Internal Resistance Loss Research Articles

Evaluation of Electrolytic Characteristics with a Single Cell Developed as SOFC

In recent years, it is concerned that a power supply and demand balance of power grid become unstable because of large introduction of variable renewable energy such as solar photovoltaic power generation. The reversible solid oxide cell (rSOC) can operate both SOFC and SOEC modes reversibly. Therefore, the rSOC can be used as a flexibility device for the power supply and demand adjustment by operating reversibly in response to power grid balance.Furthermore, CO2 electrolysis and co-electrolysis, which can generate synthesis gases such as H2 and CO, which are raw gases for methane or liquid fuels, from CO2 and H2O by adding an electric power, are promising carbon recycling technologies.In this study, the electrolytic characteristics were evaluated with a single cell developed as SOFC. It was confirmed in CO2 electrolysis test that CO2 can be directly electrolyzed to CO with about 100% current efficiency. In addition, the electrolysis voltages were clarified under various gas conditions in co-electrolysis and the cell performance factors were analyzed by our original method. In this method, the cell performance factors can be described by the internal resistance loss (IR loss, measured value), the fuel electrode overvoltage, the oxygen electrode overvoltage, and the Nernst loss (calculate value). As a result of this analysis in co-electrolysis mode before and after all tests, it was shown that the increase in IR loss was the main factor of the decrease in cell performance.

Development of SOEC Performance Model Based on Cell Performance

Central Research Institute of electric Power Industry (CRCIEPI) has developed original SOFC performance evaluation method and applied to a wide variety of cells. Based on the SOFC performance evaluation method, a new SOEC performance evaluation method has been developed this time. By this evaluation method, the difference between the open circuit voltage and the cell voltage can be expressed by the internal resistance loss (measured value), the fuel electrode overvoltage, the oxygen electrode overvoltage, and the Nernst loss.In this study, cell performance before and after the CO2 direct electrolysis test was compared by SOFC and SOEC evaluation methods and clarification of cell degradation factor by CO2 direct electrolysis.

Electric vehicle internal resistance test and optimization

In order to improve the energy-saving effect of a pure electric vehicle, this paper analyzes the causes and influencing factors of the internal resistance loss of the automobile, and expounds the necessity of internal resistance optimization. Select a model in research and development, determine the resistance through the sliding resistance test, and evaluate the energy saving potential of the vehicle through the benchmarking method. A method of resistance decomposition is proposed. The resistance values of key components are tested and analyzed, and the optimization scheme is given. In order to verify the effect of the optimization scheme, this paper proposes a theoretical calculation method. After verification, the proposed optimization scheme finally improves the energy-saving effect of the vehicle by 3%.

Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization

A national project in Japan for SOFC development has been initiated from FY2020 to FY2024 in NEDO’s project in order to establish the method for degradation diagnosis of SOFC stacks with durability and reliability for 130,000 hours or the method for evaluation of expanding application. Central Research Institute of Electric Power Industry (CRIEPI) has operated three types of SOFC stacks, which are developed by KYOCERA, MORIMUA SOFC TECHNOLOGY, and DENSO and investigated their long-term durability in this project. We have developed the electrode polarization model for SOFC performance which is able to express the SOFC performance such as Nernst loss, cathode overvoltage, anode overvoltage, and internal resistance (IR) loss under various conditions with high prediction accuracy. Each SOFC stack has been operated with high fuel utilization (Uf = 80% and 85%) as a severe condition for high efficiency towards 20,000-hours operation, and degradation factors for SOFC durability has been analyzed by using our electrode polarization model. Analysis results until now showed that dominant degradation factors for both Uf = 80% and 85% were increase of cathode overvoltage or IR loss as same as that of the SOFC stacks in the previous term [1]. Although anode overvoltage was a minor degradation factor, increase rate of anode overvoltage under Uf = 85% was relatively larger than that under Uf = 80%. In addition, thermal property testing will be conducted for each SOFC stack in order to include temperature term into our electrode polarization model. This new model can predict SOFC performance more accurately under various operating conditions. This work has been carried out under the project of the New Energy and Industrial Technology Development Organization (NEDO), Japan as a contract research. We would like to express our gratitude to NEDO, KYOCERA, MORIMUA SOFC TECHNOLOGY, Denso as well as to university partners and National Institute of Advanced Industrial Science and Technology (AIST).Reference[1] A. Ido et al., ECS Transactions, 91(1), 801-808 (2019).

