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Old 04-09-2015, 02:36 PM   #1
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Exclamation A modified evaporative cooler for solar camping

Okay, so I have been studying up on solar powered cooling options and a/c's just use too much power...so I have been looking at evaporative cooler designs both manufactured versions for retail sale as well as many diy projects...they all basically are the same principal, a water tank pumping water down a cooling pad with a fan circulating air over the pad being cooled by evaporation...

I am looking to improve upon this concept and here are my thoughts and observations...

First, these work well in dry climates like Arizona, but not so well in humid areas like here in Georgia...so why not dry the air being cooled first or heat the water before pumping it to the cooling pad? Or even better yet why not both? Logic tells me warm water will evaporate faster, and drier air will cool faster with the evaporation process...so, obviously, I don't want to use batter power to dry the air or heat the water as this will tax the battery system...but what about building in a solar box onto the evaporative cooler with cooper coils for water to pass through and warm up before trickling down the cooling pad? And on top of that air flow could pass through the same solar box to dry the air as well before being passed over the cooling pad?

Second, all the evaporative coolers use outside air cooled and pumped inside...what if, instead of using the outside air, you circulated inside air back to the evaporative cooler through a return to the solar box to get a truer and constant lowering of inside ambient temperature?

Third, what if you added a thermostat and logic boards to the equation to speed up or slow down the air flow and/or water flow depending on the temperature of the circulating air, the humidity in the air, and the effects of the solar water warmer/air dryer box?

It just seems to me there should be a way to build a more elaborate evaporative cooler that can perform more like an air conditioner using a fraction of the power consumption used by a/c....maybe even a hybrid unit combining both the evaporative cooler and an a/c unit? Use the cooler and cycle the a/c unit on less frequently but enough to really provide good cooling?

Anyone got any thoughts to my ideas?
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Old 04-09-2015, 03:16 PM   #2
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Well, I don't mean to be negative, but the laws of thermodynamics are hard to get around. To dehumidify, you need to cool and drop out the water. This is how an air conditioner does it. The other approach would be to absorb the water in something like a silica gel. This typically is not fast, and would saturate quickly. Once saturated it would have to be cooked at a high temp to dehydrate again.

Heating the water would defeat the cooling process. You would end up with warm moist air. Not ideal.

Recirculating the air would only work if you did in fact dry the air again, after the evaporative cooling had occurred, (see above).

Everything you have suggested would result in more energy consumption.

Sorry.
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Old 04-09-2015, 03:25 PM   #3
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Okay, points well taken, and thank you for the reply...so do you have any ideas on how I could use solar energy to remove humidity from the air before passing through the cooling pad?
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Old 04-09-2015, 04:06 PM   #4
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"Swamp coolers" don't work very well anyplace with high humidity. Last time I was in Georgia (deep south?) my close were soaking wet just from walking across the street. No evaporation at all.
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Old 04-10-2015, 08:42 AM   #5
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Quote:
Originally Posted by Johnny M View Post
Okay, points well taken, and thank you for the reply...so do you have any ideas on how I could use solar energy to remove humidity from the air before passing through the cooling pad?
The method of cooling is evaporation. Just like sweating. You can move more air, like sitting in front of a fan. The heat is lost when a molecule of water, that is warmer then the rest, jumps from liquid to gas, carrying that extra warmth, and the energy of phase change with it. Once the air is saturated with water, this cooling stops. The only way to get it out is to reverse the process. That is cool the air, (or scrub with desiccant). The desiccant would be great, but it can only absorb so much, so fast. You would have to carry tons of it.

So the short answer to you question is to get enough solar cells to run an air conditioner. Maybe about 2000 watts. I suppose that in time this will not be so costly.
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Old 04-10-2015, 09:27 AM   #6
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Solve this issue with an extremely affordable solar solution that will work in high humidity and heat and you will become rich beyond your wildest imagination. Then you can paint a picture of a Boler on the side of your luxury motor home and private Jet just to remind yourself of those fiberglassrv camping days.
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Old 04-10-2015, 02:35 PM   #7
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They make an RV swamp cooler but it is not cheap.
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Old 04-10-2015, 06:51 PM   #8
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We cool with a swamp cooler in central California. The secret to using one is high air volume. As long as you can keep the pads wet the more air you blow through them the cooler. When traveling I have been known to put a damp thin beach towel over the intake side of a box fan blowing in the window. If you could find a way to keep the towel wet.....

