The A/C in our old house was a chiller system back 100 years ago.In fact most of the old pluming for it is still downstairs! There are cisterns on the north side of the house. Pull cold water off the last one and pump it back to the first one. We get a lot of humidity so the newer "refrigerant" A/C system makes more sense. Upper 70's is comfortable when it's 50% humidity or less.