The effect of wind direction on the cooling capacity of short dry natural draft cooling towers operating in close proximity

The layout of multiple natural draft dry cooling towers could have a significant influence on the performance of the cooling system in concentrated solar power (CSP) plants, however this has never been quantified. Hence, this work used computational fluid dynamics (CFD) modelling to analyze the cooling capacity of two short natural draft dry cooling towers (NDDCTs) on a common site for a range of tower spacings, wind speeds and wind incidence angles. The results show that the cooling performance of the towers is a strong function of tower spacing and their orientation with respect to the wind direction. It was found that when the wind came at a 90° wind incidence angle (i.e., normal to a line drawn between the two towers) that their cooling capacity was improved at tower spacings of less than 1.8 tower diameters (1.8D), though for the other tower spacings there was no interaction between the towers. However, with wind at 45° to the towers, the flow around the towers resulted in a decrease in their cooling capacity at tower spacings of 1.8D and 2.6D. Most interestingly, it was found that orienting the towers in line with the prevailing wind direction delivered improvements in the cooling capacity of up to 30%. This is due to the windward tower acting as a passive windbreak. Hence, as CSP plant capacity is increased, and additional cooling towers are required, these should be placed close to any existing tower and oriented along the line of the prevailing winds.