CSR Edmonds in Australia added a motor to their gravity ventilator and came up with their EcoPower series of hybrid rooftop ventilators – the first of its kind in history. That resulted in the world gaining a brand new class of ventilators, “Hybrid Rooftop Ventilator”.
The Edmonds engineers made the decision to motorize the turbine top rather than placing a propeller in the way of gravity driven air flow. That decision resulted in excellent performance in free air but poor performance when static pressure is present.
Invisco Industrial improved on that design in 2016 by adding a propeller on a motor under the turbine. The result, the Hybrid Tornado, offers excellent gravity air flow plus hgih performance powered air flow. See it here – http://inviscoindustrial.com/hybrid-tornado/