantage of batteries. Unfortunately, there is at least one fundamental reason for which critical disadvantage of batteries - high price for a unit capacity – is basically incurrable even with cheapest materials. This fundamental reason is the ratio between volume and mass of the electrochemically active materials which can be put into a reasonably operable battery on one hand and the overall volume and mass of all other parts necessary for this reasonable function. This unfavourable ratio can significantly, in several orders of magnitude, improve in „flow“ batteries, and even more if we split the function of the flow battery into a separate electrolyzer designed solely for „charging“ our storage system and a separate fuel cells designed solely for „discharging“ (electricity recovery from the storage system). Unfortunately, the only electrochemically active medium that is more-less applicable in such „ideal“ electricity storage systems (that enable both high capacity and high storage efficiency by combining the high efficiency of direct electrochemical energy conversion with high energy density of a neat „fuel“ used as the energy storage medium), is still hydrogen – which, however, suffers from the costly storage due to low volumetric energy density in comparison with conventional fuels. As soon as we try to improve hydrogen energy density by converting it chemically into a form which is more favourable form the viewpoint of the cheap storage and transport (e.g. into liquid ammonia having energy density above 4 kWh/L, or, by carbon dioxide reduction, into carbon-based synthetic fuels), we will necesarily lose a significant part of the energy originally conserved in hydrogen, as a Gibbs energy of the respective reaction dissipated on the expense of a thermodynamically „spontaneous“ chemical conversion. For example, by simple hydrogen conversion into ammonia by its reaction with atmospheric nitrogen that is achievable on an industrial scale by well-known Haber-Bosch process, you unavoidably lose about 30 % of the renewable electricity which you originally conserved in the „green“ hydrogen. Very similar numbers apply for carbon dioxide conversion into synthetic methane by well-known Sabbatier process, and you can take as a rule of thumb that the more complicated conversion, the more of the originally conserved energy you have to sacrifice. Even worse, none of the synthetic fuels currently considered for large scale energy storage can even approach hydrogen in technical maturity of its direct electrochemical re-conversion into electricity. For example, known ammonia fuel cells are still at least order of magitude worse in their performance than hydrogen fuel cells. And, to my best knowledge, reliable and highly efficient hydrogen fuel cells are - after decades of development - still impossible without use of precious and therefore pretty expensive platinum metals. Finally, as soon as you resort to simply burning your synthetic fuel in an internal combustion engine or any similar equipment, the efficiency of electricity recovery from the respective fuel drops to some 40 %. The second part will follow.

