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Next-generation high efficiency U.S. Navy chiller compressor

Customer Specifications – Johnson Controls Navy Systems (JCNS), a supplier of heating, ventilation, air conditioning and refrigeration (HVAC/R) systems for use on all types of Navy vessels selected Calnetix Technologies to provide design and engineering assistance for the drive portion of its next generation, two-stage, variable speed, hermetically-sealed centrifugal chillers. They required a robust, compact, low-maintenance and low-emission shipboard HVAC system to increase cooling capacity and performance, while reducing acquisition and lifecycle costs. Improvements to mission critical cooling were required for newer/advanced command and control systems.

High-efficiency compressor prototype undergoes shock and vibration testing at NuLabs in Annandale, New Jersey. (Photos courtesy of the U.S. Navy, YORK® Navy Systems and NuLabs.)

Solution – The high-efficiency super capacity (HES-C) Chiller was developed jointly by Calnetix and JCNS. Calnetix supplied key components for the HES-C chiller system, consisting of the HES-C Chiller and the HES-C Variable Speed Drive. The variable speed economized two-stage compressor is comprised of Calnetix Technologies’ Powerflux™ oil-free magnetic bearings, a Magnaforce™ sensorless high-speed permanent magnet motor, a magnetic bearing controller and a backup bearing system. The variable speed centrifugal chiller compressors with active magnetic bearings save energy as compared to the conventional chillers by eliminating losses due to bearing friction and reduce maintenance costs. Calnetix also provided the variable speed power module and controls for the HES-C variable frequency drive (VFD).

Challenges – The HES-C chiller had to be subjected to a series of four different shock impacts by high-explosive charges generated from varying angles and standoff distances under the water. The chiller successfully demonstrated operation during the three blasts and in standby mode for the fourth blast. The backup bearing system of the compressor absorbed the shock impacts, and the magnetic bearings recovered levitation as designed.  The motor performed without any issue. The U.S. Navy program has been an important validation of Calnetix’s patented magnetic bearing technology, permanent magnet motor expertise and power electronics technology. All of the Calnetix supplied components and technologies meet the required specifications with a comfortable margin, satisfying the U.S. Navy’s key objective of a robust design.

Results – The systems are projected to save 1,000 barrels of oils per year per ship, all with no change in the system’s weight or seawater chiller capacity. The compressor has also been designed as a retrofit option to improve the performance and energy usage of more than 200 chillers already in fleet use. The next generation HESC Chillers are expected to:

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