Or even fixed-on-a-pole rotors. The fans they were likely talking about are probably the horizontal-style fans you see in orchards for (mainly) frost preventio

Or even fixed-on-a-pole rotors. The fans they were likely talking about are probably the horizontal-style fans you see in orchards for (mainly) frost prevention (they look like small windmills). But why not very large rotor fans - maybe mounted HVLS fans, perhaps a bit larger, and maybe spinning a bit faster. Surely something like those would be cheaper to install and run 24/7 - assuming they worked as well?