Introduction: How I Use the Sun to Cool My House.

Picture of How I Use the Sun to Cool My House.

This instructable will show you how I converted a 240 volt rooftop Evaporative air conditioner to a Mobile unit run on my DIY 12 volt solar setup.
My setup supports the 2 most important things in the house.
The 12 volt Beer fridge and the Air Conditioner.
Without either of these the summers here would be unbearable.
There is also something quite satisfying about sitting in a cool house sipping icy cold beer on a stinking hot day knowing the sun has done all the cooling.

Step 1: The Beginning.

Picture of The Beginning.

First you need to obtain an old evap air cooler.
I bought mine on ebay for around $200. Winter is the cheapest time to buy one.
A trip to the local rubbish tip netted me an old BBQ on a stand with wheels at one end. I left the rusted out BBQ there and took the stand home.
A wooden pallet went with me.
The Air Cooler then had all the electrics, the huge 240 volt motor (unfortunately not permanent magnet) and the 240 volt pump unceremoniously ripped out (taking up space in my shed now if you want them).
It was then attached to the aforementioned pallet which was screwed to the top of the BBQ stand.
Now it's ready for step 2.

Step 2: The Pump.

Picture of The Pump.

After a look around I found that ebay had the cheapest 12 volt pumps that looked capable of doing the job of running enough water up to the top of the cooler panels.
I chose a 360 gallon per hour one purely on cost and Amps used (it uses about 2 amps).
It proved to be not quite powerful enough so I stopped the water flow to one of the panels so there was an adequate amount going to each of the other three ( I covered the now unused panel with plastic).
If your 12 volt system can support a bigger pump then buy a bigger pump.
About 500 gph would be perfect.
I have to be careful with every amp my panels produce.

Step 3: The Fan.

Picture of The Fan.

The hole that the old fan came from is 20 inches in diameter.
The Fan I chose for the unit is a single speed 16" after market car Radiator Fan.
It pumps lots of air and only draws 7 Amps.
I had to make an adapter to attach the fan to.
I used Masonite.
I cut a 20" circle and cut a 15" hole in the center of that.
I drilled a few holes and attached the fan with cable ties.
I mounted the wire cover off an old fan over the top of the fan to keep the Frogs out of the fan.
I should have mentioned earlier that the Air cooler has become a Frog habitat. Seven were living in it at last count. Any port in a drought eh.

Step 4: The Bendy Shiny Stuff.

Picture of The Bendy Shiny Stuff.

After a bit of a play with the kids 3 meters of the bendy shiny stuff, ducting to us grownups, was attached to the bottom of the cooler with duct tape.
I made a square wooden adapter for the house end and mounted it in an open window.
I bought a ducting vent attachment and screwed that to the wooden adapter.
The ducting was attached to that and the cooler was ready to be wired up.

Step 5: Wiring.

Picture of Wiring.

I built a switch box out of an old pc power supply case, added 2 automotive on/off switches and 2x10 amp fuses and ran the wires from the pump and fan through that to the load outlet on my solar controller .
Sounds simple because it was.

Step 6: Water.

Picture of Water.

Our water pressure is too high to connect the float valve in the cooler directly through a hose so I trickle water into a 10 liter container and it flows from that to the float valve and into the cooler reservoir as required.
Any excess flow into the 10 liter container runs through an overflow pipe to a bucket.

Edited 30/11/2012.
We have moved into the village of Bethungra where the water pressure is much lower.
This has enabled me to connect the cooler to the town water mains and has simplified things immensely. No more filling containers to gravity feed into the cooler and much better water flow over the pads.
Still have Frogs living in it though. I have no idea how they get in there but they seem to love it.

Step 7: Enjoy.

That's it.
Now turn it on, grab a beer and sit back and watch the Cricket (the Aussies are playing South Africa) in style.


fuzvulf (author)2011-06-10

To each his own on what they drink, nice "able".
There is a version of this which uses one more step that doesn't send moist air through your house. It sprays the water over the inward facing slats and then pumps it from the catch pan at the bottom through a heat exchanger through which air that is already in your house is circulated and blown back inside so that you don't have to cool hot outside air. moisture is in fact removed from the air in the house condensing on the cooler surface of the heat exchanger. This moisture (if any) is then routed to the catch pan reducing slightly the demand on municipal water. From the heat exchanger the water then flows to the spray nozzles over the inward facing slats of the enclosure and the process starts over again. everything else is the same as your setup, although using solar to run it is ingenious. Great Job!

