Climate clippings 64

I’m currently working on another project, which is taking up much of my time. This week we had about 200mm of rain in one day. That could have been why my cable connection to the internet disappeared for 36 hours. I’m grateful to John D who sent me the links for each item in the following except the last.

Zero-emissions engine that runs on liquid air

A new zero-emissions engine capable of competing commercially with hydrogen fuel cells and battery electric systems appeared on the radar when respected British engineering consultancy Ricardo validated Dearman engine technology and its commercial potential.

The Dearman engine operates by injecting cryogenic (liquid) air into ambient heat inside the engine to produce high pressure gas that drives the engine – the exhaust emits cold air. It’s cheaper to build than battery electric or fuel cell technology, with excellent energy density, fast refuelling and no range anxiety. It just might be a third alternative.

Among the advantages are that it doesn’t catch fire or explode and doesn’t require rare materials.

Residential green building trends

According to a post at Climate Progress the total green building market is expected to be worth $135 billion in the US in the next three years, with non-residential activity set to triple. Residential opportunities are growing as well. The post lists some top trends that will help accelerate growth in the residential market, as compiled by the Earth Advantage Institute.

These include greater urban density, multifamily homes, energy auditing and retrofitting, new materials, monitoring and tracking devices, and the broader adoption of residential energy ratings for homes.

Energy labelling systems are appearing in many states, offering a miles-per-gallon style estimate of a home’s energy consumption for home buyers and home owners. The Energy Performance Score and the Department of Energy’s own Home Energy Score have been rolled out in different climate zones across the US to encourage home owners to compare energy use and undertake energy upgrade work.

Blowing bubbles to reduce friction on ship hulls

Mitsubishi Heavy Industries (MHI) and transport company Nippon Yusen Kaisha (NYK) have been investigating a system intended to reduce the frictional resistance between a vessel’s hull and the seawater using a layer of air bubbles known as the Mitsubishi Air Lubrication System (MALS).

To verify the CO2 reduction efficiency of MALS, MHI has installed it on the “YAMATAI,” a module carrier operated by an NYK subsidiary. A module carrier was chosen as the first permanent installation of the system because they have a shallow-draft hull that generates relatively low water pressure, which minimizes the amount of electricity required by an air blower to supply air to the vessel’s bottom. Additionally, the flat, wide bottom is able to better retain the supplied air under the vessel’s bottom.

Initially they expect a reduction in CO2 emissions of around 10% but with additional design features they expect an overall cut of 35%.

Alarming outlook for urban water supply

This post at Climate Progress looks at the issue of the impact of drought especially on urban water supply in the US and the world. It draws from a post by Jay Kimball at 8020 Vision. Concerns include:

  • By 2020, California will face a shortfall of fresh water as great as the amount that all of its cities and towns together are consuming today.
  • By 2025, 1.8 billion
 people will live in conditions of absolute 
water scarcity, and 65 percent of the worlds population will be water stressed.
  • In the US, 21 percent of irrigation is achieved by pumping groundwater at rates that exceed the water supplies ability to recharge.

Mitigation strategies suggested include greater urban density to allow more water catchment to remain, green housing development to capture and treat water before it becomes urban runoff, and reviving rust-belt cities rather than continuing to expand in the sunbelt.

A criticism of the article is that the maps focus on the present and recent past. The world map, for example is from 2003. An earlier post which linked to a NCAR study of drought contained this scary map:

Drought forecast 2060-2069

It should be noted that drought involves more than precipitation. Here’s an image from IPCC AR4 that includes soil moisture, runoff and evaporation as well:

IPCC AR4 WG1 Figure 10.12

I don’t think you can place a high degree of confidence on these forecasts on a regional basis, but the chances that significant and problematic change will occur are quite high.

The true effect of Kyoto

Marcus Preist in the AFR did a recent article on a study by Rahel Aichele and Gabriel Felbermayr on the effects of outsourcing industries to developing countries in implementing the Kyoto Protocol. Here’s the abstract:

The carbon footprint of a country refers to the flow of CO2 emissions caused by domestic absorption (i.e., consumption and investment) activities. Trade in goods drives a wedge between the footprint and domestic emissions. We provide a new panel database on carbon footprints and carbon net trade. Using a first-differenced IV estimation strategy, we evaluate the effects of ratification of binding Kyoto commitments on the carbon footprint and emissions. Instrumenting countries’ Kyoto commitment by their participation in the International Criminal Court, we show that Kyoto commitment has reduced domestic emissions in committed countries by about 7%, has not lowered carbon footprints, but has increased the share of imported over domestic emissions by about 14 percentage points. It follows that the Kyoto Protocol has had at best no effect on world-wide emissions. The results highlight the difficulties of unilateral climate policies. (Emphasis added)

Here, I think, is at least a version of the paper, which I haven’t had time to read.

