Over time, increasing power density and growing number of installed servers had increased the heat load on Telecity data center cooling system which operates on a 24/7 basis 365 days on the year. Existing fixed-speed chillers installed during the building’s construction could not meet the cooling demand and provide the necessary redundancy Telecity required. As a result, the cooling system needed to be upgraded to keep pace with the data center’s growth.
The original chilled water plant was served by air-cooled chillers operated in sequential mode. Additional chillers came online when the cooling demand rose above the capacity of running chillers. These fixed-speed chillers ran inefficiently, resulting in excess energy use. Additionally, the original chillers were so maintenance-intensive that plant operators had doubts about their reliability.
After an analysis of the potential efficiency improvements and costs, Kaltra engineers recommended to replace original chillers with the last generation, variable-speed chillers with increased supply/return water temperature. The site’s mild climate promised the great opportunities for airside economization, and it was therefore decided to design the new cooling plant with the free cooling chillers.
The offered Lightstream Freecool chillers are capable of extracting 1200kW each at the site temperature conditions with inverter screw compressors and twin refrigerant circuits is one of the most efficient chillers on the market. When their free cooling system is fully engaged in the winter months, these chillers provide rapid system payback and annual energy cost savings of up to 60% compared to the previously running system. Increased water temperature enables excellent free cooling opportunities: as ambient temperature falls below return water temperature by just a 4 degrees, free cooling becomes available. Using intelligent controls to continuously monitor ambient temperature, Lightstream Freecool chillers can operate using only compressors, only free cooling, or a combination of the two. To protect free cooling coils against freezing in low ambient conditions, the system has been charged with glycol mixture.
Built on experience from the established Lightstream Screw chiller family, the Lightstream Freecool range features inverter-driven compressors and aluminium microchannel heat exchangers for free cooling and condenser coils. Furthermore, Lightstream Freecool chillers are tailored around the low-GWP R1234ze refrigerant which offers an environment-friendly alternative to R134a.
The original cooling circuit has been modified into a variable-flow system which enabled major savings also on pumping energy as the plant can effectively adjust the water flow when needed. The turn-key Telecity project involved a full scope of works, including decommissioning and removal of the existing chillers, installation of the new units, commissioning and start-up works.