A new air-conditioning system manages without nasty gases | Hacker News Reader

A new air-conditioning system manages without nasty gases

economist.com

78 pointsprostoalex63 comments

You can use propane for the refrigerant. The halflife in the atmosphere is pretty short. Its cheap, non toxic and fairly well understood.

In the EU/UK it also has the advantage of not needing a license to install yourself.

Obviously this new technology is important, but its not here now.

> You can use propane for the refrigerant.

Used in medical/scientific freezers that go down to -80C:

* https://www.thermofisher.com/ca/en/home/life-science/lab-equ...

A combination of R290 (propane) and R170 (ethane) + R290 mix.

A mix of propane and iso-butane can be used (perhaps illegally, depending on where you are) as a replacement for old R12 refrigerant.

Confusingly labelled as R12a and sold under brands such as RedTek. This is the only type of refrigerant available to unlicensed consumers in Canada, and it is widely available in stores everywhere. R134a is not sold in stores here. The US is the opposite—R134a is available to DIYers everywhere, but R12a is banned because it is flammable.

r1234yf is already in wide use. It a little bit expensive, but it does not pose the global warming concerns of HFCs, doesn't deplete ozone like CFCs, and isn't as flammable as hydrocarbons.

https://en.wikipedia.org/wiki/2%2C3%2C3%2C3-Tetrafluoroprope...

R1234YF is ridiculously expensive compared to R134A, like 10 times the price. (For reference - I can buy a 10 pound cylinder of R1234-YF on eBay for $500. A 30 lb cylinder of R134A is $150 - $200.)

It is also takes more expensive equipment and a significantly longer amount of time to charge a R1234-YF system. All around, it is a terrible refrigerant for an end-user.

152a is another cheap alternative, and can even be bought without any license, at least in the US - it's the gas in "gas dusters".

While 134a operates at a higher pressure than 12, 152a is a close match and works well as a replacement for old R12 systems.

Most portable air conditioners I've seen use "R290" (propane) as a coolant, both from expensive brands and budget brands. I'd say propane is very popular in that industry, it's not just an option.

Of course, there are some risks to using propane (which is why these devices come with warnings not to store them in small rooms) but I suspect many people will already be using propane cooling somewhere without even knowing.

Rational people turn into tantrum throwing toddlers and absolutely go crazy if you suggest using a flammable hydrocarbon as a refrigerant (never-mind that many refrigerants are already flammable hydrocarbons or nasty in indoor spaces to the point where propane isn't worse).

They sell them in appliance stores now, most people wouldn't even know, it's called R290. My fridge used it, sadly it died and was replaced with a conventional refrigerant model.

they seem concerned about labeling it as propane

the one I bought had "R290 ECO-FRIENDLY REFRIGERANT" all over the box, with the chemical name nowhere to be found

(of course I immediately wanted to know what R290 was and googled it...)

Before freons, ammonia was used. Getting rid of ammonia refrigerants was considered a big step forward.

Ammonia was never used in home refrigeration, except in absorption units (where it is still used today); the other toxic one that was widely used is SO2 (sulphur dioxide).

In large commercial applications ammonia is still commonly used.

Getting this crazy crap out of our homes and stuff is indeed a big step forward, though

idk. I'd be happy to run ammonia at home. When I looked years ago no one make small enough compressors though.

to be fair I was a bit sceptical about it when I first put it in. Its pure, rather than having the tell-tale smell. So I was a bit worried about silent leaks.

However as you point out, some other refrigerants are pretty flammable, or otherwise generally a bit shit for your health.

Also, in my unit, there is something like 66grams, although I suspect 10 grams of that was bled off to purge the lines of air. So if there was a slow leak, its unlikely to persist for long, or cause an explosion.

Evaporated I think 66grams of propane is about 1cuft of gas. which doesn't seem to me to be that scary. A perfect air to fuel ratio would require mixing 16 cuft of air. And flammable range is narrow. Comparison, your kitchen is probably 1000 cuft.

So I think you are right, slow leak isn't much of a hazard.

66 grams of propane are 35.1 liters. The lower explosive limit is 2.1%. So if the content leaks out slowly enough to mix with at least 2 cubic meters of air, it's going to be fine. However, if it leaks a bit more quickly, I can totally see it creating an explosive mixture in the space behind your fridge (or inside), to be ignited when the compressor/light switch trigger next.

I can see why people aren't super happy with the prospect. A stoichiometric mixture forming inside your fridge and blowing up when you open it would definitely ruin your day.

On one hand, this is true. On the other hand it’s not like refrigerants are anywhere close to the only source of explosive fumes in American houses. Even sticking to just propane, the propane chilled chest freezer in my garage is sitting right next to my spare cylinder of grilling propane, which is your standard beat to hell Home Depot exchange cylinder. If I had to guess what would leak propane into my house, my money is on the grilling cylinder, not my chest freezer. And that’s before we talk about natural gas lines, cars full of gasoline, and god knows what kind of nasty solvants are sitting on the typical garage work bench.

