Materials Solutions to Meet the Need for Large-Scale Energy Storage
With the recent Department of Defense pledge to increase military effectiveness by using a greater portfolio of renewable energy, the DoD and Department of Energy are forging closer working relationships to bring new technology to market. Specifically, the inaugural edition of the DoD Operational Energy Strategy1 states that the Department will concentrate its operational energy investments in the three profiled areas: demand, supply, and future force planning. This focus has manifested as new solicitations and organizational structures on the part of the U.S. Navy, Air Force and Army to support this vision.
Large-scale energy storage (LSES) is an enabling technology that frequently enters the decision space in systems that promote renewable energy, fuel savings and energy security. New advances in materials research and prototyping are enabling LSES to provide cost-effective solutions in several compelling ways. The use of LSES maximizes the value of renewable resources in a system by compensating for their intermittent power-producing profiles. Power is provided when the renewable source is inactive; and likewise, excess generated power can be stored. LSES supplies peak demands, allowing for a smaller and more efficient power system. LSES can also significantly improve fuel utilization by allowing tactical generators to operate at maximum efficiency. Furthermore, to accomplish the objective of operating solely from renewable sources (i.e., zero net energy consumption), LSES must be an integral component of the system solution.
With this emergence of new energy and storage technologies, the hybrid power system paradigm is evolving to meet the need for multiple system configurations and value propositions. Figure 1 shows how storage integrates into a power system that utilizes a combination of multiple loads and energy sources. Power can come from multiple origins: AC sources of power (such as the electric grid, generators and wind) and DC sources of power (such as fuel cells and solar photovoltaics [PV]). The AC/DC and DC/DC power conversion electronics are needed when routing power to the loads or to the energy storage system.
The power system in Figure 1 is flexible and reconfigurable, designed to meet changing supply and load demand scenarios through algorithms resident in the intelligent power and energy controller (the bottom of the figure). The power system can be optimized for efficiency, maximum continuous and/or peak power, minimal fuel consumption, lowest cost operation, maximum run-time, intelligent load shedding, silent watch (silent auxiliary power), volt-ampere reactive (var) compensation or other scenarios as required. Large-scale energy storage is a key enabler for this efficient smart system’s operation.
In the following two articles, Raytheon highlights two promising areas of development: zinc-bromine flow batteries and liquid metal batteries.
Gami Maislin, Peter Morico
1Energy for the Warfighter: OPERATIONAL ENERGY STRATEGY, May 2011. http://energy.defense.gov/OES_report_to_congress.pdf