The Australians came up with these. CSR Edmonds in North Ryde, New South Wales, invented their Hurricane gravity rooftop years ago and have sold 1000s around the world. in about 2002 they decided to add a motor to it, thus creating the first hybrid combining free gravity air flow with built-in motorized air flow.
In 2015 I was asked by Allan Ramsay, their Export Sales Manager, to become their United States distributor. I opened https://edmondsusa.com/ and signed on sales reps for Greenheck and Loren Cook in 27 states. But the product was not suited for most application here due to the inability to pull air in an static pressure about 0.1
So I improved the design and created the Invisco Tornado. See it here – https://inviscoindustrial.com/