While the idea is workable, I don't think it will work as well as you imagine, mainly because computer fans just don't move enough air (certainly not enough to cool a garage space, which is what I imagine you are trying to do?); larger fans (say, perhaps a 12VDC automobile radiator fan) would work better, but would of course require a larger array (mainly for the current needed to run such a fan at a useful speed). In order to know how many cells you would need, you would want to measure the current capability of a single cell, plus its voltage output, in full sunlight at noon-time.