I do feel its worth pointing out that it is dependent on just how cold it is outside as well. I use a mini split for heating and cooling a tiny house (of sorts), and winters here are very mild, so usually it works well. The coldest nights coincide with warmish clear sunny days, so running the split for heat for a few hours in the evening and early mornings works well, when I know I'll have sun during the day for topping the batteries back up. But sometimes we can get days of not so cold(12-15C), but dark cloudy wet weather. I can only do maybe 2 days straight like that before I need to go looking for more watts if I want to keep the split running.
I am always fantasizing about having a energy efficient air conditioner for van life, anyone seen any concepts in tech news or anything?
- Thread starter oldspice
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I was on an Australian offgrid facebook group and saw another option that looked like the best I've seen for small vans, although probably only suitable for more technically inclined folks. This guy bought an 12v automotive A/C compressor from aliexpress, the kind that is meant for electric and hybrid cars. He mounted it underneath the van. The rest of system seems to be standard automotive air conditioning components, with a condensor and electric fans also mounted under the fan next to the compressor, and the evaporator inside is the aftermarket underdash kind you would put in a classic car.
I would imagine to tackle something like this you would want to mount all the components yourself, maybe even run the hoses, and then have a automotive air con guy crimp the fittings on the hoses, plumb them up, then vacuum the system and gas it up.
He had 3x275w panels on the roof (covering the whole roof, it was a little Toyota Hiace van) and claimed that they could just keep up with the compressor without touching the batteries, in full sun.
If your van was passenger type van, that already had rear a/c fitted, that could take some of the work and cost out of it, you could have the rear evaporator disconnected from the main engine driven compressor, and plumbed to a new electric compressor and condensor.
I would imagine to tackle something like this you would want to mount all the components yourself, maybe even run the hoses, and then have a automotive air con guy crimp the fittings on the hoses, plumb them up, then vacuum the system and gas it up.
He had 3x275w panels on the roof (covering the whole roof, it was a little Toyota Hiace van) and claimed that they could just keep up with the compressor without touching the batteries, in full sun.
If your van was passenger type van, that already had rear a/c fitted, that could take some of the work and cost out of it, you could have the rear evaporator disconnected from the main engine driven compressor, and plumbed to a new electric compressor and condensor.
eXodus
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I've posted a bunch of 12V or 24V compressor those systems in the beginning of the threat. They work - but are not very efficient.
They need about 30-50A @12V to produce 8000 BTU
this is a great idea for integration in a Van - saves a lot of space and weight! I would even say - why not throw out the regular engine driven A/C compressor and replace with a 12V Compressor and a larger alternator.
I used to run the engine to cool down the whole Van sometimes, just need to bypass a couple of wires to get the Dash-Fan running without the key in the ignition. The Cab-condenser is very large and should be much more efficient then that tiny radiator thing which comes with those 12V sets.
I think this guy in particular bought only the compressor out of china. I don't know of course what efficiency he is achieving but I think there would be gains to be had by over sizing the condenser. I don't know enough details but his appears to a larger one from a car and not one of the tiny ones in those kits. He claims he can easily cool his van down to 19C drawing 65 amps, which is much cooler than I would run, if its 30+ outside, 23-24 is pretty nice, and will require less energy to maintain.
If I was to do it I would go with a 24v compressor anyway, as they seem to be higher performing and a 24v electrical system should be a little more efficient.
I guess you could convert the entire A/C system to the electric compressor, but I don't know if it could keep up with cooling the whole van when you have the hot engine running at the front and a hot exhaust underneath. Plus having two separate systems offers some kind of redundancy.
eXodus
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you can buy all the parts of the system separate on Aliexpress.
My former Prius had an electric A/C compressor and it kept the cab nice and cold. Sure - it's not a giant Van.
65A x 12V = 780W. to produce roughly 6000-8000 BTU My 12000 BTU midea Inverter Window units needs 400-600W at full blast.
So you get roughly 2-3X more BTU out of the same battery / Solar with a Inverter Unit.
Dreo also makes a Inverter Window Unit now:
Vigo
Solar Addict
Cars have ac systems the size of small houses because their heat load can be huge. Replacing the engine driven compressor with a smaller electric one would be a downgrade any time the engine was running.
Since the ac compressor on most older vehicles is clutched to the drive belt pulley and the compressor shaft is visible out the front, conceivably in some cases one could do a shaft extension out the front to a secondary pulley or sprocket and then mount an electric motor off to the side of it and drive the compressor with your electric motor while the engine/belt/pulley all stood still.
