Matt's RV refrigerator powered by woodgas

I was looking at the chemistry aisle at Walmart. I noticed that electrical contact cleaner contains di-flouroeathane. This the main component of r-134a.
Wasn’t brake clean non-flammable? What was in that?
I found that the Walmart brand of r134a sold in the small single container, is a steel container. I could solder or braze a fitting on the can, to accept a refill.
Anybody else fool with this before? I know one guy who used propane for refrigerant. I was thinking about butane/propane or diethyl ether/heptane.
Anybody? Wild ideas? Opinions?


Butane and propane make excellent refrigerants with the only downside of being flammable.

Iso-butane is more or less a drop in replacement for R134a. In refrigeration circles it is called R600a. The one thing to be careful with is the lubricant. Refrigeration systems typically lubricate the compressor by mixing oil in with the refrigerant. I think some oils work with both R134a and R600a but some do not.

You can buy small canisters of iso-butane for camp stoves. It may not be as pure as you would want but it’ll work.


My grandpa used to fill refrigerators and chest freezers with propane as far as i know there was never a problem with them.


Someday I would like to explore woodgas fired Air Conditioning. Like my RV Fridge it is ammonia based and has a boiler that is fired via propane. No reason woodgas couldnt be used in place of the LP.


So that would mean 24/7 year around wood gas heat right? Or are you going to have another back up source like LP to auto switch over to if the wood gas runs out.


The gasometer system that developing will deliver woodgas 24/7 with no interruption. This is why it has two of the gasometers, that run from one gasifier. Application’s like this and other gas appliances are low volume. So the idea is that the gasometers will be able to supply enough volume to keep up with all gas appliances and possibly heat and A/C in the future.


If you leave to go to Lets say Argos or some where for a week or so it will last for days with no problems?


You could if you have a big enough hopper. But that wont be practical, I am planning to use a 55 gallon drum for the hopper on the VersiFire, so that should be plenty of fuel for a 24 hour supply.


That’s really interesting Matt. So the gas becomes the primary energy source. Certainly a lower tech approach then electric storage then heat pump driven cooling. efficiency wise though? It will be fun to watch it develop.
Cheers, David


R600a (Iso-Butane) is refrigerant grade Iso-Butane used as a replacement for R12 and R134a in a variety of high temperature refrigeration applications.

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I dont know what the efficiencies are. However, my RV’s fridge will run from 4 to 6 weeks on 40 lbs of propane or around 40 bucks worth. Versus if I run it on A/C off of my battery bank, it will cost 20 bucks a day in gasoline cost keeping the bank charged enough to supply the power. If ran on woodgas then instead of direct converting the gas to heat, we lose 75% in engine and other conversion losses to run on electric. Besides I need charcoal for my gasifier, so why not use a gasifier to make clean gas for appliances while it mass produces charcoal?


Sounds like a Win Win to me. More nontaxable monies in your pocket. That is a 25% tax extra savings on top of the monies you are saving. If you keep working you going to figure out how to have people pay you to make your fuel like Wayne does. All except the chunking and bagging.

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Hmm that is not a true comparison though. The absorption cycle on the RV fridge when run on electricity uses a resistive heat load to replace the flame. An electric fridge uses the heat pump. The heat pump driven one is more efficient. Quantifying that would be hard and it would be am extra system so “efficiency” becomes a hard word to define.


To your point, a woodgas fired engine turning a compressor (heat pump/etc) would we much more efficient than woodgas as the heat source of an adsorption frig. Though a person could use the exhaust alone to run the adsorption frig. Tough to beat the efficiency of that one!

Liquid desiccant tech was a big rabbit hole of mine for cooling. That’s a fun rabbit hole if heat driven cooling strikes your fancy. The concentrated brine used can be very cheap and storable as a cooling “battery”


Believe it or not Einstein invented that type of fridge…

On a serious not there are commercial large size absorption units on the market used on fishing boats to make ice off the engine’s waster heat.
Search Aliepress for that.

You could use an automotive compressor and components to make an IC powered unit, and. charge it with Propane.
You already know about the lubrication issues ( I would look for a unit like a Chrysler or tecumseh with an oil sump ).
I don;t know how you would charge it though.