Greg Hunt of course said, we told you so. A spokesman for Greg Combet said, well that’s why we are giving assistance to trade exposed industries.

Erwin Jackson of the Climate Institute said the research was not robust, because while most countries ratified Kyoto in 2002 they were not obliged to cut emissions until 2007, so they didn’t have to do anything to meet targets.

Be that as it may, the authors main contention is that while Kyoto may have been an important first step, a broader international approach is needed.

59 thoughts on “Climate clippings 64”

  1. Tom, coming to think of it, I had no warrant from the article to say it wouldn’t explode. But it’s surely not as dangerous as hydrogen.

    Also we are talking about liquid air. Does that make a difference? I get the impression it does.

  2. I have done a lot of work with liquid nitrogen and can say categorically that it is impossible to explode it.
    This engine has a lot going for it.
    It is easy enough to distill off the oxygen from the air if you wish.
    About 20 years ago a Professor or at Melb Uni published a paper on the use of liquid NO2 for transport – I cannot find the paper.
    For years I had this vast spherical tank of liquid NO2 outside our works.
    I used it along with methanol to reduce powdered iron ore to pure iron.
    Unfortunately the steel industry is too totally stupid to abandon blast furnaces. I understand that India has taken up the technology as alow carbon way to reduce iron ore to iron/steel.
    Huggy

  3. “Liquid nitrogen is a cryogenic liquid. At atmospheric pressure, it boils at −195.8 °C. When insulated in proper containers such as Dewar flasks, it can be transported without much evaporative loss.[27]”
    The big sperical tank I had was a Dewar flask and we kept it at at atmospheric by keeping it cool, in facr tyou can use the gas to run the refrigerator.
    Fucken atmospheric pressure ma petites.

    You inject it into a hot chamber and THEN the pressure rises – Capish?????????

  4. Unfortunately guys, it will take a lot of energy to refrigerate air until it liquifies. (N2 liquifies at something like -200C). The energy required to create the fuel is going to be much larger than the mechanical energy available when it warms, turns back into a gas and expands.

    Pretty batshit crazy.

  5. Bill, you make out like the “respected British engineering consultancy Ricardo” are a mob of nongs. But I’ll leave it to people who are technically qualified.

  6. Bill, I was wondering about the energy required to liquefy (or even pressurise) it as well. I guess you could use it as a storage device for when you’re generating excess solar- or wind-generated electricity.

  7. Bill, the energy recovery from liquid nitrogen is about 90% if you do it right.

    This is certainly better than the “Redfow” (75% on a good day). It is up there with Lithium and advanced lead acid.

    Wish I could find that paper.

    Huggy

  8. DI(nr) I think that might be the point – you could use it as a buffer to store the energy when you’re producing too much, and dump it back into the grid during times of peak load. Especially if (as they claim) it’s so cheap to produce.

    Given that the energy density of the Dearman engine is so low though, I can’t see it replacing Li-ion for vehicles though. And once you’ve vaporised your liquid nitrogen/air, you can’t recharge it like you can with a battery (I’m thinking in terms of regenerative breaking here). Also, I wonder what they’re making the pistons out of – must be something good to withstand rapid changes in temperature from -200 to 25 degrees C and back again.

  9. They might be using ceramics, Jess.

    It’s a pity that the Gizmag article was a bit light on detail.

  10. From the Abstract, quoted above:

    Instrumenting countries’ Kyoto commitment by their participation in the International Criminal Court,….

    What on earth has the International Criminal Court got to do with the Kyoto Protocol? Surely they must mean some other body. A search or the paper itself, to which you have provided a link, reveals no reference to the ICC.

    Depressingly though, it reveals that introducing carbon taxes et al by Kyoto Protocol signatory countries has led to no overall reduction in carbon emissions but instead to a transfer of carbon emitting activity to non protocol signatory countries.

