Tidalenergy thanks for adding the graphic and extra information as requested it makes things clearer for the reader However you have still not addressed the fundamental issue regarding a claim of efficiency of 3 times higher then the Betz Limit of 59 3 Noone here has contested that a shroud can lead to 3 4 times higher energy extraction than a similar sized turbine The problem I still have is that you are using the word efficiency and implying 180 efficiency a value over 100 As I m sure you know energy efficiency can never go over 100 see energy conversion efficiency for exactly why If you replace the words efficiency with energy extraction I will be happy