Just an idea

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Old 04-12-2015, 06:36 AM   #9
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How does a dehumidifier work? Might be some clues there. I suggest super insulating the camper. More on that in my reno

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Old 04-12-2015, 09:32 AM   #10
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It works like an air conditioner by cooling a coil and the cold coil collects water out of the air and between cycles, the water fills a container. When the container gets full, it powers down the machine. You can also connect a hose to run the water elsewhere instead of filling up the container. I use one in our camper and drilled a hole in the floor where the hose connects and drops the water under the camper. It only runs when the humidity gets to the turn on point meaning, it does not run full time. Keeps mold away from inside the camper in the off season.
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Old 04-18-2015, 10:34 PM   #11
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Thanks everyone for the good information & replys...I am still trying to think of a way to come up with the perfect energy efficient a/c for a small fbrv......now after looking at youtube videos I am trying to figure out how to make a magnetic powered a/c vent that will also serve as a dc generator to power the lights...
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Old 04-19-2015, 08:46 AM   #12
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Sail boats use windmills to generate DC voltage.
As far as a cheep way to cool your egg, try a fan.
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Old 04-19-2015, 09:37 AM   #13
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A lot of the ideas that the OP is trying to perfect already exist, but usually only in places like the International Space Station (that just got it's first Espresso Maker this week) where $$$$$ is not a primary consideration.


Energy = Energy, you can't create it without using some from some other form.


The first plane I ever flew in (A Late 40's(?) Taylorcraft), had a smaller propeller powered generator hanging between the landing gear, worked great, as long as you were above 60 MPH and, if you weren't, you were busy solving that problem anyway.....



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Old 04-19-2015, 10:27 AM   #14
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A bicycle generator. And you had to peddle harder.
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Old 04-19-2015, 10:20 PM   #15
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Seems like solar panels to recharge the battery(s) as they are harvesting energy while you are away or at least not needing the A/C. Not much point camping if you are sitting in the trailer most of the day.

Problem with running an a/c compressor in a camper is two fold. You need an inverter to get 120 vac and a system capable of handling the very short but very high starting current. I'd try to figure out how to drive the compressor with a 12 v dc motor to eliminate the big and expensive TSW inverter and incorporate a clutch so the motor could get up to speed before it takes the compressor load.

Here's a thought, Toyota Prius, at least since 2004 use an electric motor driven A/C compressor since you need A/C to work even when the gas engine shuts off. Maybe you could get the complete A/C system from a junk yard. You would need to do the numbers to see how much solar and battery capacity you'd need but this might be doable with a couple of hundred watts of solar and 2-300 aH of battery. Especially if you only needed to cool the camper from, say, 6 to 10 PM.



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Old 04-19-2015, 10:57 PM   #16
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Originally Posted by MCDenny View Post
Seems like solar panels to recharge the battery(s) as they are harvesting energy while you are away or at least not needing the A/C. Not much point camping if you are sitting in the trailer most of the day.

Problem with running an a/c compressor in a camper is two fold. You need an inverter to get 120 vac and a system capable of handling the very short but very high starting current. I'd try to figure out how to drive the compressor with a 12 v dc motor to eliminate the big and expensive TSW inverter and incorporate a clutch so the motor could get up to speed before it takes the compressor load.

Here's a thought, Toyota Prius, at least since 2004 use an electric motor driven A/C compressor since you need A/C to work even when the gas engine shuts off. Maybe you could get the complete A/C system from a junk yard. You would need to do the numbers to see how much solar and battery capacity you'd need but this might be doable with a couple of hundred watts of solar and 2-300 aH of battery. Especially if you only needed to cool the camper from, say, 6 to 10 PM.



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Denny I like your way of thinking! I found a site today Solar Air Conditioner | Affordable Solar Air Conditioning that has a solar powered window ac unit designed to run strictly off solar panels with a battery built into the ac unit, however the solar window unit costs almost $3 grand, that's more than we paid for our used fbrv
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Old 04-20-2015, 07:24 AM   #17
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The $2.9k unit weighs 200 lbs, has an 16,0000 BTU output and draws about 850 watts. Not much argument there vs using a standard home ac unit and a monster inverter that I can see. BTW: $2.9k price does not include the battery bank or the solar cells, it's the ac unit only, with a 48 volt compressor and a 20 a/h 48 volt battery that "might" power it for an hour.



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Old 04-20-2015, 08:20 AM   #18
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A modified evaporative cooler for solar camping

The little 5000 btu model that came in our Snoozy takes 515 watts so not remotely as efficient as the one cited above. I'm sure it was selected for its small size and low price.

515 watts is 43 amps at 12 V! If starting current is 5x, that's a surge of 215 amps!

Cheapest way to get remote A/C is with a gas powered generator.


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Old 04-20-2015, 08:25 AM   #19
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Scratch that Prius idea. It runs on 206 v 3phase ac current supplied by the same battery that drives the car. Lots of complicated electronic controls too.


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Old 04-20-2015, 05:40 PM   #20
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So maybe another avenue to investigate. What about the cooling system of a propane fridge or freezer paired with a fan. Your ac would then need just the fan to run off your 12v. Build it and I'll buy your plans!!

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