• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.641-648
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• 2011

KEPRI (KEPCO Research Institute) designed and operated the lab-scale high temperature electrolysis (HTE) system for hydrogen production with $10{\times}10cm^2$ 5-cell stack at $750^{\circ}C$. The electrolysis cell consists of Ni-YSZ steam/hydrogen electrode, YSZ electrolyte and LSCF based perovskite as air side electrode. The active area of one cell is 92.16 $cm^2$. The hydrogen production system was operated for 2664 hours and the performance of electrolysis stack was measured by means of current variation with from 6 A to 28 A. The maximum hydrogen production rate and current efficiency was 47.33 NL/hr and 80.90% at 28 A, respectively. As the applied current increased, hydrogen production rate, current efficiency and the degradation rate of stack were increased respectively. From the result of stack performance, optimum operation current of this system was 24 A, considering current efficiencies and cell degradations.

• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.117-127
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• 2022

The present study has investigated the performance of hydrogen gas generators for inhalation purposes based on polyelectrolyte membrane water electrolysis (PEMWE). The system applied two watering methods. One is pumped water (pumping system) and the other is gravity-fed water without a pump (non-pumping system). The cell efficiencies were compared by measuring the cell voltage and temperature in the hydrogen gas generator, respectively. The results show that the cell voltage and temperature increase with the cell current. The cell temperature is lower in the pumping system than that in the non-pumping system at a given cell current. Even though the amount of hydrogen production is the same regardless of the pumping system, the cell efficiency of the hydrogen gas generator in the non-pumping system is better than that in the pumping system.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.1
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• pp.64-71
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• 2010

This paper deals with an economic evaluation of domestic immersing type photoelectrochemical hydrogen production. We also make some sensitivity analysis of hydrogen production prices by changing the values of input factors such as the initial capital cost, the solar to hydrogen conversion efficiency, and the system duration time. The hydrogen production price of the immersing type photoelectrochemical system was estimated as 8,264,324 won/$kgH_2$. It is expected that the production cost by photoelectrochemical hydrogen production can be reduced to 26,961 won/$kgH_2$ if the solar to hydrogen conversion efficiency is increased to 14%, the system duration time is increased to 20,000 hours, and the initial capital cost is decreased to 10% of the current level. The photoelectrochemical hydrogen production is evaluated as uneconomical at this time, and we need to enhance the solar to hydrogen conversion efficiency and the system duration time as well as to reduce prices of the system facilities.

• Transactions of the Korean hydrogen and new energy society
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• v.7 no.1
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• pp.3-9
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• 1996

Hydrogen generation by electrical discharge through metal/water system is a viable method for on-demand applications. But its success depends on high energy efficiency defined as the ratio of the amount of consumed metal for a complete reaction with water to the electrical energy input. To improve the energy efficiency the electrical discharge has to sustain the hydrogen generation reaction with a minimal energy dissipation. Some experimental results on the discharge voltage-current profiles are reported and discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.4
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• pp.409-417
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• 2006

The characteristics of hydrogen-oxygen mixture gas generation stack was experimentally studied in terms of efficiency. For this purpose, the mixture gas generation stack was fabricated by connecting 7 cells in series following the Tero Ranta report. In order to avoid the instrument inaccuracy, all measuring equipments were re-tested and calibrated by Korea Laboratory Accreditation Scheme (KOLAS) certified laboratories. Since the amount of produced gas is most crucial in determining the efficiency, two gas collecting methods such as bottle trap method and wet gas meter method were adopted. From the experimental results, it was found that both KOH fume and steam evaporated along with hydrogen-oxygen mixture gas, and these by-product gases could cause the misestimation of the stack efficiency. The current, voltage, and energy efficiencies of the hydrogen-oxygen mixture gas generation stack was evaluated based upon the stack efficiency calculation method summarized in this work.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.4
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• pp.335-347
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• 2003

