By Jacqui Barker, Naval Surface Warfare Center Panama City Division
Naval Surface Warfare Center Panama City Division engineers are developing tools to enable U.S. Marine Expeditionary Forces to more accurately predict energy consumption needs in theater.
NSWC PCD Expeditionary Systems Division, or E30, engineers were asked by Marine Corps Systems Command to reduce the energy consumption of Marine Corps Combat Operations Centers. MCSC acquires and provides life-cycle support of ground weapon and information technology systems that U.S. Marines rely on to fight and win.
Together, leaders from MCSC and NSWC PCD analyzed the COCs and noted that almost 70 percent of all the energy was being used to heat and cool the shelters. Additionally, all of the predictions were based upon vendor specifications or calculations. The engineers thought there was a better way. The first problem to be addressed was the prediction of the shelter heat transfer.
In July 2012, Steve Gorin, E30 Senior Systems Engineer, visited National Renewable Energy Laboratory, located in Golden, Colo., to determine if they may be able to help. What he found was a heat transfer model being used for building evaluations, but would it work for shelters? They decided to give it a try. NREL conducted the modeling and NSWC PCD conducted the validation testing. Not only did the model work, but it proved to be very accurate. Their model prediction varied from the measured by less than one degree Celsius of error over the span of several days.
Given the shelter modeling, a large part of the energy consumption could be accurately modeled but how about the other 30 percent. The engineers determined that the power consumption of the equipment could be easily measured but they were concerned about the heat output of the equipment. Any heat output by the equipment required additional air conditioning. Dr. Tanisha Booker and Dr. Lee Fry came up with a solution: measure the heat output with a calorimeter. After a search however, they couldn’t find a calorimeter that would allow the equipment to be measured. So they designed and built one.
“We measured the heat output in a lab environment using a calorimeter that we created. We measured pieces of equipment within a shelter that might be used in an operational environment, such as computers, monitors, and lights,” said Gorin.
The goal was to reduce energy consumption. Since heat and cooling of the shelter was where majority of the energy was being consumed, improving the energy efficiency of the shelter seemed a good place to start. Since the shelter model is physics based, variables such as shelter material, colors, radiant barriers, air vents, shades, and air infiltration rates can be varied to determine their effects.
The engineers evaluated variances, one being how much air is being lost due to air gaps in shelter assembly and opening the flap of the doors. What they discovered with a tracer gas test is that the infiltration rate was 10 times greater with one door unzipped than with the tent sealed. NREL modeled a shelter with a radiant barrier and the model predicted a 26 percent heating or air conditioning saving for a year with a radiant barrier than without a radiant barrier. Further efforts are underway to determine other means to further reduce energy consumption.
“This new computerized model allows users to incorporate shades, radiant barriers, and tent colors into the heat transfer calculations to determine the need for heating and air conditioning,” said Gorin.
Since the model utilizes a weather input file, it can predict tent temperatures anywhere in the world, thus allowing field units to predict supply needs before deployment. Gorin said the new algorithm and model have been shared with the Marine Corps and the Army for consideration of use.
Gorin’s team have since further expanded their efforts now that they have the computerized model that allows them to predict energy consumption in theater. To date, Gorin’s team has built an energy compound in Panama City, Fla., that incorporates energy technologies that has the potential to further improve field tactics.
“We’re also looking at hybrid energy systems that will enable the Marines and the Army to match their supplies to demand,” he said. “Unlike your house where you only pay for the energy you consume, the military fires up a generator that frequently is lightly loaded and wastes energy. The hybrid system’s aim is to use the generators efficiently by turning the generators off when not needed and using stored or renewable power.”
The Energy Team is presently completing an Analysis of Alternatives for Hybrid Power Systems that will result in new power systems for the U.S. Marines. One of the hybrid solutions is a U.S. Army micro-grid that utilizes six, 60 kw generators that are switched on or off as needed. NSWC PCD is expected to receive one U.S. Army micro grid for project testing in the summer of 2013.