Coolant fuel cell performance

Other than the contaminant sources mentioned above, some contaminants can also come from coolants and deionized water (e.g.. Si, Al, S, K, Fe, Cu, Cl, V, Cr), compressors (e.g., oils), and sealing gaskets (e.g.. Si), as summarized by Cheng et al. [150]. In recent studies [151-153], silicon was detected in a fuel cell catalyst layer after long-term operation. Silicon released due to gasket failure will get into the fuel cell catalyst layer, adsorb on the Pt catalyst surface or the interface of the Pt and ionomer, and thereby cause degradation in fuel cell performance. 

An optimum relationship between the DL and the flow field channels is a key factor in the overall improvement of fhe fuel cell s performance at both high and low current densities. Currently, flow field designs are typically serpentine, interdigitated, or parallel [207,264]. The FF plate performs several functions If is a current collector, provides mechanical support for the electrodes, provides access channels for the reactants to their respective electrode surfaces and for the removal of producf water, and it prevents mixing of oxidant, fuel, and coolant fluids. 

An internal power supply module provides the power needed by certain components within a fuel cell system. The components include sensors, control boards, pumps, fans, blowers, compressors, solenoid valves, contactors, switches, and so on. The IPM also provides the power to start the fuel cell system and helps carry some load when the fuel cell stack is inadequate to handle a sudden load jump. There are many types of sensors in a fuel cell system, such as the H2 concentration sensors, the H2 pressure sensors, the fluid flow rate sensors, the coolant-level sensors, the temperature sensors, the current sensors, the voltage sensors, the door-open sensors, the vibration sensors, and the flooding sensors. These sensors monitor the corresponding parameters to indicate the situation of the entire fuel cell system. The control boards may include a main board for controlling the system and several sub-boards for controlling various modules discussed in this chapter. Pumps, fans, blowers, compressors, solenoid valves, contactors, and switches all require power to perform the corresponding functions. 

The operating temperature of practical fuel cells, similarly to operating pressure, taken into account not only the cell performance but also the system requirements. A fuel cell generates heat as a by-product of the electrochemical reaction. To maintain the desired temperature, heat must be away from a fuel cell. Same heat dissipates from the outer surface of the fuel cell and same must be taken away with a cooling system. Medium that taken away the heat may be air, water, or a special coolant. The... 

Ethylene glycol (EG, C2H6O2) is ubiquitously used in the automotive industry as an engine coolant, and hence a distribution infrastructure already exists. Also, EG has a crossover current density roughly half that of methanol [69]. However, PEFC performance with EG is still relatively low, with a fuel cell specific energy density about 20-40% less than that of the same fuel cell utilizing methanol. Additionally, EG has been shown to rapidly degrade PEFC elecfiolyte material, which obviously limits its potential PEFC applications. 

The condition of a balance can be obtained in practice through tailoring the inlet humidity, flow rates, exit temperature (through coolant flow manipulation), and pressure drop though the fuel cell. Since a condition of exact balance is rarely achieved and an overall balance may not satisfy the desire for maximum performance, the fuel cell is typically operated in a slightly flooded situation, and a periodic growth and rejection cycle of liquid droplet slugs from the fuel cell achieves a quasi-steady balance condition. 

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