Small-scale urban Venturi wind turbine: Direct-drive generator

There is a growing interest for the use of small-scale wind turbines at buildings. In most situations the deployment of existing (small les 5 kW) wind turbines will not be very successful due to the fact that they are not adapted to the complex wind environment. Several novel wind turbines have been developed to be able to extract a large amount of energy from these urban environments. This paper concerns a new horizontal Venturi wind turbine (2.0 m diameter), which has a comparable power per rotor cross-sectional area in respect to various other wind turbines, due to its direct-drive generator. This direct-drive external rotor permanent magnet brushless generator system has been selected for this application due to its power density, where a total system efficiency of ges80% has been achieved over a large speed range.