When engine was driving compressor it would also drive your motor, so may have to use a centrifugal or overrunning clutch type pulley/sprocket on the electric motor to avoid overspeeding it since youd probably need a big reduction in the motor to compressor pulley/sprocket ratio which would become a massive overdrive when driven in reverse.
Or just plumb an electric compressor in parallel with the existing compressor. When electric is running the check valves in the engine driven compressor should keep it from being back-driven or bleeding off high side pressure.
Just ideas..
Since the ac compressor on most older vehicles is clutched to the drive belt pulley and the compressor shaft is visible out the front, conceivably in some cases one could do a shaft extension out the front to a secondary pulley or sprocket and then mount an electric motor off to the side of it and drive the compressor with your electric motor while the engine/belt/pulley all stood still.
When engine was driving compressor it would also drive your motor, so may have to use a centrifugal or overrunning clutch type pulley/sprocket on the electric motor to avoid overspeeding it since youd probably need a big reduction in the motor to compressor pulley/sprocket ratio which would become a massive overdrive when driven in reverse.
Or just plumb an electric compressor in parallel with the existing compressor. When electric is running the check valves in the engine driven compressor should keep it from being back-driven or bleeding off high side pressure.
Just ideas..
Yes I'm sure you can.
Engine driven compressors can be 40000-50000 Btus.
Thats just a guess. We don't know how many BTU this guy is getting for his 780w.
That's all well and good if you have somewhere to mount a window unit, and if you can even get one. In the US you guys miss out a little bit on the split systems that are super common here. But in Australia at least we miss out big time on the window units. Sure, you can buy one, but I can't find single inverter unit on the market here, and the cheapest "regular" style ones are $4-500 ($300US+). There's no going to walmart and buying an air con for $130.
I think there's some stupid quirk of Australian bureaucracy that actually prevents inverter window units being sold here. We also can't buy portable units with twin hoses. Only the crappy single hose ones are available.
Vigo
Solar Addict
Well, that sucks but youll have to console yourself with mini splits! Much easier to mount in a vehicle anyway. ‘Nicely’, anyway..
As far as the Midea consumption, i have seen my 8k midea hit 1000w. Considering how it operates there isn’t really a way to ‘force it’ to run at its full capacity short of setting it to a low temp and auto fan (which sometimes goes ‘higher than high’ on some units) while the inside and outside temps are both high.
I would expect the ‘true’ max power draw of a 12k inverter midea to be around 1200-1300watts.
As far as the Midea consumption, i have seen my 8k midea hit 1000w. Considering how it operates there isn’t really a way to ‘force it’ to run at its full capacity short of setting it to a low temp and auto fan (which sometimes goes ‘higher than high’ on some units) while the inside and outside temps are both high.
I would expect the ‘true’ max power draw of a 12k inverter midea to be around 1200-1300watts.
Has anyone tried
www.globalindustrial.com
Global Industrial Portable Spot Air Conditioner, 6,200 BTU, 115V
Global Industrial Portable Spot Air Conditioner, 6,200 BTU, 115V. Usually ships in3 days. Buy it and Save at GlobalIndustrial.com
www.globalindustrial.com
curiouscarbon
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have not triedHas anyone tried
Global Industrial Portable Spot Air Conditioner, 6,200 BTU, 115V
Global Industrial Portable Spot Air Conditioner, 6,200 BTU, 115V. Usually ships in3 days. Buy it and Save at GlobalIndustrial.com
It would have to be mounted outside of course but it isnt that big and with just one hose of cold air entering the vehicle would create a positive air pressure situation pushing/keeping hot ambient air out of the space. On a minivan you could put it on a hitch cargo rack with a generator right next to it. In summer just mount the rack up and take it off in the winter when its not needed.
Ive been working on a generator hush box, got about half done last year then someone stole the generator. I replaced it with one slightly smaller that will work better in the box. I bet you could build a hush box for that AC too.
Then someone could steal BOTH of them.
curiouscarbon
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darn, sorry to hear about the gen. hoping for folks to leave yer stuff be going forward!
Vigo
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I am planning to do a ‘through wall’ mounting of a regular 5000 btu window unit in one of the back barn doors of my 94 conversion van. A unit like the above would be nice for something more modern because it would not require (as much?) irreversible mods to the vehicle itself. But it’s 4x the price of the window unit which puts it in competition with mini splits which could conceivably have just as clean an install. It’s definitely an option..