Sure, we absolutely should take precautions when chilling things with propane. Some sort of smelling agent like we put into natural gas lines seems wise to me, but it’s not like it’s some sort of weird and new threat we’re introducing into our home; we use all kinds of explosive liquids and gases all the time already, often for burning and exploding!

Sure, but you can also get a stochiometric mixture of air and flour that will give you a bad day.

A typical natural gas range probably releases more than 66g of unburnt hydrocarbons into your home.

Natural gas is basically methane, which is around 16g/mol. 1mol of gas at STP is 22.4L, so 66g of methane is around 90L.

A typical gas range has a flow rate of a few cubic meters per hour, or a few liters per minute. So just to get 66g of unburnt gas released, you'd need to leave a burner un-ignited for most of an hour, or considerably longer if it was burning.

this is true, but it stinks, so you know its doing it.

If there was no added smell, I could easily leak 66 grams into the house without knowing.

Not to mention that gaseous hydrocarbons are widely used within homes, and not in hermetically-sealed devices either, as would be the case when used in a heat pump.

What, you mean this methane spewing stove that causes really bad air quality, and is no more responsive than an induction stove and far less powerful than an induction stove?

"Cooking with gas" is great marketing, but not so great in reality unless it's an outdoor wok.

Can't say I have a good reason why, but I HATE cooking with an induction stove. Just not interested in learning how to manage heat. OOGA OOGA, I do understand fire.

People remember things like this: https://en.wikipedia.org/wiki/Cocoanut_Grove_fire

edit: please READ the article before you think of downvoting.

... which had absolutely nothing to do with refrigerants.

This one did: https://en.wikipedia.org/wiki/Tamahere_coolstore_fire

I know the article is lengthy, but did you even try to search for refrigerant or freon in it?

The air-conditioning also used flammable gas, because Freon was in short supply

Which wasn't determined to be a source or contributor to the fire.

> The Boston Fire Department investigated possible causes of ignition, the rapid spread of the fire and the catastrophic loss of life. Its report reached no conclusion as to the initial cause of ignition, but attributed the rapid, gaseous spread of the fire to a buildup of carbon monoxide gas due to oxygen-deprived combustion in the enclosed space above the false ceiling of the Melody Lounge. The gas exuded from enclosed spaces as its temperature rose and ignited rapidly as it mixed with oxygen above the entryway, up the stairway to the main floor and along ceilings. The fire accelerated as the stairway created a thermal draft, and the high-temperature gas fire ignited pyroxylin (leatherette) wall and ceiling covering in the foyer, which in turn exuded flammable gas.

Yes, they used flammable gas in the AC, no that was not determined to be a source or contributing factor to the fire.

Keep reading...

During the 1990s, former Boston firefighter and researcher Charles Kenney discovered that a highly flammable gas refrigerant, methyl chloride, had been used as a substitute for freon, which was in short wartime supply.[18] Kenney reported that floor plans, but not the fire investigation report, showed air-conditioning condenser units near street level on the other side of a non-structural wall from the Melody Lounge, and that these units had been serviced since the start of the war. Kenney also reported that photographic evidence indicates an origin for the fire in the wall behind the palm tree and suggested ignition of methyl chloride accelerant by an electrical failure caused by substandard wiring.

So the claim is that people fear flammable refrigerants because a 1940s fire was blamed on flammable refrigerants by a single researcher in the 1990s contrary to the original reports half a century prior? That is an extraordinary claim, and frankly one that seems quite implausible.

I’d need to see any evidence whatsoever that people’s preferences here are driven by reports of fires like this. Honestly, I’d be surprised if most people are even aware of anything about the refrigerants used other than the fact that Freon is bad for the ozone layer. My chest freezer has a giant “uses propane” sticker on the side and the flammability of that never even crossed my mind, to be honest.

Also, complaining about down votes will always get you more downvotes.

It should not be surprising at all that reviewing the evidence with a few decades more knowledge would yield slightly different conclusions. If you read more about the history of that fire, you'll find that they still don't completely understand what happened.

Back then, they knew nothing about ozone depletion, for example.

> they still don't completely understand what happened

Which is a very different assertion than your original, "People remember things like this".

I have home heating and cooking powered by propane. So do millions of other people. Nobody (except you apparently) seriously considers an obscure incident 70 years ago to justify irrational fear of a flammable gas that is alredy piped into millions of homes by the cubic foot.

So, anyone care to actually offer a rebuttal?

Apparently not...

Here's a guy who recharged an old fridge with propane:

http://www.sparkbangbuzz.com/els/refrig2-el.htm

Note the buildup of frost on the return tube all the way to the pump.

That's a clear sign that you've massively overcharged it! I agree with his position about environmentalists, but I think he should at least learn a bit more about the science first. YouTube can help: https://www.youtube.com/watch?v=lLauVofEDzY

(All the refrigerant should boil off in the evaporator, and the return out of the cabinet should contain only room-temperature vapor. Frosting all the way back to the compressor wastes power cooling what doesn't need to be cooled, and can damage the compressor with liquid refrigerant.)

