Jim Dankowski, Eaton
Reducing demand for energy on the battlefield is a key challenge facing many U.S. military forward operating bases (FOBs). Tactical generators consume millions of gallons of fuel keeping FOBs up-and-running each year. Safe and reliable access to fuel to power each generator is important to the success and security of military operations, and it can come with a high price tag.
The per-gallon price of fuel is not a small number. One cannot comprehend the “fully burdened” price of fuel without considering other factors. Fully burdened refers to the actual cost of buying, moving and protecting a gallon of petroleum – from the cost of transportation to the cost of troops defending the convoys, the costs of supplying battlefield generators is sizable.
The military’s dependence on reliable energy, and the threat it faces in military zones, led the U.S. Army to consider both energy alternatives and resource management strategies. Reducing energy needed on the battlefield would reduce the amount of fuel needed, lowering both the financial costs and the high level of risk undertaken by troops to protect the fuel in transport.
In addition to reducing overall demand for fuel, the military needed to ensure a constant stream of available power without requiring more complex coordination.
Facing the challenge of helping the U.S. military reduce demand for energy on the battlefield without adding to the already challenging logistics of supplying energy to an FOB, Eaton worked to develop the Intelligent Mobile Power Distribution System – a reliable and energy efficient way to manage generator output and guarantee a continuous stream of power for force support.
An Intelligent Mobile Power Distribution System (IMPDS) works by transforming an independently operating system of generators into a scalable demand-managed microgrid, providing power only where and when it is needed instead of employing all generators at all times. Figure 1 illustrates the concept for the IMPDS demand managed microgrid. By integrating tactical or commercial off the shelf generation dispatching, optional solar and energy storage connectivity, distribution bus protection and load management, the IMPDS provides the highest level of cost effectiveness and efficiency for the 150 personnel FOB camp or 5500 personnel expeditionary airfield.
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Figure 1 illustrates the IMPDS with communications and distributed energy resource (DER) source connections
Load Shed – For each of the IMPDS distribution manager (DM) units, three load shedding contactors are provided and controlled comprehensively across the complete IMPDS. All DM units will communicate with each other over an open architecture communications link. Every contactor in the system may be assigned a load shed priority or characterized by type.
Loads are shed and reconnected according to severity of a contingency or online generation capacity. Low priority loads are shed first, high priority loads last. From the DM human machine interface (HMI) it is possible to set load shed priorities, as well as override automatic load shed for each individual contactor, forcing it to the opened or closed position. From the HMI, it is possible to designate the connected sub-system (latrine, billeting, food system, etc.) and designate load shed priorities automatically. For systems in operation at FOBs this method will provide the highest reliability and cause the least disruption to service.
Load Demand – Through the IMPDS communications system, each DM shares its load data with every other DM. The IMPDS will sum all the load data, and via setpoints configured on the HMI, will determine if a generator or DER can be removed from operation. By communication connection the IMPDS will dispatch the generators or DER. The IMPDS will have the option of being commissioned with generator or DER performance and name plate data, via the HMI. The sources with the longest running hours or other critical performance data may be cycled the least.
Distribution circuit interruption – The DM has three phase circuit breakers for interruption of distibution bus contingencies. The circuit breakers are manually resettable from the top panel of the DM.
Distribution contingency management – A common deployment of IMPDS is composed of 6x MEP-806B TQG, operation at 208 volts has a 166 amp output, connected to a 200 amp ring bus. Failure scenarios could exist where the ring bus may carry significantly more than 200 amps at a given point. IMPDS comprehensive load management will be employed to insure that priority load shedding prevent the development of this situation. Figure 2 illustrates the potential contingency that will be mitigated in the previously described scenario.
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Figure 2 illustrates a contingency that requires comprehensive load management
The system also provides FOBs with critically needed power surety – a top priority in mission critical environments. Utilizing intelligent load management technology, Intelligent Mobile Power Distribution System prevents grid collapse in the event of generator fault. If one generator were to fail, the system prevents a stoppage of energy flow by shifting demand onto supporting generators, providing a constant, safe supply of power.
In a field test of the Intelligent Mobile Power Distribution System at U.S. military base Fort Devens, the installation was able to become self-sufficient through the demand-managed microgrid that transformed independently operating generators and reduced fuel consumption at the base by more than 30 percent.
This demand-managed system can be enhanced with optional solar and energy storage connectivity, allowing seamless integration with renewable energy resources and increasing the availability of reliable energy sources on the battlefield.