Vents for dry van trailer used for hay storage

Hello all!

We just obtained a 53’ dry van trailer (semi-container) from a neighbor for hay storage and since it is quite humid where we live I know it is necessary to add vents.
Does anyone have any experience with adding vents to these? Not sure if we need to go all out and find a solar-powered fan-type venting system or if we could get by with a few regular passive vents situated at the top of the trailer…

Thanks for any tips!