The weakness it has it that it needs a clear sky to work. For overcast muggy days or even a high coverage of cumulus clouds, performance will be absent or degraded.

It works at night, however, and for best results you could maximize insulation and "thermal mass" inside the building and minimize radiative transport through the windows.

The best thing about air conditioning, however, is de-humidification and that is a matter of cooling the air more than you have to and then re-heating it. I live in an 1850 farmhouse and the reason I want a ground source heat pump is that the humidity destroys books and other printed matter. I have inkjet prints curling off the walls and detailed logs of how 3M's best products only work 90% of the time in my applications.