We have several at work in the "stores" area, but they are never on. The building is air conditioned and I have no idea why they even have them.
My understanding is that they are unbelievably expensive, edit: don't want to mislead anyone, and I misspoke. The fans use 3 phase current except for the new shop fan. Deleted my statement about taking single phase and making 3 phase and control the speed with variable frequency drive. They start at 8 ft and go to 24 ft.
I would not have minded to have a 10 or 12 ft one for the shop, but had to settle for three of the Home Depot 60 inch industrial fans.
Good to let everyone know about them however, someone on here has the money for one, its just not I.
Charles