Fuel cell working and thermal management
Fuel Cell Working
In contradiction to standard internal combustion engines, fuel cells convert chemical energy into electrical energy to be used in the application. In principle, Fuel Cell consists of an anode, a cathode, Membrane electrode assembly (MEA) and bipolar plate, see below Fig.1 .
Fig.1 PEM FC Assembly
For PEMFC (Proton Exchange Membrane Fuel Cell) porous carbon and platinum (used as a catalyst: called Pt/C) are typically used for the anode and cathode materials. Characteristically for PEMFCs is that the electrolyte consists of a proton (H+)-conducting polymer membrane. The (anode) fuel is generally pure hydrogen (H2) and the cathode supply is air or oxygen (O2).
As shown in Fig. 2, at the anode, in the presence of the catalyst, the H2 molecules are dissociated into H+ and free e-. Further, the e- are conducted as usable electric current through an external circuit, while the H+ migrate with water (H2O) through the membrane electrolyte to the cathode. On the cathode side O2, H+ and e- are combine into H2O. The only additional byproduct is heat.
An important component of the PEMFC is the bipolar plate. The bipolar plate is a multi-functional component, whose primarily roles are to supply the reactants to the electrodes and provide electrical connection between adjacent cells.
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Anode reaction: 2 H2→4 H++4 e-
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Cathode reaction: O2+ 4 H++4 e-→2 H2O
Thermal Management
In order to ensure FC system perform properly, one needs to address the thermal management challenges seriously since it is vital to the PEMFC performance. FC can only work well in a certain temperature range which is optimal 50~80℃ for a PEMFC type cell.
The main purpose of the thermal management system in a liquid cooled fuel cell is to maintain the stack temperature within tight and acceptable limits. This is achieved by regulating the temperature and flow rate at which the coolant enters the fuel cell stack. One additional key point that should be highlighted is the required low Electric Conductivity (EC) of FC stack coolant. Ideally it should be < 5 μs/cm in working system what is a reduction of more than 90% in comparison with our standard ICE type coolants. To accommodate this need and ensure it remains that low, an ion exchange resin is needed to remove the ions that move up the electrical conductivity. Moreover, in a stack cooling system, low viscosity MEG-based coolant is also used for corrosion protection of metal Al, Ti, stainless steel …and should be compatible with EPDM, Silicone and other materials as well.