|Fig. 1: Solar PV battery system developed by the Office of Naval Research. (Source: Wikimedia Commons)|
Energy enables the U.S. Department of Defense (DoD) to provide the military forces and capabilities needed to maintain the national security of the United States. As the primary energy consumer within the U.S. government, the DoD hinges on the availability, delivery, and reliability of energy to fuel operations across the sea, air, and land domains. Amidst reductions in defense spending over the past several years, the DoD understands the critical role that energy plays in achieving mission success and has committed to a more efficient, cost-effective, and sustainable energy future. Moving forward, the department seeks to reduce its overall energy demand, expand its supply base to renewables, and incorporate energy analyses into operational and strategic planning.
Energy within the DoD is divided into two categories: operational and installation energy. Accounting for 70% of the DoD's total energy use, operational energy is the energy required for transporting, training, and sustaining personnel and weapons for military operations. Alternatively, installation energy is the energy required to operate military installations and bases. Combined, DoD energy consumption accounts for approximately 75% of the total energy consumption across the U.S. government. 
DoD energy demand is on a downward trajectory. In 2014, the department reached its lowest level of energy consumption in over a decade. The DoD has reduced its energy demand by investing in energy efficient retrofit projects. These retrofits include improvements to infrastructure lighting, heating, air conditioning systems, windows, control systems, and roofs. Other on-site project initiatives have further contributed to reductions in demand by employing cogeneration systems and enhancing energy awareness. 
Augmenting efforts to reduce its energy demand, the DoD hopes to increase its access to and generation of renewable energy. The incorporation of renewable energy into the department's energy mix has the potential to bolster resilience against supply disruptions and reach long term financial goals. The utilization of renewables on DoD installations would be particularly useful, where more predictable and standing conditions for supply and demand exist compared to mobile and expeditionary assets. Additionally, on-site renewable infrastructure could provide a cheaper and more reliable energy solution than commercial alternatives, and mobile renewable systems could alleviate deployed forces' consistent demand for external fuel. The DoD hopes to consume 30% renewable installation energy by 2025 and diversify its energy mix to combat potential supply disruptions. 
Examples of renewable energy projects within the DoD include the Navy's China Lake geothermal power plant in California, the Army's Fort Drum biomass facility in New York, and the Air Force's solar photovoltaic (PV) power station at Nellis AFB in Nevada. These examples illustrate several renewable avenues that the DoD can take in diversifying its energy mix. Other renewable resources include solar thermal, wind, ground source heat pumps, and nuclear energy.
Planning for how the DoD will access and consume energy in the future is paramount in ensuring mission readiness and the reliable delivery of energy to warfighters. Outlined in its 2016 Operational Energy Strategy, the DoD seeks to better implement energy supportability analyses in the development of future warfighting capabilities. Defense operations are conducted all over the globe with a variety of different missions; however, those locations and circumstances are constantly changing. Therefore, the DoD must develop resilient means to provide the warfighter with the capabilities needed to do his or her job, regardless of where and when they are called to duty. 
Looking forward, the DoD plans to incorporate energy analyses into capability development and foster innovation to improve combat effectiveness. Maintaining accurate and up-to-date support assessments will not only be vital in the ability to plan and develop future combat systems, but also in evaluating and retrofitting current systems. With these goals in mind, the DoD will be able to better identify operational risks and function with less dependence on foreign energy sources. Lastly, investment in energy research and innovative technology can unlock new materials, designs, and systems that can be used in the development of the next generation of warfighting capabilities. 
Fig. 1 depicts a solar PV battery system developed by the Office of Naval Research. The battery system was designed to reduce remotely deployed units' demand for external fuel and mitigate the threats associated with providing them with logistics support. The development of this system exemplifies the DoD's commitment to leverage energy analyses and innovation to boost security and combat effectiveness.
The DoD recognizes the crucial role that energy plays in powering the operations necessary to uphold the national security of the United States. The department's commitment to reducing overall energy demand, increasing renewable energy supply, and incorporating energy analyses into planning will improve future capability, sustainability, and security.
© Christopher DiOrio. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "Annual Energy Management Report: Fiscal Year 2014," Department of Defense, 3-4DBD001, May 2015.
 "2016 Operational Energy Strategy," Department of Defense, 5-240277A, December 2015.