Water is the new green by Doug Mohney
Energy has long been the primary focus for most green data centers. But water is evolving into a focus point for many, a valuable commodity needed for cooling in many centers. I expect bragging about reduced water usage as much as PUE numbers to be the next big thing -- and with good reason.
First, let me say I'm happy with the unquantifiable -- but small -- number of data centers that don't need water-based cooling. The "Let's just open the bay doors" crowd of "free cooling" locations above 60 degrees North latitude have already done their bit to emphasize the need for little or no HVAC-esque hardware as an energy saving measure, with bonus points for not needing water pumping through pipes to transfer heat from point A to point B and then removing heat via evaporative cooling or towers or something else.
But for the rest of the world's data centers, water -- specifically, clean water -- is a vital commodity to keep things cool. Amazon says a 15 megawatt data center can use up to 360,000 gallons of water per day. The National Security Agency (NSA) data center in arid Utah could use up to 1.7 million gallons of per day for operations and cooling when it peaks up, according to local officials.
Apple's New Carolina facility is a good example of the good and bad when it comes to water usage. Most of the time, Apple uses "free cooling" with cool outside air pumped into a heat exchange to supply cold water for cooling systems. When temperatures get very warm, Apple goes to an off-peak chiller system, chilling water when power is not in demand and then using the water during peak hours so as not to cause a power drain.
But data centers aren't always located where there is abundant water. California and the rest of the Southwest are staring at a multi-year drought which is affecting both water and power usage -- there's a lot of hydroelectric power generated at places like Hoover Dam. If water levels at Lake Mead drop to 1,000 feet, there could be electricity issues for the surrounding area. Earlier this month, Lake Mead was at 1,079 feet, the lowest level since the dam was built.
Not all is gloom and doom. Cooling systems designed to use lower amounts of water have already been designed and built, so it's "just" a matter of getting them deployed into operation. California already has a system of state and local incentives to encourage the use of renewable power and to lower carbon emissions, so it is no big stretch to see similar programs with utilities to encourage the deployment water-conservation-cooling (WCC) systems in data centers.
Using grey and/or recycled water is also a potential option. Google and Microsoft have both built treatment plants to use non-potable water with the treated product used to cool the data center. The flip side is that you need energy -- more carbon, depending on your power source -- to purify water. How data center system trades work on energy vs. water are an interesting topic that goes beyond this piece.
Intel has long encouraged free cooling, operating data centers in desert conditions with minimal use of HVAC-esque equipment. New generation chips are expected to run cooler as while delivering better performance per watt while the company has hinted at future servers that may not need external cooling at all.
Water usage is not a one-sizes-fits all for data center operators. You can be sure water usage will become a growing part of the green data center conversation over the next year.