• 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.16 no.4
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• pp.372-378
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• 2005

Ni/YSZ ($Y_2O_3$-stabilized $ZrO_2$) composite powder for a cathode material in high temperature electrolysis(HTE) was synthesized by a mechanical alloying method with Ni and YSZ powder. Microstructure of the composite and cell thickness for HTE reaction has been analyzed with various techniques of XRD, SEM to investigate effects of fabrication conditions. Employing the composite material, furthermore, the unit cell for HTE has been studied to evolve hydrogen from water. XRD patterns showed that the composites after wet mechanical alloying were composed of respective nano-sized crystalline Ni and YSZ. While ethanol as additive for mechanical alloying increased to $20\;{\mu}m$ of average particle size of the composites, alpha-terpineol effectively decreased to sub-micro size of that. This study has been found out the evolution of hydrogen by HTE reaction employing the fabricated cathode material, showing 1.4 ml/min of $H_2$ generation rate as increasing $20\;{\mu}m$ of cathode thickness.

• 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.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.61-64
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• 2007

Ni/YSZ ($Y_{2}O_{3}-stabilized$ $ZrO_{2}$), Cu/YSZ and CuO/YSZ composite powder for a cathode material in high temperature electrolysis (HTE) was synthesized by a mechanical alloying method with Ni (or Cu, CuO, Co) and YSZ powder. Microstructure of the composite for HTE reaction has been analyzed with various techniques of XRD, SEM to investigate effects of fabrication conditions. And conductivity of electrode was measured, Cu/YSZ cermet showed the higher electrical conductivity value than Ni/YSZ.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.2
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• pp.150-158
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• 2005

Added ratio of 8YSZ powder and organic compounds (solvent, plasticizer, dispersant, binder) properly. It manufactured electrolysis membrane by wet process that make slurry and dry process that do not use organic compounds. In the case of wet process, harmony combination and method of organic compound are an importance element in slurry manufacture. This slurry did calcine at temperature of 140$^{\circ}C$ in Furnace and manufactured electrolyte disk by Dry pressing method. Like this, manufacturing disk sintered at temperature of $1300^{\circ}C,\;1400^{\circ},\;1500^{\circ}C$ in Furnace and completed electrolysis membrane. Confirmed change of crystal structure and decision form through analysis of density, SEM, XRD according to change of sintering temperature, and considered relation with ion conductivity.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.764-767
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• 2006

Ni/YSZ $(Y_2O_3-stabilized\;ZrO_2)$ composite as an electrode component for High Temperature Electrolysis (HTE) was fabricated by mechanical alloying method using Ni and YSZ powders. Characterization of the synthesized composite was investigated with various analysis tools, including XRD, SEM and PSA, and a self-supporting planar unit cell prepared with the Ni/YSZ composite was prepared to study the electrochemical reactions for the production of hydrogen. The Ni/YSZ cermet is composed of crystalline Ni and YSZ, in a sub-micro scale, and has an even distribution without aggregated particles. In addition, under an electrochemical reaction, the unit cell showed an $H_2$ evolution rate from steam of 14 Nml/min and $600mA/cm^2$ of current density at the electrode.

• Nuclear Engineering and Technology
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• v.39 no.1
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• pp.1-8
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• 2007

Hydrogen and electricity are expected to dominate the world energy system in the long term. The world currently consumes about 50 million metric tons of hydrogen per year, with the bulk of it being consumed by the chemical and refining industries. The demand for hydrogen is expected to increase, especially if the U.S. and other countries shift their energy usage towards a hydrogen economy, with hydrogen consumed as an energy commodity by the transportation, residential and commercial sectors. However, there is strong motivation to not use fossil fuels in the future as a feedstock for hydrogen production, because the greenhouse gas carbon dioxide is a byproduct and fossil fuel prices are expected to increase significantly. An advanced reactor technology receiving considerable international interest for both electricity and hydrogen production, is the modular helium reactor (MHR), which is a passively safe concept that has evolved from earlier high-temperature gas-cooled reactor (HTGR) designs. For hydrogen production, this concept is referred to as the H2-MHR. Two different hydrogen production technologies are being investigated for the H2-MHR; an advanced sulfur-iodine (SI) thermochemical water splitting process and high-temperature electrolysis (HTE). This paper describes pre-conceptual design descriptions and economic evaluations of full-scale, nth-of-a-kind SI-Based and HTE-Based H2-MHR plants. Hydrogen production costs for both types of plants are estimated to be approximately $2 per kilogram.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.141-148
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• 2006

This study was carried out to analyze the microstructure characteristics of electrolyte membrane through XRD, SEM and AC impedance measurement for using in high temperature steam electrolysis(HTE). It was investigated that thermal stability and electric characteristics by sintering condition using dry and wet process, and confirmed growth of particle and density change by sintering temperature. The sintering temperature and behavior had an effect on the relative density of the ceramic and the average grain size. The more amount of dispersant in organic compound increase, the more the density increased. But the binder was shown opposite phenomenon. It was analyzed that electrolyte resistance and electrical characteristics using AC impedance. The electrical properties of YSZ grain boundary changed with the sintering temperature.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.455-458
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• 2006

최근 들어 고체산화물 연료전지(SOFC) 기술이 급성장함에 따라 고온 수증기 전기분해(HTE) 기술이 물로부터 수소를 대량으로 제조할 수 있는 환경 친화적인 기술로 주목 받고 있다 고온 수증기 전기분해는 기존의 액상 전기분해보다 총 에너지 요구량이 작고 전기분해에 필요한 최소의 전기에너지가 온도가 증가할수록 감소하며 고온 수증기 전기분해에 요구되는 에너지의 일부를 전기에너지 대신 열의 형태로 공급이 가능하여 보다 높은 효율을 기대할 수 있다. 따라서 off peak시 기저부하전력을 이용하고, 공정의 열원으로 고온가스의 폐열, 천연가스의 부분산화 반응열 또는 고온 가스원자로의 폐열을 활용하면 SOFC 이용 고온 수증기 전기분해 공정은 수소경제사회에서 요구되는 수소를 대량으로 제조할 수 있는 경제적인 공정이 될 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.228.2-228.2
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• 2010

In this work, the hydrogen production costs of the nuclear energy sources are estimated in the necessary input data on a Korean specific basis. G4-ECONS was appropriately modified to calculate the cost for hydrogen production of HTE process with Very High Temperature nuclear Reactor (VHTR) as a thermal energy source rather than the LUEC (Levelized Unit Electricity Cost). The general ground rules and assumptions follow G4-ECONS. Through a preliminary study of cost estimates, we wished to evaluate the economic potential for hydrogen produced from nuclear energy, and, in addition, to promptly estimate the hydrogen production costs for an updated input data for capital costs. The estimated costs presented in this paper show that hydrogen production by the VHTR could be competitive with current techniques of hydrogen production from fossil fuels if $CO_2$ capture and sequestration is required. Nuclear production of hydrogen would allow large-scale production of hydrogen at economic prices while avoiding the release of $CO_2$. Nuclear production of hydrogen could thus become the enabling technology for the hydrogen economy. The major factors that would affect the cost of hydrogen were also discussed.