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Energy Storage Modeling and Simulation

Image showing a series of battery pack components next to a thermal image of a full battery system.

Knowledge of the interplay of multi-physics at varied scales is imperative to successful battery development.


Illustrations of increasing domains of a battery, from particle level (represented by two round shapes abutting one another), to electrode level (represented by a layered rectangular shape), to a cylindrical cell (represented by a cylindrical shape cut away to reveal layers), accompanied by a scientific equation.

NREL's multi-scale multi-domain model makes it possible to resolve battery geometry at the particle, electrode and cell levels.

NREL is a recognized leader in battery thermal and electrochemical design, performance, safety, lifespan, and reliability modeling and simulation. The lab's state-of-the-art multi-physics models are used to examine thermal, electrical, electrochemical, chemical, and mechanical behavior of energy storage cells and systems.

Battery development through the build-test-break cycle is time consuming and expensive. Multi-physics computer simulation of energy storage devices provides a less expensive, faster, and more controlled supplement to in-lab testing of batteries—which eventually leads to longer-lasting, dependable, and affordable batteries powering electric-drive vehicles (EDVs). To ensure that computer models produce verifiable results, NREL bases its models on real-world data supplied through partnerships with major automotive and battery manufacturers, combined with data collected in NREL's thermal characterization laboratories.

MSMD: Expandable Multi-Scale Multi-Physics Framework

Physicochemical processes in lithium-ion (Li-ion) EDV batteries occur in intricate geometries over a wide range of time and length scales. As battery size increases to meet EDVs' energy storage system demands, macroscopic design factors and highly dynamic environmental conditions significantly influence the electrical, thermal, electrochemical, and mechanical responses of a battery system. Better knowledge of the interplay across interdisciplinary multi-physics at varied scales is imperative to the development and design of affordable, long-lasting, high-performing, and safe large battery systems.

NREL pioneered a multi-scale multi-domain (MSMD) model to overcome challenges posed by the highly nonlinear multi-scale response of battery systems. The model resolves battery geometry into three coupled computational domains:

  • Particle-domain models (PDMs), to solve collective response of electrically and ionically connected particle-batteries
  • Electrode-domain models (EDMs), to solve collective behavior of PD-batteries.
  • Cell-domain models (CDMs), to solve single- or multi-cell battery response.

The MSMD's modular architecture is highly flexible and expandable. Model domain separation for the physicochemical process interplay is carried out where the characteristic time or length scale is segregated. Computational efficiency makes it possible to run the model on a standard desktop computer. The MSMD model has been implemented in multiple programing platforms (i.e., Matlab, C++, fluent API library).

Computer-Aided Engineering for Electric Drive Vehicle Batteries

NREL's success with the MSMD model provided the framework for the U.S. Department of Energy's Computer-Aided Engineering for Electric Drive Vehicle Batteries (CAEBAT) project. NREL is leading teams of auto manufacturers, battery makers, and automotive simulation tool developers in the modeling innovation needed to accelerate the battery design process—which will contribute to more widespread adoption of EDVs by boosting performance and consumer appeal. Electrochemical-thermal models developed and validated through the CAEBAT project are now commercially available in the following software packages from partners:

  • STAR-CCM+ (CD-adapco). This software contains battery simulations modules developed under CAEBAT.
  • Fluent 15 (ANSYS). This flagship CDF package includes CAEBAT-developed battery simulation tools.
  • AutoLion-3D (EC Power). This simulation package can be used to simulate battery safety aspects, in addition to electrochemical-thermal simulations.

Lifespan/Reliability

With its extensive portfolio of validated simulation tools, the lab's energy storage experts also evaluate solutions to optimize battery lifespan and reliability. Physics-justified degradation models are used to predict the calendar and cycle life of batteries. Life-predictive model and systems-level vehicle thermal design models assess battery:

  • Chemical and mechanical degradation caused by environment and cycling
  • Life span, performance, and cost tradeoffs
  • Excess power and energy sizing to meet life requirement.

Safety

Certain conditions can trigger exothermic chemical decomposition of Li-ion battery component materials, leading to potentially catastrophic escalations in temperature, known as thermal runaway. Battery behavior during overheating is affected by complex interactions among various physics. Dangerous temperatures may also result from an overcharged individual cell or entire system; an internal short circuit due to a latent defect or physical cell damage; an external short circuit of cells, modules, or packs; and/or exposure to abnormally high temperatures due to fire or failure of neighboring components. Building upon its MSMD model platform utilizing several other models NREL has substantially enhanced the battery safety modeling capability to capture the complex and interrelated thermal, electrical, electrochemical, and chemical responses.

Publications

NREL's Publications Database offers a wide variety of documents related to the lab's energy storage modeling activities and the MSMD framework, including:

Contacts

For more information on NREL's:

  • MSMD, CAEBAT, and safety modeling activities, contact Gi-Heon Kim, 303-275-4437.
  • Energy storage lifespan modeling activities, contact Kandler Smith, 303-275-4423.