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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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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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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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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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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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!
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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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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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Re: My first solar air conditioner setup

Post by TheBlindcafe » Sat Jul 27, 2019 11:19 am

Hi Sparrr... my name is Brian Rocheleau I live in Boulder Colorado

I’m reaching out to problem solve how I could purchased rent or set up at Powersource at a festival to run a AC unit that would make our music and social change in the dark Dome experience that is held in 100% darkness meaning there’s no airflow so we have to have an AC unit as opposed to a swamp cooler… comfortable.

I have this really unique event the tall and 100% darkness called the blind café experience and it’s basically I’m gathering 50 to 100 people in the pitch dark room breaking bread together we have conversations from blindness and what it means to relate beyond our visual conditioning social etiquette and then I perform music in the dark is well with my band.

Anyhow we’ve been invited to go to arise music class for next week and we have a dog a 24 foot dome fifth I think it’s 14 feet high and they won’t allow us to have regular generators.

Any suggestions on resources for creating a power source that would run a portable air conditioner that pulls about 1000 W or 1500 W etc. still learning how that works anyhow if you respond I will I guess I can try to look at this for responses I’m not sure how forms go My number is 7204957797 If anyone has some ideas what could help me figure this one out we’re doing a cool thingAnd I can you really use the support thanks guys bye bye-bye

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Re: My first solar air conditioner setup

Post by Captain Goddammit » Sun Jul 28, 2019 3:44 pm

An air conditioner that only draws about 1000 Watts is nowhere near powerful enough for what you’ve described.
If I were you I’d set that thing up somewhere and see how much AC you need to chill it.
I think your estimate is way low, I think you’ll need several of those units.
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Re: My first solar air conditioner setup

Post by Token » Mon Jul 29, 2019 8:25 am

A 24’ dome is just shy of 500 square feet, so an efficient 1-ton would probably suffice IF you have somewhat decent insulation... say in the 4-6 R range.

But most domes don’t have any measurable insulation so that’s a problem.

Power needed for a 1-Ton unit is ~ 4KW.

That’s a shit-ton if solar panels and a metric ton of batteries. Looking at 16 or so 300W panels and a couple of Tesla power walls worth of battery storage.

How about just a big fan at the apex and you run your event at night only with all the guests naked?

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Re: My first solar air conditioner setup

Post by sparr » Mon Jul 29, 2019 9:16 am

I would really appreciate not derailing this thread and clogging my notifications with unrelated messages.
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Token
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Re: My first solar air conditioner setup

Post by Token » Mon Jul 29, 2019 9:34 am

sparr wrote:
Mon Jul 29, 2019 9:16 am
I would really appreciate not derailing this thread and clogging my notifications with unrelated messages.
Awwww, that is so precious...

Whatever happened to helping a fellow out? Sharing the knowledge...

... or was your post made just to stroke your ego?

You’re funny Sparr!

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Re: My first solar air conditioner setup

Post by FlyingMonkey » Wed Jul 31, 2019 10:07 am

sparr wrote:
Mon Jul 29, 2019 9:16 am
I would really appreciate not derailing this thread and clogging my notifications with unrelated messages.
No Problem buddy. I will refrain from responding to this thread (in the future).

Have an awesome burn!
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Re: My first solar air conditioner setup

Post by Canoe » Mon Aug 12, 2019 12:20 pm

TheBlindcafe wrote:
Sat Jul 27, 2019 11:19 am
... in the dark Dome experience that is held in 100% darkness meaning there’s no airflow so we have to have an AC unit as opposed to a swamp cooler… comfortable.
... a 24 foot dome fifth I think it’s 14 feet high and they won’t allow us to have regular generators. ...
We don't know what the outside surface material heat gain is. And you have a fair number of people inside it producing heat. Plus possibly band amps, etc.?

If the inside surface is black, then it won't be reflecting people's own radiated heat back at them. So while their body heat will heat the air, radiated heat not immediately reflected back results in the perception of more cool/comfort than if that heat was immediately radiated back. But a black interior will radiate more of the heat that gets through from the outside...

If the outside temperature and humidity is such that an evap-cooler(s) can do the job, why can't you use light-absorbing coatings inside ducting that source/ends in light-absorbing boxes - no direct light path, absorbing reflections. Rather than expensive light-absorbing coatings, you can use flat-black paint, and the same in rattle-cans to mist the surfaces again. Some canned paint is available with carbon black pigment - follow the cautions.

And if you run a duct inside up to the apex for feeding the exhaust ducting and venting, it will be exhausting the hottest air inside and providing a cooling flow on the roof underside, while providing part of the light-absorbing duct run. With A/C, you would need to channel some airflow up there to try for the same benefit, else you'll have that hot air sitting up there radiating down.

You'd still need to power evap-coolers - but they should use significantly less power than A/C - and use quiet fans (?), and have adequate potable water.
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