Reducing Water Usage
While the initial design of the ESIF HPC data center eliminated expensive and energy-demanding chillers, the side effect of using evaporative cooling towers (which are energy efficient and much less expensive than chillers) is that approximately two million gallons of water was being drawn annually to support cooling of the IT load—approaching an hourly average of 1 megawatt.
Our Sustainable Solution
NREL partnered with Johnson Controls and Sandia National Laboratories to evaluate a new approach to reducing onsite water consumption. In August 2016, a prototype thermosyphon cooler was installed at NREL. The thermosyphon cooler is an advanced dry cooler that uses refrigerant in a passive cycle to dissipate heat. It was placed upstream of the HPC data center cooling towers to create a hybrid cooling system. The Johnson Controls system coordinates the operation for optimum water and operating cost efficiency—using wet cooling when it’s hot and dry cooling when it’s not. The unique design and controls of the thermosyphon cooler prevent freeze-ups, even during subfreezing conditions. Picture below shows the thermosyphon cooler to the left of the cooling towers.
Here is a link to a paper detailing the full heat rejection system simulation and installation of the thermosyphon cooler at NREL.
Because the thermosyphon cooler helps to reject heat without consuming water, it is expected to yield significant water savings for the ESIF—cutting the annual water use for cooling by over half (more than one million gallons) without experiencing any negative impacts on the HPC data center’s efficiency. The thermosyphon should be able to handle the majority of the HPC center's heat rejection needs in the fall through spring seasons without the need for evaporative cooling.