Greenpeace, the environmental campaign group, recently estimated that the world’s data centers would use just under 2,000 billion kilowatt hours (kWh) of electricity by 2020, more than the energy currently consumed by France, Germany, Canada, and Brazil combined. There are two approximately equal sources of data center power consumption-the data processing equipment itself and the cooling systems required to remove the heat. For the foreseeable future, data processing energy consumption is projected to rise steadily while the power per square foot in individual data centers will increase with computing power and server density. Currently, design heat density in large data centers is typically 200 to 400 watts per square foot (W/sq ft) with higher density systems achieving 1,000 W/sq ft and higher. Therefore the greatest opportunity to save power in data centers is in their cooling systems, which account for approximately 50 percent of data center power.
The ASHRAE standard 2008 Environmental Guidelines for Datacom Equipment was recently updated to incorporate wider temperature and humidity limits in response to current, more tolerant server designs, while reducing energy consumption as a direct result. ASHRAE 90.1 was recently updated to include various economizers for the purpose of lowering energy costs in commercial buildings-especially data centers. Cooling the overall data center has been the traditional approach for many years, but this design philosophy is now being challenged based on the changing face of the industry. Managing the heat removal path from the servers to the external air has become an increasingly critical part of data center design. Heat densities vary widely from rack to rack while the distribution of the heat load within data centers is subject to dynamic change, especially in co-location sites. This means in-room cooling solutions must lend themselves to rapid change at minimal cost to the user in response to system upgrades.
Three main drivers influence thermal management and the in-room cooling equipment selection process:
The data center thermal management problem is here to stay and will become more severe in the future. Computer room air conditioning (CRAC) units in data center cooling have been the norm for many years but may not satisfy the three critical requirements listed above in a modern, energy-conscious data processing environment.