It depends on if you have transformers that give off heat. Try to get the electrical engineer to set them outside or hang them on a pole. If you have VFD's they can also give off heat. See the manufacturer's data for how much. If outside air is not too hot then you can ventilate with outside air to cool the space. Outside air will only get you down to 10 or 15 degrees above outside air temp, depending on how much air you move.
However, some of the electronic devices such as VFD's, TVSS panels or tranfer switches may not be able to handle much heat so you may need to air condition.