  11. GregM, I read that rather quickly and didn’t notice the “International Criminal Court”!

    Various studies have been saying about Britain that the emissions reductions have been offset by greater imports. Now it is being said about the whole lot, unfortunately.

  12. The ICC is cocerned with crimes against humanity

    As yet, causing rises in global temperatures have not been so termed by the States parties to the establishment of the Court.

  13. GregM, here’s another paper by the same authors:

    What a Difference Kyoto Made: Evidence from Instrumental Variables Estimation

    Make of it what you will, but:

    “We find that countries’ membership in the International Criminal Court (ICC) predicts Kyoto ratification in a panel model.”

    And here:

    The EU as an ‘Intergovernmental’ Actor in Foreign Affairs: Case Studies of the International Criminal Court & the Kyoto Protocol

    Brian, sorry I didn’t reply back to that Der Spiegel article you linked to in #63. Very informative. I went looking though German newspapers via google translate (before accidentally closing my browser with about 15 pages open! gave up in frustration at that point…) and found a bunch more problems attached to that project…coastal grid permits not the least, and other tech co-ordination problems…waiting on parts, and even the construction vessels themselves are yet to arrive from Korea.

    All a bit of a mess by everyone involved it seems.

  14. Brian I don’t want you to take my comment as in any way criticizing you.

    I read your comments about the demands that were upon your time when you posted and I am grateful that you published Climate Clippings 64. I appreciate that you were rushed and therefore would not have read closely what you posted.

    I always find the Climate Clippings posts valuable and I find that most of the posters who respond to them are thoughtful, insightful and informative.

    I was concerned only that the Abstract was so extraordinarily wrong in its reference to the ICC that I wondered if its authors could lay claim to the same excuse.

    The good thing though is that that led me to read the substantive paper to which the Abstract referred.

  15. Nick, thanks for those references.

    I had thought that that was what the Abstract may have been referring to. But then I looked into the paper that Brian linked to and could find no such reference or attempt at correlation in it.

    I should say however that correlation between ratification of the Kyoto Protocol and ratification of the Rome Statute of the International Criminal Court hardly needs any serious study or the production of academic papers.

    Both are European projects and all Europe’s forty-four member states have an equal vote with every other country in the world so that Finland (population less than Victoria), Austria (population less than NSW) Ireland (population less than Queensland) Slovenia (population less than WA) Estonia (population less than SA) Cyprus (population less than Tasmania) all have an equal vote with Australia in the world’s affairs, subject of course to the EU rules that bind them on collective decision making on foreign policy – ie both the Kyoto protocol and the Rome Statute.

    Does not that make you wonder why such countries such as China, Russia, the United States and India are not parties to those treaties?

    Perhaps international decision making would be improved if that little european farce was exposed by allowing each of China’s 22 to 33 provinces, Russia’s 87 and India’s 28 states, along with the US’s 50, to each have a vote at the direction of their national governments. We could throw in our six (or eight) votes as well.

  16. Not much media attention to the La Nina effects of a warmer Indian Ocean and Perth’s heatwave this past month. Seems very distinctive to me here on the eastern, cooler, wetter coast. I’m savvy enough to be dreading the next El Nino, but official analysis of the current situation seems muted IMHO.

  17. Liquid air power: I sent the link to Brian partly to highlight a possibility for zero emission ground transport that does not depend on technical breakthroughs and partly to highlight the relative costs of a number of alternatives and partly to highlight the relative energy storage densities of these alternatives. As a rough approximation, the diagrams suggest that storing power in lithium batteries will give a 25% increase in energy density in return for a capital cost increase of 800%.
    I would like to see some hard figures but liquid air may be attractive for applications where clean power is important and the daily travel distance would make it necessary to recharge an EV several times per day.
    Liquefying air is fairly simple and would probably be done at the service station. After all, all you need is air and electricty.

  18. GregM, no probs, I didn’t take it as a criticism. I’m amazed though at what is obviously a stuff up. You wouldn’t expect it from a couple of Germans.

  19. Liquid N2 is probably the safest energy storage material of all .
    Have held it in my cupped hands at – 200C. How come?
    Th liquid upon release, immediately generates a film of room temperature N2 gas which is between you and the liquid.
    If it gets spilt all over the road just walk through it.
    You have to work really hard to burn yourself with it.
    Huggy

  20. John D, as that graph is using a log scale, the difference between the energy density of liquified air and Li-ion looks like a factor of something like 2 or 3 (and the range of estimates for the Dearborn engine is very wide).

