Energies

2024

Jump to: 2023, 2021, 2020, 2019

15 pages, 2795 KB

Open AccessEditor’s ChoiceArticle

Electrochemical Performance of a Hybrid NiCo₂O₄@NiFelt Electrode at Different Operating Temperatures and Electrolyte pH

by Ataollah Niyati, Arianna Moranda, Pouya Beigzadeh Arough, Federico Maria Navarra and Ombretta Paladino

Energies 2024, 17(15), 3703; https://doi.org/10.3390/en17153703 - 26 Jul 2024

Cited by 5 | Viewed by 1753

Abstract

Transition metals such as nickel and cobalt as an alternative to Pt and Pd can be used for oxygen evolution reactions (OERs) and hydrogen production reactions (HERs) in alkaline environments, facilitating green hydrogen production as a sustainable alternative to fossil fuels. In this [...] Read more.

Transition metals such as nickel and cobalt as an alternative to Pt and Pd can be used for oxygen evolution reactions (OERs) and hydrogen production reactions (HERs) in alkaline environments, facilitating green hydrogen production as a sustainable alternative to fossil fuels. In this study, an NiCo₂O₄ catalyst was produced by a sono-hydrothermal method using urea as a hydrolysis agent. The electrochemical performance of the catalyst-coated NiFelt electrode was evaluated at different KOH concentrations (0.25, 0.5, and 1 M) and four operating temperatures in the interval of 20–80 °C. The electrode characteristics were investigated via electrochemical spectroscopy (cyclic voltammetry, EIS, multistep chronopotentiometry, multistep chronoamperometry) using two different reference electrodes (Ag/AgCl and Hg/HgO), to obtain insight into the anodic and cathodic peaks. XRD, SEM, EDS, and TEM analyses confirmed the purity, structure, and nanoscale particle size (20–45 nm) of the NiCo₂O₄ catalyst. The electrode showed symmetric CV with Ag/AgCl, making this reference electrode more appropriate for capacitance measurements, while Hg/HgO proved advantageous for EIS in alkaline solutions due to reduced noise. The overpotential of the catalyst-coated NiFelt decreased by 108 mV at 10 mA/cm² compared to bare NiFelt, showing a good potential for its application in anion exchange membranes and alkaline electrolyzers at an industrial scale. Full article

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2023

Jump to: 2024, 2021, 2020, 2019

12 pages, 2972 KB

Open AccessArticle

Structure and Thermoelectric Characterization of p-Type SnTe Nanobulk Material Synthesized by Charge Compensation Chemical Reaction

by Ryosuke Fujiwara, Yuta Ikeda, Takuto Kawaguchi, Yohei Takashima, Takaaki Tsuruoka and Kensuke Akamatsu

Energies 2024, 17(1), 190; https://doi.org/10.3390/en17010190 - 29 Dec 2023

Cited by 2 | Viewed by 1745

Abstract

SnTe is the most widely studied p-type thermoelectric (TE) alternative to PbTe. In this study, we prepared a nanostructured SnTe bulk material via spark plasma sintering from a precursor synthesized by a chemical precipitation process without using organic molecules. The sintered sample comprised [...] Read more.

SnTe is the most widely studied p-type thermoelectric (TE) alternative to PbTe. In this study, we prepared a nanostructured SnTe bulk material via spark plasma sintering from a precursor synthesized by a chemical precipitation process without using organic molecules. The sintered sample comprised tiny grains (100–300 nm) with high-density grain boundaries. Eventually, because the material would contain no impurities acting as scattering nodes of charge carriers, the material exhibited a relatively high electrical conductivity of 7.07 × 10⁵ Sm⁻¹ at 310 K. The material demonstrated low lattice thermal conductivity (0.87 Wm⁻¹K⁻¹ at 764 K), which can be owing to the increasing phonon scattering at grain boundaries. The maximum ZT was 0.31 at 764 K in the measured temperature range. This study provides a method for the design of phase-pure and surfactant-free SnTe thermoelectric materials that exhibit low lattice thermal conductivity and high carrier mobility using a chemical synthetic approach. Full article

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2021

Jump to: 2024, 2023, 2020, 2019

15 pages, 5518 KB

Open AccessArticle

Performance Analysis of Bifacial PV Modules with Transparent Mesh Backsheet

by Juhee Jang, Andrea Pfreundt, Max Mittag and Kyungsoo Lee

Energies 2021, 14(5), 1399; https://doi.org/10.3390/en14051399 - 4 Mar 2021

Cited by 15 | Viewed by 5094

Abstract

Due to their transparent rear side, bifacial modules can take advantage of rear side irradiance as opposed to monofacial modules. Glass or transparent backsheets are conventionally used as rear side encapsulation material. To increase coupling gains achieved through internal reflection at the module [...] Read more.

