Akademik Veri Yönetim Sistemi
INTERNATIONAL JOURNAL OF ENERGY RESEARCH, cilt.46, ss.23939-23962, 2022 (SCI-Expanded)
The self-cold start ability of the proton exchange membrane (PEM) fuel cell system is limited due to the inadequate heat generation by the cell and the restricted effect of operating conditions. Fresh and useful heat may be provided by an external assisted technique that is adopted in the current study. The operation duration effect of the pump and the heater which are the most energy-consuming components of the coolant heating assisted method on the cold start performance of a PEM fuel cell stack was investigated, experimentally. Firstly, the inadequacy of the single-cell operation was proved by self-operation tests. The test was conducted at -10 degrees C and the temperature was raised to -7.5 degrees C levels during the test thanks to exothermic reactions that occurred in the cell. It manifests the cell may not be survived without any assistance and an external heat source is required. This fresh heat was supplied to the cell by the closed coolant cycle. Ethanol which can be operated at subzero temperatures was circulated throughout the machined external channels to the backside of the bipolar plates. The case studies were established considering various operation durations of the pump and the heater and the cold start tests were performed at -10 degrees C, -15 degrees C, -20 degrees C, -25 degrees C, and -30 degrees C temperatures. The effect of the pump and the heater operation durations on the temperature, voltage, and current profiles of the single-cell were investigated under the same energy consumption levels. The cell was operated throughout the whole case study and generated electricity successfully. It put forward the accomplishment of the proposed heating mechanism even at -30 degrees C. The time required for the cell temperature to rise above zero is increase with the decrease of the cold start test temperature. The cell temperature increased to zero at approximately 18, 39, and 53 seconds at -10 degrees C, -20 degrees C, and -30 degrees C operations, respectively. The PEM fuel cell stack, which does have not the capacity to operate itself at sub-zero temperatures, was successfully operated with the help of the established mechanism. No higher starter energy is needed for a -10 degrees C operation and the cell may be survived with a low operation of the auxiliary equipment. Failed starts were experienced with long heater and low pump cases at -20 degrees C and -25 degrees C temperatures. It is thought that a sharp drop in temperature after a pump shutdown prompts the cell into an unstable situation and fluctuations in voltage and current profiles. Although failed starts were recorded with implemented case studies at -30 degrees C at the initial stage, successful cold starts were achieved by the extended durations of the pump and heater, proportionally 2.6 and 5.5 A stable current, and 23.7 degrees C and 20 degrees C maximum temperature values were obtained with long heater operation and long pump operation cases, respectively. Although long heater operation provided a higher temperature increase, the long pump operation enabled a more homogeneous temperature distribution and stable current profile. This study revealed the strong sides of energy-consuming components and benefits at maximum to achieve a more stable cold start operation.