3 ms·
It's useful though, as I think (correct me if I'm wrong) that the gases generally used in HVAC tends to have much worse warming effect than co2 per volume. We
by alex_duf 23d ago
It's useful though, as I think (correct me if I'm wrong) that the gases generally used in HVAC tends to have much worse warming effect than co2 per volume.
We do need heat pumps deployed at large scale, but sometimes I worry we don't understand they need to be handled with care at the end of their life
- PunchyHamster 23d agoIf it is outside you can just use propane as refrigerant. Low warming value and it leaking to outside doesn't matter, not gonna catch on fire. There are indoor devices using propane but they generally come with caveat "must be installed on room at least this m3", precisely so if it leaks it doesn't get to density that allows explosion
- jabl 23d agoI believe there are propane using split AC systems where propane is used only in the outside unit. The outside unit has a heat exchanger transferring the heat to some glycol-water solution which is what then circulates through the inside unit.
- 27183 23d agoI currently have R410a heat pumps with minisplits, when they're off warranty sometime in the future I might consider putting propane in them. The main question would be whether the oil used with R410a is compatible with propane as a refrigerant. This is probably a little bit "dangerous" in the sense that I'll have high pressure propane in the line sets and minisplits inside the house, but it's a very small volume of propane and not really any more dangerous from a fire perspective than my propane fired condensing gas boiler. [edit] a little internet sleuthing indicates that hydrocarbon refrigerants "might be" compatible with basically any oil, so I can probably just continue using whatever oil is in it.
- moepstar 23d agoYes, that dangerous effect is indexed as GWP - global warming potential. CO2 has a GWP of 1 in this context, while other refrigerants are worse - for example, R32 has a GWP of 675 (so 675x worse if it escapes), not sure about R290 (Propane), which I believe is either about 40 or 14… Regarding EoL: At least around here, household appliances such as fridges are brought to a recycling yard and are properly taken care of in that regard… and as for heatpumps - those are only to be installed by certified professionals, for this very reason.
- jabl 23d agoPer the latest IPCC report, GWP of propane is estimated to be 0.02, previously it was estimated to be around 3.
- ZeroGravitas 23d agoR32 also got rated higher: GWP went from 675 -> 771
- xhkkffbf 23d agoSo it went from three times worse to 98% better?
- raisedbyninjas 23d agoR32 is on the safe side of common refrigerants. R410 just started its phase out in the US and carries a GWP of >2000.
- himinlomax 23d agoThe global warming potential of hydrocarbons as such is generally overblown, since they oxidize into CO₂ in the atmosphere with a half-life of a decade or two.
- callmemclovin 23d agoThat's true, old school refrigerants like R-12 are awful. The downside of modern replacement refrigerants are high operating pressure (>100 bar for R-744/CO2) or high flammability for natural refrigerants like R-290 (Propane) and R-600a (Isobutane). But these are solely engineering problems, and I'm happy to know that my R-290 heat pumps at home (Panasonic L & Wolf FHS) and A/C (Midea Xtreme Save Blue) aren't awful to the environment, once they reach EOL.
- ErroneousBosh 23d agoThe neat thing about propane as a refrigerant is that it's a really powerful one, actually rather better than R12 in practical applications. If you replaced an R134a fill with R290 you'd need about half as much gas and if it got out, it's got a Global Warming Potential of 3, making it three times as bad as carbon dioxide and about 475 times better than the same amount of R134a. Even in a very large air conditioning system like in my elderly Range Rover, the 500g or so of propane it would need is about the same as the engine sucks up in about four miles. The effect of that escaping into the atmosphere is about as bad as the amount of petrol you spilled the last time you refilled your lawnmower. If you're worried about the ZOMG IT IS GAS IT WILL MAKE A GINORMOUS EXPLODISHION aspect like a lot of people are, ask yourself this - how many aerosol cans are in your car right now? Tin of deicer, tin of magic tyre inflater, maybe a tin of air freshener or WD40 or something? You're already carrying more propane around with you, rattling around loose at your feet.
- pbhjpbhj 23d agoAnd you can just replace r134a with r290? No need for compressor configuration, change of seals or anything?
- ErroneousBosh 23d agoMostly yes, you need to vacuum it down well and make sure you have compatible oil in the compressor. Some types of plastic tubing aren't particularly compatible but for cars it's okay.
- PowerElectronix 23d agoYeah, ammonia can also be used, it's, IIRC, more efficient to use it and a bit safer because you don't high pressure, buuut enough ammonia in the air will suffocate you. It's lighter than air so it will go away by itself if allowed to. For a purely exterior instalation it's much better than anything else.
- codeduck 23d agoI feel like potential suffocation is not what I'd be most concerned about if I were in an atmosphere with high concentrations of gaseous ammonia.
- stephen_g 23d agoI have a heat pump that uses R290 (propane) (as well as an CO2 one for hot water) and would take that any day of the week over ammonia! The charge of propane is pretty tiny and the safety standards extremely strict, so not really concerning in terms of flammability, ammonia I would consider far, far more dangerous.
- pbmonster 23d ago> enough ammonia in the air will suffocate you. It will suffocate you on account of all that blood pulp in your lungs. And eyes, and nasal mucosa... Having a high pressure ammonia leak indoors is a death sentence for anybody in the same room. Same building, if it's large enough...
- quickthrowman 23d agoThe “common” places I’ve seen ammonia refrigeration in use are hockey rinks and cold storage warehouses. I assume it’s used in industrial installations as well for heat rejection.
- tdeck 23d agoI always wondered why we don't see more Sterling Engine based heat pumps. IIUC they can use almost any gas including air.
- formerly_proven 23d agoBecause they're sensible heat machines, instead of latent heat machines. In a perfect frictionless vacuum, both of these can achieve the same theoretical efficiency. In practice, not so much. In particular, the isothermal heat exchange of the ideal Stirling cycle requires heat exchangers with no thermal resistance (and therefore no temperature difference). A latent heat pump has a much easier time to very closely approximate isothermal heat exchange because condensation/evaporation temperatures at a given pressure are essentially constant.
- tdeck 23d agoWhat is the back of the envelope efficiency penalty we're talking about here?
- formerly_proven 23d agohttps://www.sciencedirect.com/science/article/abs/pii/S0140700723004826 https://www.sciencedirect.com/science/article/abs/pii/S01407... Looks like 30-50% less efficiency.
- tdeck 23d agoThank you!
- deleted 23d ago[deleted]
- BHSPitMonkey 23d agoWould mandating the use of CO2 as a refrigerant also somehow economically motivate efforts to capture more CO2 out of the atmosphere, in a kind of virtuous cycle? Or would there be a Cobra Effect in there somewhere? I'm not familiar with the industries that refine and bottle the stuff.
- duskwuff 23d agoNo, neither - the amount of CO2 that'd be needed for use as a refrigerant is insignificant. There's already a lot of CO2 produced as a byproduct of industrial chemical processes like petroleum refining. Some of it is captured for reuse (e.g. in drink carbonation); most of it is released to the atmosphere.