Here in steamy NJ, we have 1) ridge roof vent as Jingle mentions; 2) windows in both gable ends of the house; 3) traditional 'attic' fan but stuck in one of the windows. We open the drop-down stairs a bit and turn on the attic fan on those days when the humidity level is not too horrid. It is also required code to have an 'energy box' in the attic to cover the drop down opening. For us that is the 3" thick rigid insulation duct-taped to form an open-sided box that we slid over the opening as needed. Does help with keeping the cold winter wind in the attic or the excessively hot air in the summer when we do have the AC on.
Sorry, no help with the solar fans.