My first solar air conditioner setup

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sparr
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My first solar air conditioner setup

Post by sparr » Wed Sep 06, 2017 6:35 pm

This year I compartmentalized the rear of my box truck and put a small "window" A/C unit in the bedroom space. The space was about 4 cubic meters, with walls made of moving blankets then air gap then aluminum sheet painted white on the outside, then some directions had another air gap and a layer of shade structure (tarp or solar panels). For power I had three 235W solar panels (of the four that I brought), a MPPT solar charge controller that could handle a max charge rate of 40A@24V, four 12V batteries in 2S2P configuration making a ~50AH 24V battery pack, and a 24V 1500W inverter. The A/C was rated at 5000BTU/hr, and pulled about 450W in normal usage, with a higher power-on current draw that I couldn't measure well. The electrical system also ran our interior and exterior lights, phone charging, etc, as most solar power setups do in BRC.

This worked remarkably well. After we got everything set up, we rarely wanted more cool, or for longer, than we could produce. For the middle ~6 hours of the day we could run the A/C full blast, bringing the room down past 60F, and still be charging the batteries. For morning we mostly just ran the fan to circulate air while the body of the truck was still cool. For evening we ran the A/C on 20-60% duty cycle using the thermostat, which gave us 4+ hours of cooling even with no sunlight.

I will be doing this again, possibly on a larger scale, and recommending it to anyone who can handle the necessary infrastructure. The one major improvement I would make next year would be to make the panel tilt adjustable. If I had been able to set the panel angle to three specific angles for morning, noon, evening, then I could have collected 30% more energy over the course of the day, and run the A/C full blast during the early evening before sunset.
Last edited by sparr on Wed Sep 06, 2017 6:44 pm, edited 1 time in total.
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Admiral Fukkit
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Re: My first solar air conditioner setup

Post by Admiral Fukkit » Wed Sep 06, 2017 6:43 pm

Nice!

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Token
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Re: My first solar air conditioner setup

Post by Token » Wed Sep 06, 2017 7:47 pm

sparr wrote:The space was about 4 cubic meters
4 m^3 is a tad larger than; 3 feet wide, by 6 feet deep, by 6 feet tall.

Could fit a cot in there for a short person but other than that ... ???

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Re: My first solar air conditioner setup

Post by fireheadwhale » Wed Sep 06, 2017 8:08 pm

First person I've heard of running AC on solar. Like you said,"lotta infrastructure". But you did it. Often I see newbies on RV forums asking if their 100 watt panels will run the AC in their RV. The answer is NO, you can charge the batteries. Nice start, Mr Sparr.
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some seeing eye
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Re: My first solar air conditioner setup

Post by some seeing eye » Wed Sep 06, 2017 8:39 pm

Well done!!!

Low cost box truck playa pad with solar AC is a great accomplishment. Adapting to a rental truck is the next Figjam cooler. Doable.

Maybe we can be less critical on ePlaya.
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sparr
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Re: My first solar air conditioner setup

Post by sparr » Wed Sep 06, 2017 10:31 pm

Token wrote:
sparr wrote:The space was about 4 cubic meters
4 m^3 is a tad larger than; 3 feet wide, by 6 feet deep, by 6 feet tall.

Could fit a cot in there for a short person but other than that ... ???
The sleeping space was roughly 5x7x4ft. A queen bed, plus a bit of room for shelves, all just tall enough to kneel in the bed.
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Admiral Fukkit
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Re: My first solar air conditioner setup

Post by Admiral Fukkit » Thu Sep 07, 2017 7:03 am

Hats off, you're the the first and only one I've heard of running REAL air conditioning on solar ar BRC. That's actually inspiring.

Do you think you had enough A/C to handle a bit of living space, or was the sleeping compartment all it could do? Or did you keep the chilled space small just so you could really freeze it?

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sparr
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Re: My first solar air conditioner setup

Post by sparr » Thu Sep 07, 2017 9:58 am

The small space was mostly a side effect of our unrelated efforts to keep the bed dust-free. If our target temp was 75F (instead of the <60F that it proved capable of doing in that small space) then the A/C could have easily handled 3x the volume, probably more, during the peak sunlight hours. We would have needed larger batteries to get us through the evening as the sun waned but the heat remained. Better insulation and/or tilting solar panels would have also addressed that concern.

We used about 3/4 of our roof for active solar panels (and 1/4 for a spare). A larger vehicle could have used more panels and cooled a proportional amount of its interior to the same degree.
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Admiral Fukkit
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Re: My first solar air conditioner setup

Post by Admiral Fukkit » Thu Sep 07, 2017 10:20 am

Compare burning man's numbers to the numbers for the NFL, or pretty much any other vacationing.
Everyone knows this shit. Burning man isn't claimed to be "green". This isn't the Rainbow Festival, which Incidentally is a way bigger mess.
The Pacific Northwest is choking in a thick layer of smoke right now from massive wildfires. It FAR outdoes what burning man did. It's not even close.
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Re: My first solar air conditioner setup

Post by BBadger » Thu Sep 07, 2017 3:40 pm

Really nice work! You're really pushing technology boundaries at BM.
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Re: My first solar air conditioner setup

Post by EGAZ » Thu Sep 07, 2017 7:00 pm

I read your other post on Reddit and watched the vid. Nice job!

As FigJam says: "Build Your Burn!" That you did. :coffee:
2nd time better than the first. And the first was pretty Freakin' Great!
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Joeln
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Re: My first solar air conditioner setup

Post by Joeln » Thu Sep 07, 2017 7:18 pm

Kudos!
Much nicer than having to mess around with gas cans, refilling generators, the noise.
Collapse first and avoid the rush

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Admiral Fukkit
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Re: My first solar air conditioner setup

Post by Admiral Fukkit » Thu Sep 07, 2017 8:39 pm

Well, you only do that if you're an amateur that doesn't bring a 50-gallon tank and plumb your generators into it.

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Re: My first solar air conditioner setup

Post by EGAZ » Fri Sep 08, 2017 3:33 pm

On-Board Fuel Station FTW! :mrgreen:
2nd time better than the first. And the first was pretty Freakin' Great!
I am Camp2. - A solo camp - Stop by and say Hey!, 8) Gotta beer?

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Re: My first solar air conditioner setup

Post by worldjoe » Tue Oct 24, 2017 9:22 am

This is so awesome. I watched your video too (in another post). Great setup!

What is the reason for the 24V setup? Would sticking with 12V have been fine?
Also did you have to use a pure sine wave inverter?

Thanks,
Joseph Elwell.

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sparr
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Re: My first solar air conditioner setup

Post by sparr » Tue Oct 24, 2017 5:33 pm

worldjoe wrote:What is the reason for the 24V setup? Would sticking with 12V have been fine?
Also did you have to use a pure sine wave inverter?
My charge controller is is current limited, so it can handle twice the power at 24V (960W) as at 12V (480W). I ended up with 705W, and was very happy to not be stuck with 480W.

I did not have a pure sine wave inverter.
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