“My job is to eventually put cooling towers out of business,” said David J. Martinez, pictured here, who led development on the new supercomputer cooling method. (Image courtesy of Sandia National Laboratories.)
It’s a hot summer day and you’re crushing it on the tennis court. Suddenly, you feel the salty sting of sweat in your eye. As you miss your serve, you curse your lousy sudoriferous glands. But your sweat is actually providing an important function: it cools you off and prevents overheating.
Supercomputers have the same need, and currently utilize a system analogous to your sweat glands. However, while you perspire a maximum of about 3.5 gallons a day, a midsize computer data center uses roughly 350,000 gallons – that’s the equivalent of 100,000 humans at their sweatiest, every single day. This adds up to millions of gallons of wastewater every year.
But before you get too worried, a team of engineers is working on a new cooling method that could save a significant amount of water. The method, called the Thermosyphon Cooler Hybrid System, works more like a refrigerator than a human body.
Keeping Computers Cool
First, let’s go into a little more detail about how conventional water cooling works. Water absorbs the heat given off by servers in a data center, and this warm water is piped into what’s called a cooling tower. In the cooling tower, the heated water creates water vapor, which evaporates into the atmosphere. The now-cooled water is circulated back into the data center to repeat the process, but requires a top-up because of the evaporated vapor – hence the large amount of water consumed.
The Thermosyphon Cooler Hybrid System, on the other hand, uses a liquid refrigerant instead of water to remove heat. While water is still used to absorb heat given off by the servers, it’s pumped into a closed system rather than a cooling tower. This closed system is proximate to another closed system that contains the refrigerant. The refrigerant absorbs the heat from the water, which then circulates back into the data center without any loss. The heated refrigerant vaporizes and rises within its system, exchanging heat with the atmosphere, eventually condensing back to liquid form to absorb more heat from the water and repeat the cycle.
“There’s no water loss like there is in a cooling tower that relies on evaporation,” explained David J. Martinez, engineering project lead at Sandia National Laboratories where the system was designed. “We also don’t have to add chemicals such as biocides, another expense. This system does not utilize a compressor, which would incur more costs. The system utilizes phase-changing refrigerant and only requires outside air that’s cool enough to absorb the heat.”
This last requirement means that the system is only suitable for certain climates and times of year, meaning you still need to use traditional water cooling when the outside temperature is too hot. Nevertheless, improving computer architectures to operate at higher temperatures will relax these requirements and see even more water savings.
“If you don’t have to cool a data center to 45 degrees Fahrenheit [7°C] but instead only to 65 to 80 degrees [18 to 27°C], then a warmer outside air temperature—just a little cooler than the necessary temperature in the data center—could do the job,” Martinez said.
So while you and I will probably always have to sweat to keep cool, computers may soon outgrow the need.
For more on the future of computing, meet IBM’s brain-inspired neurosynaptic processor.