Minyah (author)2016-10-29

Rob can you tell me where to get a radiator fan using 7 watts or less as most I've looked at are high amps. My system at this time is very small too.

Minyah (author)2016-10-29

Nice project... I've been trying to do a 12v system for my little cabin in Angledool. It's good to see what others have done. I couldnt find an old cooler so I am modifying a bar fridge as the 'box' cutting in vents and using it on its back so that the door 'lid' seals the system and a couple of computer fans push air into the cabin with water reservoir being the inside of the fridge. I would have preferred to have an old evap cooler though.

Thanks for the ideas

rblythe (author)2015-05-18

Do you have information on Indirect Evaporative Cooling systems.

marcdraco (author)2014-08-02

Frogs! ;-)

Sweet. That's a great project Rob. Very innovative.

campingisgood (author)2009-06-17

This looks very interesting, but I don't understand how it cools. Thanks

My unit cools in the same manner as it would if it was still a 240 volt unit. Hi campingisgood; The hot outside air is pulled through the wet "batts" and the water evaporating off the "batts" cools the air. To test the principle stick a finger (preferably one of yours) in your mouth, wet it then pull it out and blow on it. Amazing isn't it. I hope this helps. All the best. Rob.

tbone56 (author)Rob Patterson2010-11-03

Thanks for making this instructable.
It is a brilliant idea!
However, here in East Texas, we have pretty high humidity and the house would get 'wet' from using an evaporative cooler. In west Texas they are everywhere.

So, as an alternative, could this be used to cool the attic area of the house? Would this save enough on the main A/C unit to be worthwhile? Would it cause too much moisture in the attic?

Do you know where I might find the answer to these questions?

Rob Patterson (author)tbone562010-11-03

Hi tbone56;
Thanks for your nice comment and question.
This type of cooler can be used effectively in areas that experience moderate to high humidity but you MUST allow the cooled air to flow THROUGH your house. At least one window or door needs to be left open to allow the cooled air to escape.
In effect what you are aiming to achieve is a cool breeze through your house.
Simply pumping the cooled air into a room would soon cause problems.

Your Attic.
Does your house have ceiling insulation?
If it does then cooling your attic area might not make a lot of difference.
If it does not then cooling that area and using ceiling fans inside your house would make a difference I'm sure.

Does the air in your attic area get "baked" ( and dried ) by the heat of the Sun?
If it does then it might be much lower in humidity and therefore more suitable as the air source for the Cooler. You might even be able to have your cooler mounted in the attic area and ducted directly through the ceiling.
Just a thought.

tbone56 (author)Rob Patterson2010-11-03

Thanks Rob. Yes good tip on the airflow.

Yes, our house has insulation between the ceiling and attic. However, all the central A/C ducting runs through the attic space. My feeling is that if the attic space had cool air coming in at the eaves and the hot air drafting out at the roof peaks, then this may lower the attic temperature, and then reduce the heating of the cool air ducts.

When I first began thinking of making solar panels to generate electricity, I was kind of at a loss for how to use this energy in a way that would help reduce our energy costs rather than just give me more ways to use free energy.

After reading your instructables I think that I might be able to use your idea to reduce our energy costs without the issues of tapping into the house electrical system.

Thanks. You have given me some good inspiration here.

jsadler1 (author)tbone562011-05-28

Normally your air ducts are insulated to keep attic air from warming them.
Evaporative cooling has severe limits in humid areas. For example large buildings use chillers with water towers. The water towers use high horsepower fans and pumps to drop the water down through the towers. The idea being that evaporation will cool the water that makes it to the floor of the tower. That turns 95 degree air into 85 degree water. That water chills the hot side of a huge compressor so that large amounts of freon are not pumped through the building. The reason being that people could drown in freon in those quantities. The cold side of the freon loop is used to chill water down to about 52F and that cold water is pumped to coils in various rooms where fans behind the coils push air through them to cool the rooms.
That is the only use of evaporative cooling in humid areas that bears fruit at all. It is expensive beyond imagination and the water bills alone would break you.
The best bet is to get a central AC unit and replace it more often than you usually do. The rotary compressors are a good bet these days and a great energy rating is vital. The days of keeping an AC for 15 years are not with us anymore and decent AC units are expensive.

