Short 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.
The 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.
Seems 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.
Over 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.
You 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).
> 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)...
For things like window units and fridges, this will at least allow one of the better drop-in replacements for HFCs to be on the market. The charge size limit of 150g will still prohibit things like central AC units and mini splits, unfortunately.
People are so worried about a little isobutane or propane in their refrigeration devices but we have constant pressure tubes forcing methane into many of our homes at 60psi. HCs would be great refrigerants and I think we can deal with the flammability...
The natural gas pressure at a stove inlet is supposed to be something like 0.25 PSI, not 60 like in the underground service lines. A pool boiler might need slightly higher, but in general the pressure in the building lines is very low.
Fight (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.
Spend 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.).
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. The amazing thing is your dietary choices impact those around you as well so you end up having a > 1 person impact!
That 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.
Not 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.
I’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.
Was 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.
If 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.
Piezo 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.
But, 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.
Would 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?
As 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.
This 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.
> somewhat controversial because they compromise the excellent safety of the earlier halogenated refrigerants.
I suspect that modern refrigerators designs/manufacturing can negate a much of that. Higher efficiency better insulation means less refrigerant. Better construction means lower chances of a leak. And flammability of HC refrigerants varies wildly. All you really want to if there is a leak not to create a flammable mixture in a standard sized room.
I 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?
I 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.
A 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.
Yeah, I read another article about this material a few days ago and I was trying to figure out how exactly to handle actually moving the heat. Easy to do with a liquid, you can pump it fairly easily and piping can be pretty flexible with routing. Maybe some sort of rotating disk design, with rods rotating from cold zone to hot zone and static blowers in each zone?
I like that design idea for the rotating disc. It makes me wonder the best way to stress the material while on the "compressed side."
1. Make the edge of the disc rub against a low friction, spring-loaded compressing element (similar to commutator brushes, but designed to really transfer a large load). This is probably infeasible because friction would eat more energy than your cycle would move.
2. Have electric actuators that are mounted on the disk itself. These would have to be powered by slip rings via the shaft. These would be active for half of the cycle and inactive for the other half. Not sure whether they should be radial, azimuthal, or axial mounted. Seems kludgey.
3. Have the disk pass through a magnetic field, exploiting the magnetic effects the article mentions. I have no idea of any of the implementation details of this, but it sounds like a better idea than 1 or 2...
Put a heat sink on the outside and a water cycle on the inside of the pump.
If you want to cool, you pump heat outside by stopping the water cycle when the material is cold, thus allowing the water to dump it's heat into it.
If you want to heat, you pump heat inside by stopping the water cycle when the material is hot, thus allowing the water to absorb the heat from the material.
You can increase the efficiency of this by having more water touch bot the inside and outside phases (increase material surface area in contact with water and increase surface area of water cycle heatsink).
If you want to allow sub-zero temperatures, add anti-freeze to the water.
I have a couple of thoughts on how this material might be able to be used - but I'm not a mechanical engineer, so what I mention might be (probably is) worthless:
1. Mechanical compression using hydraulic fluid and electric pumps?
2. Could the hydraulic fluid be used as the heat transference mechanism?
3. Could this material be used in a liquid Sterling cycle pump?
I'm thinking a combination of these might be the answer; the material at one end of a closed cylinder with a piston compressing hydraulic fluid, and the reciprocating motion through some means (and the hydraulic fluid) moving the heat from the material one end to the other end of the cylinder (where it could be dumped).
Scanning 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.
I'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.
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.
You 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!
In 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.
I'm no refrigeration engineer, but I figure you might need some sort of pulsed cooling. Compress the solid so it gets hotter, run liquid coolant through it to extract the heat to a radiator. Then let the solid decompress, and switch to a coolant circuit that extracts heat from the interior of the fridge and dumps it in the solid. If you needed continuous operation of both coolant circuits, you could add a second block of solid material, and switch the cooling and heat-exhaust circuits between the two.
Thanks! I think the idea you outlined would definitely work, but it is different than current refrigerants a few ways. For example: the secondary liquid loop you mention would probably vary in temperature with time. Right after the pulse starts the fluid would be very hot (or cold). As the solid material changes trends back toward the mean temperature, the secondary loop would follow. The secondary loop would need to then exchange heat with the system being heated or cooled. This would require the heat exchanger to work over a variety of temperatures for the fluid loop. This in itself is obviously not impossible but it does prohibit important optimizations to efficiency that you can get by assuming more steady operating conditions.
There is an interesting similar concept using magnetic fields instead of compression - some materials rise considerably in temperature when immersed in a strong magnetic field.
Extract heat to a radiator, turn off the electromagnet, open the coolant circuit valve. It's called Magnetocaloric effect and they were considering it for in-car AC a few years ago, dunno what came of it.
Small 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.
maybe 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
I'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.
I'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?"
> 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.
One 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.
Part 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.
I wonder if the use of these same gases for canned air is at all significant compared to its use as a refrigerant. Regulators seem not to care if people squirt off KGs of the gas to dust off keyboards!
Mercedes is already doing CO2, and the next-gen EV platforms are going that route as well, from what I hear. The high pressure of CO2 systems mean that they're very compact, and thus much easier to integrate with battery pack temperature regulation, AFAICT.
I think the interest for EVs might be due to CO2 systems being capable of working as heat pumps as well, producing hot air. Otherwise you'd waste a lot of electricity in cold climates.
Exactly this, both that they're able to heat the interior of the car, but also that they can play the role of battery cooling system (just heat a small radiator instead of inside of car).
The "problem" with R12 was that it breaks down in the atmosphere in short order (less than 10 years by some calculations). Most of the replacement refrigerants are basically inert. The estimated lifetime of r134a is 50,000 years. So even tiny leaks over a long period are going to do incredible damage to the climate. This was known from the beginning and is by design (the stable molecule bit).
But even now decades later the political ideology that AC units were the "problem" persists, despite the fact that its well documented that CFC's were used for everything from propellants in consumer products like silly string and hairspray, to large scale industrial uses like popcorn production (again recently in china).
Yet in all this time, we haven't really found a better set of refrigerants.
In the end, we would be better off bringing R12/22/etc back with the stringent controls for licensing/recovery/recycling/leak detection/etc that was put in place when they were banned. Combined with proper systems engineering to avoid leaks that are now required due to the refrigerants being extremely flammable or generally dangerous to human life we would both solve the problems of them being in the atmosphere, while avoiding the engineering problems of designing AC units that have to compress azeotropic compounds to extreme pressures, or function close to their critical points in tropical climates or any number of other problems with lubrication/etc.
Unfortunately 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.
There 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.
Can 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.
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