Crosswind effect on the cooling performance of large natural draft dry cooling towers (NDDCT) has been verified to be unfavourable by many researchers. Small size natural draft cooling towers (height <30 m) proposed for geothermal and other renewable power plants are expected to be more negatively affected. CFD modelling has been carried out to numerically analyse the heat transfer performance of a 15 m-high small NDDCT under different crosswind speeds. Simulations show that, at certain crosswind speeds, the crosswind significantly degrades the cooling performance. However, the negative effect of the crosswind can be turned into positive in small natural draft cooling towers by introducing windbreak walls that guide the air mobilised by crosswind through the heat exchangers. When windbreak walls are used, the results show that the tower performance improves with increased crosswind velocity. (C) 2013 Elsevier Ltd. All rights reserved.