There are many ways to cool data centers. The choice you make depends on the size, computer capacity that must be cooled, regional energy costs, and data load and density. Options for cooling data centers include:
- Water-cooled chiller plant (including chiller system, pumps, cooling tower and plate/frame heat exchanger in series with the chiller).
- Air-cooled chiller plant (including chiller system and pumps).
- Direct evaporative cooling without mechanical refrigeration (also referred to as “swamp cooling”).
- Adiabatic cooling (air-cooled system assisted by water-cooled system during peak conditions).
Data center operators weigh the options and look for systems that reduce operating costs and environmental impact. They pay close attention to power use effectiveness (PUE), which is defined as the ratio of the total amount of energy used by a data center to the energy delivered to the computing equipment. A PUE of 1 means the heat rejection power equals the power used for the computing equipment. Data center operators are also concerned about water use effectiveness (WUE). Cooling towers evaporate water, but the impact depends on location.
An evaluation of the benefits of cooling towers in data center cooling must consider variable flow, which is another method to reduce energy consumption. Variable flow enables users to reduce the water flow from the cooling tower to the chiller during cooler seasons. Fans are operated at a lower speed, which reduces energy usage. Taking advantage of free cooling and variable flow modes can dramatically reduce cooling tower energy use.
Cooling tower modularity provides another advantage. Data center owners may prefer to build out their facilities over time as server demand grows. To control initial capital expenditures and operating costs, data center operators may add cooling capacity as needed by utilizing systems that incorporate factory-assembled modular cooling towers as the facility grows.