The shape of the bag, long and thin, causes the air passing through it to be at a higher velocity through the grain than in a steel silo. That air has less time to pick up moisture from the grain which in turn cause the air leaving the bag not to be saturated. Yes the system dries the grain from the one inlet ( underneath the solar collectors) towards the other, but is does not have a drying front that is wetter than the grain originally put into the bag like in a steel silo. But you need a certain minimum airflow through the bag to achieve drying it. That is why the system has this patent pending layout on the bag.
If one wants to force the air across the bag through the grain you will have to many outlets (suction hoses ) which will make the system to cumbersome to move around etc. Also you will destroy the integrity of the bag.
After drying the moisture fluctuates by about 0.5 % Which is not a problem as the grain mixes anyway when out loaded.
The system has been teste in summer temperatures between 15 and 40 deg C and in winter between -10 and 20 deg C It works a little bit better in winter because the ambient air is drier. It has not been tested in snowing conditions, but adding more heat to the system is easy. It is getting enough air through the grain that was the big challenge. One way to add more heat is to increase the self regulating heaters underneath the solar collectors capacity.
The solar collectors heat the air the same way as a solar water heater would. No electronics or electrical equipment in the solar collectors. When dirty you wash them with water.
No the grain does not have to be re-bagged after drying. You reseal the holes and can keep it in the original bag. Holes can be sealed with duct tape or vinal stickers cut to size. (the same stickers they use for signage on vehicles etc.) A 75m bag will have 6x140mm and 48 x 50mm holes in the bag after drying