A system for cooling a heat generating enclosure includes a first array of one or more fans of a first size and a second array of one or more fans of a second size, where the second array is in series to the first array. The system also includes a measuring unit configured to measure at least one process variable. The system also includes a control unit configured to control at least one of the fans in the first array or at least one of the fans in the second array based on the process variable, wherein the fans are controlled to achieve an optimization criterion.