Due to their transparent rear side, bifacial modules can take advantage of rear side irradiance as opposed to monofacial modules. Glass or transparent backsheets are conventionally used as rear side encapsulation material. To increase coupling gains achieved through internal reflection at the module rear side, a white or reflecting mesh structure can be applied in the areas between the cells on the rear side material. In this study, an existing optical model based on a simplified ray tracing approach is extended to describe the effects achieved though this mesh structure. The model is further integrated into a complete cell-to-module loss and gain analysis. The performance of the mesh backsheet concept is assessed under varying parameters. The impact of mesh reflectance, bifaciality of the cell and width of the mesh compared to the cell spacing are investigated. Losses due to increased module temperature and gains due to internal reflection gains are compared. We confirm that the optimal power gain can be achieved when the width of the mesh is the same as the spacing between the cells. We find that the power gain due to the improved internal reflection outweighs the power loss due to increased module temperature. Full article

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17 pages, 7260 KB

Open AccessArticle

The Impact of Cracks in BIPV Modules on Power Outputs: A Case Study Based on Measured and Simulated Data

by Kyung-Woo Lee, Hyo-Mun Lee, Ru-Da Lee, Dong-Su Kim and Jong-Ho Yoon

Energies 2021, 14(4), 836; https://doi.org/10.3390/en14040836 - 5 Feb 2021

Cited by 10 | Viewed by 4090

Abstract

Crack issues afflicting a building integrated photovoltaics (BIPV) system are major concerns in terms of the system’s maintenance and power degradation. Although there may be many circumstances that bring about cracks in BIPV modules during the installation process, identifying the degradation of PV [...] Read more.

Crack issues afflicting a building integrated photovoltaics (BIPV) system are major concerns in terms of the system’s maintenance and power degradation. Although there may be many circumstances that bring about cracks in BIPV modules during the installation process, identifying the degradation of PV module efficiency resulting from the effects of cracks tends to be a very difficult task unless actual indoor or outdoor tests or detailed electroluminescence imaging tests are conducted. Many current studies have demonstrated that cracks may or may not impact the output performance of PV modules depending on the damage levels or where the damage is located. For BIPV applications such as replacement for building materials, there is still a lack of information and case studies addressing crack issues in a quantitative manner for evaluating BIPV output performance. Therefore, the objectives of this study are to investigate the effects of cracks in BIPV modules on power outputs and to identify detailed relationships between the cracks and power output based on experimental and simulated analysis. An experimental facility located in Daejeon, South Korea, was used to gather data from cracked and non-cracked BIPV modules. By using the field-measured data and facility’ information, a simulation model was developed using SolarPro software, and a simulated-based analysis was conducted to evaluate the impact of cracks in BIPV modules on output values after proper validation of the model. The results from this study reveal that cracks in BIPV modules exhibit significant degradation in BIPV modules’ outputs of up to 43% reduction during the experimental period. From the annual comparative results, output degradations of 34.6–35.4% were estimated when the BIPV modules included cracks. As a result, the cracks in the BIPV modules could be carefully addressed as issues occurring in the BIPV installation process. Full article

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11 pages, 2821 KB

Open AccessArticle

Numerical Simulation Analysis of Ag Crystallite Effects on Interface of Front Metal and Silicon in the PERC Solar Cell

by Myeong Sang Jeong, Yonghwan Lee, Ka-Hyun Kim, Sungjin Choi, Min Gu Kang, Soo Min Kim and Hee-eun Song

Energies 2021, 14(3), 592; https://doi.org/10.3390/en14030592 - 25 Jan 2021

Cited by 7 | Viewed by 2763

Abstract

In the fabrication of crystalline silicon solar cells, the contact properties between the front metal electrode and silicon are one of the most important parameters for achieving high-efficiency, as it is an integral element in the formation of solar cell electrodes. This entails [...] Read more.

