Dear Hans
After reading your post I thought of how much of a good idea it was and started experimenting for a few weeks here in sunny (mostly) Australia. Seems bananas need to be dipped in some form of ascorbic acid first to prevent them from going black - SO...

- first tried lemon juice:
peel, slice bananas in half lengthways, dip in pure lemon juice all over and arrange on flyscreen wire frame, this frame is made just like a frame used to stretch canvas for an artist i.e. stretch wire over a frame of wood and tack down underneath tight.Cover over with another flyscreen wire frame to keep bugs off, pin the two together and put up off the ground (ants!) - I put mine on top between two washing line wires. (put rocks or brick on top to stop the wind from blowing it off)

Turn every few hours. After 4-5 days of good sun bananas are brownish, chewy and very tasty.

- next tried pineapple juice. Exactly same screen set up and same dipping proceedure and same dring time, BUT while bananas did dry (sort of) they became quite a bit browner, not tasting the same. perhaps the odd cloudy day caused this, not sure, but is worth trying out.

I don't know how easy it is for remote farmers to use lemons in Phillipines perhaps pineapples are easier to come by. Flyscreen wire can usually be found in scrap heaps etc and a frame can be made from any old wood batons. I think maybe orange juice may work as well.

Banana skins can make good compost too. Lemon skins have an oily juice inside which if squuezed out can be used to clean greasy things without harm.

Good luck

Love
Ian