USA: A Johnson Controls BlueStream thermosyphon cooler is said to have saved 554,000 gallons (2,518,534 litres) of water in just six months at a supercomputer centre in New Mexico.
The dramatic decrease in water use from the cooling unit installed on the roof of the Sandia National Laboratories’ facility in Albuquerque is seen as a potential model for cities and other large users in water-starved areas.
The thermosyphon cooler unit also saved over 195,000kWh of electricity during the same time period by making it unnecessary to pump thousands of gallons of water around the clock through mechanical chillers.
The system integrates the control of a dry heat rejection device, the thermosyphon cooler, with an open cooling tower. It uses evaporative cooling when it is most advantageous and then saving water and modulating toward increased dry sensible cooling as system operations and ambient weather conditions permit. Innovative fan control strategies are said to ensure the most economical balance between water savings and parasitic fan energy. The low-pressure-drop design of the thermosyphon cooler allows water to be cooled directly by the evaporator without risk of bursting tubes in subfreezing ambient conditions.
In New Mexico, the system works for three seasons, but in summer, only at night. On hot summer days, the thermosyphon shuts down and water must be pumped to a mechanical chiller and then to a cooling tower, which evaporates water, like sweat from a body, into the atmosphere.
Because minerals don’t evaporate, the remaining water, recycled, has a higher concentration of contaminants, which means it must be frequently changed out before it fouls the cooling pipes. The evaporated and discarded water must be replaced. Those problems are almost eliminated with the new system.
Saving more than money
The solution is not cheap. According to Sandia, Thermosyphons cost $200,000 each. Sandia has installed one, bought two more, and may buy a fourth.
According to David J Martinez, engineering project lead for Sandia’s Infrastructure Computing Services, for four units the annual cooling costs would drop from $181,000 to $116,000 – a payback of approximately 10 years.
The real savings would come in water: “When the data center reaches full design load, each thermosyphon unit will be capable of saving over 4.2 million gallons of water per year,” says Martinez.
Sandia National Laboratories is a multimission laboratory operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc, for the US Department of Energy’s National Nuclear Security Administration. Sandia Labs has major research and development responsibilities in nuclear deterrence, global security, defence, energy technologies and economic competitiveness, with main facilities in Albuquerque, New Mexico, and Livermore, California.