Prototyping A Solar Paneled Evaporative Cooler For the Non-Technical Techie

Over the past few months, I’ve been running through different prototypes as part of my Evaporative Cooler project. If you can recall, this was the original design:

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I needed a cooling solution that would cool the air in my space without the need to be plugged into an AC adapter. I don’t have an engineering background so a lot of the information I gathered, I had to learn by talking to engineers and reading related materials on the net and how other DIY’ers have done it (special credit to Figjam for his original prototype).

For the non-technical techie, there are a few things that matter when determining how you want to build your cooler:

  • Cubic Feet of the Space You Want to Cool– This will affect how powerful of a fan you need
  • Environment of the Space You Want to Cool– Evaporative coolers only work in dry heat because they rely on being able to draw heat from the environment during the process of evaporation, leading to the cooling effect (this is also known as the latent heat of vaporization.)
  • Power and How you Want to Connect All the Different Devices
  • The Voltage, Amps, and Wattage  of all the devices, connectors, and power sources (AC or DC)

Over the course of the prototyping process, I was trying to come up with a solution that hit directly at the intersection of effectiveness, cost, and complexity. Ideally, the right solution would reduce complexity, be reasonably priced, and still achieve all of the things I needed.

Prototype #1: USB Fan + Portable Solar Panel

For my  first prototype, I thought about using a USB Fan and hookup to a portable Solar Panel. After doing some research about solar panels, it looked like my options were either to buy a highly portable, but low power, solar panel or a higher power non-portable panel. Given that I live in an apartment building and face a brick wall, I currently don’t have any use for a rigid solar panel. I decided to go with a panel I could later use while hiking and camping.

The problem with this, however, ended up being fan, not the solar panel. The space I needed to cool was 855 cubic feet, which means the fan needed to push air at ~171 cubic feet per minute (CPM) if I wanted to replace all the air in my space within 5 minutes. Most USB fans are not powerful enough to do this and most of the ones available on Amazon didn’t even include CPM metrics to be able to gauge their effectiveness.

So, a USB hook up was not going to be ideal.

Prototype #2: More Powerful AC Adapter Fan + Deep Cycle Marine Battery

So, the next order of business was to upgrade my fan. I looked into available options and found that the most powerful fans were not only high voltage but high amperage as well and I was concerned that the Solar Panel would not generate enough energy to run a larger fan.

Introduce the Deep Cycle Marine Battery. Deep cycle marine batteries are lead acid batteries that you can use to power an evaporative cooler but they have all these specific rules you need to follow (i.e. you shouldn’t be using more than 50% of the charge of the battery or it starts to decay the battery) that became tedious to account for. Furthermore, deep cycle marine batteries introduced an additional layer of complexity, particularly if I wanted to hook it up to  the solar panel. The ac adapter from the fan which would require that I also buy a charge controller and inverter and all the additional wiring, sockets, and connections needed. Also, deep cycle batteries themselves are expensive and heavy. They would need to be recharged using a car generator or something similar, if not trickle-charged through a more powerful solar panel than what I bought.

It became clear that I needed to find a fan that could hook up directly to the 18V solar panel I had purchased (on DC power) and run.

So, Prototype #3: Upgrading the Fan and Using a Solar Panel

Introducing prototype #3 which involves using a computer fan. The cheapest (but still powerful) computer fan I found was a Delta fan on Amazon for $12 that ran at 148 CPM (which would cool my space within 5.7 minutes. Not ideal but decent). The Delta fan had exposed wiring that I needed to be able to connect to the portable solar panel that I got. After a bit of research, I found a DC cable adapter that I could wire to my fan on Amazon. Perfect for my purposes. The guy at Home Depot said I would I have to build one but most of these wire connections are available somewhere online…just gotta find them.

Once I had these things issues thoroughly understood, everything else was more like plug and chug. The list of materials I used included:

  • 1 orange gallon bucket from Home Depot
  • 1 Solar- Paneled Fountain Pump
  • One PVC Pipe (3/8 inch)
  • 1 Pad of Duracool
  • One Computer Fan (which you use here matters)
  • 1 Portable Solar Panel
  • One DC connector with exposed wires
  • 1 large 4 inch PVC pipes (90 degree angle)
  • T-connector
  • Screen
  • All the basics: Scissors, glue, power drill, ruler, appropriately sized screws and nails

One of the important parts of gathering all the difference devices and connectors was making sure everything was aligned in powering capabilities:

So here’s what I did:

1) Laid out all of my materials so I could see what I’m working with. One thing missing from this picture- T-connector for my PVC pipe.

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2) Used the corners of the computer fan to sketch out the holes to drill. The screws broke through the plastic pretty easily, no power drill needed. I did not actually install the the fan yet, only used it to project where the screws should go.

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3) Used a sewage pipe (4″) and outlined the circle for the fan.

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4) Cut a few millimeters within the outline.

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5) Installed the fan on the underside of the cover.

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6) Flip the cover over and it looks like this:

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7) Next, I measured the dura cool pad and cut it to fit the inside of the bucket.

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8) Also cut some screen to a similar size.

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9) Next, I drilled holes into the bucket. 8 in total.

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10) After drilling the holes, the bucket looked like this:

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11) And with the screen and dura-cool pad, looked like this:

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12) I was excited to power my fan so I spliced the fan wires next.

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13) And used electrical tape to connect to the DC cable IMG_5509

14) Took my solar panel out into direct sunlight and tested my fan! And it worked 🙂

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15) Next, I connected the fountain pump to the pvc pipe I had.

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16) And connected the pvc pipe with a T-connector.

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17) So, the inside of the bucket cooler looked like this.

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18) Took a needle….

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19) And poked holes in the halo of the pvc pipe to let water drip down the side.

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20) Using glue, I glued the 4″ pipe to the fan opening.

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21) Here’s what the total system looks like (complete with Netflix entertainment :] ) This swamp cooler only works in complete sunlight. Notice how the fountain pump is run off a different solar panel than the fan is. 100% solar-powered.

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I’ll post a video of the swamp cooler in action next weekend. Hopefully, the weather will hold up! I think in the next version of this, I will either upgrade my water pump or add a rechargeable battery to store solar charge since one of the drawbacks of this design is that it won’t work when the sun goes down.

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