USB Powered Air Cooler

Due to the recent circuit breaker measures, most of us have to work from home. With the perpetual summer heat that Singapore has, the air-conditioning units at home run almost everyday as we are more used to working in cooler environments (thanks to office life). Then, the air-con died on us. For some unknown reason, it tripped.

The white towel is there, because I was drinking chilled water and there is condensation dipping from the cup.

To reduce the air-con usage, I bought a USB powered cooler from AliExpress on 11 May. It came on 29 May.

Recently (re)popularised by NexFan on Indiegogo, the premise is simple. Using the cooling effect of evaporated water, a fan will blow water vapour out and it will cool down the immediate volume of air. However, this is not a new technology. There are similar products been sold before. As a household hack, you can simply place a bucket of ice water in front of a fan to achieve the same effect.

There are DIY tutorials that you can follow to make something similar for a fraction of the unit.

What came with the box are the cooling unit itself, a USB power cable and one filter. Noticing the packaging, this seems to be an OEM version. The cooler measures at roughly 15x16x16 cm (b x l x h). The filter consists of several sponge-like pads in a plastic holder. Rather than filtering the air through the pads, the air would be blown past the filter, lift water molecules off the pad. I have placed the cooler in front of my monitor so that it can blow directly at me.

The usage is simple:

  1. Pull out the filter holder through the front grill. Then, take out the filter.
  2. Soak the filter in chilled water. For a colder effect, freeze the filter first.
  3. Place back the filter, shut the tray.
  4. Top up the water reservoir with water, about 500ml to 600ml. I used chilled water for this.
  5. Turn on the fan.

There are 3 fan speeds and the lowest speed is sufficient for me. Also as the fan is spinning, it introduces some background noise. Using the Sound Meter app on my phone, I had the volume measured. Without the fan running, my room is at about 10dB – 20dB, around the sound of breathing. With the fan at the lowest, it will jump to 30-40dB, around the sound of a whisper. The fan at the highest speed is at 40-50dB, around the background volume in a quiet library. As I typically listen music from my laptop speakers while working at home, the noise from any speed higher than the lowest fan speed may end up distracting me.

There will be some white mist coming out at the start. This mist is condensed air and eventually disappear as the frozen filter gets heated up over time. The water reservoir should last at least 3 hours before needing to top up.

The cooling effect is greater under these conditions:

  1. The soaked filter should remain as cold as possible.
  2. Likewise, the water reservoir should also be as cold as possible.
  3. Lastly, the air should not be relatively very humid.

As water vapour escapes into the air, the air will be cooled down. Using a colder water source will ensure that the air coming out feels cooler as well. With this in mind, I would recommend putting ice cubes into the reservoir at the 2-hour mark to bring the temperature back down.

Evaporation rate varies inversely with the humidity in the air. Hence, the now moistened air has to be removed constantly for the evaporation rate to remain constant. If it is too humid, we will start feeling clammy anyway. Additionally, wet weather will reduce the effectiveness of the cooler as well.

In the product guide, there are instructions to maintain the cooler, by washing the filter and the unit on a weekly basis or soaking it into 1-1 water/vinegar mix if there is mold or musty smell. However for prolonged storage of the unit, the product guide recommends running the fan at full blast for 4 hours to dry out the unit and the filter.

I bought the unit at USD18.41 from AliExpress with a dollar off. As an OEM version and a comparable one, it is definitely cheaper than branded ones (USD 39.88 on Amazon or NexFan on Indiegogo).

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