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Electrochemical Supercapacitors for Energy Storage and Delivery
6.6.2 Polymer Electrolyte Membrane Fuel Cell Modeling
Modeling of a PEMFC is presented here to review the important parameters
of operational control. The operation of a PEMFC relies on electrochemical
oxidation and reduction reactions that take place at the anode and cathode of
the cell, respectively. The anodic oxidation reaction catalytically splits hydrogen gas supplied to the anode into protons and electrons. The produced
current travels through an external load circuit to provide electrical power,
while protons permeate through a proton-conducting polymer membrane.
Both products arrive at the cathode in addition to a supplied oxygen gas
stream in which a second catalytically driven reduction reaction takes place
at the cathode, reducing oxygen and hydrogen protons to water.
The dynamic model of a PEMFC can be realized in MATLAB and Simulink
software for implementation in power systems [10]. Beginning with hydrogen flow, the three significant factors are input, output, and reaction flows
during operation [11]. The thermodynamic potential of the chemical energy
that can be converted into electrical energy is derived from Nernst’s law
and is dependent on the partial pressures of the reactants and temperature.
For reaction kinetic consideration, overpotentials at both anode and cathode essentially constitute the energy required to drive a reaction beyond the
state of thermodynamic reversibility.
Activation overpotential, as the preceding notation implicitly states, is the
energy necessary to overcome the energy barrier for electron transfer from
the electrode to the analyte or vice versa. Similarly, the diffusion overpotential describes the potential difference required to overcome the concentration gradient of the reactants or charge carriers between the bulk solution
and the surface of the electrode. This is generated when the electrochemical
reaction occurs at a sufficient pace to reduce the concentration of the reactants at the surface. Each of these overpotentials can be described in relation
to cell current, voltage, energy, and power parameters used for whole HESS
modeling [10].
6.6.3 Power Systems Modeling
Power system designs are required in every application and are achieved by
the implementation of a chosen topology. These system integrations often
include one or multiple power electronic converters through a parallel or
series connection of supercapacitor banks with FCs or batteries as mentioned
earlier. Each direct or indirect connection imparts both positive and negative
aspects related to the intended use of the power system and more specifically
to the robustness of control, system efficiency, and cost. As with design, power
system modeling and control can be achieved by a variety of methods. A simplified method is presented here. Approaches that rely heavily on an electronic or computer engineering basis can be further explored in the literature.
Electrochemical Supercapacitors for Energy Storage and Delivery
6.6.2 Polymer Electrolyte Membrane Fuel Cell Modeling
Modeling of a PEMFC is presented here to review the important parameters
of operational control. The operation of a PEMFC relies on electrochemical
oxidation and reduction reactions that take place at the anode and cathode of
the cell, respectively. The anodic oxidation reaction catalytically splits hydrogen gas supplied to the anode into protons and electrons. The produced
current travels through an external load circuit to provide electrical power,
while protons permeate through a proton-conducting polymer membrane.
Both products arrive at the cathode in addition to a supplied oxygen gas
stream in which a second catalytically driven reduction reaction takes place
at the cathode, reducing oxygen and hydrogen protons to water.
The dynamic model of a PEMFC can be realized in MATLAB and Simulink
software for implementation in power systems [10]. Beginning with hydrogen flow, the three significant factors are input, output, and reaction flows
during operation [11]. The thermodynamic potential of the chemical energy
that can be converted into electrical energy is derived from Nernst’s law
and is dependent on the partial pressures of the reactants and temperature.
For reaction kinetic consideration, overpotentials at both anode and cathode essentially constitute the energy required to drive a reaction beyond the
state of thermodynamic reversibility.
Activation overpotential, as the preceding notation implicitly states, is the
energy necessary to overcome the energy barrier for electron transfer from
the electrode to the analyte or vice versa. Similarly, the diffusion overpotential describes the potential difference required to overcome the concentration gradient of the reactants or charge carriers between the bulk solution
and the surface of the electrode. This is generated when the electrochemical
reaction occurs at a sufficient pace to reduce the concentration of the reactants at the surface. Each of these overpotentials can be described in relation
to cell current, voltage, energy, and power parameters used for whole HESS
modeling [10].
6.6.3 Power Systems Modeling
Power system designs are required in every application and are achieved by
the implementation of a chosen topology. These system integrations often
include one or multiple power electronic converters through a parallel or
series connection of supercapacitor banks with FCs or batteries as mentioned
earlier. Each direct or indirect connection imparts both positive and negative
aspects related to the intended use of the power system and more specifically
to the robustness of control, system efficiency, and cost. As with design, power
system modeling and control can be achieved by a variety of methods. A simplified method is presented here. Approaches that rely heavily on an electronic or computer engineering basis can be further explored in the literature.