  21. Nick @ 16, I was working on my post on renewables in Germany the other night when the internet connection went down. Unbeknown to me the autosave function on WordPress hadn’t been working and I ended up losing everything I’d done.

    I’ve recreated it now. Not entirely happy, but I’ll look at again on Sunday and post on Monday.

    GregM @ 18, fair comment.

  22. The Dearman engine seems to be a really promising development but it is always helpful to look for the downside. Could this be the energy cost of liquefying air on a sufficient scale? Does anyone know anything about this?

  23. I dare say its to early to tell the effect of Kyoto: because the sleeper factor is the incentive it gave to the production of renewable technologies in signatory countries, many of which are yet to play out their reduction potential.

    That is not to suggest that the critique of offshoring is invalid.

  24. gregM, they use the term “instrumental variable” (IV) so, without reading the paper, I guess they’re trying to find a way to model ratification of the Kyoto protocol that isn’t confounded by the problem of public awareness of AGW in the target countries.

    By which I mean: ratification of kyoto is associated with all sorts of domestic political pressures to reduce carbon emissions, so using Kyoto ratification directly to predict the effects of Kyoto could just mean that you are modeling the effect of those domestic pressures. But by finding some alternative variable that you think is unrelated to those pressures, and using that instead, you get around the problem. In theory.

    I’m extremely dubious about IV analysis. Economists love it, but I think it is an example of several tricks they use (like their mathematical tests for causality) that load too much of the interpretive tasks onto the data. After all, the best Instrumental Variable would be the one that perfectly predicts Kyoto ratification – in which case, haven’t you got the same problem all over again?

    But what you read is not a mistake, and the authors definitely aren’t confusing Kyoto and ICC.

  25. Doug: I googled “liquid air package plants” and came up with this 300 litres/h liquid nitrogen plant The implication is that production of liquid air doesn’t need to be large scale. The logical place to produce it is the service station so you don’t have to have tankers of liquid air shuffling around the countryside.

  26. Kyoto helped focus world attention on AGW and the need for serious action. However, it is debatable whether the commitments themselves made much difference.
    Part of the problem with international agreements on climate action is that countries will be jostling to avoid commitments that will put them at a disadvantage, particularly if they are “legally enforceable.” It may be smarter to encourage countries to set aspirational targets that give them the option of backing off if it really is having an effect on their economy.

    It may also help if some forms of climate action were excluded from the WTO rules. It is much easier to sell climate action if is going to create jobs in the country that is doing the climate action and not making balance of payment problems more difficult.
    Climate action is far less attractive if what climate action means is that countries like the US have to go even deeper in debt to import even more than they do now because the WTO rules force them to buy from some other country.

  27. @29, Great presentation,
    Mabye in conjunction with sundrop and their seawater greenhouse at Port Augusta.

    Used to be this mob.

    Can’t find anything recent, commercial secrets i spose.

  28. John D, for some strange reason your comment @ 28 on small-scale liquid nitrogen plants lodged in spam for a while. Clearly Askimet doesn’t like it!

  29. Meanwhile, the Tasman Sea is an ocean warming “hot spot” – http://csironewsblog.com/2012/01/30/warming-in-the-tasman-sea-a-global-warming-hot-spot/

    Paper co-author, CSIRO’s Dr Wenju Cai, said that while the finding has local ecological implications in the region surrounding the hotspots, the major influence is upon the ocean’s ability to take up heat and carbon from the atmosphere.

    In Australia’s case, scientists report intensifying east-west winds at high latitudes (45º-55ºS) pushing southward and speeding up the gyre or swirl of currents circulating in the South Pacific, extending from South America to the Australian coast. The resulting changes in ocean circulation patterns have pushed the East Australian Current around 350 kilometres further south, with temperatures east of Tasmania as much as two degrees warmer than they were 60 years ago.

    “We would expect natural change in the oceans over decades or centuries but change with such elevated sea surface temperatures in a growing number of locations and in a synchronised manner was definitely not expected,” said CSIRO’s Dr Wenju Cai.

  30. Pumping air bubbles underneath a ship to make it go faster/more slippery is highly likely to work. The Russians have a torpedo, the Shkval, that flies through the water at 200 kt or more.

