The diagram shows the characteristic curve of the stack voltage *U _{Stack}*, the power
curve of the system

The diagram shows the efficiency curves of the fuel cell system and the fuel cell stack, including the present load point, in function of the stack current. The system efficiency is lower than the stack efficiency because the system needs power for its internal electrical consumption, which is required for the operation of the system components.

Fuel Cell animation

The animation illustrates a detailed view of a single cell from a fuel cell stack schematically. The electrolyte of a Polymer-Electrolyte-Membrane (PEM) fuel cell consists of a polymer membrane that isolates the anode and cathode electrically. This means the membrane is permeable for protons but impermeable for electrons. Hydrogen is fed at the anodic side and oxygen is added at the cathode. With the aid of a platinum catalyst, hydrogen is oxidised resulting in the electrons being separated. The potential difference between the electrodes generates direct current.

Depending on the load point, the (stoichiometric) process of the fuel cell reaction is animated in the cell. The present values of current and voltage are displayed next to the fuel cell stack. In addition, the "consumed" electrical power at the load (light bulb) and the resulting heat flow of the fuel cell stack are shown schematically.

Variable:

Formula:

Formula with numeric values:

Result:

Power FC stack

$P}_{Stack$

$P}_{Stack$

$U}_{Stack}\cdot {I}_{Stack$

$5\text{}\mathrm{V}\cdot 4\text{}\mathrm{A}$

$20\text{}\mathrm{W}$

Internal power consumption
FC

$P}_{Internal$

$P}_{Internal$

$P}_{Stack}-{P}_{System$

$20\text{}\mathrm{W}-15\text{}\mathrm{W}$

$20\text{}W$

Input of chemically stored
power

$\stackrel{\dot{}}{H}}_{{H}_{2}$

$\stackrel{\dot{}}{H}}_{{H}_{2}$

$\stackrel{\dot{}}{m}}_{{H}_{2},in}\cdot {H}_{{H}_{2}$

$1.56\cdot {10}^{-6}\text{}\frac{\mathrm{k}\mathrm{g}}{\mathrm{s}}\cdot 400000\text{}\frac{\mathrm{k}\mathrm{J}}{\mathrm{k}\mathrm{g}}$

$20\text{}\mathrm{W}$

FC stack efficiency

$\eta}_{Stack$

$\eta}_{Stack$

$\frac{{P}_{Stack}}{{\stackrel{\dot{}}{H}}_{{H}_{2}}}$

$\frac{5\text{}\mathrm{W}}{6\text{}\mathrm{W}}$

$60\text{}\mathrm{\%}$

FC system efficiency

$\eta}_{System$

$\eta}_{System$

$\frac{{P}_{System}}{{\stackrel{\dot{}}{H}}_{{H}_{2}}}$

$\frac{5\text{}\mathrm{W}}{6\text{}\mathrm{W}}$

$60\text{}\mathrm{\%}$