In the fabrication of crystalline silicon solar cells, the contact properties between the front metal electrode and silicon are one of the most important parameters for achieving high-efficiency, as it is an integral element in the formation of solar cell electrodes. This entails an increase in the surface recombination velocity and a drop in the open-circuit voltage of the solar cell; hence, controlling the recombination velocity at the metal-silicon interface becomes a critical factor in the process. In this study, the distribution of Ag crystallites formed on the silicon-metal interface, the surface recombination velocity in the silicon-metal interface and the resulting changes in the performance of the Passivated Emitter and Rear Contact (PERC) solar cells were analyzed by controlling the firing temperature. The Ag crystallite distribution gradually increased corresponding to a firing temperature increase from 850

^{\circ}

C to 950

^{\circ}

C. The surface recombination velocity at the silicon-metal interface increased from 353 to 599 cm/s and the open-circuit voltage of the PERC solar cell decreased from 659.7 to 647 mV. Technology Computer-Aided Design (TCAD) simulation was used for detailed analysis on the effect of the surface recombination velocity at the silicon-metal interface on the PERC solar cell performance. Simulations showed that the increase in the distribution of Ag crystallites and surface recombination velocity at the silicon-metal interface played an important role in the decrease of open-circuit voltage of the PERC solar cell at temperatures of 850–900

^{\circ}

C, whereas the damage caused by the emitter over fire was determined as the main cause of the voltage drop at 950

^{\circ}

C. These results are expected to serve as a steppingstone for further research on improvement in the silicon-metal interface properties of silicon-based solar cells and investigation on high-efficiency solar cells. Full article

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19 pages, 4378 KB

Open AccessArticle

A Method to Improve the Accuracy of Simulation Models: A Case Study on Photovoltaic System Modelling

by Aekkawat Bupi, Songkiate Kittisontirak, Perawut Chinnavornrungsee, Sasiwimon Songtrai, Phassapon Manosukritkul, Kobsak Sriprapha, Wisut Titiroongruang and Surasak Niemcharoen

Energies 2021, 14(2), 372; https://doi.org/10.3390/en14020372 - 11 Jan 2021

Cited by 2 | Viewed by 2250

Abstract

This research presents a method to improve data accuracy for the more efficient data management of the studied applications. The data accuracy was improved using the preciseness function learning model (PFL model). It contains a database in which the amount of data is [...] Read more.

This research presents a method to improve data accuracy for the more efficient data management of the studied applications. The data accuracy was improved using the preciseness function learning model (PFL model). It contains a database in which the amount of data is more or less dependent on all of the possible behavior of the studied application. The proposed model improves data with functions obtained by optimizing curves to represent the data at each point, which estimate the database’s diffusion behavior, and functions can be built around all of the various forms of databases. The proposed model always updates its database after processing. It has been learning to optimize the processing precision. In order to verify the precision of the proposed model through its application to a PV system simulation model, the process’s database should contain at least one year. This is because the overall behavior of the PV power output in Thailand depends on the seasonal weather; Thailand has three seasons in a period of one year. The testing was performed by comparing the PV power output. The simulation results with the actual measurement data (12 MW PV system) can be divided into two conditions: the daily comparison and the seasonal PV power output. As a result, the proposed model can accurately simulate the PV power output despite the sudden daily climate change. The average nRMSE (normalized RMSE) of the proposed model is very low (1.23%), and ranges from 0.30% to 2.26%. Therefore, it has been proven that this model is very accurate. Full article

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2020

Jump to: 2024, 2023, 2021, 2019

21 pages, 5531 KB

Open AccessArticle

Theoretical Investigations of the BaRh₂Ge₄X₆ (X = S, Se, Te) Compounds

by Pascal Boulet and Marie-Christine Record

Energies 2020, 13(23), 6434; https://doi.org/10.3390/en13236434 - 5 Dec 2020

Viewed by 2050

Abstract

The thermoelectric (TE) properties of the BaM₂Ge₄X₆ compounds, where M = Rh and X = S, Se, Te, were investigated by computational approaches using density-functional theory and semi-classical Boltzmann theory for electronic transport. It was found that these [...] Read more.

