Development of water cooling system for a ۲ KW PEM fuel cell stack

By increasing the demands for energy, limitation in fossil energy sources and environmental problem makes to use renewable and zero emission energy like hydrogen and fuel cell. PEM fuel cell technology has a variety application and high power stacks need a cooling system for controlling the stack operating temperature. Using water as working fluid in cooling system can increase the volumetric energy density and performance of PEM fuel cell Power system. For designing of a water cooling system for a PEM fuel cell stack, controlling the operating temperature, water flow rate and conductivity of cooling water is the main criteria. In this research a water cooling system is developed for a PEM fuel cell stack and this system was tested by a ۲ kW stack in laboratory. According the test result, by flowing ۸ LPM cooling water through the stack the operating temperature of the stack is controlled in design target value (۷۰°C) and the temperature difference for water inlet and outlet temperature remain less the ۳.۹۵°C. The water flow rate in deionizer was about ۲ LPM and the conductivity of water at the end of the test was less than ۶ μs/cm.The proton exchange membrane fuel cell (PEMFC), which is characterized by high efficiency, low noise, fast start-up, long service life, and so on, has been applied as a portable power source for small distributed power systems [۱]. A major factor that determines the large-scale applicability of PEMFC is the effectiveness of its heat management system [۲]. To be more specific, the operating temperature of the stack distribution in PEMFC poses a considerable influence on the factors including the pressure and humidity of gas in the stack, water content of the proton exchange membrane, catalytic activity, chemical reaction rate, as well as output performance and service life of the stack [۳].Figure ۱ shows a schematic view of a water cooling system. The electric power of the stack is about ۲ kW, with ۵۰% efficiency in mind, the heat output is about ۲ kW, which according to the calculations and the temperature difference between the inlet and outlet water, the more pump flow requires LPM, this is used in the system. Other components used in the system are the solenoid control valve and the deionizer, where the solenoid valve is responsible for controlling the water path, and the deionizer is responsible for reducing the circulating water ions that may contain ions stack. The maximum opening of the solenoid valve is about ۱۵%, the electrical conductivity ofthe water was about ۶ μS/cm, the cooling system was able to maintain a working temperature ofabout ۷۰ ° C, according to Figure ۲, the maximum difference between the outlet and inlet watertemperature is about It was ۳.۹۵ ° C.

Keywords:

Fuel cell , heat management , hydrogen , energy , power system