MSC’s energy conservation program: iHVAC

The following blog is part of an ongoing series on Military Sealift Command’s Energy Conservation program (ENCON), written by the MSC ENCON team. This week’s post focuses on Intelligent Heating, Ventilation and Air Conditioning system being installed aboard the command’s newest class of dry cargo/ammunition ships:

Variable Frequency Drive application on HVAC fan motors on board USNS Lewis and Clark

Variable Frequency Drive application on HVAC fan motors on board USNS Lewis and Clark

The Intelligent Heating, Ventilation and Air Conditioning (iHVAC) system for the Lewis and Clark Class of ships is a major class implementation of an energy conservation measure. In a nutshell, iHVAC delivers required HVAC and refrigeration services more efficiently. USNS Lewis and Clark (T-AKE 1) received a prototype iHVAC system in 2011, with data collected during 2011 and 2012 to verify performance and savings. Full implementation for the entire class is expected by 2017.

After demonstrating and validating the prototype system on Lewis and Clark, Military Sealift Command awarded a contract in December 2012 for class implementation on the rest of the T-AKEs. Currently, dry cargo/ammunition ship HVAC/R plants consume about 36 percent of the total ship’s power generated, and lack the ability to be optimized to variable demands. The system typically operates at 60 percent power to deliver around 20 percent capacity – more power than is really needed for certain tasks.

By improving the automation of the plant control systems, matching plant generation to demand, and using variable air volume design, upgrades make the current system more efficient operating under a range of conditions while retaining the ability to reach maximum capacity.

Major component modifications include air handling unit supply and exhaust fans, which are able to vary air flow using Variable Frequency Drive (VFD) controls. VFD-controlled HVAC and cargo chiller plant motors have increased life and reduced maintenance and will eliminate the need to run generators when connected to shore power. The six engine room ventilation fans will have automated VFD control from a central panel.

Bottom line, the iHVAC upgrade will improve air quality and crew comfort level while saving about 13 percent of system energy usage.

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