I dont know if it has been menchened. But there is that Inviro safe refrigerent that works real good and is the most afordable, ad they are getting away from the more toxic refrigerents. Just type in ivirosafe refrigerant ob ebay, or google it.it runs about 180.bucks for 30 pound tank.I am not sure what types they have, they have r134 replacement and works in r 12 in home refrigerators.or r134.frigerators. Due too the fact it is compatable with both oils.
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The aren’t allowed to sell it in the states except for industrial or retail use and only for new equipment. I assume that is because it is flammable. You develop a leak, the motor kicks on and sparks, then kaboom all at 2am when you and your kids are sleeping.
Ammonia is a bit more dangerous. Although I think they do allow it for industrial applications where in theory it is monitored a bit more closely, and they have studier designs.
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Ammonia is still common in most camper refrigerators or in larger home refrigerators like the old Servels or the newer Dometic. Not enough ammonia to be very dangerous and if it leaks you will know! Of grid choice a few gallons of propane or a lot more panels and batteries. Fred
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I will stand corrected. The last time I looked it up i they were using something else but now that i have relooked it up. I might have confused the sodium chromate as a coolant, and instead it is a rust inhibitor used to line the internal tubing to protect it from the corrosiveness of the ammonia. 
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In Canada we have had the propane - isobutane refrigerant replacements available for at least 15 years. From what I understand the combustibility concern is a bit of a red herring, as ordinary freon poses a combustion / explosion risk just due to the entrained lubricant oils. Maybe ask DOW or Dupont what their concerns were… At any rate I don’t hear about firey vehicle explosions. In fact, apart from not being hellishly persistent and damaging in the environment I hear the hydrocarbon refrigerants are more efficient.
Regards,
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I heard the hydrocarbon refrigerants were actually better then freon a long time ago like the 80s when the stuff about the ozone layer was brought up as a problem. I wonder if part of it is dupont, but part of it is the flammability and the extra precautions you need to make to the pump itself. A spark proof motor is insanely expensive relative to a normal motor.
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Refrigerant compressors are generally fully enclosed / sealed so there should be no spark risk from the motor. Also induction motors aren’t a spark source. I believe Europe opted for hydrocarbon refrigerants, and without checking I expect there’s no great incidence of disaster associated.
It does sadden me that the so called “better” fluorine based freon replacements were worse than the original products in certain ways, and without much fanfare it was announced this fall that they will be eliminated. And many billions to the shareholders…
Regards,
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Hey all!
Professor of HVAC here weighing in… you guys pretty well covered it. Absorption systems are not easy to come by on a residential scale and typically have a pretty miserable Coefficient of Performance, 0.3 or so, if I recall correctly. (Meaning you can only move 0.3 units of heat for every unit of heat moved from the souce to the sink)
This works well if you have a LOT of waste heat from some (typically commercial) activity you’re already engaged in.
Vapor compression systems - what we’re all use to when we thing of A/C and refrigeration, are much better. The current federal minimum SEER rating is 13, which is a COP of 3.8. Which is absurdly better.
Other then using conventional green building technology, my only recommendation would be using as high of SEER system as you can get a hold of. 18 SEER units are commonly available. If you have lots and lots of money, a ground source system can get you into the mid 20’s SEER wise. If you have a body of water very, very close, you could reject heat into that as well for good gains.
Another adaption that you don’t see on the residential side but is used commercially is the wet cooling tower. Open, wet cooling towers help improve cycle efficiency by lowering the temperature that the system has to reject heat into on the condenser side.
Consider, for instance, outdoor conditions of 95 degrees, and 40% RH. An standard air conditioner will be maintaining the condensing coils at 115-125 F in order to shed heat into 95 F ambient. But, a wet cooling tower in those same conditions will have water entering the condenser in the upper 70’s F. (Close to the wet bulb temperature) This buys a lot of efficiency.
The reason we don’t see this at small scales is because it is maintenance intensive. Open water systems have to be treated, periodically descaled, and carefully monitored to prevent bacterial growth. Legionnaires disease, etc
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You are right. Absorption has two main advantages when looking at wood gas. First, you have copious amounts of unutilized heat energy, the second is it requires no mechanical input which means you don’t need electric to run the motor for a compressor. This can be important if you are trying to reduce electric loads for off-grid or are planning for EMF events.
However, because of the low COP they aren’t able to chill down to temp as fast or as low and use more energy in the process. Then the main reason why freon was developed was to prevent fires and explosions, but it also reduced chances of CO poisoning and ammonia asphixiation.
