Energy at MSC: Energy audits for USNS Spearhead

The following blog is part of an ongoing series on Military Sealift Command’s Energy Conservation program (ENCON), written by the MSC ENCON team. As part of the Energy Use Tracking and Reporting pillar of the program, energy audits are being conducted to assess the baseline energy use of our vessels. These audits range from pier-side assessments of energy consumption while in port, to Class Energy Profile Exercises, where a ship is run through a comprehensive list of operating conditions. In late 2012 and early 2013, the ENCON team completed shoreside and underway energy audits for USNS Spearhead (JHSV 1).

ATLANTIC OCEAN (Aug. 20, 2013) USNS Spearhead (JHSV 1) conducted high-speed trials, reaching speeds approximately 40 knots off the coast of Virginia. (U.S. Navy photo by MC1 Phil Beaufort)

ATLANTIC OCEAN (Aug. 20, 2013) USNS Spearhead (JHSV 1) conducted high-speed trials, reaching speeds approximately 40 knots off the coast of Virginia. (U.S. Navy photo by MC1 Phil Beaufort)

During an audit, energy consumption measurement data is collected using an array of data loggers and retrofitted Coriolis-type fuel meters. This data is used to develop shore-side and underway power profiles for all systems and subsystems. The power profiles are used to identify energy conservation opportunities, develop models, and establish a baseline for validation and energy savings.

For Spearhead, a team collected energy consumption data in the form of fuel and electrical energy usage rates over a broad range of operational states including “cold iron,” with engines off, using shore power; “not underway,” with the ship generating its own power pier-side and at anchor; and “underway” at a variety of speeds. Preliminary baseline class energy profiles followed.

In September 2013, the ENCON team led a Class Energy Profile Exercise for Spearhead. The ship completed a series of speed, power and fuel trials with multiple propulsion plant configurations across a range of displacements, representing various fuel loads. Electrical power usage, propulsion engine fuel consumption, and generator fuel consumption data, along with operating state characteristics were collected during the entire underway period. The data from the trial will enable an accurate estimation of the JHSV’s fuel consumption, as well as recommendations for efficient operation and energy conservation. Information collected also helped to shape the development of the Ship Energy Efficiency Management Plan.

The resulting, more-accurate, fuel curves for the JHSV class could not have been completed without the use of the ENCON-funded Coriolis-type fuel meters, which are accurate to 99.8 percent. ENCON is working with the ship design community to incorporate the requirement for Coriolis-type fuel meters in design specifications.

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