Cooling with water—not chillers
The electricity that powers a data center ultimately turns into heat. Most data centers use chillers or air conditioning units to cool things down, requiring 30-70% overhead in energy usage. At Google data centers, we often use water as an energy-efficient way to cool instead.
We trap hot air and cool our equipment with water.We've designed custom cooling systems for our server racks that we've named “Hot Huts” because they serve as temporary homes for the hot air that leaves our servers—sealing it away from the rest of the data center floor. Fans on top of each Hot Hut unit pull hot air from behind the servers through water-cooled coils. The chilled air leaving the Hot Hut returns to the ambient air in the data center, where our servers can draw the chilled air in, cooling them down and completing the cycle.
We take advantage of evaporative cooling.
Evaporation is a powerful tool. In our bodies, it helps us maintain our temperature even when outside temperatures are warmer than we are. It also works similarly in our cooling towers. As hot water from the data center flows down the towers through a material that speeds evaporation, some of the water turns to vapor. A fan lifts this vapor, removing the excess heat in the process, and the tower sends the cooled water back into the data center.
We use the natural cooling power of sea water.
Evaporating water isn't the only way to free cool. Our facility in Hamina, Finland uses sea water to cool without chillers. We chose this location for its cold climate and its location on the Gulf of Finland. The cooling system we designed pumps cold water from the sea to the facility, transfers heat from our operations to the sea water through a heat exchanger, and then cools this water before returning it to the gulf. Because this approach provides all of our needed cooling year round, we haven't had to install any mechanical chillers at all.
We save and recycle water.
To better conserve water, we power two of our data centers with 100% recycled water, and capture rainwater for cooling a third. The idea is simple: instead of using potable (or drinking) water for cooling, we use non-drinkable sources of water and clean it just enough so we can use it for cooling.
We use recycled water from various sources. Our Douglas County facility treats city waste water, while our Belgium facility pulls water from an industrial canal. There, we use a large tank filled with fine sand to filter out small particles, leaving the water completely clear (although not suitable for drinking). While it's not always possible or cost-effective to use recycled water, we're optimistic that we can find sustainable solutions for the majority of our water use.