High temperature electrolysis (HTE) can become a key target technology for fulfilling the hydrogen requirement for the future hydrogen economy. This technology is based upon the partial replacement of electricity with heat energy for the electrolysis. Although the current research status of high temperature electrolysis in many countries remains at the small laboratory scale, the technology has great potential for producing hydrogen at a higher efficiency than low-temperature electrolysis (LTE). The efficiency of LTE is not expected to rise above 40%, whereas the efficiency of HTE has been reported to be above 50%. The higher efficiency of HTE would reduce costs by more than 30% compared to LTE. In this study, the technical data regarding the HTE of water and the resulting hydrogen production are reviewed, with an emphasis on the application of high temperature solid electrolyte and oxide electrodes for the HTE process.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.337-342
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• 2022

In this study, a water electrolysis was studied to investigate the effect of ammonia on current density and H2 gas production. A H type cell with three electrodes was used and KOH solution was used as electrolyte. The conventional platinum foil was used for working electrode, whereas nickel foam was used for counter electrode. CV experiment was performed to see the activity of ammonia oxidation reaction. In addition, CP experiment was done to examine the dependence of Faraday efficiency of hydrogen on current density and NH3 concentration. The CV result shows the 0.5M NH3 concentration required for highest current density and reliable operation. The CP result shows the increased current density leads to higher H2 generation. The higher H2 production and subsequent energy efficiency was observed for 0.5M NH3 using a Pt/13%Rh coil for a cathode as compared to those in water electrolysis.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.63-70
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• 2022

Compared with hydrogen, ammonia has the advantages of high gravimetric hydrogen densities (17.8 wt.%), ease of storage and transportation as a chemical hydrogen storage medium, while its application in small-scale on-site hydrogen production scenarios is limited by the need for complex separation equipment during high purity hydrogen production. Therefore, the study of PEMFC, which can directly utilize ammonia decomposition gas, can greatly expand the application of fuel cells. In this paper, the output characteristics, fuel efficiency and the variation trend of hydrogen concentration and local current density in the anode channel of fuel cell with the output voltage of PEMFC fueled by ammonia decomposition gas were studied by experiment and simulation. The results indicate that the maximum output power of the hybrid fuel decreases by 9.6% compared with that of the pure hydrogen fuel at the same inlet hydrogen equivalent. When the molar concentration of hydrogen in the anode channel is less than 0.12, the output characteristics of PEMFC will be seriously affected. Employing ammonia decomposition gas as fuel, the efficiency corresponding to the maximum output power of PEMFC is approximately 47%, which is 10% lower than the maximum efficiency of pure hydrogen.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.120-126
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• 2002

Ni-5%Al alloy powder is widely used as the bond coating powder to improve the adhesive strength between the substrate and coating. The important properties in the bond coating are the deposition efficiency and surface roughness. In this study, it was tried to optimize the plasma spray parameters to maximize the deposition efficiency and surface roughness. In the first step, spray current and hydrogen gas flow rate were optimized in order to increase the deposition efficiency. In the next step, the seven plasma spray variables were selected and optimized to improve both the deposition efficiency and surface roughness using the Taguchi experimental method. By these optimization, the deposition efficiency was improved from about 10 % at the frist time to 51.2 % by the optimization of spray current and hydrogen gas flow rate and finally to 65.2 % by the Taguchi experimental method. The average surface roughness was increased from about $12.9\mu\textrm{m}$ to $15.4\mu\textrm{m}$.

• Journal of Environmental Science International
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• v.13 no.6
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• pp.551-560
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• 2004

The feasibility and efficiency of the hydrogen peroxide produced by an electrolysis cell reactor was investigated, From regulating voltages for the given reaction time, the concentration of the hydrogen peroxide was gradually increased with increasing voltages. Optimal voltage range was found to be 10～15 V. The concentration of hydrogen peroxide was much higher with oxygen gas than without oxygen gas in the cathodic chamber. But there was a little difference in the generating rate of hydrogen peroxide regardless of the presence of nitrogen gas. Under given conditions, the maximum value of ICE(Instantaneous Current Efficiency) was about 38%, and then current density was 74 $mA/\textrm{cm}^2.$ The specific energy consumption was $0.694[kWh/kg-H_2O_2].$ Since Esp (Specific Energy Consumption)was very little value, It did not demand high energy in this system. Using the hydrogen peroxide gained in the experiment, Fenton's reaction was conducted and the removal of nitrobenzene, 3-chlorophenol and dye wastewater was studied. This results were very similar to the Fenton's reaction by using commercial hydrogen peroxide.