FCSys

Information

FCSys is an open-source library of declarative, dynamic, and flexible models of proton exchange membrane fuel cells (PEMFCs) in the Modelica language. The dynamics include chemical, fluid, thermal, and electrical effects. There are options to adjust the assumptions, spatial discretization and dimensionality (1D, 2D, or 3D), and the present chemical species and material phases. In fact, the framework could be easily extended to model other electrochemical devices like batteries.

A fuel cell is similar to a battery except that the reactants (fuel and oxidant) are externally stored or drawn from the environment. The electrochemical reactions of a PEMFC are:

2(H2	⇌	2e- + 2H+)	(anode)
4e- + 4H+ + O2	⇌	2H2O	(cathode)
2H2 + O2	⇌	2H2O	(net)

Figure 1 shows the seven primary layers of a typical PEMFC. Fluid enters and exits the cell through channels in the flow plates (FPs). It spreads through the gas diffusion diffusion layers (GDLs) and reacts in the catalyst layers (CLs). The proton exchange membrane (PEM) prevents electronic transport; therefore, electrons must pass through an external load to sustain the net reaction. As shown in Figure 2, a PEMFC model may be constructed from models of the same layers in FCSys. The model is modular; the gas diffusion and catalyst layers could be combined, or microporous layers could be inserted.

Figure 1: Layers and primary flows of a PEMFC.

Figure 2: Diagram of the PEMFC model (FCSys.Assemblies.Cells.Cell).

The models describe the advection, diffusion, and storage of material, momentum, and energy. Upstream discretization is applied in a manner that reduces to pure diffusion (i.e., Fick's law, Newton's law of viscosity, and Fourier's law) when the bulk velocity is zero. The transport equations do not use the Modelica stream operator since both diffusion and advection are important in fuel cells.

Each layer may be divided into a number of rectilinear regions. Storage and transport phenomena are co-located (e.g., no distinction between a vessel and a pipe). Regions may be directly connected without producing nonlinear systems of equations, and species may be independently included in each region. This is different than Modelica.Media, where each media model contains a predefined set of species.

A cell may simulated under specified boundary conditions, as shown in Figure 3. Adapters are available to interface with Modelica.Fluid.

Figure 3: Diagram of a test model (FCSys.Assemblies.Cells.Examples.CellProfile).

Licensed by the Georgia Tech Research Corporation under the Modelica License 2
Copyright 2007–2013, Georgia Tech Research Corporation.

This Modelica package is free software and the use is completely at your own risk; it can be redistributed and/or modified under the terms of the Modelica License 2. For license conditions (including the disclaimer of warranty) see FCSys.UsersGuide.ModelicaLicense2 or visit http://www.modelica.org/licenses/ModelicaLicense2.

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name	Description
UsersGuide	User's Guide
Blocks	Imperative models (inputs and outputs only)
Conditions	Models to specify and measure operating conditions
Assemblies	Combinations of regions (e.g., cells)
Regions	3D arrays of discrete, interconnected subregions
Subregions	Control volumes with multi-species transport, exchange, and storage
Connectors	Declarative and imperative connectors
Characteristics	Packages with data and functions to correlate physical properties
Units	Constants and units of physical measure
Quantities	Quantities to represent physical properties
BaseClasses	Base classes (generally not for direct use)