Evaporative coolers (or swamp coolers), are a cooling option for nomadic living in areas with low humidity. They do not cool by a certain number of degrees, but rather air ~5-7F above the wet bulb thermometer reading.
Compared to air conditioning, evaporative coolers use significantly less electricity, so they can be a good option for nomads in hot, dry climates. However, they may not make things as cool as you like, and they do use a fair amount of water. They will not be effective in humid climates. Other methods of keeping cool may be more effective.
Sizing for the space
Standard sizing[1]:
cooler cfm = cubic feet of area / 2
Example: a Ford Transit Long Length High Roof has a cargo volume of 404 cubic feet. Theoretically that would be 202cfm, but additional challenges of vanlife (direct sun, less insulation) make 405cfm a safer bet. For purposes of numbers only, a unit with those specs would cost ~$300 and use ~150w of power on HIGH. A smaller spot cooler might be 150cfm, $100, and use 50w.
Evaporating a gallon of water pulls about 8,700BTU from the air.[2].
Estimating water consumption
Concerning water consumption (working backwards from residential numbers), it takes about 7 gallons per hour for 1500sq ft house. For a 50sq ft van like an American low-roof, that would be .23gal/hour. So ~2 gallons for 8hrs of cooling, ~4 gallons for 16 hours, and ~6 gallons every 24 hours.[3] Our Transit example might consume 1.5x those amounts.
As you can see, this will have an impact on your fresh water consumption, and sourcing water during hot weather will become a bigger task for you. Soft water is recommended to reduce mineral buildup[4], but not required.
The water used by the evaporative cooling pads is dependent on three primary factors:
- outside temperature
- outside humidity
- the amount of air being drawn through the evaporative cooling pads
Available units
Manufacturers:
Portable units
Portable units are not a perfect fit for nomads since they were made for stationary use. If you go this route, don't install any rollers that come with the unit, and restrain the cooler safely. Since small coolers put out relatively little cold put it somewhere it can blow air directly on the areas you spend the most time in.
Units with electronic controls should be run off pure sine wave inverters.
Thermador swamp coolers that used to be mounted to car windows
Cooling towels
Cooling towels (or evaporative towels) are specially designed towels intended to be soaked in water and placed on your skin. They provide significant cooling effect as the water evaporates. This can be an effective way of keeping cool on hot days, though they are more effective in drier climates.More …