Data Centers are energy hogs. A recent project had computer racks which consumed 35 kw for each rack. When the computer consumes 35 kw of energy, all of it becomes heat. That's 10 tons of cooling for a rack about the size of your desk.
Fortunately, the computer manufacturers have agreed that the air entering the racks can be as high as 80°. We use 75° to provide some cushion. The fans on each computer unit draw air across the computer. When the air enters at 75°, it exits at 95° +/-.
Therefore, for the cooling system, the load is 95° air.
Indirect Evaporative Cooling (IEC) is ideally suited for this load. The 95° air exiting the racks is conveyed (ducted) to an IEC unit located outside, the IEC unit then returns the air to the room at 75°. Since this is the air temperature entering the rack, the load has been met.
In Louisville, an IEC system can meet 100% of the load, approximately 75% of the time. It does this with only two fans and a small pump. No compressor. Cooling is at 0.2 kw/ton as opposed to 1.2 - 1.5 kw/ton for conventional Air Cooled Computer Room Air Conditioners (CRAC).
For the few hours when the IEC cooling cannot meet 100% of the load, it still meets most of the load. In this way, IEC will save approximately 75% of the energy for the HVAC of the Data Center on an annual basis.
Also, the IEC equipment is located outside. Therefore no "white space" is lost for HVAC equipment.
When most of us struggle for 10% energy increase, 75% is phenomenal. And, are you ready for this? It cost less to install and far less to maintain than a CRAC system.