Page 61 - Introduction to Transfer Phenomena in PEM Fuel Cells

50 Introduction to Transfer Phenomena in PEM Fuel Cells
current) and unidirectional current. The static converter generally provides
an interface between the battery and a continuous bus where, depending on
the application, other energy storage components such as batteries,
supercapacitors or other (DC/DC or DC/AC) converters are connected,
which make it possible to form an interface between the DC bus and the
charge (e.g. an electric motor) [BLU 07].
1.3.4.4. The cooling circuit
The conversion of hydrogen and oxygen into electricity also produces
heat, which must be removed in order to keep the battery temperature
constant. The evacuation of this heat, for low power, can be done using a fan
(forced air convection) which can be the same as that supplying the cell with
air. In the case of higher power batteries, forced air convection is no longer
sufficient to remove heat. Other types of more complex cooling systems
such as water cooling systems are used. This system operates in a closed
loop thanks to a pump that circulates deionized water in a secondary circuit
inside the cell [BLU 07].

1.3.4.5. The humidification circuit
Generally, PEMFC-type cells require a gas humidification circuit so that
the membrane is not dehydrated (drying of the membrane results in an
increase in ionic strength of the membrane) or the electrodes are not
oversaturated due to excess water. This circuit therefore has the role in
humidifying the incoming gas, usually from the water produced by the
battery recovered via a capacitor. The control of the humidification is very
delicate. More and more research aims to find solutions to overcome such a
circuit by increasing, for example, the operating temperature of the battery
(high temperature membranes) [BLU 07].

1.4. Conclusion

This first part allowed us to present the hydrogen sector, to define the
functioning of a highly developed electrochemical system, the fuel cell.
Special interest was later attributed to PEM battery technology. However,
these benefits are still outweighed by the significant marketing costs.