VTB Utilization of Developed Battery Models in Aerospace System Simulation

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VTB Utilization of Developed Battery Modelsin
Aerospace System Simulation

• Presented by Shengyi Liu
• Contributors William McKay, Qingzhi Guo
• Roger A. Dougal, Ralph E. White

College of Engineering University of South
Carolina Columbia, SC 29208
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Objectives

• Incorporate the latest and best lithium ion
  battery models developed by electrochemists into
  the VTB system simulation environment
• Demonstrate use of those battery models for cycle
  life prediction in a complex satellite power
  system environment (rather than with simple load
  profiles)

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Significance

• VTB Fortran wrapper interface can make the best
  use of intellectual resources
• Many physics-based models were developed in
  Fortran language due to
• Suitable for scientific calculation
• Ease with programming
• One of the earliest computer language (back to
  1950s)
• VTB utilization of high-fidelity models improves
  the dependability and reduces the uncertainty of
  the simulation results
• Most Fortran written models are described by
  partial-differential equations and solution
  algorithms are of higher order accuracy.

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Approach
VTB Environment (MFC C Based)
VTB Wrapper
Battery Model (Fortran-based)
Complex system time-domain simulator

• Develop wrapper object that
• Synchronizes the Fortran executable to the system
  simulation
• Provides an interface that can accomodate
  natural, signal and data coupling, and an
  icon-based method for connecting to the system
• Extracts data for viewing, plotting, or 3D
  animation of battery data
• Maintains the integrity of the Fortran-based
  model (no change of math and algorithm)

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High-Fidelity Battery Models

• Advantages
• Chemistry-principle-based
• Mathematical description in PDEs
• Highly accurate and reliable
• Problems
• Model development assumed use in stand-alone
  simulator, not in generic simulation environment
• Programmed in Fortran language which does not
  support the class structures of the MFC
  (Microsoft Foundation Class) C native model
  format for VTB
• Solution
• Apply VTB wrapper techniques to step the Fortran
  code and to map signal connections into
  natural connections that allow topological
  definition of the study system

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Features of MSA Li-Ion Battery Model

• Physics-based pellet model programmed in Fortran
• Intercalation processes at positive and negative
  electrodes are considered
• Average and surface concentrations of Li at the
  intercalation particle are predicted
• Capacity fade effects are represented by
• Loss of active material at the cathode
• Growth of SEI during the recharging process

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Chemical Processes in MSA dual insertion Cell
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Half-Cell Lithium Polymer Battery Model (Doyle)

• Based on the concentrated solution theory and the
  transport equations.
• Li insertion into the active cathode is solved
  by application of Duhamels superposition
  integral.
• The solution includes the spatial distributions
  of potentials, current densities, concentrations
  for each time step.

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Doyles Half-Cell Lithium Polymer Battery Model

• Doyles 1-D half-cell model

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Wrapper verified by comparing simple system to
original stand-alone simulation
Constant current load 0.5 C rate (0.83 A)
All results are identical
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Wrapper verified by comparing simple system to
original stand-alone simulation
Constant current load 0.1 C rate discharge
All results are identical
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Cycling (75x2000 s) performance at 1C rate
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Capacity Fade Effect Voltage Decrease
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Capacity fade effect Change of SOC
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Capacity Fade SEI thickness increase
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Battery performance in complex system
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Load Current Profiles
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Solar Array Voltage and Current (2 orbits)
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Li-ion Cell Voltage and Current (5 Orbits)
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Battery SOC (5 Orbits)
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Side Reaction Current in battery (5 Orbits)
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SEI Buildup in battery (5 Orbits)
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Battery Behaviors for More Complicated Load
Profiles (5 orbits)
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Conclusions

• Wrapper was developed to incorporate lithium ion
  and lithium/polymer battery models into VTB
  system studies.
• Tests prove the wrappers work correctly and
  allow the advanced battery models to now be used
  in simulations of complex systems.
• Satellite power systems that use these battery
  models now allow realistic study of cycling and
  aging phenomena.