Rob Patterson (author)jsadler12011-05-28

Hi jsadler1;

I'm not sure what your message is.
My instructable is not intended as a forum for discussing the virtues of one type of air cooling over another.
The message my instructable is intending to give is this:
We have the necessary skills to make a difference to both our lives and the environment if we try. And we can do it on a small budget.
A simple conversion from an energy guzzling ( ergo carbon producing ) commercial air cooler to a recycled, self converted 12 volt unit running from solar panels, preferably home built, makes a difference.
We get to feel good about what we're doing and we produce less carbon.
I am not the only person who believes this.
The number of people who buy sets of solar cells from me (bigpat004) on Ebay (Aus) to build their own panels with is a testament to the truth of it.
If evaporative cooling is not suitable in your area simply get your thinking cap on and use my experience to help you convert a refrigerated unit to 12 volts, or......seeing how quickly my 12 volt car aircon defogs my windscreen (pulls the humidity out of the car) has me thinking that it could be used as an air "dryer" in conjunction with an evaporative unit in the house.....Maybe....

I think us common people have to be the leaders in changing the way our environment is being destroyed.
On our own our voice is merely a whisper easily ignored...together it becomes a roar that can only be quieted with positive action.

All the very best.
Rob Patterson.

tdc2202 (author)Rob Patterson2012-07-25

Very good response Rob! You are right on about "us common people"! We have allowed the big money corporations to exploit our world for far too long - we need to do something - ANYTHING that helps. Thank you.

Rob Patterson (author)tbone562010-11-03

G'day Tom;
A small point on the Air cooler.... We had power blackouts on 3 days over 40 degC last summer. My solar setup and air cooler made ours the only house in town with air conditioning and a working 'Fridge. It felt good :-) .
You could, perhaps, install yours to cool the attic space during normal times but be directed into the existing ducting in case of a power outage.
Cheers Tom.

lloydrmc (author)Rob Patterson2011-08-04

Very cool (pun intended)!

tbone56 (author)Rob Patterson2010-11-03

Nothing like a good idea put into action paying off bigtime!
Glad to hear that bit of news!

MTJimL (author)tbone562011-02-24

Great 'able. Just a thought about air flow through a house in East Texas. A powerful ceiling exhaust fan is a godsend, when taking air in from the shady side of the house and blowing it out through the attic. Just that will make a sweltering afternoon feel tolerable. If the incoming air is routed through a swamp cooler, so much the better. If the house is air-tight, the ceiling fan should provide all the air exchange you need, and prevent moisture buildup in the house and attic.

Hi, Thanks for the info. The design is simple, yet brilliant.

jose.miole (author)2011-07-21

are those "Frogs"? (referring to step 3)

tdc2202 (author)jose.miole2012-07-25

Don't you read the steps? It SAYS they are frogs!

Omegaman 2.0 (author)2012-07-11

Ironman, I think he means hiw water is treated with chloramines -.chloramination

I am not chemist so I cannot explain the ammonia. chlorine relationship but here:

IronManMC (author)2012-04-23

Chlorine and ammonia? There's a warning on all ammonia containers to AVOID mixing with chlorine. That potentially produces deadly free chlorine gas, and several other deadly toxic poisons, depending on the ratio of bleach to ammonia. This article ought to scare the **** out of you.

Do a search for "ammonia chlorine" and see all the disasters listed. It's scary!

Other than your mention here, there is no other reference to "clormanated". Could you please check with your water supplier and let me/us know? Thanks in advance.


Evaporative coolers REQUIRE a free flow of air FROM OUTSIDE through the wet pads into the house and out open doors, windows, etc.

Some think this works like a refrigeration type air conditioner (it doesn't) and try to "keep the cool air inside" by closing doors and windows. All this does is make the house HOT and HUMID. To remove heat, you must evaporate water with free flowing air.

