Akshay Gupta developed a 3d printing filament dehumidifier you can build yourself. It is made from common polycarbonate sheets and uses an Arduino, a cross flow fan, silica gel desiccant, sensors and a 100W heater to maintain a specific temperature and humidity in the chamber.
As you can see it can hold many spools of filament:
Looks like the great solution to keep your filament dry.
Detailed build guide: