you would have to have enough air flow thru and out the top. I dont know. Maybe you could ask someone who uses one for a shed what they think. Its a good idea if its not too hot. In your area would you need an enclosed shed? If not you could leave it open front. My dad has an aluminum building of the same shape that actually stays pretty cool in the summer when theres a breeze and he has one of these tanks out in the open he stores farm chemicals in, I dont think he could do that if it got real hot.
I think it might get to hot during the summer and to cold in the winter. Could there be a hazard from remenants of oil or chemicals? I look at everything too as a possible coop. My DH just shakes his head at me.
If you're not concerned with aesthetics, it looks like it would make a great bomb shelter. It's probably nicer buried underground. I'd keep looking for a hen house, but that's just me.