Thread: AC Refrigerant Alternatives

AC Refrigerant Alternatives

Key
There are three Ratings of refrigerants, they are rated by how flammable and toxic they are. Class A's should be non toxic in the as is state, while class B will be toxic. I have not seen any widely used Class B refrigerants.

Please keep in mind that some Class A refrigerants may become toxic when exposed to a flame or other chemicals.

Class A1: Non Flammable
Class A2: Flammable
Class A3: Highly Flammable

Please refer to this document for further details.

Terms
GWP - Global Warming Potential

R-XXXX - Refrigerant-Model Number. Before the item is approved by EPA, that item will use the abbreviation name HFC, HC, CFC, etc.

Car Preparation - Keep in mind this does not include the federal requirement to switch the fittings to be unique. This is done to avoid cross-contamination of the different refrigerants. It is generally a good idea to have warning stickers if you switch refrigerants to something other then factory OEM.

Flammability - This will cover the *F degree at which the refrigerant will ignite at.

Dangers - This section will cover the dangers of that refrigerant.

R-12 (CFC)

Very good cooling ability, uses mineral oil, banned by EPA for depleting the Ozone Layer, Otherwise safe for humans in the as is state. When burned produces a poisonous Phosgene gas.

GWP: 8100 (CO2 = 1)
Class: A1
Flammability: Nonflamable
Car Preparation: Drain and flush is required, R134a compressors might be compatible. License is required to obtain R-12, thus retrofiring from anything to R-12 can be costly.
Compatible Oils: Mineral Oils
Dangers: Toxic Phosgene Gas when burned
Operating Pressure: Low-Medium



So-so cooling ability, especially on R12 retrofits. PAG oil and others, not compatible with mineral oils. Produces very high GWP (Global Warming Potential), does not deplete the Ozone Layer.

R-134a is banned in EU as of 2011.

Dangerous to touch, inhale, or ingest. Produces a very poisonous gas (Hydrogen Fluoride), when burned.

May cause death without notice.

GWP: ~1300
Class: A1 - Not flammable at ambient temperatures. Can be flammable under-pressure and with oxygen mixed in.
Flammability: 1,411*F @ 0psi: 368*F @ 5 psi
Car Preparation: Drop in replacement for R134a systems. For R-12 systems a complete drain and flush is required.
Compatible Oils: PAG Oils
Dangers: Toxic Hydrogen Fluoride Gas when burned
Operating Pressure: Medium

More on R-134a flammability



Source

I added *F numbers in parentheses

R-152a (HFC)

Essentially the propellant in canned air, fairly safe but flammable. When burned produces a toxic gas.

EPA's only approved Class 2 (Flammable) Refrigerant. EPA does not recognize this as a retrofit-able refrigerant, because of of additional safety measures that will need to be implemented into the current Car AC systems.

GWP: 140
Class: A2
Flammability:
Car Preparation: Should be a drop in replacement, a system flush is suggested. Not sold in ready cans, will have to tap Compressed air cans.
Compatible Oils: N/A
Dangers: Flammable, Toxic when burned, it also seems to be fairly toxic in the plain form.
Operating Pressure: Low

Due to the low operating pressure, the AC compressor doesn't have to work as hard, thus improving engine efficiency.

This R-152a has been retrofitted into current cars a few times without any noticeable problems, while being as good as R-12 at cooling.

Keepin'Cool... the auto A/C service and repair market ezine

HFO-1234yf

HFO-1234yf was created by DuPont and Honeywell in response to the EU ban of R-134a. While it has a low GWP, it is Flammable. Ont op of that, it has a chemical reaction with water that produces a poisonous gas.

GWP: 4
Class: A2
Flammability:
Car Preparation: Advertised as drop in replacement, not on market thus unknown.
Compatible Oils: N/A
Dangers: Flammable, can be toxic when burned, is toxic when mixed with water.
Operating Pressure: Not sure (not available to general public)

Here is a test that shows how flammable HFO-1234yf is compared to R-134a
YouTube - Eco friedly air conditioning - it depends on the content

CO2

Carbon Dioxide, a natural substance, is being considered. The problem with CO2 is, it requires a very high Operating pressure to be effective. This would require a complete overhaul to the current system. Ont op of that CO2 is not as efficient on cooling as chemical based refrigerants.

I'm not sure how CO2 will be widely accepted when the current administration declared CO2 as a pollutant.

GWP: 1
Class: A1
Car Preparation: Not retrofitable, Complete system replacement is required.
Compatible Oils: N/A
Dangers: Other then system being under very high pressure, none other.
Operating Pressure: Very high (Above 1,000psi)



Essentially propane, thus is a class 2 refrigerant. Usually a mixture of butane and propane.

In this case I'm going to be referencing the ES-12a, which is a product of the ENVIRO-SAFE.

Please familiarize yourself with EPA's regulations on Hydrocarbon Refrigerants. Also some states make it illegal to have flammable Refrigerants.

A good information source/how to on Hydrocarbon systems.

Here are some good emails about the Hydrocarbon (non-)dangers.

GWP: 8
Class: Probably A3, looking for a reputable source*
Flammability: 1,585 *F
Car Preparation: Drop In Replacement for R134a systems, sold in designated cans. Should be easy as pie.
Compatible Oils:
Dangers: Flammable
Operating Pressure: Low

*Notice that R290 (Propane) and R600a (isobutane) when used individually is in Class A3.

ES-12a MSDS Sheet

Now here is what I don't understand, why is EPA so hesitant against HC-12a. Other then being flammable, it is a natural substance, thus very environmentally friendly. It is efficient at cooling and operates at lower PSI's thus easier on the compressor, which translates to higher engine efficiency.

