Data Center Chiller Retrofit Cuts PUE from 1.42 to 1.30
- Cooling & Heat Recovery Data Centers Efficiency & Optimization News
Marin Holt
- 0
- 5 minutes read
- Magnetic bearing centrifugal chiller retrofit at a UK financial services data center cut PUE from 1.42 to 1.296
- Annual energy cost savings of 38,000 pounds through reduced cooling power consumption
- Magnetic bearing chillers achieve COP improvement of 6.7% over conventional centrifugal units (ScienceDirect 2021)
- DOE FEMP benchmarks magnetic bearing compressors at up to 49% power savings at part-load versus oil-lubricated alternatives
- Retrofit required no facility rebuild and maintained cooling capacity during changeover
A UK financial services data center reduced its Power Usage Effectiveness from 1.42 to 1.296 by replacing conventional chillers with magnetic bearing centrifugal units, saving 38,000 pounds annually. The retrofit required no facility rebuild and maintained cooling capacity throughout the changeover process.
Technology and Results
Magnetic bearing centrifugal chillers use oil-free, frictionless compressor technology. The compressor shaft floats on electromagnetic fields, eliminating mechanical contact and associated lubrication maintenance. Variable-speed operation reduces compressor speed as cooling demand drops, maintaining high coefficient of performance across partial-load conditions where data centers typically operate. The U.S. Department of Energy FEMP benchmarks magnetic bearing compressors at up to 49% power savings compared to oil-lubricated alternatives at part-load. Research published in ScienceDirect finds annual COP improvements of 6.7% for magnetic bearing units versus conventional centrifugal chillers in data center applications.
Data Center Cooling Context
PUE measures total facility power divided by IT load power. A PUE of 1.42 means 42% of incoming power goes to cooling, lighting, and distribution rather than computing. Reducing to 1.30 means the same IT workload draws 8.4% less total power from the grid. A 10 MW IT load at PUE 1.42 draws 14.2 MW total. At PUE 1.30, it draws 13 MW, saving 1.2 MW continuously. At European electricity rates, chiller retrofit capital costs recover in two to four years at that scale.
Critical Analysis
Magnetic-bearing centrifugal chillers use variable-frequency drives (VFDs) for compressor speed control; unlike constant-speed induction motors (THDi < 5%, near-linear load), each 6-pulse rectifier VFD front-end injects dominant 5th and 7th order current harmonics with THDi of 35–100% without input filtering. The retrofit reduces site peak demand by cutting cooling overhead from 42% (PUE 1.42) to 30% (PUE 1.296) of IT load, reducing transformer utilization and deferring capacity upgrades for the UK financial services data center.
5-Year Projection
By 2031, operational data from facilities like this will become the standard requirement for securing interconnection agreements, as ISOs prioritize proven Magnetic Bearing Chiller profiles.
Critical Perspective
The article highlights a PUE reduction from 1.42 to 1.296. While impressive, this improvement is comparable to efficiency gains seen at other data centers adopting similar technologies. For instance, Google’s DeepMind reported significant PUE reductions through AI-driven cooling optimization. Historically, similar equipment upgrades have faced unforeseen operational challenges, such as the early issues with variable speed drives in large industrial applications. Given the emphasis on future interconnection agreements, will the grid’s capacity to absorb the *increased* overall IT load, enabled by these efficiency gains, be the next bottleneck?
