Introduction: Solar Powered Air Conditioner

About: Fixer, Finder, Fabricator. I teach engineering to high school students, at St Marys Secondary College in Nathalia VIC Australia

I was given a design challenge by the residents of foot rot flats*, build an air conditioner that requires no mains power and no piped water. After a bit of thinking I decide to have a go at a solar powered evaporative cooler and it worked so well I thought I would make another one, and make it a bit different to make it even easier to build. The first cooler was not photographed during the build so the second cooler is better documented for instructables.

*Foot rot flats small community with no power, water, toilet or pretty much anything else you would expect in a western country. There are a number of permanent residents living in illegal shacks, caravans, buses, shipping containers or camper-vans and a number of others who stay for a few weeks or months of the year but usually leave before the hot weather as it can get to 45 degrees C (113 F) for days at a time and is not unlike a small version of slab city in the US.

Step 1: Is a Evaporative Cooler Right for Your Location?

Before you start you need to understand that an evaporative (or swampy) cooler will only work if you live in an area with low humidity. If your not sure if your area is suitable, a good indication is have a look at houses in the area, do they have swampy coolers on the roof, or are they all refrigerated coolers?

Swampy coolers have some advantages over a refrigerated coolers, the most attractive though is there low energy consumption.

The good stuff

  • You can leave windows and doors open so air is fresh and healthy
  • Won't dry your skin, nose and eyes
  • Energy efficiency means better for the environment
  • Get a good night's sleep as the are whisper-quiet
  • Will still work well in a poorly insulated drafty building.
  • The technology for evaporative coolers is very simple, and there are fewer working parts, which means maintenance and repair costs are low.

  • The wet pads filter out much of the dust, and pollen in the air before it cooled and blown into the building

The not so good stuff

  • Swampy coolers use a lot of water around 1000 liters a week.
  • Cant be used in areas of high humidity, evaporative cooling works best in dry climates. Too much moisture in the outside air makes the system work inefficiently and moisture can build up, causing condensation and make the air muggy and uncomfortable.
  • Pads can harbor mold if not serviced, which is very unhealthy if mold spaws are blown inside.

Step 2: Stuff You Will Need.

Because evaporative coolers are so simple you wont need many parts, but you will need to think about the voltage you want to use and also the availability of a tread mill motor, which can be difficult to find. I have found them at the local dump, but they are sometimes available on ebay. The motors are a permanent magnet type and are rated at 100 volts or more, but run well at at 24-48 volts and are perfect for an air conditioner with a fan.

If you want to run your air conditioner on 12 volts you can use a big thermo fan with a speed controller, to cut down the speed and noise of the fan.

Parts list

  • Treadmill motor or large thermo fan
  • Speed controller
  • 12 or 24 volt water pump
  • If you don't have running water you will need a reservoir, an IBC container is perfect as is can double as a stand for the air con unit.
  • Second hand evaporative cooler, you only really need the box and the pads.
  • Wires, switch, screws, tape, tools, etc.
  • solar panel with regulator and battery, or capacity on your existing system.

Step 3: Air Condtioner Number One

This is the first solar air conditioner I built, I didn't take many photos of the build (silly me), but it was a little hard to take photos every few minutes as the resident and his kids were helping.

It runs on 24 volts from an existing solar power system, and uses a tread mill motor and the original fan with no speed control. The pump is a 24 volt unit, and both the fan and pump are wired to a single switch, so the unit is either off or on. The IBC container is full of water and acts as a reservoir and surprisingly only lasts for a week or so before having to be refilled.

The pitch on the blades were adjusted to tune the motor / fan to get the best air flow from the power supply.

The air con has been fitted to a window on the building, which is a shipping container with a lean to. The temperature inside the building used to be unbearable, and a health hazard on hot days 45C + is now very comfortable and at times a little too cold.

The unit works just as well as the factory cooler I have on the roof in my own home, so overall well worth the time an effort.

Step 4: Air Con Number Two

This air conditioner unit is quite different internally to the first one as it has a squirrel blower fan. I decided to remove the whole assembly and use a radiator thermo fan on the side of the unit and sits on the ground for a number of reasons.

  • The resident wants to run it on 12 volts and the minimum voltage for a tread mill motor to produce a useful amount of power is 24 volts.
  • Unless I could find another tread mill motor I would have to buy one at twice the price of the 16inch thermo fan
  • The vee belt would introduce losses
  • The blower unit could be sold to offset the cost.
  • The unit is much bigger than it needs to be for the space it will cool, so losing one pad wont be a problem.
  • The unit will sit on the ground and blow through a hole in the wall, so having the outlet on the side will reduce the ducting needed.
  • As the unit is on the ground I wont have to pump water 4 meters into the air or worry about mounting the contraption on an already rickety and leaky roof.

