Carcoon Or Similar

[fruitcake]

I have an electric dehydrogenator

 

Are you pumping out all this hydrogen you're producing, also don't light a match afterwards

 

Seriously though, don't fanny around with silica gel etc.  That's only used for modest moisture removal on small spaces and at a slow rate.  For what you need you want one of those poly tunnels like you posted and seal an electric dehumidifier inside with it draining through a pipe to the outside.  Will keep the inside at a decent low level.  If the whole place is damp like you say noting will compete with the humid air coming in unless you fully seal it in.