TECHNOLOGY CHILLERS
The new chiller with an integrated 90-tonne variable-speed compressor used to replace one of the existing 100-tonne reciprocating chillers at NUWC, Newport, RI
providers are concerned about shutdown risks. Many data centre users have migrated from leases based on cost/ft2
to leases based
on ‘service level agreements’ (SLAs), which compensate data centre users for time periods in which they cannot access critical data. Cooling system reliability affects shutdown
risk. Given that 80% of chiller problems in data centres have been attributed to failures in compressor-oil return, oil-free compressors are an attractive option for data centre service providers.9
Also, data centre applications
benefi t from the low inrush current required to start a magnetic bearing compressor, which permits downsizing of standby generator equipment. CJ
Eliminating lubricating oil from the system results in incrementally better refrigerant-side heat transfer performance, particularly in the evaporator
respectively. Using this incremental project cost for payback calculations yields payback periods of 1.1 years for San Diego; 0.3 years for Newport; and 0.8 years for Jacksonville.5
Market potential Small centrifugal compressors are now commercially available from multiple sources and are expected to replace reciprocating and screw compressors for chilled-water systems in the 25 to 80-tonne (88 to 281 kW) range.7 Comparatively high fi rst costs can be, and have been, substantially offset by improved energy effi ciency. Mechanical contractors serving the
school construction market report that magnetic bearing chillers are among the new technologies of interest to this market.8
With
overall school construction demand down by 50% from pre-recession levels, the major drivers for selection of building products and technologies in this market have been life-cycle costs and return on investment, rather than LEED or sustainability. In New England, with electric rates hovering around $0.15/ kWh, data storage centres with water-cooled chillers are realising reduced power consumption, as well as lower maintenance costs and high reliability from use of oil-free, magnetic bearing compressors.9 Both data centre users and data centre service
Project/type San Diego/
third compressor added
Newport/ new chiller
Jacksonville/ compressor retrofi t 80 120 $0.115 $0.054 240 Tons
Utility rate ($/kWh) Annual energy savings
$0.121
$21,206 (£13,651)
$26,192 (£16,860)
$15,358 (£9,886)
References
1 Brondum, DC, et al. 1998. High-speed, direct-drive centrifugal compressors for commercial HVAC systems: proceedings of the 1998 International Compressor Engineering Conference.
2 US Department of Energy’s Federal Energy Management Program 2012: Selecting and Evaluating New and Underused Energy Technologies. Transcript, April 5.
tinyurl.com/cz3d2sh
3 US Department of Energy: Federal Energy Management Program 2012: Selecting and Evaluating New and Underused Energy Technologies. Presentation, April 5.
tinyurl.com/ccckzyz
4 US Department of Energy’s Federal Energy Management Program 2010: Evaluation of a Variable-speed Centrifugal Compressor with Magnetic Bearings,
tinyurl.com/ ae2dx5h
5 Kistler, P. 2009. ‘Magnetic Bearing Chiller Compressor: Naval Facilities Engineering Service Center’, www.
docstoc.com/docs/41611943/Magnetic-Bearing-Chiller- Compressor
6 GovEnergy 2006. ‘Oil Free Magnetic Bearing Chiller Compressors’,
www.achrnews.com/articles/u-s-navy- studies-oil-free-compressor-technology
7 Navigant Consulting 2011. ‘Energy Savings Potential and RD&D Opportunities for Commercial Building HVAC Systems’, September 30.
tinyurl.com/cgf6m3j
8 ACHR News 2012. ‘Contractors Give K-12 Schools Failing Grade’, July 30.
tinyurl.com/cwcbb69
9
BuyMass.org 2012: ‘Five Things to Know About Cooling Data Centres,’ Nov. 28.
tinyurl.com/d8ee6hl
MILDRED HASTBACKA is a director and emerging technologies scout for TIAX LLC, and JOHN DIECKMANN is a director in the Mechanical Systems Group of TIAX LLC, Lexington, Mass. ANTONIO BOUZA is a technical manager with the US Department of Energy, Washington DC
Per cent energy savings
40% 65% 41% Project cost $178,787
(design through installation)
$100,783
(design through installation)
$107,592 (installation, including compressor)
56 CIBSE Journal June 2013 7.0 3.8 Payback (years) 8.4
www.cibsejournal.com
COURTESY OF SEI GROUP, INC
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