I have come across some window mount unit solar cell that power little exhaust fan that claims to coll down the car cabin that parked under hot summer sun. However since the fan is not powerful enough to drive the heat out of the car effectively, is it enhance it with: 1. larger solar panel (higher output) 2. high flow rate axial fan (to minimize required amperage to power) 3. air temperature sensitive thermostat (to provide continuity when temperature reached a 'set point' say.. 37C) 4. rechargeable battery unit to prevent fan speed fluctuation due to inconsistent solar panel output anyway, this is how roughly my idea works. Might be some installation issue with the exhaust fan, but let us just assume that it can be installed and it can drive the hot air from cabin out. The ideal condition of this setup is try to reach equilibrium temperature with outside ambient temp. However i was told that this is not possible due to increased entropy level in car interior?