Metal building condensation
I bet you could you make a cheap dehumidifier out of an old air conditioner or freezer. Same thing really. We used to run one in our basement all the time, but it did freeze up occasionally. It was pretty simple. It had some refrigeration coils and a small fan to blow air through it. Water condensed on the coils and dripped down to a catch pan. If the air conditioner were fully inside the building it would also put heat into the air which might also help.