The thermoelectric (TE) properties of the BaM₂Ge₄X₆ compounds, where M = Rh and X = S, Se, Te, were investigated by computational approaches using density-functional theory and semi-classical Boltzmann theory for electronic transport. It was found that these compounds bear good TE properties, in particular BaRh₂Ge₄Te₆, for which the figure of merit was estimated to reach 1.51 at 300 K. As this compound has not yet been proved to be stable, we also investigated BaRh₂Ge₄S₄Te₂ by assuming that replacing tellurium by sulphur could stabilize the tellurium-containing structure. It was found that the TE properties are good. The quantum theory of atoms in molecules was used to investigate the nature of the chemical interactions that prevail in these compounds. A wide variety of interactions were evidenced, from van der Waals interactions to ionic and polar-covalent ones, which could explain the good TE performance of these compounds. Full article

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20 pages, 6387 KB

Open AccessArticle

Structural, Optical and Photocatalytic Characterization of Zn_xCd_1−xS Solid Solutions Synthetized Using a Simple Ultrasonic Radiation Method

by Luis Fernando Morelos Medina, Rufino Nava, María de los Ángeles Cuán Hernández, Omar Said Yáñez Soria, Bárbara Pawelec, Rufino M. Navarro and Carlos Elías Ornelas Gutiérrez

Energies 2020, 13(21), 5603; https://doi.org/10.3390/en13215603 - 26 Oct 2020

Cited by 7 | Viewed by 3105

Abstract

A simple ultrasonic radiation method was employed for the preparation of zinc and cadmium sulfide solid solution (Zn_xCd_1−xS; x = 0–0.25 wt.%) with the aim to investigate its efficiency for H₂ production via a visible light-driven water-splitting reaction. [...] Read more.

A simple ultrasonic radiation method was employed for the preparation of zinc and cadmium sulfide solid solution (Zn_xCd_1−xS; x = 0–0.25 wt.%) with the aim to investigate its efficiency for H₂ production via a visible light-driven water-splitting reaction. The catalyst characterization by X-ray diffraction confirmed the formation of solid solution (Zn_xCd_1−xS) between CdS and ZnS phases. All catalysts exhibited hierarchical morphology (from SEM and TEM) formed by aggregated nanoparticles of Zn_xCd_1−xS solid solution with crystals showing mainly (111) planes of cubic CdS phase. The crystal size linearly decreased with an increase in Zn incorporation in the crystal lattice (from 4.37 nm to 3.72 nm). The Zn_xCd_1−xS photocatalysts showed a gradual increase in the H₂ evolution, with an increase in the Zn concentration up to 0.2 wt.% making the most effective Zn_0.2Cd_0.8S catalyst toward H₂ production. From the catalyst activity–structure correlation, it has been concluded that the twin-like CdS structure, the (111) plane and specific morphology are the main factors influencing the catalyst effectivity toward H₂ production. All those factors compensated for the negative effect of an increase in band gap energy (E_bg) after ZnS incorporation into solid solution (from 2.21 eV to 2.34 eV). The effect of the catalyst morphology is discussed by comparing H₂ evolution over unsupported and supported Zn_0.2Cd_0.8S solid solutions. Full article

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15 pages, 5991 KB

Open AccessArticle

Power Generation from Concentration Gradient by Reverse Electrodialysis in Anisotropic Nanoporous Anodic Aluminum Oxide Membranes

by Yunhyun Lee, Hyun Jung Kim and Dong-Kwon Kim

Energies 2020, 13(4), 904; https://doi.org/10.3390/en13040904 - 18 Feb 2020

Cited by 15 | Viewed by 4563

Abstract

In this study, reverse electrodialysis power generation using an anisotropic anodic aluminum oxide membrane with nanopores of two different pore diameters is proposed and experimentally investigated for the first time. A number of experiments were carried out for various combinations of concentrations to [...] Read more.