When you sweat, a fan blowing lots of air across your wet skin and wet clothing cools you. If you wrap up in a plastic rain coat, you will be VERY hot.

I rebuilt an old evap cooler (a large window mount with a 1/2 HP blower motor) and set it up in the back yard for testing. It was well over 110 degrees that day, with very low humidity. It literally cooled the entire back yard.

The less restricted the air flow, the more water it evaporates, and the cooler it gets.

jholsinger (author)2011-04-25

BEER IS GROSS Thats what I think in the nicest way I can say it of course you may all fill in the blanks with far more Graphic words

love4pds (author)jholsinger2011-08-18

LOL, are you serious?

jimvandamme (author)jholsinger2011-08-11

You have never tasted good Belgian beer.

The_3rd (author)jholsinger2011-06-09

So drink lemonade?

kooljon (author)2011-07-13

Interesting idea, I must admit.

labtecmike (author)2011-04-20

Swamp coolers are terrible for high humidity climates. No matter how much air flow you have it won't cool your home enough to make it worth your while. The rising humidity level will only make it unbearable.

Shiftlock (author)2010-09-07

How well does a system like this work? By how many degrees will it lower the temperature? For example, if it's 100F outside, what temperature will this system keep your home?

Rob Patterson (author)Shiftlock2010-09-19

Hi Shiftlock;
Thanks for your question.
The system works very well.
On a day of 100F outside it would be low to mid 70's inside.
Our Summer gets much hotter than 38C (100F).
January and February days are usually between 35 and 45C.
On a 45C day the inside temp would peak at around 27C late in the afternoon.
If I start to feel uncomfortably warm inside I simply go outside for 5 or 10 minutes.
Remarkable how cool it feels inside after that.
The evaporative system works very well if you use it to create a flow of cooled air through your dwelling ie: in one end/side and out the other.
Simply pumping the cooled air into a closed space will not be effective.

Hi Rob;
I have an idea but don't know if it works well (or if really works).

Remove the hot section of your evap. Make a larger, without radiator, with only copper pipe (it needs a long and thin pipe). Take the thin pipe on the roof for the sun to warm it, connecting the pipe coming from the roof to the other side of evap system again. Fill the system with gas normally.

The pipe takes the sunlight and will be warmer. This heat will increase the pressure inside roof pipe and your evaporator will do the rest like using electricity to compress the gas in the pipeline. You just change the place and size of the radiator.
The system remains the same, except that it is not necessary to turn on the compressor, only the fan (there is a refrigerator that runs on kerosene or gas flame - this would be the mode of operation of your system, however, bigger).
Well, you may need to call a professional to do the calculations on the amount of gas, change valves or something more, but it can work. You also need to paint the roof pipe black to absorb more sunlight. I think that more pipe on the roof, more sunlight taken and more heat absorbed in evaporator side.

If it works, will be for a lifetime without power consuption, except the fan electric motor.

You can see something here (in portuguese)
and translate here:
Watch here:

Search by Adam Grosser - Stanford - fire refrigerator - new gas. It may be your solution.

Shiftlock (author)Rob Patterson2010-09-20

Right, I understand the way to use this kind of system is to create an air flow through the area you're cooling. This seems odd to most Americans, because we don't have that kind of cooling system here. Everyone here has power-hogging compressor A/C systems that work like big refrigerators. Most Americans make their large homes 20C inside 24 hours/day, no matter what the outside temperature is. Even if it's over 40C outside. It uses an incredible amount of power. Just another part the wasteful power-hungry society here that had better change if we're to keep this planet habitable. Your comment about going outside to feel the relative coolness of the inside was a perfect example of something most Americans would never consider doing. What, take all that effort to walk outside? We're too lazy. Just pump the A/C down a little more. Really sad.

Troy_187 (author)Shiftlock2010-09-30

i put a big block of ice in my swamp cooler on really hot days. it works great

Rob Patterson (author)2010-09-19

G'day Reader;
I thought it pertinent to add some thoughts here.....

