Darrieus turbine is used as a hydrokinetic turbine to extract energy from flowing fluid in river, canal or drainage systems. In the present investigation, the performance of a Darrieus turbine is enhanced using a blocking plate optimally located at the upstream side of the retarding vane. An experimental investigation is carried out to obtain a specific width and the location of the blocking plate which would enhance the coefficient of power of the turbine. Three blocking plates (75 mm width, 100 mm width and 170 mm width) are investigated for five different locations. The coefficient of power of a turbine without blocking plate is enhanced from 0.125 to 0.36 by using an optimized blocking plate width and location. An empirical correlation for coefficient of power is suggested in terms of Reynolds number, Froude number, width ratio and location ratio. (C) 2018 Elsevier Ltd. All rights reserved.