    Huggbunny, that micronuke sounds great! Do I detect a slight waning in your endless nuclear FUD?

  31. Wilful,
    I have no Fear, no Uncertainty and no Doubt that nuclear power is total crap especially if you live near a waste dump (guess whose land??)
    http://www.youtube.com/watch?v=7iTp7VcqYBk

    Agree on air bubbles suggested them years ago to my Brother in Law whose students raced model boats in some competition or other. He thought it might have been cheating.

    Huggy

  32. Huggy asked:

    Do I see a slight waning in your endless nuclear advocacy?

    I don’t accept your characterisation of my advocacy. I’m interested in what what works to reduce CO2e emissions/inventories on a world scale on the timelines we need it to work at a cost that is politically plausible at the lowest environmental footprint. In some settings, that may include nuclear power and in others, it won’t. You may be confusing my refusal to say no in principle to nuclear power for advocacy. That’s a mistake.

    As to Australia, I think nuclear power politically improbable in the short term, and so, desirous as I am of the sharpest and earliest reductions in combustion of fossil HC possible, I am very chuffed when I read of apparent improvements in the feasibility of technologies most people are willing to support. Having a greater suite of credible options available is a very good thing IMO, whatever one thinks of nuclear power here or anywhere.

    If everyone took this approach, I believe we’d have a much better context for debate over energy infrastructure policy.

  33. Fran, your refusal to say no “in principle” is problem for uneducated unsophisticated clods such as myself. People who support torture take the exact same position, for example.
    I take the view that people who are comfortable with the dumping of nuclear wastes on aboriginal lands – People who are comfortable with the manifestly corrupt nature of the nuclear “industry” and the entirely avoidable Fukishima incident cannot stand back and say “in principle” nuclear power is a good thing. Gas chambers are “in principle” a good thing when used painlessly kill cattle. Not so good when you fill them with people.
    Fran, you obviously mean well but you are an idealist, the nuclear power industry as it exists in this universe is founded upon nepotism, corruption and the nuclear arms industry and will continue thus – Iran and Pakistan come to mind.
    If “in principle” segregation of students on a racial basis was shown to be a good thing would you support it ? No you would oppose it “in principle” – I presume.
    Huggy

  34. Huggy, I thought that your first comment @33 was light-hearted. Fran, as is her nature, doesn’t do light-hearted terribly well or often. But do you have to try and turn this into another nuclear stoush? I believe that Fran and others have answered your points re nuclear waste on anyone’s land, and the structure of the nuclear industry, many many times. I think they’re all strawmen, a waste of time to answer, but your making an analogy to gas chambers is a new low. You’ve godwinned the thread, you lose.

  35. Huggy

    I’m not going to be party to another nuclear power stoush where we simply revisit old arguments. I don’t accept your framing of the issues at all. I will note that your description of Fukushima as “entirely avoirdable” is an odd view for someone chastising me for my refusal to exclude nuclear power on principle.

    Some brief responses to your other remarks:

    Fran, your refusal to say no “in principle” is problem for uneducated unsophisticated clods such as myself. People who support torture take the exact same position, for example.

    Superficially, it may seem so, but it’s not the same thing. Torture concerns how one human being may deal wittingly with another. It really is a matter of ethical principle, and one either warrants it in principle, or not. Whether it secures advantages or not is a discussion those who warrant it have after declaring it OK in principle. Nuclear power is no more a matter of ethical principle than is any other power production technology, including coal or gas or oil combustion. Which mix of technologies one chooses may raise other ethical principles — the legacy question prominently among them — but these are inevitably subject to the broad calculus or risk trading that has informed all of human history. The data which will inform that calculus is measurable.

    If “in principle” segregation of students on a racial basis was shown to be a good thing would you support it ? No you would oppose it “in principle”

    Hypothesis contrary to fact or perhaps, argument by equivocation. There is no way of showing that racial segregation is good in principle. All data on the results of such a policy would point to its feasibility or lack thereof in practice. In principle, it strikes at the conception of human community, which is foundational, IMO, to human possibility. It could never be right in principle. It would always be an exercise in misanthropy and spring from the worst forms of angst and fear noted in human history.

    To compare nuclear power to either torture or racism is patently absurd.

