I've changed my mind re solar fridge fans.... I found a solar panel in my shed and a muffin fan as well so I'm going to use those and make my own...
Dosen't matter what type of fridge you use, ADSORBTION (not absortion) http://en.wikipedia.org/wiki/Adsorption or compressor the  thing is acting as a heat pump and pumping the heat from inside to the outside so the hot part ( condensor) should be kept as cool as practical to keep the cold bit ( evaporator) working at peak efficiency. Now I have to say that there is a lot of hubris re spaces and clearances but the manufactures do specify the exact requirements.  Adsorbtion cycle fridges slow down in extremes of heat simply because the heat cannot get away from the condensor. Sometimes they can be made to work by removing some of the void at the back of the fridge so that the natural thermocycle works more efficiently, either way a fan either sucking or blowing that causes air movement over the condensor will make either type of fridge work more efficiently, natuarally for max efficiency the fan should assit the thremocycle action ie hot air rises so if you can only put a fan down low let it blow if you can get it up high eg on the back of the top vent let it suck air out.