The best option without ac is plenty of airflow and changing the lights off time for the hottest parts of the day. So because I live in a hot as fuck climate outside I do my lights off time 10am - 4pm in veg.
Depending on the degrees outside will effect garage so you will have to have source of heat or air. Now if you switch and run LED you will get good results depending on genetics. I run LED in the house and i move the air around quite a bit i dont have to do anything extra. My 1 setup gives me about 2 to 3 pounds And my electric went up $1.77.
Can you insulate the shed.my summers here are nowhere near what you get but it does get hot..insulating has helped greatly.i actually built a room in the shed then built another inside of that lol..the rooms 2.4x3.0 mtrs my grow room is 1.5x1.5 flower veg 90cmx1.5..i think the warmest it has got it 27.5 lights off outside was mid 30s.no ac no chillers.
I was wondering myself this too...
I think that chillers are effective only when the intake air is dry...i cant imagine em to perform ina sealed wet room....
Maybe as part of a vent system , but giving fro granted that you are ina very dry area.....