For more critical applications, engineers will specify either two separate towers sized for 50% or two separate towers at 100%.
While this is all well and good with respect to redundancy, this approach of two separate units requires a lot of space. This is due to the required airflow clearances between the towers to ensure proper performance.
To make the most of your jobsite real-estate, select one tower with two-cells. This essentially combines your two towers into one while accounting for the airflow lost on the shared side. Each cell can be sized for 50%,100%, or whichever level of backup you prefer. Though adjacent, each cell will operate independently of the other to provide redundancy. When you eliminate the gap between the units you minimize the overall footprint clearance required.
This same concept is also applicable to selecting multiple towers to match numerous chillers. For example, do not select three towers for three chillers. If you have three 150 ton chillers, request a single 450 ton three-cell tower. You'll have the staging capabilities with the smallest footprint available.
The key is identifying the application and selecting the tower cells to match the required staging or redundancy.
This is just one space saving method. Do you have a tower layout that could use improvement? Or a tower that must fit in a challenging space? I would be happy to help.