I have a need for dehumidification and since it is solar powered, both efficiency and low start-up load are important. It's a storage facility, so heat is not an issue but mold and rust are.

One option is to wait for the new Samsung inverter based dehumidifier to be widely available. I assume it will be efficient and have low start-up amps.

Another option might be to buy an inverted based mini-split with a dehumidify mode and put both the compressor and the head inside. Sounds strange, but should work.

I don't know much about powered or solar dessicant based dehumidification.

Any thoughts?

where is it? I mean what sort of climate?

It's very humid, mostly sunny and always well above freezing. Options:

a) solar panels, batteries, inverter and a compressor based dehumidifier (default plan)

b) one could just treat it as a solar heating application. At ~15F above ambient, the %RH is fine. This would require thermal mass and insulation to maintain an elevated temperature at night.

c) one could solar heat it (ie, dry it) in the day and then use a desiccant (like bentonite clay, aka kitty litter) to absorb moisture at night. No need for insulation or thermal mass.

It will be well air/vapor sealed, so it shouldn't take much. But doing nothing is a disaster.