How I Use the Sun to Cool My House.




About: I'm just an ordinary bloke with an inquiring mind. I love to help people and find "Instructables" a terrific place to do that.

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.

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.

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.

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.

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.

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.

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.



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    104 Discussions


    7 years ago on Step 7

    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!


    2 years ago

    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.


    2 years ago

    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


    3 years ago on Introduction

    Do you have information on Indirect Evaporative Cooling systems.


    4 years ago on Step 6

    Frogs! ;-)

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

    Rob Pattersoncampingisgood

    Reply 9 years ago on Step 7

    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.

    tbone56Rob Patterson

    Reply 8 years ago on Step 7

    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 Pattersontbone56

    Reply 8 years ago on Introduction

    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.

    tbone56Rob Patterson

    Reply 8 years ago on Introduction

    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.


    Reply 7 years ago on Introduction

    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 Pattersonjsadler1

    Reply 7 years ago on Introduction

    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.

    tdc2202Rob Patterson

    Reply 6 years ago on Introduction

    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 Pattersontbone56

    Reply 8 years ago on Introduction

    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.

    tbone56Rob Patterson

    Reply 8 years ago on Introduction

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


    Reply 8 years ago on Step 7

    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.