By far the most cost effective method to cool your tent is by building your own DIY Tent Air Conditioner (evaporative cooler). For under $100 and less than 2 hours of work you will have a great tool to cool your tent. You can scale the cooler to any size to suit your needs but the basic construction stays the same.
The 5 gallon version is the easiest to make but no need to stick to this size.
What you will need to make your own DIY tent air conditioner:
5 Gallon Bucket
Fill the bucket with about 1.5 to 2 gallons of water and mark the water level. Drill holes in the bucket above the waterline, I used a 2.5 inch drill bit. The more holes the better but make sure it does not weaken the structure to the point where it is too unstable.
Fit the cooling pads. You can use the this organic pad (Aspen)
or this synthetic (Duracool)
one. I found the Duracool one is easer to cut.
Cut the first pad 33.5”x13” and glue the ends together with some bathroom sealant (or stitch it if you want).
Cut the second pad to 24”x13”. Roll it tight and insert it inside the other one (no need to seam this one.)
Use some 3/8” tubing (depending on the size of you pump) with a T-connector and spike some holes every 1-2 inches apart for uniform dripping.
Install the waterpump. Any submersible pump will do, just make sure it is 12v.You do not need a very strong pump, all it needs to do is feed enough water over the pads to keep it moist. The less power it uses the better, I used this one. Connect the hose and test. Make sure that when you close the lid on the bucket it seals the hose against the lid so that no air can be sucked over the top, bypass the pads and hence no cooling.
Install the fan (12V). You can use a PC fan
or something stronger depending how much air you want to move. Remember the stronger the fan the more power it will use, if you are going to run it from your car the bigger the fan the better. I like the idea of having the fan under the lid so you can use ducting on the top.
Duct the air to your liking. The cooler will have to be outside the tent for maximum cooling effect so a septic line glued to the top of the lid and then some AC ducting to your tent entrance.
This swamp cooler uses minimal water, adding a litre of water every couple of hours will be fine. You can expect about 2 days of continuous running on a car battery but adding a solar panel
will charge it enough so that power is not an issue. I spliced the pump and fan into this 12v car connector
and run it straight of my car.
Here is a link to a different way to make the evaporative cooler: