I'm keeping a thin but rigid 4x4' sheet of polished and coated aluminum for rigging an efficient solar oven like this one, WTSHTF:


In fact, mine could be folded into a parabolic shape as well to get even up to forging temperatures.

Regarding affordable solar panels: in just one evening I built a 20W solar panel out of 25 65x65mm modules. Got them off ebay for just $16 (sixteen!) with all the tabbings, bus lines, and soldering flux. The resulting panel size is slightly over a square foot (pending a protective polycarbonate screen on top of it). Tested it today under the hazy sky - 14V 1.2A.

You don't have to be an EE guru to rig your own solar charging or even house powering station. Get panels you can afford (e.g. 150W 3'x3' solid plate on a frame is around $200, truly portable folding album sized solarfilm at the same wattage is around $700). Get the universal solar charger (~$40), get a set of generic batteries (lithium - for portability, sealed gel for longevity and household power storage, or wait a bit for the Tesla Wall for ultimate power storage and with the charging controller already builtin), some inverter to hold expected consuming wattage, and just connect them all together with 8 pieces of thick wire - that's it.