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Green Material for Refrigeration Identified
- makerofspoons 8y agoDrawdown.org ranks refrigerant management as the number one way to fight climate change: https://www.drawdown.org/solutions-summary-by-rank https://www.drawdown.org/solutions-summary-by-rank
- _verandaguy 8y agoShort of digging a pit and lining it with salt, is there anything that a regular person not actively involved in research about this can do? I'm specifically curious about things that can be done in apartments or condos, where flexibility is low, but I'm also interested tangentially in solutions for (detached) home owners living in sparser settings with more control.
- torpfactory 8y agoThe big issue is what happens to the refrigeration gases at end-of-life because they have such high global warming potential. The units are nominally hermetic, so they should last their entire life without leaking much refrigerant. If you have an old AC unit, try to dispose of it responsibly by not sending it to a landfill. A responsible recycler/disposal facility will reclaim the refrigeration gases for recycling or disposal. There really aren't good alternatives available for purchase right now. Almost all units sold today will contain gases which have low Ozone Depletion Potential but still have high Global Warming Potential (~2000-9000x as potent as CO2). There is a heat pump hot water heater available from Sanden using CO2 (ironically) as a refrigerant, which has a GWP of 1. It is pretty darn expensive. This whole area is really a place we need some startup innovation. Both products that use something other than HFCs for refrigeration and some kind of business model or non-profit which will have the goal of getting old units out of the hands of consumers responsibly.
- Brakenshire 8y agoSeems like it would be easy to fix within any particular jurisdiction by requiring some deposit on any new fridge which could be redeemed when it was disposed of.
- Causality1 8y agoThat would effectively just be a tax on fridges since they last so long.
- baybal2 8y agoCO2 is not an efficient refrigerant, its critical temperature is 31C, but CO2 is darn cheap
- jabl 8y agoOver here it seems CO2 refrigerators are increasingly common for supermarkets, warehouses etc. AFAIU it can be made about as efficient as HFC's, but the up front cost is higher due to higher pressures. OTOH CO2 is cheap, as you say, and there's no risk the next iteration of the F-gas legislation will make your new investment EOL.
- torpfactory 8y agoYou can also operate the CO2 in a 'trans-critical' mode which gets around some of the issues of the low critical temp. This is done by using a gas cooler to cool supercritical fluid in place of the typical condenser. There aren't really many good alternatives that are cheap, have very low GWP (less than 100), are non-toxic and non-flammable. HFOs are probably the closest to this, but even these are often mildly flammable and typically quite expensive (often > $50/kg).
- cr0sh 8y ago> If you have an old AC unit, try to dispose of it responsibly by not sending it to a landfill. Considering someone stole the AC unit off the roof of the house next door to me in the middle of the night (it was a rental property and nobody was currently living there). You know - meth. Anyhow - something tells me there might be some valuable material inside an AC unit, so why anyone would just take it to the landfill (unless it has an A/C recycling program - some do)...
- rplnt 8y agoFight (lobby, voice your opinion, etc) at your local level to preserve (and expand) trees in streets. Fight against parking lots replacing greenery, fight for the opposite. Ask your municipality to spray down roads in the evenings when it's really hot (if your area does not suffer from drought). Learn to use morning cool air to cool down the flat (depending on where you live). Don't AC your house to (extremely) low temperatures. Get good shades.
- toasterlovin 8y agoSpend less money. That can mean buying less stuff (or used stuff), or it can mean not paying other people to do stuff for you (learn how to fix/build things your self, eat out less, etc.).
- wes-k 8y agoAwesome site I never heard of, ty! Worth noting that coming in at #4 is the one we can all contribute to right away -- https://www.drawdown.org/solutions/food/plant-rich-diet https://www.drawdown.org/solutions/food/plant-rich-diet. The amazing thing is your dietary choices impact those around you as well so you end up having a > 1 person impact! My partner answered a TON of vegan questions, worth checking out if anyone is interested or has questions: https://www.wikiful.com/@MsKapow/the-vegan-inquisition https://www.wikiful.com/@MsKapow/the-vegan-inquisition
- nightski 8y agoThat statistic only true when looking globally. If you look at U.S. statistics, greenhouse gasses from meat is only 3% of total. Plant farming represents 6%. If you want to make the argument that cows eat plants, while true, often they spend the majority of their lives eating grass. Feed lot stage is generally near slaughter. In addition, many farms use by-products of things such as sugar production to feed animals (molasses, beet pulp pellets, etc...). The only reason corn is used is because it is the single most subsidized crop in America. This is not a clear cut statistic at all.
