Swamp-cooler in a bay-window T2 Volkswagen station-wagon
It's not so hard to spot trucks with swamp-coolers in Brazil, since it's a cost-effective alternative to improve the thermal comfort inside the cabin even with the engine off, unless a regular air-conditioner which usually requires engine power to drive the compressor. There is actually no compressor in a swamp-cooler, neither a synthetic gas. Only water stored in a tank that can be mounted in virtually any compartment of the vehicle (or built-in to the swamp-cooler) and on-board electric power (there are 12V and 24V devices, the one to be fitted into a T2 might be the 12V) are required.
The air is aspirated thru an axial fan, pre-filtered to remove larger particles, dust and small insects, then goes thru a straw filter soaked with water and then the specific heat of the air induces a small amount of the water to vaporize, absorbing the heat and increasing the air relative humidity, all controled thru an electronic processor which adjusts the ventilation speed and the humidity increasement ratio. Altough it's often not the easiest position to ensure a perfect integration with the vehicle's original appearance, swamp-coolers are usually assembled at the top of the vehicle to allow a natural flow of the cooled air. The device used in this T2 is from the Resfriar brand, known in Italy as ResfriEuro and in England and Germany as TopCooling, with a tank mounted inside the vehicle instead of built-in to the evaporative unit.