With a Fridge I can fudge things and watch the motor load and frost line on the evap and guess pretty close to how much refrigerant it needs, but I have never tried that on something homebrew like this.
I really would have no way to know based on the engine load and would have to guess on pressures and frost line.
Its possible but I am not the guy to tell you how.

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You lose nearly 80% of the energy just in the engine conversion. Are you sure about that? A direct gas conversion will always be more efficient than converting that gas to engine power.

Propane, butane and isobutane are cheap and don’t harm the environment. You overcharge the system (fill totally even) and slap on a pressure relief valve that will vent the system to it’s target pressure when it’s at working temps. That’s an environmental no no and expensive with HFCs like R134a.

I’d wick some solder into the tube section leading to the relief valve. Then you can melt the solder and squeeze the tube flat for a permanent seal. Clip off the now isolated stub with the valve and you can reuse that piece on another project. Also relief valves tend to leak a touch and it’s better to have the refrigerant charge stay as stable as possible.

Anyhow - just a trick for folks that don’t have a set of HVAC tools and gauges. There is a DIY heat pump thread over on that is a total monster. Really, really good. A bunch of HVAC pro’s chimed in as well so I’d consider the collective wisdom as vetted as you could ask for.

Adsorption chillers / RV frig are really interesting and there is a good amount of industry and academic research on various configurations and temperatures. I am particularly interested in some of the silica gel based versions which are very DIY friendly. More typically it’s ammonia or lithium bromide in chillers. Ammonia has toxicity, corrosion and pressure handling complications. Lithium Bromide can be sourced but is a bit expensive and exotic. It is also to be handled with care. Silica gel is super cheap, non-toxic and solid state in all parts of the cycle.

Off grid I actually think a water chiller is best. Cold water can be stored for some hours if not days so a chiller could use intermittent power and heat sources to “recharge” either from generator waste heat or solar thermal. The downside is that you still need to deal with dehumidification, either by over cooling the household air or running it through a separate desiccant loop.


Well I am just going to throw out a thought based on what I see…
You can buy fridges that run on gas and you ca n buy electric ones.
But I never see anyone put a gas fridge in to save money where they have Utility mains, so its likely that electric is cheaper.

But electric is not cheaper for anything else like heating…

But if you have a heat pump its cheaper than burning gas direct fro home heating…

Cars already have gasoline in them so why use the engine to drive a compressor it the absorption cycle was cheaper and easier than the compressor?

No math here just some observations Matt.

I did read a technical paper about using absorption in home AC system from the 50s.
They said back then it was easier and free to use solar tiles to an absorption system and cool a home.
But that’s based on free solar energy.
( also it was a Silica based system zeolite )


Yes if you only looking at this from a partial and incomplete perspective and not factoring in the the energy will not be provided by the mains and solely on a woodgas system. In this case you must look at it from the full perspective from gross biomass in to net energy out.

I get that an electric fridge is more eficient than a gas one. But when you are converting biomass to provide that energy via an internal combustion engine you are at a huge loss running the electric. The gas version is FAR more eficient.

Considering there is an abundance of basically free heat from engine exhaust I would have to assume and absorption system is too complex or higher cost to implement in an automobile. I dont know I cant answer that. But my observation and also living this, is my Fridge is nearly a full size and I could litterally run that fridge from a candle if there was a way to put one in there. The burner runs on a tiny little flame. Any refrigerator is going to run around the clock, no way am I going to run a gasifier around the clock. And then the entire goal is to make charcoal and using this gas that would otherwise be completely wasted. You guys really need to step back and look at the big picture here I mean step way waayyyy back so you can see all it the entire picture not just a tiny snap shot.

Sorry Bruce didn’t mean to hijack your thread. We can move this over to mine.


I remember there were some old order Mennonites not too far from here that sold a kerosene conversion for propane fridges…

You raise some very interesting ideas chum!
I thought about wood to engine and direct drive compressor for cooling before but I assumed a lot about the efficiency compared to absorption and direct fire.
You might be onto something here…

You might also look into that water Zeolite thing if you can any info.
You don;t need extreme cold just cool…

This harkens back to other ideas in the past.
I am not a raw wood guy but the economics of charcoal are flawed unless you do it at scale and use some sort of heat recovery system.
You might have found a summer use for that heat.