In this study, reverse electrodialysis power generation using an anisotropic anodic aluminum oxide membrane with nanopores of two different pore diameters is proposed and experimentally investigated for the first time. A number of experiments were carried out for various combinations of concentrations to show that the anisotropic anodic aluminum oxide membrane is superior to the conventional isotropic membrane. As a result, the highest power density that was measured from the anisotropic membrane was 15.0 mW/m², and it was 7.2 times higher than that from the isotropic membrane. The reasons why the anisotropic membrane is superior to the isotropic membrane are explained in detail. The experiments on the anisotropic membranes with various active layer lengths and pore diameters were also conducted for exploring the effects of these engineering parameters on the power generation performance. As a result, it was shown that the length of the active layer is a more important engineering parameter than the pore diameter of the active layer. Additionally, it was also shown that a low concentration solution should be brought into contact with the active layer side of the membrane whenever an anisotropic membrane is used for reverse electrodialysis. Full article

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10 pages, 2635 KB

Open AccessArticle

Properties of Thermally Evaporated Titanium Dioxide as an Electron-Selective Contact for Silicon Solar Cells

by Changhyun Lee, Soohyun Bae, HyunJung Park, Dongjin Choi, Hoyoung Song, Hyunju Lee, Yoshio Ohshita, Donghwan Kim, Yoonmook Kang and Hae-Seok Lee

Energies 2020, 13(3), 678; https://doi.org/10.3390/en13030678 - 5 Feb 2020

Cited by 22 | Viewed by 6000

Abstract

Recently, titanium oxide has been widely investigated as a carrier-selective contact material for silicon solar cells. Herein, titanium oxide films were fabricated via simple deposition methods involving thermal evaporation and oxidation. This study focuses on characterizing an electron-selective passivated contact layer with this [...] Read more.

Recently, titanium oxide has been widely investigated as a carrier-selective contact material for silicon solar cells. Herein, titanium oxide films were fabricated via simple deposition methods involving thermal evaporation and oxidation. This study focuses on characterizing an electron-selective passivated contact layer with this oxidized method. Subsequently, the SiO₂/TiO₂ stack was examined using high-resolution transmission electron microscopy. The phase and chemical composition of the titanium oxide films were analyzed using X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The passivation quality of each layer was confirmed by measuring the carrier lifetime using quasi-steady-state photoconductance, providing an implied open circuit voltage of 644 mV. UV–vis spectroscopy and UV photoelectron spectroscopy analyses demonstrated the band alignment and carrier selectivity of the TiO₂ layers. Band offsets of ~0.33 and ~2.6 eV relative to the conduction and valence bands, respectively, were confirmed for titanium oxide and the silicon interface. Full article

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2019

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10 pages, 3354 KB

Open AccessArticle

SiNW/C@Pt Arrays for High-Efficiency Counter Electrodes in Dye-Sensitized Solar Cells

by Junhee Kim, Sanghoon Jung, Han-Jung Kim, Yoonkap Kim, Chanyong Lee, Soo Min Kim, Donghwan Kim and Yongseok Jun

Energies 2020, 13(1), 139; https://doi.org/10.3390/en13010139 - 27 Dec 2019

Cited by 5 | Viewed by 3622

Abstract

Modern energy needs and the pressing issue of environmental sustainability have driven many research groups to focus on energy-generation devices made from novel nanomaterials. We have prepared platinum nanoparticle-decorated silicon nanowire/carbon core–shell nanomaterials (SiNW/C@Pt). The processing steps are relatively simple, including wet chemical [...] Read more.

Modern energy needs and the pressing issue of environmental sustainability have driven many research groups to focus on energy-generation devices made from novel nanomaterials. We have prepared platinum nanoparticle-decorated silicon nanowire/carbon core–shell nanomaterials (SiNW/C@Pt). The processing steps are relatively simple, including wet chemical etching to form the silicon nanowires (SiNWs), chemical vapor deposition to form the carbon shell, and drop-casting and thermal treatment to embed platinum nanoparticles (Pt NPs). This nanomaterial was then tested as the counter electrode (CE) in dye-sensitized solar cells (DSSCs). SiNW/C@Pt shows potential as a good electrocatalyst based on material characterization data from Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy shows that the surface reactivity of the SiNW/C is increased by the decoration of Pt NPs. These data also show that the carbon shell included both graphitic (sp

^{2}

hybridization) and defective (sp

^{3}

hybridization) phases of carbon. We achieved the minimum charge-transfer resistance of 0.025

Ω

· cm

^{2}

and the maximum efficiency of 9.46% with a symmetric dummy cell and DSSC device fabricated from the SiNW/C@Pt CEs, respectively. Full article

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10 pages, 5463 KB

Open AccessArticle

Anti-LID Process with a Remote Direct Heating Method Using a Half-Bridge Resonance Circuit for a PERC Solar Cell Module

by Soo Min Kim, Sanghoon Jung, Yoonkap Kim and Junhee Kim

Energies 2020, 13(1), 110; https://doi.org/10.3390/en13010110 - 24 Dec 2019

Cited by 30 | Viewed by 3107

Abstract

As the importance of the levelized cost of electricity (LCOE) increases in the solar cell industry, the demand for high-efficiency solar cells is rapidly increasing. Typically, p-type passivated emitter rear contact (PERC) solar cells are the most commonly used in the industry, and [...] Read more.