- toasterlovin 8y agoNot to mention that the thing which really matters is impact per calorie provided and, most importantly, there is a 50x range in the amount of calories that plants provide per unit of input. So the real advice should be: replace high cost/calorie foods with low cost/calorie foods. Which could mean replacing berries and leafy green vegetables with chicken as much as it means replacing filet mignon with sweet potatoes.
- gdubs 8y agoI’ve poured through the EPA tables on the contribution of agriculture production to greenhouse gases, and the high level number is misleading. Typically estimates look at emissions directly contributed from agriculture, but they separate out a ton of linked factors. Like, the production of petrochemical fertilizers are not included in the “agriculture” emissions category; only the emissions that are released in using them to farm. Then there’s transportation emissions, etc, all in their own categories. (It makes sense to look at agriculture as a whole, since so much of it is geared towards feeding animals...) Then there’s the opportunity cost for all the land that is used to farm annual crops for animals. That land could be regenerating healthy soil, and capturing carbon. Bottom line, the official numbers aren’t by far an accurate picture. Animal agriculture, even in America, is a huge piece of the climate puzzle.
- peteradio 8y agoWas going to make some cynical comment about how it's just a new liquid/gas that we don't know enough about to be scared of yet. Sounds like it's a solid material that generates cooling from material stresses sounds similar to piezoelectric.
- _Microft 8y agoIf you're interested in generation of an electric or thermal current with heat/electricity, the names to search for are Seebeck-effect and Peltier-effect. The piezo effect is when there's charge separation due to mechanimal stress.
- CompelTechnic 8y agoPiezo crystals can produce electricity in response to mechanical stress; this material can produce temperature differentials in response to mechanical stress. In that regard GP's analogy holds.
- hajhatten 8y agoGreat, but it doesn't solve how most AC units are powered by electricity from coal.
- solarkraft 8y agoAnd that was not the point of the research.
- giarc 8y agoThe link provided by another user indicates that the problem with AC units is improper disposal of HFCs contained within. "HFCs, the primary replacement, spare the ozone layer, but have 1,000 to 9,000 times greater capacity to warm the atmosphere than carbon dioxide." https://www.drawdown.org/solutions/materials/refrigerant-management https://www.drawdown.org/solutions/materials/refrigerant-man...
- pariahHN 8y agoBut, it could lead to easier to repair/maintain refrigerators. Right now, if you puncture the cooling tubes and the coolant escapes its usually more cost effective for someone to buy a new fridge. A solid refrigerant can't leak out and would be much easier to replace.
- _Microft 8y agoPaper (open access): https://www.nature.com/articles/s41467-019-09730-9 https://www.nature.com/articles/s41467-019-09730-9
- rmbryan 8y agoThe original article: https://www.nature.com/articles/s41467-019-09730-9 https://www.nature.com/articles/s41467-019-09730-9
- ulrikrasmussen 8y agoWould this be usable for improving heat pumps as well (i.e. for heating the building instead of cooling it)? It is my understanding that they basically work as "reverse refrigerators", and that current designs are able to move about four times as much heat energy as they consume. Would this be able to improve their efficiency even more, or is there something about the thermodynamics that I have missed?
- alexhutcheson 8y agoAs far as I understand it, "green material" doesn't mean it's more efficient in operation, it just means that it would be less harmful at the end of the system's life. When HFCs from air conditioners, heat pumps, refrigerators, etc. are released into the atmosphere (often when the system is disposed of) they have a disproportionately high greenhouse gas effect compared to vehicle emissions and other common sources.
- mrob 8y agoThis doesn't aim to improve efficiency. Most refrigerators use phase change of volatile liquids to gases and back again. Most suitable liquids were toxic and/or flammable, so chemists invented the much safer replacement of fully halogenated hydrocarbons (CFCs). The first to gain widespread use was R-12: dichlorodifluoromethane (a.k.a. Freon). CFCs turned out to break down in the upper atmosphere, releasing chlorine that catalyzed destruction of ozone. The worst ones were banned under the Montreal Protocol treaty, and less damaging partially halogenated hydrocarbons (HCFCs and HFCs) were developed as a replacement, e.g. R-22. Modern HFCs like R-134a have even lower ozone depleting potential. However, ozone depletion isn't the only problem. CFCs/HCFCs/HFCs are also very effective greenhouse gases, often trapping thousands of times more heat than CO2. In an attempt to solve this problem, another class of refrigerants was invented: the hydrofluoroolefins (HFOs). These have low ozone depletion potential, and low global warming potential, but they are somewhat controversial because they compromise the excellent safety of the earlier halogenated refrigerants. Solid state refrigeration avoids the whole problem, so if it's possible without harming efficiency, as the article suggests, then it's an obviously good idea.
- 8y ago
- dm3730 8y agoI wish I could understand this article better. I'm wondering how does this material compare to regular coolants like R22? If I used 1000 watts to compress this solid versus 1000 watts for a traditional compressor/coolant scheme, which would generate a lower temperature?
- baybal2 8y agoI have no idea how will it gonna work. First you squeeze it, put it into fridge, unsqueeze it, make it absorb heat, get it out of the fridge, and repeat. Don't seem to be an easily automatable work
- code_duck 8y agoPretty sure the mechanisms to do that are built into the fridge - a compressor, just like current refrigerators but using solids instead of gas.
- CompelTechnic 8y agoA few thoughts after reading this as a mechanical engineer: 1. My understanding: this material relies on mechanical work (force x distance = work energy) to add energy to the material by compressing (or tensioning, or "magnetically stressing", which I don't understand) it. Some fraction of this energy is converted phase transitions which absorb heat, and some fraction is retained as spring potential energy. If the material is then heated by ambient air, and then the material is allowed to expand, it will now be at a temperature above the ambient temperature at the start of the cycle. In this way it is similar to a standard refrigeration cycle- just without pipes. 2. The cycle described in point 1 is not particularly unique to this material. You could do a similar process with any mechanical spring (google "rubber band heat engine"), and achieve similar results. This material is likely uniquely well suited to this application because it has usefully large amounts of heat associated with phase transitions at temperatures that correspond well with the temperatures used in a refrigeration cycle. 3. You want the material to dump heat to a hot reservoir while hot and suck heat from a cold reservoir while cold. Standard, fluid based refrigeration cycles do this by pumping the refrigerant to different locations (the condensor and evaporator). (I am assuming) This process would have to open and close dampers to get the hot reservoir air and the cold reservoir air to flow across the material; otherwise you have to move the material between the two locations. Both of these sound expensive/tricky to me. 4. A large challenge here is creating an electrical actuator that can compress the material. It would the following design objectives/constraints: 4a. The material should be shaped into long, narrow rods, or another shape with a large surface area, to be ideal for maximum heat transfer with the air of the hot and cold reservoirs. 4b. The actuator must recover the work energy provided when the material is allowed to expand. 4c. The actuator will have a very short stroke (solids do not compress very far), and large force. 4d. The actuator must last many thousands or millions of cycles without wearing out. 5. This style of refrigeration does not have any higher theoretical or actual efficiency than a fluids-based cycle. However, refrigerants have historically been environmentally damaging when released to the atmosphere. R-12 kills ozone, and is obselete/ outlawed. R-134a is currently in a lot of new systems, there are also newer refrigerants being put into new cars. The only thing particularly bad about R-134a is that 1 kg of R-134a equals several thousand kg's of CO2 in terms of global warming effect.
- 8y ago
- leguminous 8y agoScanning the original paper linked by _Microft and rmbryan, it looks like the pressures the researchers used were very high, 0.25-0.5GPa. Maybe someone with more domain-specific knowledge can answer this: are such high pressures actually practical? My understanding is that one of the reasons R-744 (CO2) is not more common is that it requires high pressures, which means specialized equipment. But the pressures involved here seem to be an order of magnitude higher even than required with R-744.
- CompelTechnic 8y agoI'm having a hard time confirming it (can't find the original paper w/o a link), but you are probably referring to mechanical stress instead of fluid pressure. if you hang a tensile load of 1000 Newtons from a 1mm x 1mm rod, the rod is under 1 GPa of stress.
- leguminous 8y agoHere's the original paper: https://www.nature.com/articles/s41467-019-09730-9 https://www.nature.com/articles/s41467-019-09730-9 This is all I saw to address the pressures required: > Our higher operating pressures do not represent a barrier for applications because they can be generated by a small load in a large volume of material via a pressure-transmitting medium, e.g., using a vessel with a neck containing a driving piston, whose small area is compensated by its distance of travel.
- foxyv 8y agoYou can get hydraulic pressures as high as this. Usually they are very low volume though. You don't store much energy in liquids and solids due to their low compressibility so the chance of explosions is a lot less. Gasses can store tons of energy if you get them up to these pressures so it's a hazard to anyone near the thing. If you have gasses in your high pressure system and something fails it can result in shrapnel. Hydraulics can do something similar with spring forces in the casing of the machine, but it isn't nearly as energetic!
- torpfactory 8y agoIn this case they are compressing a solid, which is much safer than compressing a gas. There is no explosion risk if the high "pressure" solid is suddenly released from its container because its volume has not changed by much. Looks like this solid changed its volume by ~2x (fig 2e). For CO2 the change is about 28x. If your high pressure CO2 suddenly gets out of its container, it will immediately expand to 28x its volume. There is of course a question about how exactly you build a mechanical device to implement this cycle. In current devices the material which changed temperature physically moves around a circuit and removes and deposits heat energy at different places in the circuit as it moves. They definitely don't talk much about how a practical device could be constructed.