Hedges
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I see window units from $160 to $350. But here's a new one for $92, free shipping??
GE 5,000 BTU Mechanical Window Air Conditioner, White 84691862529 | eBay
Find many great new & used options and get the best deals for GE 5,000 BTU Mechanical Window Air Conditioner, White at the best online prices at eBay! Free shipping for many products!
www.ebay.com
I'm considering using a window mount air conditioner backwards as heat pump. Goal would be heating more efficiently than resistance (oil filled radiator.)
1 BTUIT = 0.00029307107017 kWh, 3.4 BTU from resistance heating with one watt-hour
A/C label:
CEER: 11.0 Btu/h. W, so 1 W of electrical input extracts 11 BTU, and hot side gets 11 + 3.4 = 14.4 BTU.
14.4 BTU/W / 3.4 BTU/W = 422% efficient at heating. (at whatever hot/cold side temperatures that single CEER number comes from.)
Operating under mild conditions, after starting surge 5x label current, running was 0.5x, so about 240W electrical input and 1kW worth of heat output. Could work as energy efficient substitute for space heater in a small room. The idea is to be able to operate during peak utility rates at a cost savings.
Is 600w enough
I plan on putting 600w of solar panels on the roof of a small camper. The Panels will be able to tilt so I can get as much power as I can. My main use is to run a 5000 BTU AC tha draws 450w in the summer and a 500w space heater in the winter & a few little items like phones, tablets and led...
diysolarforum.com
Vigo
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By no means am i against doing the math but just as people say a mini split makes heat 3-5x more efficiently than a space heater, so does basically any air conditioner 'run backwards'. 300-500% efficient.
@rcrracer has actually run a window unit backwards and discovered some issues such as that for the evaporator to 'pull' heat from ambient it must be colder than that, and somewhere near 38f ambient, the colder evaporator starts to ice over from condensation, at which point no heat really transfers since ice is a good insulator and totally blocks the airflow. Without a 'flow reverser' like a real mini split has, it can't run a defrost cycle on itself. You'd either have to invent a separate 'defrost' mechanism, or just turn it off and wait.
I have honestly thought a little about using a window unit i have sitting around run on an interval timer (say 15 minutes per hour?) to pump heat from the rest of my house into my bedroom overnight via a connecting water heater closet, but it's robbing peter to pay paul or something like that. I still have to heat the house back up when i wake up. ?
@rcrracer has actually run a window unit backwards and discovered some issues such as that for the evaporator to 'pull' heat from ambient it must be colder than that, and somewhere near 38f ambient, the colder evaporator starts to ice over from condensation, at which point no heat really transfers since ice is a good insulator and totally blocks the airflow. Without a 'flow reverser' like a real mini split has, it can't run a defrost cycle on itself. You'd either have to invent a separate 'defrost' mechanism, or just turn it off and wait.
I have honestly thought a little about using a window unit i have sitting around run on an interval timer (say 15 minutes per hour?) to pump heat from the rest of my house into my bedroom overnight via a connecting water heater closet, but it's robbing peter to pay paul or something like that. I still have to heat the house back up when i wake up. ?
Last edited:
Hedges
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Good point.
Ambient temperature in my San Jose location is rarely below freezing, but the coils will get colder and could ice up.
Manual intervention (shut it off and use a space heater) might be my actual solution.
Getting creative, there are defrost thermostats for freezers, could be wired to open an NC contact and turn off the unit. Those have about 20 degrees hysteresis, would need to select an upper temperature that it is expected to reach so it cycles again.
Alternatively, since heating is going to be needed anyway, a heating element before the evaporator but after expansion valve, controlled by thermostat after the evaporator (and only powered when compressor is running.) Would need to be more powerful than compressor, to deliver net heat.
Ambient temperature in my San Jose location is rarely below freezing, but the coils will get colder and could ice up.
Manual intervention (shut it off and use a space heater) might be my actual solution.
Getting creative, there are defrost thermostats for freezers, could be wired to open an NC contact and turn off the unit. Those have about 20 degrees hysteresis, would need to select an upper temperature that it is expected to reach so it cycles again.
Alternatively, since heating is going to be needed anyway, a heating element before the evaporator but after expansion valve, controlled by thermostat after the evaporator (and only powered when compressor is running.) Would need to be more powerful than compressor, to deliver net heat.