  36. Thanks for the Dearman link Doug. It all sounds like early days. One thing that would be good to know is how the efficiency of a liquefaction, storage, motor system compares with a battery, electric motor system.

  37. John D
    It would be good to have that comparison but even if the balance leans heavily to battery-electric systems the provision of emissions-free motive power with superior range and performance without reliance on rare materials might just be justification enough to prefer this system over battery-electric. Apparently Dearman engines are seen to have potential for cooling. I wonder if they might provide back-up energy storage for large scale solar or wind power plants for when the sun don’t shine or the wind don’t blow?

  38. Doug: It looks like storage density is about 50 kWh/m3. A large below ground tank could store a useful amount of electricity and may be justified for converting off peak power to peak power. But I haven’t done any serious sums.

  39. Thanks Salient Green: 70% is not as good as lithium batteries but costs would be much lower and relatively large scale storage is feasible. Use of liquid air should also be feasible at small scales. I could imagine a city skyscraper, suburban block etc. using the process to avoid expensive grid up grades and take advantage of much cheaper off peak power. (Ditto industries where a peak demand charge is an important part of power costs.)

  40. I agree with you guys, cryogenic storage has a lot going for it.
    The materials required are really abundant and low cost 🙂
    It is safe, unless some real dumb arse blocks up all the ports in the cryostorage system. If located on an open second floor (not the basement) you could sell off the liquid N2 and sell it. (See if you can work out why an open second floor).

    Huggy

  41. A lack of good storage solutions are the main reason I remain sceptical of most proposed solar electricity generation. If cryogenic air is sufficiently scaleable, efficient and affordable, that makes PV or solar thermal much more realistic.

    Though I have to wonder why this hasn’t been thought of before, I mean I’ve heard of compressed air cars since the 1970s, is this just the latest overhyped buzz thingy that will amount to nothing?

  42. Wilful, compressed air cars out this year, damn ugly, maybe Tata could use some of Jaguars stylists since it owns em.

    I prefer the Yamaha.

    Jess, Noooo!!!, don’t introduce them to Australia, they’ll eat my esky ( that i use to keep the cane toads out of the garage).

  43. Don’t conflate compressed air storage with cryogenic. Cryogenic is NOT pressurised; it stores at atmospheric pressure and operates at a pressure that is determined by the temperature rise induced by heat transfer into the working space work is then done as the pressure reduces to atmospheric. Temperature also rises to close to ambient.
    OTH pressurised air is stored at some high pressure, operates by extracting some of the work required to get the high pressure.
    This is really simple and basic stuff guys.
    Huggy

  44. Huggy: the advantage of compressed air energy storage for cars is that it provides the option of energy recovery during braking. Liquid air sytems don’t do this.

  45. HB, I’m not conflating them, I’m merely observing that conceptually they’re not such a leap from each other. People have been trying to get compressed air working for a long time now (also, Stirling engines), I am surprised that cryogenic air is a new thing. Which makes me sceptical.

  46. Braking with Liquid air systems.
    Sorry JohnD I am really stupid; of course you can recover braking energy. All the brakes have to do is heat up some mass or other and then the energy from this mass is transferred to the working fluid and the energy recovered.
    You know it makes sense 🙂 Huggy

  47. To make cryo work you first have to add energy by bringing the temperature up to or greater than ambient. When you do this the pressure of the gas rises. This pressure rise is available to do work. When you do work with the gas its temperature falls. You need to stop extracting work at 0C. Same applies to compressd air, you don’t want ice clogging up the works.
    Advantage of cryo is that it is intrinsically safer – no pressure vessel.
    You could refuel in seconds whereas recharging a pressure vessel involves heat exchangers and all sorts of stuff
    Sorry if this is all a bit cryptic, I am not well.

    Huggy

  48. Huggy: There are a number of ways you could recover braking energy as heat and re-use to boost energy recovery extra energy from the liquid air. Would have to think through the practicalities though. If I am right in thinking that urban trucking, buses and taxis are the logical starting points it may actually make more sense to use the cryogenics to to provide most of the power to a plug-in hybrid or similar. You could even use the heat from the electric motor/battery cooling system to increase the energy recovery from the liquid air.
    BTW it takes about 50% more heat to convert liquid air to air @ 20 deg C compared with converting ice to water @ 20 deg C. Unlike ice the liquid air gives the option of recovering some of this stored energy as power.

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