tomas_kalisz 6y ago

Hallo everybody, Apologies again for the length. This is the second part of my comment. 3) Consequences for the economical feasibility of renewables if supported by currently considered power-to-fuel concepts On the basis of previous considerations, we can conclude that should the electricity from renewable resources storage (using currently considered storage techniques as discussed above) become economically competitive with fossil fuels as a mere heat source, the primary energy from renewables should be at least three times, possibly rather four or five times cheaper than the electricity generated from fossil fuels in conventional coal- gas- or oil-fired power plants. Although the price of electricity from renewables has the decreasing tendency, expecting that it becomes competitive with heat from fossil fuels in a near future, especially if we will waste more than a half thereof during the energy storage and recovery, may not be realistic. Therefore, should we wish a “carbon neutral” economy, we may basically have two options: (i) either dispute if we should subsidize rather the renewable electricity in combination with costly hydrogen storage or with one of currently disputed, still highly inefficient power-to-fuel concepts, or, rather, comparably inefficient state-of-art nuclear technology (I am going to add a remark to nuclear technology below), (ii) or seek for an alternative electricity storage method which is so cheap and efficient that it could make, at least in the annual average, the electricity generated from renewables cheaper than the electricity generated from conventional sources. I personally prefer the option (ii). 4) Remarks regarding nuclear energy as a possible solution for “carbon neutral” future I do not like to discourage others, however, I am somewhat sceptical with respect to perspective of nuclear energy in view of the current state of nuclear industry. Please note that, basically, the single concept which they can currently offer are huge PWRs with poor adaptability to grid conditions and extremely poor efficiency of entire power plants about 25 %, on the level of 19th century steam engines. For the extreme regulatory hurdles, they can hardly offer anything significantly improved in a reasonable timeline. Everything is even more complicated by concerns about nuclear weapon proliferation, resulting in plans for burying the spent nuclear fuel forever instead of reprocessing it. In this respect, it appears that what we can currently afford is heavily subsidized, technically outdated wasting with valuable fissile natural nuclides which are definitely a consumable natural resource. 5) Open space for a quick development in metal-based power-to-fuel concepts towards reversibility / high efficiency Although just the concept of energy storage in metallic aluminium as presented in the disputed article currently suffers from the common disadvantage of all currently considered alternative fuels – namely, form the absence of a reliable, industrially scalable method for direct metal reconversion into electricity – there may exist other options, wherein this goal could be achievable within a reasonable time schedule. In 1970-ties, a visionary American inventor Stephen F. Skala filed a series of patent applications proposing cheap alkali metals sodium and potassium as media for a feasible energy storage and transport. Likely, he assumed nuclear energy as a cheap and clean electricity source then, however, this assumption obviously failed: https://1url.cz/AKtDH https://1url.cz/AKtDH https://1url.cz/zKtDR https://1url.cz/zKtDR https://1url.cz/7KtD8 https://1url.cz/7KtD8 https://1url.cz/lKtDy https://1url.cz/lKtDy https://1url.cz/OKthL https://1url.cz/OKthL https://1url.cz/UKtht https://1url.cz/UKtht https://1url.cz/sKthz https://1url.cz/sKthz In my opinion, his vision of Diesel engines fuelled with liquid Na-K alloy and water and producing sodium and potassium hydroxide from which the respective metals can be recovered by electrolysis (the well-known Castner process) may be still appealing, although some aspects like a possible wreckage of a re-build oil tanker full of the alloy explosively reacting with sea water shall be considered very carefully. Similarly, his idea of pipelines serving in parallel for the liquid Na-K alloy transport and as electricity transmission lines might perhaps still deserve an attention of those who consider various alternatives for economically feasible energy transport from sunny desert areas to densely populated regions with a high energy demand. Interestingly, although Skala obviously researched the relevant state of the art thoroughly and strived to address possible improvements in the efficiency of Castner process, he missed the document which may be crucial for feasibility of the sodium economy, because it possibly opens the doors towards direct reconversion of sodium into electricity. It is the Lockheed patent US 3 730 766 by Geisler, https://1url.cz/5KthN https://1url.cz/5KthN describing a membrane-free fuel cell, operating with a consumable alkali metal anode and aqueous solution of the respective alkali metal hydroxide as the electrolyte. If a rapidly flowing very thin electrolyte film may indeed tame the spontaneous sodium reaction with water the way that it may produce useful electricity as described in Geisler’s patent, I believe that this principle could be developed in reliable electricity generators having megawatt outputs within a few years, and reshape the entire landscape of electricity production, storage and transmission within 10-15 years. The third part will follow.

tomas_kalisz 6y ago

Hallo everybody This is the third and final part of my comments. 6) Broader context with a few illustrative examples I provided a scheme showing the requirements and possible consequences of econokmically feasible large-scale electricity storage in publicly available application OrgPad. The scheme is directly accessible under link https://orgpad.com/s/5BfLP-cxj-7 https://orgpad.com/s/5BfLP-cxj-7 A few technical instructions (which might be useful if you will use OrgPad for the first time): Mouse click-and-draw serves for moving the entire canvas, mouse wheel for zooming the entire picture, cells having a fine shadow have a hidden content which can be opened by mouse click on the respective cell. The application does work in modern web browsers like Chrome, Chromium, Mozilla, Opera, Safari, not (or only very poorly) in IE. 7) Conclusion The crucial question is why the relevant laboratory and technical records pertaining to this potentially game-changing invention quietly sleep in Lockheed archives. Myself, I have not a capacity to test a model device in laboratory, nor find out what Lockheed exactly tested and with which outcome. Should any of the readers, however, have such opportunity, I believe that clarifying the crucial question (whether or not Geisler’s device might have indeed worked) might be worth of the respective effort. Thank you very much for your patience.