My old fridge used propane from the manufacturer, sadly it only lasted a few years and repair was more expensive than another one. The new one uses a more conventional refrigerant.

https://archive.is/y4OwA

You can use CO2 as a refrigerant. Non flammable and enables heat pumps to be practical at lower temperatures. Lots of products on the market. See https://r744.com

I assume using it results in a less efficient system though, right?

I don't know about efficiency but the pressure is much higher, making the system much more expensive.

People experimented with CO2 refrigerant around the end of the 19th century, when refrigeration had just been invented and most other refrigerants hadn't been invented yet; it was called "carbonic acid" and required much heavier machinery due to the high pressures. (Typically over 1000PSI for CO2, compared to 100-200PSI for HC, CFC, and HCFC.)

Runs at high pressure, can be quite efficient though, iirc.

The Revenge of the Circulating Fan

https://www.lowtechmagazine.com/2014/09/circulating-fans-air...

A similar amazing technology has been recently shown at a Fraunhofer Institute in Germany. And the magnetocaloric approach sounds even more promising!

https://www.ipm.fraunhofer.de/en/press-publications/press-re...

https://www.youtube.com/watch?v=6tKtc0cHrUg

Both the Economist's text and the Fraunhofer press release focus mostly on the benefit of not using certain refrigerants. But for in home AC use noise reduction might be a much stronger selling point. Especially in Europe where it is common with so called portable indoor AC units that put the noisy compressor inside the room you want to cool down.

Stirling engines can be run in reverse to act as a heat pump.

In fact, I have a two 25 liter coolers that utilize Stirling engines, they run silently and cycle between using 5 and 33 watts, averaging about 11 watts once the components the contents have settled on the 4 C set point.

Curious if anyone has looked into utilizing larger ones for cooling buildings.

Wikipedia: "At typical refrigeration temperatures, Stirling coolers are generally not economically competitive with the less expensive mainstream Rankine cooling systems, because they are less energy-efficient."

R32 (difluoromethane) or R290 (propane) both have ozone depletion potential (ODP) of 0 and are in common use with new refrigeration units.

This technology looks interesting due to its simplicity and could potentially be cheaper than existing phase-change systems which are prone to leaking and need maintenance. But refrigerants which don't directly harm the ozone layer are already here...

And propane has close enough properties to r21 that it can be used as a drop in replacement. Of course, HVAC guys flip their lid at the thought of it. Because they want to get that sweet markup on the extremely expensive, discontinued r21 or a pricey alternative.

Wish they had mentioned the efficiency and how it compares to existing options. Anyone know?

No idea. Nitinol heat engines are available in toy-size.[1] There used to be interest in shape-memory alloys as robot actuators, but they're slow and need too much power. It takes too much heat to generate mechanical motion.

Does that mean it has high heat pumping capability, since refrigeration is the inverse of a heat engine? I don't know.

[1] https://www.imagesco.com/articles/nitinol/09.html

> Tony Ennis, Exergyn’s chairman, reckons this method of cooling is not only more environmentally friendly than an HFC set-up, but will also be less expensive to buy and 30-40% cheaper to run.

Not absolutely clear, but the cheaper running cost implies it uses less electricity than existing options.

Say there’s a hypothetical AC that works very well and requires no environmentally problematic materials and lasts forever,

Does the simple act of moving heat from inside to outside do any measurable, meaningful harm to nature?

> Does the simple act of moving heat from inside to outside do any measurable, meaningful harm to nature?

No, the heat moved is trivial compared to the heat coming in from the sun. That said, urban design (concrete, asphalt, etc) that absorbs a lot of extra heat will have a noticeable effect, definitely on a local level. Cities with a lot of green are a few degrees cooler as well, in part because of shade (the heat is captured higher up), in part because of evaporation.

> Does the simple act of moving heat from inside to outside do any measurable, meaningful harm to nature?

It would still take energy to run. How is/would that energy produced?

By doing work you're contributing, in a minute but measureable amount, to the heat death of the universe in about 10^100 years.

That seems more like a philosophical opinion than a fact.

For instance, I challenge you to prevent the heat death of the universe.

No air conditioner is going to be 100% efficient. You're still going to consume a fraction of the heat energy being transferred from indoors to outdoors. Unless your home is powered by 100% green energy, you're still indirectly adding carbon to the atmosphere.

Even if its 100% green energy - which don't get me wrong is orders of magnitude better for warming of the planet - it still contributes to warming of the earth. You're taking some wavelengths of light that would normally be absorbed by say plant matter (thus using that energy to pull CO2 out of the atmosphere) over an area and/or some wavelengths simply reflected out to space without being absorbed by the solar panels (which definitely are designed to absorb as many wavelengths as possible). Then energy conversion from DC to AC and to transmissions lines to where its used all have losses which is energy dissipated in heat form. So the conversion process there can cause heating as well.

Certainly better than combustion which creates heat AND creates gasses which trap that and other radiation as heat.

rubber band fridge: https://www.youtube.com/watch?v=lfmrvxB154w

same concept, less refined.

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