My setup supports the 2 most important things in the house.
The 12 volt Beer fridge and the Air Conditioner.
Without either of these the summers here would be unbearable.
There is also something quite satisfying about sitting in a cool house sipping icy cold beer on a stinking hot day knowing the sun has done all the cooling.
Step 1: The beginning.
I bought mine on ebay for around $200. Winter is the cheapest time to buy one.
A trip to the local rubbish tip netted me an old BBQ on a stand with wheels at one end. I left the rusted out BBQ there and took the stand home.
A wooden pallet went with me.
The Air Cooler then had all the electrics, the huge 240 volt motor (unfortunately not permanent magnet) and the 240 volt pump unceremoniously ripped out (taking up space in my shed now if you want them).
It was then attached to the aforementioned pallet which was screwed to the top of the BBQ stand.
Now it's ready for step 2.
Step 2: The Pump.
I chose a 360 gallon per hour one purely on cost and Amps used (it uses about 2 amps).
It proved to be not quite powerful enough so I stopped the water flow to one of the panels so there was an adequate amount going to each of the other three ( I covered the now unused panel with plastic).
If your 12 volt system can support a bigger pump then buy a bigger pump.
About 500 gph would be perfect.
I have to be careful with every amp my panels produce.