INFLUENCES ON SOLAR POWER
Solar irradiation is measured in Peak Sun Hours (PSH). The concept is like that of a rain gauge in that fluctuations are averaged: replace rainfall by sunlight and you have the general idea. With three-way fridges, solar is practicable at 2 PSH. With an efficient chest fridge it becomes practicable at 3 - 3.5 PSH. For a medium-sized door-opening electric fridge you really need 4 PSH. It's also advisable to have generator back up
All but amorphous technology (eg. Uni-Solar) modules lose about 5% output for every 10 degrees C increase above a cell (not ambient) temperature of 25 degrees C. On a moderate 25 degree day another 10% has gone. At 35 degrees C it's 15%. Then, that '80-watt' module produces about 50 watts. Amorphous modules increase output slightly as they warm up, but they are hugely larger than anything else so this is only of value where it's hot and there's plenty of room. Modules carry a rear sticker that reveals all this. Unfortunately it's in techno-speke.
No modules work in full shade, but they differ a lot when partly shaded. Most lose nearly all output if only a small area is shaded. Amorphous modules lose output proportional to the area shaded. For the highest average output modules must face the sun but, except for lower latitudes, flat mounting loses only 10-20%. Compensate by adding 10/20% more capacity - tracking is complex and not worth the effort.