I noticed that nearly every Evaporative cooler is sitting out in the open on the roof of it's house in full Sun and figured that didn't make much sense.
The units cop the heat from the Sun and the reflected heat from the roof, which I though must be counter productive.
I checked the temp in my unit while it was shaded and then again when it was in full Sun and the difference inside the unit was +15 deg C higher and there was much more humidity.
To overcome this I insulated the top of my unit with Styrofome panels. This keeps the interior cooler and reduces humidity inside the unit ( ergo, in the house) .
A 90% ( or more ) shadecloth "hat" would work pretty well too.

I also noticed with my unit that when we have a strong breeze blowing it's possible for the unit to work very well without the fan turned on.
The wind does the work.
It'd be nice if someone out there would design a simple set of shutters that would take full advantage of this free wind energy.

That's about it.

Pedros2 (author)2010-09-19

There are no problems with swampies here in aussy, what mold we have run one for 30 or more years and think they are great, and thats a great idea to run off 12 volt thanks for the ideas, cheers

Rob Patterson (author)Pedros22010-09-19

G'day Pedros2;
Thanks for your comment.
You're spot on. No problems with mould or whatever as long as basic hygene principals are applied ie a good hose out at the start of the season and a rinse with household disinfectant as needed.
The wood shavings in the pads are Cypress Pine or similar and have their own disinfectant properties ( another good timber for the shavings would be Western Red Cedar ).
Because we have been using these things for so long here in Aus we understand how they work and use them to create a cool breeze through the room/house rather than just pumping the (cooled and slightly humid) air into a closed room.
Our domestic water is pre-treated with some "ines" and "ides" but I haven't noticed any of the associated chemical smells coming into the house.
If that was an issue then a filter would be in order.

I'm glad you found the "ible" interesting Pedros2.

throwedoff (author)2010-09-07

nadeem5476, there are no coils to this system. It is an open system with water as the coolant. The water is pumped to the top of the swamp cooler where it is trickled down the sides into an absorbant media. Air that is pulled into the vented sides through the media cause the water to evaporate thus cooling the air. Swamp coolers or evaporative coolers work very well in dry climates and do not pose any health problems in a properly maintained system. These systems are very poplular because they have less power requirements than refrigerated systems, and they are used world wide.

menahunie (author)throwedoff2010-09-12

True. My parent and grandparents were raised in the desert around Palm Springs Calif.
You will see over 90% of houses with swamp coolers.

Most if not all commercial bldgs. use this type of system on a much larger scale to cool the bldg. They would cool down a chill water loop to around 50 degrees and pump it in insalated pipes to evaporator where air would be blowing through them into the bldgs. rooms.

t.hecking (author)2010-09-12

Nicely done instructable. Perhaps you could eliminate the water pump altogether by dripping or spraying city water directly on the pads?
Using a filter could eliminate chlorine and other nasty stuff from entering your house. Insulating the feed water pipes will keep the water cool.

ihwild (author)2010-09-10

For those concerned about humidity what about running either the cooled air or the to be cooled air through something like an intercooler (explanation at bottom)similar to a turbo system on a vehicle. Then have the other air running over the fins into the house or through the intercooler into the house. I'm not sure which one would cool the house air better.

Intercoolers: Basically they are a heater exchanger for air to air or in some applications water to air (when the turbo or blower produces boost it also heats the air, the intercooler allows a chance for that heat to be removed by either air over the fins or water absorbing the heat.) They are also designed to not restrict airflow much unlike trying to force air through a car radiator where the liquid normally would be.

Just a thought. I like the idea though.

FurtherThanTesla (author)2010-08-02

Could you please explain exactly how this works? i understand its evaporative cooling with water, but whats the HVAC unit for? and where did you attach the auto raidiator fan? where does the whater evaporate? whats the 12v pump for if you already have water pressure?