A couple of years ago I tried turning an infrared heater toward the coils of the backward window AC. I build an open on both ends box using Polyiso. One end of the box encompassed the AC coils and the other end the 120v 750/1500 watt, no fan, infrared heater. This was controlled by acontactor and an Inkbird 308 that that was set at 35 F - 44 F with the thermister stuck in the output air of the outdoor part. 750 watt setting didn't do much of anything. 1500 watt did something. The on and off would cycle around seven(?) minutes or so each. So I was applying 1500 watts to an AC that while in heater mode was only using 530 watts by itself. I figured I could do better if I just removed the backward AC from the equation. That's where I am now. Output temp inside drops below around 79 F and the coils are probably frozen. Turn off the backward AC and turn on the now indoors infrared heater.
I believe why the infrared heater idea doesn't work worth a crap is that the infrared heater acts like a swampcooler in evaporating moisture off the coils. Also the infrared heater removes the humidity in the air from the coils and leaves no latent heat in the moisture on the coils for the backward AC to use.
The next thing I'll try is a DC rotary vane pump on my well, 70F north FL water temp, pumped through heater cores, situated in front of the backward AC coils. I had though of pumping indoor water through heater cores located both outside and inside the house. Take a bit of the inside heat and use just enough outside to keep the coils from freezing. I read a patent a few years back where this concept could be used for air to air heat pumps. Take a little of the COP 3.5 air to keep the coils from freezing instead of using a COP 1 heater.
Zwy
Emperor Of Solar
Saw a video on Youtube where a fella buried loops in the yard 8 feet deep for a closed loop system, ran water thru the loops using a solar powered 12V pump and thru a car radiator. Had a fan blowing air thru the radiator.
Have to admit it was efficient electricity wise (and cheap), the fan and pump used very few watts. For air conditioning, a drip pan could be installed at the bottom. For heat, it would probably transfer heat energy out of the space unless it was the only heat source. I guess for a root cellar or wine cellar it might work great to maintain temp at ground temp. He didn't use it for heat, just air conditioning.
Have to admit it was efficient electricity wise (and cheap), the fan and pump used very few watts. For air conditioning, a drip pan could be installed at the bottom. For heat, it would probably transfer heat energy out of the space unless it was the only heat source. I guess for a root cellar or wine cellar it might work great to maintain temp at ground temp. He didn't use it for heat, just air conditioning.
Ceefiveceefive
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Vigo
Solar Addict
A for keeping the evaporator de-iced with a liquid heat exchanger, a certain type of 'block heater' (ie vehicle engine block) might make this very simple. Something like this:
120v Inline coolant pump+heater $55
But preferably adjustable to something lower than 135f. More like.. 70? You could implement your own external temp control. A less powerful heater is probably fine. If you mount it below the ac unit it should thermosiphon so a pump is probably not even strictly necessary. Just some kind of 'inline coolant heater', i guess.
120v Inline coolant pump+heater $55
But preferably adjustable to something lower than 135f. More like.. 70? You could implement your own external temp control. A less powerful heater is probably fine. If you mount it below the ac unit it should thermosiphon so a pump is probably not even strictly necessary. Just some kind of 'inline coolant heater', i guess.
Zwy
Emperor Of Solar
Let us know how it works out.
Short_Shot
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I haven't caught up with the thread, but heat pump units have heaters on the coils to de-ice them in exactly this manner. Its less efficient, but still more efficient than just straight up resistive heating full stop.
Modern units are designed to operate to sub-zero temps in heating mode, and if its mobile - you still have the option of a backup diesel heater... but frankly, that's a far superior method of heating in SOME situations. Uses a lot less power at the cost of needing to supply fuel.
Which you use any given day would depend on your hookup situation. Boondocking you can rarely afford electric heat, and diesel is king for ease of use (but more maintenance than propane), but when fully hooked up you can let 'er fly on the heat pump.
I also like the idea of somehow using the engine to transfer heat into the thing above, however that require the engine be running - which... you could just use that heat inside instead. The de-icing cycle happens periodically throughout the day/night, and relies on significant insulation to keep the internal temps stable while doing so. It would be situationally useful, but not something to rely on for normal operation.
GSXR1000
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heat pumps do not deforst with heaters. they switch back into cooling mode with the outdoor fan turned off and the "hot side" of the refrigerant melts the ice
curiouscarbon
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some use the reversing valve to pump heat back to defrost, some use a heating strip, right? i thought these two (admittedly compatible) approaches were both used in heat pump devices.
admittedly i am a total amateur so it could be my ignorance ?