- exabrial 8y agoSmall point of correction: r-152a is an eco-friendly refrigerant. The article incorrectly groups all liquid refrigerants together. R12 [and R-134a somewhat] deserves it's reputation, but that has been out of use in America/Europe for a long time. It's worth to note in China/India, researchers suspect that R12 is still in use despite regulations against it.
- HillaryBriss 8y agomaybe the fastest way to fight global warming in this instance would be to commercialize the technology solely in China so that it is adopted widely there first
- exabrial 8y agoI'm not sure why you were downvoted, this is an incredibly important point. Regulations are so loose in China/India and their population is far more significant that the USA/Europe.
- jtlienwis 8y agoI'm surprised no one has mentioned propane as refrigerant. Lots of environmental benefits. I believe Whole Foods uses it in some of their stores. Look online for "Propane as a refrigerant. Whats not to love?"
- cvs268 8y agoHi there, Hank Hill. https://www.youtube.com/watch?v=9FA__4fLBos https://www.youtube.com/watch?v=9FA__4fLBos
- tomatsu 8y ago> The gases currently used in the vast majority of refrigerators and air conditioners —hydrofluorocarbons and hydrocarbons (HFCs and HCs) — are toxic and flammable. When they leak into the air, they also contribute to global warming. R-600a (isobutane) only has 3.3 times the GWP (global warming potential) of CO2 and for a fridge you only need about 80g. For safety reasons, the limit is 150g. For comparison, the GWP of R-132a is 1,430 and R-12's is 10,900. R-600a has mostly replaced R-132a in Europe. Isobutane is of course flammable, but the operational pressure is very low. Aerosol cans also use isobutane. It's comparable to those.
- baybal2 8y agoOne very interesting refrigeration cycle I heard about recently is using a proton exchange fuel cell in reverse as a compressor for hydrocarbons or ammonia in a closed loop. Protons jump across the membrane, creating a small pressure differential that is allegedly big enough to do heat pumping.
- crankylinuxuser 8y agoAmmonia refrigerators were ones of the first types. And they get very cold, quick. Of course, when ammonia leaks, it does some nasty damage.
- jabl 8y agoI think butane or propane is the standard refrigerant for household refrigerators all over the world nowadays; the US is the odd man out. R134a is still unfortunately widely used in cars. Newer cars are moving to R1234yf, which is expensive, maybe CO2 in the future.
- mohaine 8y agoPart of this is the regulation in the US around refrigerant reclamation. Once a gas is used as a refrigerant, it has be reclaimed/recycled or large fines can be assessed, even though the rules do not apply when the same gas is used in any other context. This makes switching to a new gas much harder as the infrastructure for reclaim/recycle does not exist for the new gas, no mater how safe or better it is.
- anfilt 8y agoI have read C02 can make a pretty decent refrigerant.
- Animats 8y agoUnfortunately this is in Nature Communications, not Refrigeration and Air Conditioning. They have some experimental results on a material. They didn't even get far enough to build a compressor and heat exchanger using it. No indication of what the energy efficiency is like. We already have thermoelectric coolers, which have no working fluid and don't pollute. But they're too inefficient for large scale use. Good for CPU coolers, though. Actual paper: [1] [1] https://www.nature.com/articles/s41467-019-09730-9 https://www.nature.com/articles/s41467-019-09730-9
- londons_explore 8y agoThere are already massive efficiency gains to be had in the world of refrigeration. For example, in a typical refrigerator loop, there is a restriction to slow liquid flowing from the condenser to the evaporator. A turbine here would collect energy rather than waste it in the joule-thompson effect. Also, refrigeration typically uses a phase change (liquid to gas usually), but the use of phase changes is incompatible with efficient use of counterflow heat exchangers. Future efficient systems will be entirely gas-phase. Reciprocatibg cylinder compressors also have large losses to the walls of the cylinder, which for high efficiency need to have no thermal mass, which obviously isn't possible. Turbines are the future for efficiency there.
- jhloa2 8y agoCan you explain to me how an entirely gas-phase refrigeration cycle would work? The phase change is the whole purpose of the system in a traditional refrigeration cycle.
- amitprayal 8y agoI hope something comes out of it and does not end up as brief flash in the pan.
- gnode 8y agoThis use of a solid for refrigeration reminded me of the elastic band refrigerator: https://hackaday.com/2016/08/25/a-refrigerator-cooled-by-rubber-bands/ https://hackaday.com/2016/08/25/a-refrigerator-cooled-by-rub... a not practical but still interesting use of elastic solids for refrigeration.