Design, Modeling, and Control of Hybrid Energy Storage System for Defense Installation Microgrids

July 1, 2020
Integrating optimized storage, including site-customized hybrid multi-asset storage, with Department of Defense (DoD) microgrids improves energy security performance as a function of cost compared to a similar microgrid without storage.

The project will demonstrate a microgrid and energy storage modeling and design platform, with integrated analytics and controls capability. This comprehensive platform uses a cloud analytics platform to provide a tailored energy storage solution for any installation by considering climate zone, local energy market, and location specific use cases. The platform enables custom system design and control of a fully integrated, optimized hybrid energy storage system (HESS), using a modular energy storage approach, providing system flexibility and ensuring positive economics and improved critical load coverage probability.

Four core ESS technology types can be implemented for specific use cases based on their optimal c-rate. From highest c-rate to lowest: 1) Ultra Capacitors, 2) Li-ion batteries, 3) Flow Batteries, and 4) Sodium Sulfur batteries. Each of these core technology types were selected based on their ability to excel in specific use cases.

Resource dispatch and microgrid controls are handled by model predictive control (MPC) techniques. These MPC techniques allow flexible, adaptive, and market-aware dispatching of all energy storage and other existing dispatchable generation resources on the microgrid. They incorporate specifics from each installation and local assets (diesel generators, solar, UPS, etc.), the specific energy storage technologies selected, and the ability for the microgrid to interact with its local energy market. This control software is implemented on an industrial computer that interfaces with the storage technology, other assets, and the local utility using ClearSCADA®.

The overall potential economic advantages of an optimized HESS revolve around reduced system cost (ESS capital and operational expenditures and existing asset [diesel genset, UPS] reductions), improved payback potential, better system efficiency, enhanced reliability, and longer equipment lifetime. The modeling and design approach enables a reduction in microgrid design time of 80-90%, while advanced MPC techniques further enable a reduction of ESS operational costs by up to 35%. The core HESS approach, combining smaller systems of different technologies, allows the innate benefits of each technology to be exploited. This concept has been demonstrated in peer reviewed studies and utility scale demonstrations to provide 10-20% capital expenditure reduction, up to 30% operational expenditure reductions, and a 100% increase in expected equipment lifetime compared to traditional ESS.

From a resiliency and energy security standpoint, an optimized HESS can potentially provide significant improvements in ride-through capability and additional support to meet critical load requirements, while potentially reducing diesel fuel use and generator equipment requirements to do so. Marked differences exist throughout the United States between basic electricity costs, energy portfolios, rate structures, and market policy. The flexibility provided by a combination of technologies ensures a wide range of applicability across the DoD for both economic and resiliency benefits.