If it's going to freeze, an unattended dehumidifier isn't a great
idea. Alas.
Inside, heated, dry storage is best of course.
Most hangars are not well sealed, and your solar dryer doesn't work
anymore. I picked up a lot of corrosion over a winter from a glider in
our club hangar.
Hangars also have a really cold slab of concrete under them. When
spring comes, this means everything is cold and dripping wet inside
the hangar. worse than outside, where the morning condensation will at
least eventually dry out.
Small heaters are a great idea. I got a "air dryer" from
iboats.com
(run by Bruno Vassel, glider pilot). It's 100 watts, designed to be
left alone, and won't bust like a light bulb. Over several winters
this has helped condensation a lot.
The daily condensation and hopefully drying out is a big problem for
glider storage alas.
John Cochrane