Another DIY idea to solve the AC problem (small, green, quiet)

[Luisafernandes]

I am just south of White Haven just south of the big road I-80 near the upper Lehigh whitewater under the old growth hemlocks near Hickory Run State Park.

I live in a van down by the river. LOL.

Ok, you are about 1 1/2 hours from me.

 

[Zil]

I would like to see the math. Take 4 liter bottles of water. Freeze in a 12 volt freezer on batteries at night to avoid the higher ambient temperatures. use the solar to recharge the battery during the day, hope for no clouds, do not pray for rain. Run the fan across the ice to cool my sorryazz during the hot day. OK the math I need, (1)how long to freeze a measured amount of water. How many amp hours from the battery. (2) how long cooling with the measured ice/fan before refreezing. (3) how long to restore the battery with solar.
Side notes; I spent some time in S. Arizona and found with just shade and light breeze I was comfortable. So I would only really need artificial air cooling in humid climates.
Side note; I remember cutting ice from the local mill pond, and still have the special saw. they cut ice to avoid the expense of power freezing done other times of the year.

 

[Spaceman Spiff]

Zil, this gets messy real fast :s Its late, so I hope I did the math right (my thermodynamics classes were a long time ago and I promptly forgot everything).

1 Watt x 1 second = 1 joule

One must remove 334,000 Joules of heat from 1 liter of pure H2O at sea level to effect a phase change from water to ice at 0 deg C (Thermodynamics, Wark, 3rd edition, McGraw-Hill). So, with a perfect 12 volt heat pump, it would take 7 3/4 amp-hours to freeze 1 liter of water [334,000 watt-sec/((60 sec/min)*(60 min/hr*12volts) = 7.73 amp-hours].
But.....
Most refrigerators have an efficiency of between 3 and 4 (meaning that the frig uses 3+ joules of energy to move 1 joule from inside to outside the box). So, multiply by 3 => 23.2 amp-hours to effect a phase change to 1 liter of water.
Add to that.....
You must remove about 4186 joules of heat (the specific heat of water varies with temperature) to reduce 1 liter of water 1 degree C at sea level. Add in ~0.3 amp-hours for every degree reduction in temperature before you can begin freezing.
I'll let someone else tackle (2) & (3).
Goin to be now, brain is fried. -- Spiff

 

[SoulRaven]

I'm kinda thinking that, if a person was to do the 'making ice for air conditioning' thing, that a 12v compressor cooler (hooked up to solar) would be the way to go (funds permitting). This is cuz the time needed to make the ice takes place during the hottest time of the day and, while the mounds of ice made by the 120v ice-maker in the video look impressive, the 'cubes' are really small hollow cylinders.. not much ice there at all.

I'd think that, for air conditioning purposes, one would need a considerable amount of ice and, being realistic, a 'study' should be made re. how many BTU's it would take to melt a pound of ice, and bring the resulting water up to an 'unusable' temperature, vs. how much ice could realistically be made with a cooler/ice-maker.

not trying to be a Debbie Downer here.. just been disappointed too often in life and due diligence often pays off handsomely. ..Willy.

I use a 7+ day cooler for my water reservoir, and the ice is actually insulated from the circulating water by a plastic container too. The system uses a heater core with a fan behind it, and a fountain pump.

I use the big blocks of ice, not the smaller cubes, and they will typically last 5-7 days, which is usually longer than the heat waves last wherever I'm at.

Along with my other power needs, my single house battery will last 5 days versus 7+ days without running the A/C.

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You guys are spending way to much energy to solve a simple problem. A big block of ice only costs 99¢

 

[compassrose]

Artic Cove 18 volt Bucket Top Misting Fan uses a Ryobi rechargable battery. Too pricey for me but I do know the misters do cool you down even in hot, humid GA (used a huge residential setup in Cordele). Maybe toss an ice pack or two to drop the water temps down even lower.

The last few days, the humidity here has been too high for the swamp coolers to work right. Temps are in the 90's. We have regular air conditioners and try to keep the temps in the low 80's otherwise we can't stand to step outside. And to think I grew up in FL with out air conditioning!

The only "12vDC" air conditioner that I know of that really works is an automotive unit. Ever consider buying an aftermarket kit, installing it and running it off a dedicated battery bank? I'm sure someone has done this.

 

[Zil]

automotive air runs off the engine. I can't find one for the electric cars. But remember Lexus uses hundreds of volts and has battery weighing by ton not pound.

 

[SoulRaven]

The only "12vDC" air conditioner that I know of that really works is an automotive unit. Ever consider buying an aftermarket kit, installing it and running it off a dedicated battery bank? I'm sure someone has done this.

Those after market jobs still require a belt driven compressor as far as I know.

Before retiring, I spent 30 years as a long haul driver, and we all used 12v A/C units similar to this:

These are the only type we ever found that really worked, and work anywhere in the country. Our ice chests weren't as good as what's available today, but a big block of ice would still last 2-3 days back then. All of the other types of ice coolers we tried would burn through a bucket of ice an hour. Even cubes would last all day in these.

You could build one of this type for less money than that mister job.

 

[GrayWhale]

while the mounds of ice made by the 120v ice-maker in the video look impressive, the 'cubes' are really small hollow cylinders.. not much ice there at all.

not trying to be a Debbie Downer here.. just been disappointed too often in life and due diligence often pays off handsomely. ..Willy.

Hey no sweat. I welcome the negatives, to potentially help me save money from buying stuff for a project that may not work well. In general, I've found that full time vandwellers with many years knows a lot more than me as I'm not even close to full timing it. I've been eyeing this portable ice maker, but it's true, the cubes are very hollow and probably won't last that long. Some of those YouTube videos, people are very arrogant and don't like to show any hint of failures so often times, their videos are very rosey. This gives me a good perspective on both sides. I probably won't go this route and save $150. 12V refridge is definitely the way to go, but not right now though, $800 ouch.

 

[Willy]

Hey no sweat. I welcome the negatives, to potentially help me save money from buying stuff for a project that may not work well. In general, I've found that full time vandwellers with many years knows a lot more than me as I'm not even close to full timing it. I've been eyeing this portable ice maker, but it's true, the cubes are very hollow and probably won't last that long. Some of those YouTube videos, people are very arrogant and don't like to show any hint of failures so often times, their videos are very rosey. This gives me a good perspective on both sides. I probably won't go this route and save $150. 12V refridge is definitely the way to go, but not right now though, $800 ouch.

Maybe keep your eyes on Craigslist. That's where I got my coolers/fridge off of. Basically, I ended up getting them for 1/3->1/2 of the retail price, and they're soooo reliable that I didn't worry about the warranty.

Right now, I'm waiting for a buddy and his GF to show up tomorrow and have been freezing containers of water for them to put in their cooler and am also waiting for another friend to some day drop by so I can give her that 1 kg bag of frozen blueberries I've got sitting in the cooler. Just having it makes my life, and that of my friends, so much better. ..Willy.

 

[offroad]

Is ice that costly? Have to read the thread more.

 

[highdesertranger]

for what it is ice is very costly. think of it as how much water there is in the ice you just paid x amount of dollars for. you are paying to freeze it. on another note you are never going to be ahead making ice to use for air conditioning. every conversion of energy you do is going to have a loss. so the more conversions the more loss. your best bet is to do as few conversion as possible. this would be running a small ac off a small generator. this would be three conversions, gas to electricity, electricity to the ac compressor, electricity to the fan on the ac. so with the ice method, you have to charge your batts #1 conversion, you have to make ice #2, you have to make cold water with the ice #3, you must pump the cold water though a heat exchanger #4, or yeah you need more power from your batts to do this #5, you must power a fan to move the cold from the heat exchanger #6. all the time you must remember that you lose in every step. so in review we all must remember that ac is an energy hog. no matter how you look at it or how you try to do it. imo ac is a scourge on the planet. so much energy burned for short term comfort. I just read a report that in the summer months 50% of the power generator in the phoenix, Tucson area in the summer goes to ac. what a waste. I don't use ac, imo if you think you need ac, you should be in another area. I go prospecting in the desert in the summer. I don't need ac. I don't even have it in my truck. be smart not lazy. done with my rant. highdesertranger

 

[Willy]

I think, where I'm currently hangin', ice is going for $2->3 a bag. That could add up pretty quickly if one were to use it for air conditioning purposes.

Yesterday, it got to around 90F here and, in my well insulated rig with the skookum solar extractor fan going (abt. a 6" 12v computer fan drawing 17W), I was nice 'n cool.. even took a nap. I DON'T park in the shade, only in the blazing sun. 'Course, it's gonna get considerably hotter here but, judging from past years, I'll still be nice 'n cool. ..Willy.

 

[Luisafernandes]

I think, where I'm currently hangin', ice is going for $2->3 a bag. That could add up pretty quickly if one were to use it for air conditioning purposes.

Yesterday, it got to around 90F here and, in my well insulated rig with the skookum solar extractor fan going (abt. a 6" 12v computer fan drawing 17W), I was nice 'n cool.. even took a nap. I DON'T park in the shade, only in the blazing sun. 'Course, it's gonna get considerably hotter here but, judging from past years, I'll still be nice 'n cool. ..Willy.

Willy,
I don't know if you've answered this question before, but what kind of insulation do you have?

Thanks!

 

[Willy]

At the moment, it consists of an all-round fibreglass shell with 1" polyurethane foam insulation (an '83 piece of crummy shit Bigfoot camper I picked up). The fibreglass is white and, under the blazing sun, the ceiling doesn't even get warm. If I decide to keep it, I'll add some more insulation to said ceiling and do something about the windows. ..Willy.

 

[Luisafernandes]

Thanks willy!
I hope that my metal box (cargo van) behaves the same once insulated.