Havoc 6y ago

I’d rather see them implement the European supergrid frankly. PV in the Sahara and high voltage lines up to Europe. Think that would be a win for everyone

IfOnlyYouKnew 6y ago
That’s sort of a brute force approach. And the Sahara is warm, but solar irradiation varies far less than temperatures. It’s going to be a lie mix of many of these promising ideas, blended in such a way that is, hopefully, not too expensive, not too insecure, not dirty in a new way, and not not at least a little bit fun.
- ThomPete 6y ago
  the fact that you have to blend them is what makes them expensive and for what? Less than 20% of our energy need is electricity.
bildung 6y ago
Right at the beginning of the study it is stated why that is no alternative: The seasonal production/consumption patterns could lead to "excess PV production in summer on a local, national or even international scale". As Sahara PV is still on the northern hemisphere this would not solve the problem the study tries to tackle.
- tda 6y ago
  I would like to see the numbers; how much overbuilding would be necessary. Even if you need to install say 50%-100% extra capacity to meet demand in winter, solar power would still be perfectly economically viable. And I'm sure a valid use for excess power in summer can be found, e.g. desalination. Fresh water demand is surely higher in summer in the Sahara, and otherwise fresh water is easily stored
  - stdbrouw 6y ago
    I looked up the numbers for Aswan in the south of Egypt. Roughly 360 hours of sunshine or a bit more in the summer, 290 hours in winter months [1], so about 80% of max. If we look at direct normal irradiance instead, a more appropriate metric, it varies between 7.93 kWh/m^2/day in June vs. 5.51 kWh/m^2/day in December [2], so about 70% of max. Hour-to-hour and day-to-day fluctuations are another thing altogether, and higher demand in winter (e.g. for heating) yet another consideration, but if we're purely interested in some sort of "seasonal correction" I guess you'd want to overbuild by 40% or a bit less if you set the angle of the panels in such a way as to optimize winter production at the expense of summer production, a common strategy. The closer you get to the equator, the less it matters whether you're in the northern hemisphere or the southern hemisphere. Aswan is at 24°N, a latitude at which you can still find a lot of smaller cities, but as you go to the south of that, infrastructure disappears and it might not be economical to build PV or solar thermal installations in the absolute middle of nowhere. Seems to be about the latitude to which DESERTEC proposes to lay HDVC connections. Not an expert though, just someone who can look up some numbers. [1] https://en.wikipedia.org/wiki/Aswan https://en.wikipedia.org/wiki/Aswan [2] https://www.researchgate.net/figure/Average-Direct-normal-irradiance-of-Aswan-Egypt_fig3_324538284 https://www.researchgate.net/figure/Average-Direct-normal-ir...

blueblisters 6y ago

> The efficiency of this process is approximately 50%, and it is estimated that it may be increased to almost 65% with non-consumable electrodes, wetted cathodes, lower temperature electrolysis cells, and reduction of heat losses That's not too terrible I suppose, plus aluminium is rather convenient to store.

harperlee 6y ago

Without knowing, 500kg per dwelling sounds like it would pose some supply scaling problems.

sideshowb 6y ago
Most cars weigh more than that, yet here we are
- harperlee 6y ago
  Yeah and if a home has 1.x cars, and let's say that means 500ks aluminum, we're talking about doubling demand. So perhaps that has impact in price?
- w0utert 6y ago
  Most cars are mostly plastic and steel, and only a few percent aluminum, but I see your point
CaptainJustin 6y ago
With over 38M [1] households just in Germany that would come to: 19 million metric tons of Al. Each year the people of this planet mine 160 million metric tons of Bauxite [2]. Not sure how the Bauxite ore related in weight to the final product. Maybe this could be a viable option for some energy storage? [1] https://www.statista.com/statistics/464187/households-by-size-germany/ https://www.statista.com/statistics/464187/households-by-siz... [2] https://www.aluminum.org/industries/production/bauxite#:~:text=More%20than%20160%20million%20metric%20tons%20of%20bauxite%20are%20mined%20each%20year https://www.aluminum.org/industries/production/bauxite#:~:te....
- harperlee 6y ago
  Thanks for the data, I think that makes my comment moot :)
- magicalhippo 6y ago
  Wikipedia says[1] global production is roughly 64 million metric tons per year. [1]: https://en.wikipedia.org/wiki/List_of_countries_by_primary_aluminium_production https://en.wikipedia.org/wiki/List_of_countries_by_primary_a...

VBprogrammer 6y ago

The use of non-combustable electrodes only gets a passing mention here but it seems a key part of making this system less carbon intensive. Also, if I remember correctly aluminium smelters use some pretty nasty cover gasses in the process to avoid creating a giant firework, I didn't find a reference to these in the paper.

albrewer 6y ago
I worked in an iron foundry and not an aluminum one, but I was under the impression it was just a nitrogen blanket.
- lylecheatham 6y ago
  Aluminum Nitride actually has a favorable formation so they have to use much less friendly gasses like Sulfur Hexaflouride.
  - VBprogrammer 6y ago
    Thanks, I had Sulfur Hexafluoride in the back of my head but I wasn't sure if I was misremembering that because I've been reading about circuit breakers where it is used as an insulator.