Hi FurtherThanTesla; Thank you for your questions; I'll try to answer them one at a time. # The HVAC unit? -What do you mean by that?. # Where did you attach the radiator fan? -The auto radiator fan was placed where the original fan came from, in the bottom of the unit facing into the ducting. This enables it to pull outside air through the "bats" (see answer to "where does the water evaporate") and push it into the room through the ducting. # Where does the water evaporate? and What's the 12 volt pump for? -The water is held in a reservoir at the bottom of the unit. From there the pump sends it to the top of the "batts". It then trickles down the through "batts" soaking the wood shavings that the "batts" are filled with. -A tiny amount of the water evaporates from the surface of the wood shavings as the outside air is pulled through the "batts". This cools the air. To demonstrate this wet your finger then blow on it. Any excess water returns to the reservoir. The reservoir is kept topped up with piped water through a float valve that only allows water through when the level drops sufficiently. ## It is Critical that the unit is allowed to create a through breeze in your house by entering at the ducting outlet in your room and exiting via an open window or door at the other end of the house or room. If the cooled air is just pumped into a closed room the room will get stuffy and the cooling effect will be lost. At the house where I had this unit set up the cool air came into the loungeroom through the ducting and went out through a window in the far bedroom, cooling the house as it passed through. I hope this answers your questions. Cheers. Rob.

you didnt really mention wood shavings or the "batts" in your instructable, but thanks a lot for the fast response and info! What i meant with the HVAC was, did you use the radiator pipes or any parts in it? or did you just use the metal shell to house your system? And so what you mean is that - the wood shavings are like sponges that hold the water and give surface area for evaporation. the radiator fan pulls outside air through the wet wood shaving sponges, and becomes colder as the water evaporates, then goes though the fan that pushes it through the duct. - Is that whats going on? oh, and whats holding all the wood shavings? (i live in GA and we have the AC running constantly due to recent heat waves, but are out of money and cant afford cold air anymore - $300 electric bills - ) How much of a temperature difference is there with your system?

A swamp cooler is cheap to operate, but it will add 50% or more humidity to your home thus increasing mold and mildew problems. Swampers are great in desert areas which can use more humidity, but for Georgia, I believe the problems created with the high humidity would be more costly than paying the electric bill. Plus finding a used swamper in this part of the country is next to impossible. A new unit will cost around $1000 and that figure is from 30 years ago when we lived in the state of Nevada. You can build a small swamp cooler yourself by using a window fan and a wet towel hanging in front of it. Keep the towel moistened at all times and the fan blowing will help to cool the air. This won't add as much moisture to already moist air, but it will also not cool the air as quickly. My suggestion to you is to buy a single small window unit air conditioner, 5,000 btu and cool only one room. That alone should reduce the cooling expense and you will have one comfortable room in your home.

adrian.ccs (author)2009-05-27

Hi Rob Patto, Where do you include the part that power up the whole system?

Rob Patterson (author)adrian.ccs2009-06-14

Hi Adrian;
Sorry it took me so long to get back to you but I've been busy writing the instructible on how I built my Solar setup
I hope you find it useful.

nadeem5476 (author)Rob Patterson2010-08-01

bcz the water comes in direct contact with the air so it will fill humidity in the room ! and much humidity is not good to live in .

Rob Patterson (author)nadeem54762010-08-02

Thank you for your comment. If you just pump the cool air into your room it most certainly will make the humidity in the room rise but that is not the correct way to use evaporative cooling. The idea is to create a cool breeze that flows through the room/house. The cool air comes in from the cooler and goes out an open window or door cooling the room as it does. It is very effective and is used in many thousands of buildings in all parts of the world. Cheers. Rob.

nadeem5476 (author)Rob Patterson2010-08-02

thats just a SWAMP COOLER , ok ? and for sure the swamp cooler is not using thousands of buildings , those u r saying the same thing is actually a CHILLER and thts different from this . in chillers the water is not come in direct contact with the air.

Rob Patterson (author)nadeem54762010-08-02

I'm not trying to re-invent the wheel. All I'm doing is sharing the experience of converting an existing and very common 240 volt Air Cooling unit to 12 volts so that it can be run from my DIY solar panels. But to refute your argument.... If you dive through any Australian town you will see the 240 volt Evaporative Air Cooling units on the roof of at least 25% of the houses and a large number of the bigger buildings. Maybe Australia is way ahead of most of the world with using evaporative cooling but I think not. Cheers. Rob.

About This Instructable




Bio: I'm just an ordinary bloke with an inquiring mind. I love to help people and find "Instructables" a terrific place to do that.
More by Rob Patterson:D.I.Y. Solar Setup.Building a DIY Evaporative Air Conditioner.How I use the Sun to Cool my House.
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