Step 5: Removing the AC Motors and Pumps

Striping the unit is simple just remove the pump, blower unit and any wiring. If you are going to use an IBC as a reservoir you can also remove the float valve, but if you have running water you can leave it on and mount the new DC pump inside the air con unit. If your lucky someone might want to buy the blower and pump, and i was able to sell the blower to a guy who wanted some ventilation on his plasma cutter machine.

I was able to get the blower unit working and it moves a lot of air, as you can see, Jade is testing the wind speed.

Step 6: Repairs to the Tank

I was able to get this evaporative cooler unit for 1/2 price as it had been dropped off a forklift and the plastic tank was a bit damaged. The tank was repaired with.

  • Hot glue gun
  • Plastic oil container
  • Bitumen paint.
  • Acetone

The secret to getting a good plastic repair is to clean everything with Acetone, use good quality hot glue sticks and get the glue gun really hot. It should be left on for half an hour or so before use and the glue needs to be hot enough to melt the plastic your trying to repair.

I used an plastic oil container to make patches and hot glued everything in place. You need to really watch your fingers as the glue will burn you pretty good if you get some on yourself. I used blocks of wood and a hammer to hold everything in place while the glue set.

Once the patches were fitted I also hot glued the patches on the inside of the tank, then finally used the Bitumen pant to seal the repair. The process only took an hour or so and I was also able to delete the large drain, as the unit will be working a little differently to factory it wont be needed. The water will flow out the smaller drain back into the IBC to be recycled

Step 7: Blocking Up Some More Holes.

As the cooler needs the air to exit out the side of the unit there are a few more hole the need to be blocked up. First there is a tube that runs around the top which supplies water to the pads. So the holes on one side is blocked up with hot glue, as there is very little pressure the glue will be adequate to stop the water flow on that side of the cooler unit.

The large air outlet hole was simple blocked off with a piece of plywood which is screwed into place and then two square steel bars were screwed in place across the bottom, so the cooler unit can be sat on top of the 1000 liter IBC container.

Apart from connecting the solar pumps hose to the water outlet at the top of the unit, the box is finished, so can be rolled over and fitted to the IBC tank.

Step 8: Fitting the Thermo Fan

The fan is a 16 inch 12 volt unit rated at 80 watts although dropping the speed with a speed controller will lower the energy consumption significantly and also reduce the noise.

The fan was fitted to the side of the cooler unit, but there is no reason why it couldn't be put in the bottom original position. One of the pad was removed from its cover and a hole cut with tin snips. The louvers were then flattened out with a hammer and block of wood and the inside sealed up with gaffa tape. The fan was then attached to the cover with tek screws then fitted back onto the air con unit.

Step 9: The Installation

The cooler unit was installed at the back of a shack on top of a IBC container that acts as a reservoir for the water. The hardest part of this project was cutting a hole in the wall, as it had a layer of plastic coated foam inside the wall which would melt when cut with a jigsaw and clog up the blade.

After a lot of cursing in the 40 degree heat the hole was finally cut and the cooler unit was lift onto the IBC container. The 12 volt pump was dropped into the bottom of the IBC and the hose connected to the piping that send water to the pads. The drain from unit was connected next an it goes back into the IBC tank

The speed controller wiring and switch were hooked up and connected to the 12volt battery bank. The system was turned on and it was soon blowing cool air inside. One of the problems with 12 volts is the voltage drop over distance, so the fan was only getting around 7 volts due the battery bank been about 12 meters away. So the fan wasn't moving as much air as expected, so I gave the resident the option of either use heavy wiring, or putting a battery close to the cooler unit and connecting a solar panel to it.

He choose to run heaver wiring, and as he's always strapped for cash we run 2 extension cords(1 for +and 1 for -) from the battery bank to the cooler, not perfect but much better than the other crappy wiring he had. We ended up with 11 volts at the fan, not perfect but Ok for what i had to work with.

I like to leave projects like this a little unfinished so the resident, can take so ownership and help them selves a bit. His imagination is quite good and after toying with the idea of a toilet seat.... he came up with a plastic drum lid to blank of the air con when not in use and to tidy up the hole in the wall. He also had the task of sealing the gap between the fan and the wall which he did with some old foam rubber.

In conclusion

If you live of grid in an area with low humidity this project is well worth the time effort, both coolers use about 100 watts of power running flat out, but the amount of water they use is quite significant.The performance of both coolers is very good in fact almost the same as a cooler running on 240 volts.

The tread mill motor version is slightly better as it defiantly moves more air for the same amount of power and is quieter, so if you can find a dead treadmill that would be the version I would advise you to make.

Brave the Elements Contest

Second Prize in the
Brave the Elements Contest

Full Spectrum Laser Contest 2016

Second Prize in the
Full Spectrum Laser Contest 2016