Most Department of Defense (DoD) installations are dependent on standalone diesel backup generators to supply power to mission critical facilities. In order to operate these generators during extended power outages the installation must have sufficient fuel stored in integrated fuel tanks or the capacity to deliver fuel to the backup generators throughout the duration of the outage. However, backup generators must be tested and maintained to operate effectively. With the large number of distributed generators that many installations own, maintenance can fall behind, causing unexpectedly high failure rates. In addition to high failure rates, creating n+1 redundancy for standalone generators is extremely expensive since it would require purchasing and maintaining two generators at each critical facility. A cost-effective, flexible, centrally fueled, and easy-to-maintain solution to provide redundant power generation would serve the unmet gap in installation energy resilience over long term power outages.

The objective of this project was to conduct a feasibility study to evaluate the use of existing Army diesel-electric locomotives as a mobile backup electric generation solution for DoD facilities. The study investigates how diesel-electric locomotives can be implemented from technical, operational, applicability, economic, and resiliency perspectives.

The U.S. Army owns 87 diesel-electric locomotives that are ideally suited to meet emergency energy resilience demands, while still being utilized during routine mission execution. Locomotives use diesel engines to operate generators, which in turn produce electric power to drive traction motors. However, traction motors can be decoupled from the generator, allowing the power generated to be supplied to local buildings or grids. There are 25 units rated at 1.5 megawatts (MW) each, 53 rated at 1.3 MW each, and 9 units rated at 2.2 MW each. In total, the Army’s locomotive fleet has a combined power output capability of 123 MW. Such a mobile generation capacity could economically enhance mission resilience. Additionally, locomotives have the capability to haul their fuel with them through utilization of railroad tank cars. Army Material Command estimates that one 25,000-gallon tank car of diesel represents 11.5 MW-days of energy after efficiency losses. In essence, an 820 kW load could be operated for 14-days off one locomotive and one tank car, meeting the Army Directive. If additional fuel is required due to large loads or lengthier outages, more tank cars can be hauled with the locomotive or brought in as needed.

Unfortunately, the rail-to-grid backup power solution did not pass the performance assessment to be considered as a widespread, main backup power strategy. While the technology is technically feasible, under current real-world conditions it performs worse from operational, applicability, most economic, and resilience standpoints as compared to the traditional backup power benchmark.

In addition to these, it also relies on a long list of significant assumptions that put the project at risk during the complexity of an emergency scenario. The last couple years have demonstrated the importance of investing in reliable infrastructure without the need for complex supply chains and interdependencies when it matters most. Consequently, the motto holds true: “Let us be efficient where we can, and effective where we must.” And mission critical backup power is a must.