It looks like we are back to looking at flammable gases for cooling. However much better then ammonia and freon as they typically aren’t as corrosive and offer better efficiencies with lower volumes of refrigerants especially if you want to believe everything the HCR118C webpage says about it’s product. The lower corrosion should result in longer term use with fewer leak problems thus reducing some of the fire risks. However, it doesn’t look like that is approved for in home use yet.
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Longer term use - I have a freezer which has to be 60 years old, still running on the original charge of freon, still going very strong. If hydrocarbon refrigerant would last longer, what could we be talking about - century appliances?
Good thing that appliance manufacturers don’t make refrigerant compressors like they did in the 50’s, with 50’s material science. 
Otherwise with present technology we might be buying 200 year freezers and fridges…
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The old ones had compressors that locked up and burned out the motor if the power flickered while it was cooling. The seals also dried up if you didn’t use it for like a month or so.
The insulation was literally paper, it wasn’t good and yours probably has all deteriorated by now. Most of them also don’t automatically de-ice themselves. The biggest killer of compression cooling systems however is probably not keeping the coils clean.
As far as quality. The size of the compressor has gone down to keep prices lower. The quality you want is actually commercial grade which costs more. Most people don’t open their deep freeze more then once a day. Most people don’t need the bigger cooling system.
Freon was poking holes in the ozone layer. So it was internationally banned.The problem is there was no equivalent replacement found. The hydrocarbon solutions don’t solve the flammability issue. In their defense we have developed far better synthetic sealants, that won’t dissolve as easily.
It is similar to ten years ago saying gas is 4 dollars a gallon, and we need to get rid of gas, before we had mass produced electric cars. The options were extremely limited. E10 is about the best you can do as engines are required to be able to handle e10, and I think E15 now.
Other options like NG, propane and hydrogen (hydrogen is 90+% made from NG), don’t give any economic relief because FF prices move up and down mostly together. So if oil is high, NG and Coal will be higher as well. You also need to buy a new vehicle as you have to mod the fuel delivery systems and engines as well. Which is kind of similar to E85 or E100 (E85 vehicles are like 2% of the vehicles on the road), and so you are looking at everyone having to buy new vehicles, or improve the efficiency of vehicles, drill for more oil, etc. literally the US policy is to try it all to see what improvements we could make that may develop into cost effective solutions. I would say most of the people on this board started with interest in wood gas as a way to save themselves money from higher oil prices.
They have been literally working on a freon replacements for decades, and haven’t come up with anything that is remotely as efficient or as fast. Other techs include peltiers, aborption, magnetic, etc, and many gases have been tried in compressor systems. The hydrocarbon gases don’t solve the flammability issue which is why freon was invented and became popular in the first place.
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I know I’m late to the conversation. I hope this may energize some imaginative, outside the box thinking. (My specialty) one could use a low temp Sterling engine and power it rather than using it to power something. If temperature differences make it move by altering pressure then theoretically making it move would cause pressure change therefore changing the temperature? Just a thought.
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A heat pump or heat machine, if a 50-degree femper temperature difference is used, should be solid efficiency (over 10 percent), promising the possibility of producing electricity from a low-temperature source
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I think in the mean time the butane based r600 fridges have come of age. They use significantly less energy then the r134 options… The high pressure stirlings are interesting the tesla uses one for heating and cooling i believe but its really pricey…
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I’m sure a homemade Stirling would work for heating and cooling, now I’m going to have to try it. 
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That is basic gas refrigeration. They just uses special gases. You compress a gas and it releases heat, then you remove the pressure and some systems it turns to liquid, then it absorbs heat, and boils off. then you compress the gas again.
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Heat driven cooling sounds crazy but it exists and ends up being especially practical off-grid.
Einstein or absorption refrigerators are a thing. The technology is still in use for RV refrigerators for consumers and on a much bigger scale in industrial settings.
The other rabbit hole worth exploration is liquid desiccant cooling. You won’t find consumer oriented products there but you are on a DIY website. A thousand gallons of concentrated calcium chloride solution is cheap and “stores” a surprising amount of cold air potential.
I’ve posted on Stirling engines elsewhere but in short - I wouldn’t waste my time there, especially for HVAC.
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I’ve got another rabbit hole to explore. Look up thermoacoustic refrigeration. Working on a Stirling cycle, was actually scaled up at Sandia labs to work at cooling and compression of natural gas or maybe LPG. No moving parts, any heat source could be used.
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At BMW, some time ago they tried to increase the efficiency of the engine with a “steam generator”, which would use the exhaust heat of the exhaust gases, which would also be a great way to drive the generator on wood or on concentrated heat from the sun …
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I looked at that a number of years ago. I think it was the university of Utah has the “prominent” professor in the field. Here is a standing wave generator.
Then an engine based on the principal.
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