Before you could have said, well it's flammable, and this is why it shouldn't be allowed. EPA now allowed R-152a, which is flammable and is poisonous when burned. Thus EPA is requiring additional fail-safes to use R-152a. Why couldn't we just go with HC-12 and have the same fail-saves developed?

It could be because HC-12a is cheap and very easy to obtain, and works in the current systems, thus not requiring expensive retrofits like R-134a did when it became mandated.

You forgot the term ODP - Ozone depletion potential

I'll copy paste my other post in here in a minute too. Also, that rating scale is almost right, but that's only the flammability half. There's also an A and B rating for toxicity on each.

There is a fair amount I can contribute to this thread.

EDIT: Vadim, I'm going to continue here instead of adding on later.

Notes on Table 1: COP refers to coefficient of performance, which is a measure of the operating performance of an average refrigeration system using the refrigerant in question. kW/Ton is a rating of the system cooling capacity per ton of refrigerant required. The ASHRAE Rating system rates refrigerants on a scale of A or B for toxicity and 1-3 for flammability. This table was compiled for a report based on information from several scientific journals.





As for the article, I agree with most of it, but I think the best replacement for R-134a is still debatable. The one suggested (HFO-1234yf) seems to have potential if the claims they made are true. I've found some interesting points in on of the journal articles I used for research. Here they are. [4]



HFC-152a


I dug up my paper on the subject (I wrote it last fall). Here is the section regarding R-152a. It is more environmentally friendly and exhibits better performance, but is flammable and less miscible. Because of the latter, it seems unlikely that it will take the place of R-134a in automobiles, but will become more common in general industry, where safety can be better regulated.



Here is an interesting quote from one of the articles I used. If it is to replace R-134a in automobiles, it will not be retro-fittable. New systems will have to be designed for safety. [4]



Propane (R-290)
Here is an excerpt from the section regarding propane as a refrigerant (though many of the conclusions apply to other hydrocarbons).



Take a look at the graph below, which shows refrigeration system capacity as a function of evaporator temperature. While R-134a shows a lower cooling capacity than R-12, R-290 (propane, a pure hydrocarbon) shows a marked improvement over both. [2]



Hydrocarbons in general
Pure hydrocarbon refrigerants (HC's as opposed to HFC, CFC, HCFC, etc.) are best for the environment (like propane), but pose obvious safety dangers to humans. Particularly in systems with pressures lower than the ambient air, there is a danger of oxygen leaking in and mixing with the refrigerant creating a highly explosive mixture. If that safety issue can be overcome, R-134a will most likely be replaced by a hydrocarbon refrigerant (at least as another intermediate). R-134a was never meant to be a permanent replacement for R-12.

CO2
In my opinion, CO2 does not appear to be an optimum refrigerant for use in automobiles. The higher pressure requirements not only impact the compressor, but also the seals, lines, and other system components. It seems that in general it is less efficient and more difficult to contain than other competitors. Also, in light of the carbon footprint design trend, it seems unlikely that it will be put into use for automobiles, which frequently leak.

Here's an interesting bit about it I took as an excerpt from [3].


That's all for now. I have plenty more I could add pending questions.

Sources:

[1] Devotta, S. (1995). ALTERNATIVE HEAT PUMP WORKING FLUIDS TO CFCs. Heat Recovery Systems & CHP, 7.

[2] Halimic, E., Ross, D., Agnew, B., Anderson, A., & Potts, I. (2003). A comparison of the operating performance of alternative refrigerants. Applied Thermal Engineering , 11.

[3] Powell, L. R. (2002). CFC phase-out: have we met the challenge? Journal of Fluorine Chemistry , 14.

[4] Calm, James M. (2008). The next generation of refrigerants - Historical review, considerations, and outlook. International Journal of Refrigeration, 31.

Awesome Danja! I'm still working on this, I've been reading up A LOT on this topic, now needing to do a brain dump thus started this thread haha.

I'm trying to find most information from a credited source, EPA.gov, but can't 100% guarantee it all.

ODP is not as important once we get away from R-12, don't you think?

you probably know this, but refrigerants aren't often directly interchangeable. Different refrigerants may need a different compressor, seals etc. just throwing it out there. It would be nice to see an alternative though!

There is a new refrigerant coming out next year I believe and will be on all the new cars. I think it's called R-123

HCFC-123 is not new, and is actually a temporary replacement for CFC-11. It's main downside is a relatively high ODP, but is otherwise pretty effective (it yields high cycle efficiencies).

CO2 is likely to be the next regrigerant. Higher operating pressures, sure, but we have compressors available that perform well and don't draw too much from engine power, even at extreme pressures. Besides, they are likely to be electric pumps in the future.

There you go. I just dumped way too much information. I have about 20 articles, all from respectable journals on this stuff. I was researching it last fall for my own paper (of which I posted some of above). If you want, I might be able to send you them.



It's primary purpose will then be for refrigerant comparison to help make choices about replacements. None of them will have significant ODP's, however.



I think CO2 is more likely to come into use for stationary refrigeration systems (industry, household, etc.), but we may see it play a temporary role in automobiles as well.

^This is true.

Maybe after you're done with that you can install a catalytic convertor on your car ;D

But seriously, props for looking into this Vadim. Very interesting thread. Ozone depletion makes global warming look like small potatoes. Had no idea that CO2 could be used. The high pressure of that system makes me wonder if it is really viable though ( and less prone to leaking )