 Any extraneous effects can only decrease the performance of the system (usually a turbine) since this analysis was idealized to disregard friction.Any non-ideal effects would detract from the energy available in the incoming fluid, lowering the overall efficiency.Some manufacturers and inventors have made claims of exceeding the limit by using nozzles and other wind diversion devices, usually by misrepresenting the Betz limit and calculating only the rotor area and not the total input of air contributing to the wind energy extracted from the system.