yes you need to cool the cells, but you need the cells to come into contact with a coolant in order to remove the heat, in my case the cells will be glued to a plastic or wood base, trying to exchange heat through that would be a waste of time, you can't allow water to come into contact with the cells. Remember I'm building these they are not commercially made so the cells won't be well bonded to the structure from a heat transfer point of view.
To use water i need two heat exchangers, one to take heat from the panel/cell and one to dump it into the air (the radiator). The exchanger for the panel must integrate into the panel in order to take heat away from it - not really a likely scenario without expense that outweighs the gain