Here’s a nice instructional video by Amit Ranjan showing how he made his own air conditioner out of a few spare parts.
- 1 fan
- 1 ice cooler
- 1 water pump
- a few feet of copper tubing
- a few feet of plastic tubing
- a few zip ties
Here’s his explanation:
“The fan blowing against the copper produces cold air. Copper was used since it can stay cold for longer periods. The water pump then pumps water throughout the fan and back in the cooler. The cycle repeats.”
Close! But a little oversimplified…
This explanation may be a little more accurate:
Copper is a great conductor of heat. When ice-water is pumped through the copper tubing, the heat within the warm forced air from the fan tries to equalize with the cold water in the tubing. In a sense the ice water in the tubing steals the heat from the air and delivers it back to the ice box. In doing so, it melts the ice, but if you have enough, you can keep this effect going long enough to get to room feeling comfortably cool again.
Believe it or not, this is essentially what’s happening in an ordinary air conditioner (for half of the cycle). This is what’s different:
- Instead of water as a coolant, a typical air conditioner uses a gas refrigerant (like R22) to absorb heat from the air.
- Instead of sending the heat to an “icebox,” an air conditioner has to pump the heat outside using a complex compressor and coil system, fueled by electricity.
Refrigerators and air conditioners run on a “heat pump” principle to pull heat out a cold place and pump it into a warm place, using knowledge of what happens to liquids and gasses under different pressures. This takes quite a bit of energy, which is why air conditioners use so much electricity. In the case of the homemade AC unit, you applied this energy before you started, by making the ice water!
Can you make a self-running air conditioner that uses less power… that could potentially be run on energy from, say… the Sun?
It’s an interesting question. It turns out that because the concept of a heat pump is so straightforward, it’s possible to play with different combinations of liquids, gases and materials that boil and condense at temperatures and pressures that can be hit without requiring so much energy.
With the growing interest in renewable energy, many experimenters are looking at old technologies like the Icy Ball ammonia refrigerator and adapting it with new combinations like the class of volcanic rocks called Zeolites. A few companies have actually started selling expensive solar camping coolers that run on a zeolite/water mix. The air conditioning applications are just around the corner.
Of course, if you’re strictly interested in low-power air conditioning, then it will pay to become familiar with evaporative coolers (a.k.a. “swamp coolers”). Those who live in a dry climate like the Desert Southwest grew up with evaporative cooling systems, which cool the air by blowing hot dry air across a water-soaked mesh. As the water evaporates into the air, it takes the heat with it.
Traditionally the limitation of evaporative coolers is that they don’t work in humid climates. But a number of researchers have come up with clever ways to pre-dry the air, so that evaporative coolers can work in any climate.
Once you’ve solved that issue, then (provided you have a source of cheap water) you’ve got yourself a source of low-power cooling, requiring no more than a fan.
About the author:
Mobile Rik is converting his Toyota Tacoma into a DIY Truck Camper outfitted with a completely passive evaporative cooling system suited to desert camping. Stay tuned for the full article!