IfOnlyYouKnew 6y ago

Al processing already consumes vast amounts of energy, and the plants are already being used for intraday load balancing. There was a story recently about an incident in Germany where due to weather and strange market mechanisms, the grid was in danger or collapsing. The operator’s third line of defense (after gas peakers and hydroelectric storage, IIRC), was to remotely turn off the Al plant 600 km away, something they can contractually (and technically) do up to four times per day and six times per week for an hour each. That plant uses 1 % of Germany’s electricity. It’s not the only such plant, and Hermany generally frowns on frivolous uses of Aluminum: cans are far less popular, for example, and will earn you dirty looks. The Audis may make up for it I part, but in the US it should be possible to shift some non-trivial fraction of the electricity consumption by, say, doubling processing capabilities and running them seasonally. Al isn’t too expensive, and the plant is a small part of the costs anyway, with energy making up the bulk. Of course there are countless opportunities to optimize consumption patterns once consuming devices all have data connections: heat and cooling, washing machines, dryers, dishwashers, roombas, notebooks... all these devices could shift their consumption on the hours-to-one-day scale and easily cushion even large variability in production. Once electric cars are ubiquitous, they‘ll make up the bulk of consumer electricity usage and they could even feed power back into the grid. The only real problem with Al is, obviously, that we keep misreading it as AI. The confusion will drive some lesser Al insane, and either that or the singularity will cause a bloodbath, henceforth known as Al Gore.

blauditore 6y ago
>cans are far less popular, for example, and will earn you dirty looks I never heard nor experienced this myself in Germany. After all, almost all of they get recycled because their price includes a deposit you get back upon recycling.
- Tade0 6y ago
  I believe it may have more to do with the stigma of drinking your Bier from a can, as opposed to a glass.
- arbitrage 6y ago

alecmg 6y ago

I remember reading Donald Sadoway got inspiration for developing liquid metal batteries [1] from watching how aluminum smelting is basically a battery already. These batteries are more efficient than aluminum energy storage, and were also aimed at large scale with cheap abundant materials (initially at least). But high temperatures involved make it not very convenient. [1] https://en.wikipedia.org/wiki/Molten-salt_battery#Liquid-metal_batteries https://en.wikipedia.org/wiki/Molten-salt_battery#Liquid-met...

audunw 6y ago
Donald Sadoways battery startup Ambri seems to finally be breaking through commercially, so I'm quite optimistic about them. It was quiet for a while but now there seems to be commercial progress: https://ambri.com/news/ https://ambri.com/news/
- baking 6y ago
  They had a partnership with NEC Energy Solutions which then left the integration business about 9 months later, so that was probably a business setback. I'm still hopeful that they get a chance to scale with projects like data centers and municipal electric utilities. https://www.greentechmedia.com/articles/read/storage-integrator-nec-es-halts-new-business-begins-winding-down https://www.greentechmedia.com/articles/read/storage-integra... Edit: This recent Real Engineering piece updates their current business situation: https://www.youtube.com/watch?v=-PL32ea0MqM https://www.youtube.com/watch?v=-PL32ea0MqM https://teitimes.com/teaser/2021-02/#pf7 https://teitimes.com/teaser/2021-02/#pf7 The first systems will go into the field as 40 kWh trial systems to demonstrate their effectiveness and operation. The pilot battery for Terra-Scale, which will be one of these trial systems, will be installed late 2021. A larger 1 MWh commercial-scale trial system will be installed in late 2022. Volume production will then start in 2023, at which time Ambri will build battery systems that are available in 1 MWh blocks and have discharge rates of 4 hours or longer.

tim333 6y ago

It's also potentially an energy source for space launches - the space shuttle boosters burnt aluminium.

IXxXI 6y ago

Elon Musk deployed a grid tied multi megawatt hr battery in australia that is far superior. https://www.popularmechanics.com/science/a31350880/elon-musk-battery-farm/ https://www.popularmechanics.com/science/a31350880/elon-musk...

