Seems like a cooling tower would be a better deal
Than a dry cooler.
What kind of winter time humidity levels do you run in your area? How many days of the eyar can you produce 60 degree water with the tower?
I like BAC towers and have always found their engineering people helpful. You might want to give them a call.
The payback would calculated by the time you could supply 60 degree water with the tower instead of running mechanical cooling. Take the total cost to run their present chillers now for a year. Include service and maintenance costs. Subtract away the percentage that would be eliminated by using the tower. Divide the cost of the cooling tower installation by the saving to get the payback time in years.
The conventional view serves to protect us from the painful job of thinking.