Kap-Seung Choi

Theoretical analyses of autothermal reforming methanol for use in fuel cell

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

An Experimental Study of Scale-up, Oxidant, and Response Characteristics in PEM Fuel Cells

It is important for fuel cell to become flexible in order to accommodate the situations of application areas for reducing costs and expanding coverage. Scale ups in series and parallel to 1-kW class proton exchange membrane (PEM) fuel cell stack are characterized experimentally with oxidant as air and oxygen. Through a serial scaled-up 4-cell stack with an active area of 25 cm² and a parallel scaled-up single cell with an active area of 100 cm², respectively, the 1-kW class 20-cell stack with an active area of 150 cm² per cell is scaled up from the basic unit cell with maintaining their performances. The polarization and power curves of the 1-kW class PEM fuel cell stack with the reactants H₂/air and H₂/O₂ are evaluated. Sufficient power of the PEM fuel cell can operate at flexible nominal current of 40-80 A and nominal voltage of 12-15 V for providing durability and balance between cells. The 1-kW class PEM fuel cell stack is characterized through the comparison of cell voltage differences utilizing H₂/air and H₂/O₂. Both cell voltages with H₂/air and H₂/O₂ follow well the one-twentieth of the responding stack voltages with the small difference.

Discrete regenerative fuel cell reduces hysteresis for sustainable cycling of water.

The discrete regenerative fuel cell is being developed as a residential power control that synchronizes with a renewables load which fluctuates significantly with the time and weather. The power of proton exchange membrane fuel cells can be scaled-up adjustably to meet the residential power demand. As a result, scale-ups from a basic unit cell with a 25 cm2 active area create a serpentine flow-field on an active area of 100 cm2 and take into account the excessive current and the remaining power obtained by stacking single cells. Operating a fuel cell utilising oxygen produced by the electrolyser instead of air improves the electrochemical reaction and the water balance. Furthermore, the performance test results with oxygen instead of air show almost no hysteresis, which results in the very stable operation of the proton exchange membrane fuel cell as well as the sustainable cycle of water by hydrogen and oxygen mediums.

Numerical Analysis-Based Design of PEMFC Channel, Fabrication of Channels, and Performance Test Using SU-8

Fuel cells have attracted enormous interest as new power sources because the cells can be used to solve the problem of environmental pollution as well as the natural-resource exhaustion problem. In this study, hydrogen-gas flow in microchannels of different shapes was numerically analyzed to improve the efficiency of a microfuel cell. Flow characteristics in six microchannels of different shapes but under identical boundary conditions were simulated. The analysis result shows that the flow characteristics such as velocity, uniformity, and flow rate, greatly depend upon the channel shape. This implies that the efficiency of microfuel cell can be expected to be increased by adopting the optimal configuration of channel shape for hydrogen-gas flow. The experimental results show that power density of a PEMFC with a microflow channel is higher than that of a PEMFC without a microflow channel; however, a durable catalyst is required in MEA.

Experimental Study on Autothermal Reformation of Methanol with Various Oxygen to Methanol Ratios for Fuel Cell Applications

OH는0.23이었으나실험결과는30 % 높은0.30일때최적의성능을나타내었다. 이것은혼합기체의농도차이, 반응속도, 촉매, 반응기의열손실, 반응시생성된생성물등의변화때문인것으로여겨진다.Abstract: The use of Hydrogen as a fuel is receiving considerable attention and as a result, research on novel methods ofhydrogen production is necessary so that the hydrogen demands in the future can be satisfied. This study presentsexperimental data on methanol Autothermal Reformation that quantifies the relationship between the oxygen-to-methanolratio (O