TruthWillHurt 6y ago

This is a very stupid proposition made by looking at energy-capacity figures without taking real-world application hurdles into account. Aluminum fuel cells have a slow energy discharge rate, largely due to the Oxigen-Reduction Rate (ORR) limit, even when the air Cathode is doped in exotic catalysts such as Platinum. Furthermore, fuel-cell Electrodes, be it an Aluminum-air or Hydrogen-air fuel-cell, suffer from "CO2 Poisoning", which makes their efficiency drop in open air. Not commercialy viable.

ed25519FUUU 6y ago
The unfortunate reality is energy/battery tech headlines like these are one of the reasons we haven’t been able to garner widespread support for nuclear. Everyone thinks we’re on the cusp of having a big enough or strong enough battery to power industrialized cities but in reality we’re impossibly far from that.
- Robotbeat 6y ago
  No. The reason nuclear has a hard time isn’t because of technology. It’s because of paranoia and poor scicomm. And because no one really cares about climate change enough to make it a priority. People won’t say out loud “climate change is less of a priority than phasing out nuclear (or removing hydro dams or saving a few bucks on upfront cost of postal trucks, etc),” but that’s what they’re implying. In that sense, Greta Thunberg is right that leaders just don’t care that much about climate change. Storage technology is capable of powering cities. Heck, the largest grid storage sites in the US are for backing up nuclear power plants on the East Coast (matching day/night loads with baseload supply). This silly infighting between different clean energy technologies (storage, nuclear, renewables) needs to stop.
  - whizzter 6y ago
    Imo it's a rather cruel irony that the green parties (in Europe at least) were in big part getting their growth from and membership dedication from the Harrisburg and Chernobyl accidents. So when we really need a "green" party they're filled with zealots who're unable see the harm reduction tradeoffs that needs to be done.

giantg2 6y ago

So from a residential perspective, they're just using this to produce hydrogen for a hydrogen fuel cell. The reactions that require the higher temperatures would need to be industrial (and don't seem to be more beneficial than other methods). So what are the benefits?

esperen 6y ago
Energy storage in the form of aluminum.
- Robotbeat 6y ago
  Kind of irrelevant if we don’t have carbonfree electrodes for smelting aluminum.
  - esperen 6y ago
    If it brings the net carbon footprint down, it could be relevant. Progress is typically iterative
    - Robotbeat 6y ago
      But that hasn’t been established here. The aluminum produces hydrogen (at some level of inefficiency) which then produces electricity in a fuel cell (more inefficiency). Consumable electrodes are actually doing chemical work in the aluminum. It’s not just wear from use. To produce 78 grams of Aluminum directly requires 48 grams of Carbon electrodes (using made by graphitizing some tar or coke) which oxidizes to 176 grams of CO2. Aluminum is 31MJ/kg specific energy. Assuming 70% efficiency conversion from aluminum to hydrogen and 70% from hydrogen to electricity (both fairly optimistic figures), you’re talking about 535 grams of emitted CO2 for each kWh of electricity out. Ignoring the electricity input, inefficiencies and losses in making the aluminum, and assuming perfect conversion of the tar to electrodes. Worse than a good, advanced combined cycle natural gas plant (which can get as good as roughly 350 grams per kWh for record efficiency plants). I just don’t see how this is gonna be a net win without carbonfree electrodes. It seems just about impossible here. Storing hydrogen directly looks to make way more sense.

dominojab 6y ago

That's what ambri is developing , instead they use another transition metals that have the properties described in the paper.

acvny 6y ago

350–530 kg Al would be needed per apartment. One question left unanswered is - how many cycles does this system support before it becomes substantially inefficient?

Gravityloss 6y ago

There are zinc batteries as well, that you can buy today by https://redflow.com/ https://redflow.com/ . It looks relatively simple to me, during charging it's just electroplating zinc. (I'm not a chemist.)

at_a_remove 6y ago

I know their energy densities are crap, as are their discharge rates, but boy would I love to see nickel-iron batteries take off for large projects. HN is already about scale, scale, scale, and wow would nickel-iron benefit from that. Not exactly environmentally unfriendly, either. Another reason I think about this for infrastructure projects is, well, America is terrible about maintaining its infrastructure. It's a bit like code -- don't be surprised if that thing you banged out has to be viable for a decade more than you anticipated. And no battery tech stands up to decades of wear and tear like nickel-iron. I just know that any fancy battery stack we want to offset wind or solar will suffer from neglect as the people writing the budgets turn their eyes to shiny new things. Might as well plan for it.

specialist 6y ago

Meta: I LOVE this article's "Highlights" pullout at the top. +1 For respecting the audience. This should be the norm. "Pullout" might not be the right name. Preamble? Sidebar (up top)? The bullet list is not quite an Abstract. Maybe just Bullet List?

nwah1 6y ago

95% of worldwide grid energy storage comes from pumped storage hydro. Yet almost nobody mentions this, or suggests building more.