In the past, there were many attempts to augment the power of wind turbines by means of diffuser systems or similar, but since these attempts did not respect energy- and momentum conservation, they have not been successful. We present the first fundamental discussion of the physics of shrouded wind turbines. A design results, which is different from the diffuser approach-the partially static turbine. It consists of a rotating propeller and of a static element, which allows the propeller to extract energy from an external flow of fluid, which does not pass through the propeller itself. (C) 2003 Elsevier Ltd. All rights reserved.