Preparation 8.5%-efficient submodule using 5%-efficient DSSCs via three-dimensional angle array and light-trapping layer

Expanding the application area of photovoltaics to urban environments demands high efficiency under low-intensity lighting conditions, as well as omnidirectional light trapping. Dye-sensitized solar cells are of particular interest in this regard, owing to their superior electricity production in dim light; however, an improvement in dye-sensitized solar cells efficiency is required for successful implementation. We developed a light-trapping layer within the photoanode of dye-sensitized solar cells and configured these cells into an angled three-dimensional (3D) array creating a submodule to improve efficiency. The light-trapping layer increases the travel distance of the light within the photoanode, thus improving electron generation by the photons of the omnidirectional incident light. The 3D angled array suppresses recombination and internal resistance losses, improving the collection efficiency by increasing the relative cell surface area with respect to the light projection area. Using the proposed configuration, we achieved a dye-sensitized solar cells submodule efficiency of 8.5% using 5%-efficient dye-sensitized solar cells with a pot-shaped light-trapping layer and a 60° angled 3D array for the submodule. Considering that there is room for further improvement, our proposed photovoltaics configuration is expected to overcome the current limitations of dye-sensitized solar cells, thus providing promising photovoltaics modules for urban environments.

Electromechanical conversion efficiency for dielectric elastomer generator in different energy harvesting cycles

In order to improve electromechanical conversion efficiency for dielectric elastomer generators (DEG), on the base of studying DEG energy harvesting cycles of constant voltage, constant charge and constant electric field intensity, a new combined cycle mode and optimization theory in terms of the generating mechanism and electromechanical coupling process have been built. By controlling the switching point to achieve the best energy conversion cycle, the energy loss in the energy conversion process is reduced. DEG generating test bench which was used to carry out comparative experiments has been established. Experimental results show that the collected energy in constant voltage cycle, constant charge cycle and constant electric field intensity energy harvesting cycle decreases in turn. Due to the factors such as internal resistance losses, electrical losses and so on, actual energy values are less than the theoretical values. The electric energy conversion efficiency by combining constant electric field intensity cycle with constant charge cycle is larger than that of constant electric field intensity cycle. The relevant conclusions provide a basis for the further applications of DEG.

(Invited) Alkaline Water Electrolysis: Achieving High Current Densities

The production of hydrogen via water electrolysis is currently recognized as the only option to store gigawatt electrical energy coming from renewable energy sources such as wind and sunlight. However, commercially available alkaline electrolyzers are still limited to low current densities (around 0.5 Acm-2), primarily due to its internal resistance losses. In order to reach the excellent current densities of acidic polymer electrolyte membrane (PEM) water electrolysis (ranging between 2 and 4 Acm-2), it is crucial to tailor electrolyte construction and cell design in order to overcome the high ohmic losses of conventional diaphragms and archaic cell designs used in alkaline electrolysis. Here, we demonstrate for the first time alkaline electrolysis achieving current densities as high as 2 A.cm-2 at 2 volts, not only well overcoming the performances of lab-scale and commercial alkaline electrolyzers, but also closely matching the performance of state-of-the-art PEM water electrolysis.

RuO2 nanoparticle-modified (Ce,Mn,Fe)O2/(La,Sr) (Fe,Mn)O3 composite oxide as an active anode for direct hydrocarbon type solid oxide fuel cells

Composite oxide anodes have recently attracted great attention as alternative materials for solid oxide fuel cell anodes because of their potential to overcome the serious performance deterioration associated with the traditional Ni-based cermet. In particular, oxide anodes show a greater tolerance to coke and reoxidation than existing Ni-based cermets. In this study, the anodic performance of a (Ce,Mn,Fe)O2/(La,Sr) (Fe,Mn)O3 composite oxide modified with additional amounts of catalytically active RuO2 nanoparticles was investigated. Heat treatment resulted in highly dispersed RuO2 particles (ca. 10 nm). Anodes containing 10 wt% added RuO2 exhibited fairly high maximum power densities of 0.3 and 1.5 W cm−2 in H2 and C3H8, respectively, at 800 °C. The cells showed stable power density and negligible carbon formation even after 50 h of operation at 1 A cm−2. The increased power density was assigned to decreased anodic overpotential and internal resistance losses because RuO2 nanoparticles contribute to the increase in electrical conductivity.

