An additional line of thought. Cooling radiators in summer?
I found this having the same concept for cooling. I live in south louisiana, US where 95F is vary common turning tin boxes into a slow cooker. I am going to build a decent shop for all my automotive, and construction tools.
The concept I had was some large truck radiators for a couple of non load-bearing walls and either use some city water to run through them, cooling the shop a touch and heating my water some before hitting my home water lines, or use the canal on my property with a water ram pump.
I acknowledge the potential multiple metal types causing issues and the need for a filter for the canal water and depending on the radiators I get if I go the other route a filter before the water gets near the house.
My city water right now is coming out the ground at 79F, Canal water at 76F, at noon. Ambient direct sunlight temperature of 85 sheet metal indirect sunlight 100 degrees.
Any points of interest or concern that have not already been mentioned?