Improved sintering and electrical properties of La-doped CeO2 buffer layer for intermediate temperature solid oxide fuel cells using doped LaGaO3 film prepared by screen printing process

Effects of a sintering agent for La-doped ceria (LDC) as a buffer layer to prevent a chemical reaction between Ni in anode and Sr- and Mg-doped lanthanum gallate (LSGM) electrolyte during sintering were studied for improving sintering and electrical properties. Electrochemical performance of anode-supported solid oxide fuel cells (SOFCs) using LDC and LSGM films prepared by screen printing and co-sintering (1,350 °C) was also investigated. The prepared cell with dense LDC (ca. 17 μm) and LSGM electrolyte (ca. 60 μm) films showed an open circuit voltage close to the theoretical value of 1.10 V and a high maximum power density (0.831 W cm–2) at 700 °C. The addition of 1 wt.% LSGM to porous LDC buffer layer was effective for improving the sintering density and electrical conductivity, resulting in the high power density due to the decreased internal resistance loss.

Spinel coatings for UNS 430 stainless steel interconnects

At the usual temperature of solid oxide fuel cell (SOFC) operation, ferritic stainless steels form electrically insulating or poorly conducting oxide scales, which can cause high internal resistance losses and chromium poisoning. In an effort to avoid this problem, we applied conductive copper manganite and cobalt manganite spinel coatings, with nominal composition MnCo 2O 4 and Cu 1.4Mn 1.6O 4, which were deposited on the surface of UNS 430 stainless steel by electroplating and subsequent air annealing. Microstructural evaluation indicated that the spinel layers inhibited outward diffusion of chromium. Moreover, excellent structural and thermal stability were observed after several thermal cycles at 750 °C and for up to 28 days, and the coating layers showed good adhesion to the substrate.

Relationships Between Carbon Black Cathode Material Characteristics and Lithium/Oxyhalide Cell Performance

Nine carbon blacks with iodine surface areas ranging between 60 and 1222 m2/gm and with dibutyl phthalate absorption numbers ranging between 125 and 420 cm3/100 gm have been evaluated as lithium/oxyhalide cell cathode materials. Two criteria have been considered: their ability to serve as heterogeneous catalysts for the cathodic half‐cell reaction (a function of both internal surface area and specific activity), and their ability to accommodate the continuous deposition of solid discharge products with minimal internal resistance losses (a function of both the porosity and pore size distribution of the agglomerated carbon particle aggregates). For carbons with surface areas of at least 250 m2/gm, overvoltages for reduction are practically independent of carbon black surface area. Furthermore, cathode porosities and cell discharge capacities both correlate with the DBP absorptometer numbers characteristic of the high surface area carbon blacks themselves. If the activity of a low surface area carbon is augmented via a catalytic additive (e.g., supported platinum), overvoltages similar to those obtained with high surface area carbons and complete utilization of the cathode's internal pore volume are achieved. The use of cathode “pore formers” may also lead to improved performance characteristics, particularly at very high current densities where pore former particle diameters averaging about 200 μm yield optimal performance results. Of the commercially available carbon blacks examined, Ketjenblack EC and Black Pearls 2000 function best as cell cathode materials, greatly outperforming the standard carbon, Shawinigan acetylene black.

Characteristics of Centrifugal Oil Pump

The use of centrifugal pumps on oil pipe lines and at refineries has been growing. Because they are quantity pumps and have such merits as low first cost, simplicity of operation, steady flow, and adaptability for direct connection to high-speed machinery, centrifugal pumps attract all industries which have to deal with pumping machinery. Whereas the efficiency of a properly designed centrifugal water pump runs very high, this efficiency decreases when the same pump is used in a viscous fluid. It is evident that, when pumping oil (besides all ordinary mechanical and hydraulic losses, for a viscous liquid), a new loss enters which dominates all the others. This is the viscosity or the internal resistance loss. The effect. of viscosity is to decrease the head capacity and to increase the disk friction. This lowers the efficiency of the centrifugal pump correspondingly.