As the importance of the levelized cost of electricity (LCOE) increases in the solar cell industry, the demand for high-efficiency solar cells is rapidly increasing. Typically, p-type passivated emitter rear contact (PERC) solar cells are the most commonly used in the industry, and their efficiency is approximately 22–23%. P-type solar cells are reported to exhibit a light-induced degradation (LID) phenomenon, in which their output constantly decreases during power generation under solar radiation, and the output significantly reduces as their reference efficiency increases. Ultra-high-efficiency solar cells, which are on high demand, have a considerable output reduction due to the LID phenomenon; hence, technologies to prevent the LID phenomenon are required. However, research on this phenomenon has not been conducted because there is no method to transfer heat to solar cells inside the encapsulant when the modules are produced. In this study, a regeneration state was formed by remotely heating solar cells without damaging the encapsulant of the solar cell module. This was accomplished by using a heating method based on an induction magnetic field. A half-bridge resonance circuit was used to apply the induction magnetic field, and the temperature of the solar cell was controlled by adjusting the magnitude of the current flowing through the coil. To determine whether only the solar cell was heated, the temperature distribution inside the module was analyzed using an IR camera. The minority carrier lifetime was examined by real-time observation of the open-circuit voltage pattern of the solar cell. Finally, the observed real-time open-circuit voltage data were used, and dynamic simulation of the regeneration process was applied to analyze the LID activation energy generated in the regeneration process of the solar cell module. In conclusion, research was conducted on applying the regeneration state to prevent the LID phenomenon in the solar-cell-module stage, and the LID activation energy of the solar cell module was extracted. Based on this, a nondestructive degradation prevention technology for the solar cell module was developed. Full article

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26 pages, 5668 KB

Open AccessArticle

Numerical and Experimental Study on the Heat Dissipation Performance of a Novel System

by Cairui Yu, Dongmei Shen, Qingyang Jiang, Wei He, Hancheng Yu, Zhongting Hu, Hongbing Chen, Pengkun Yu and Sheng Zhang

Energies 2020, 13(1), 106; https://doi.org/10.3390/en13010106 - 24 Dec 2019

Cited by 6 | Viewed by 3188

Abstract

In order to better release the heat generated by the electronic components, a novel heat dissipation system is proposed, which combines a microchannel heat pipe (MHP) with a high thermal conductivity and a radiative plate with a high emissivity at nighttime. First, a [...] Read more.

In order to better release the heat generated by the electronic components, a novel heat dissipation system is proposed, which combines a microchannel heat pipe (MHP) with a high thermal conductivity and a radiative plate with a high emissivity at nighttime. First, a simple testing rig was made with an MHP and a radiative plate, where the radiative plate was made of acrylic resin, a curing agent, thinner, and aluminum plate, and had strong radiative cooling at nighttime. Second, the mathematical model was initially established and verified using experiments, where it was shown that the agreement between numerical and experimental data was well within experimental uncertainties. Comprehensive simulation investigations were conducted by varying wind speed, relative humidity, the cloudiness coefficient, dimension of the radiative plate, and tilted angle. The results show that: (1) the emissivity of the radiative plate was about 0.311 in the daytime and about 0.908 in the nighttime; (2) the influence of wind speed on reducing the component surface temperature was greater than the cloudiness coefficient and relative humidity; (3) the width of the radiative plate had a greater effect on heat dissipation than on its length, and the maximum size of radiative plate was recommended to be 400 mm × 400–500 mm (length × width), which was equipped with a single MHP (width: 60 mm). Additionally, the tilted angle of the radiative plate should be kept within 30° of the horizontal level. In conclusion, the novel heat dissipation system had a superior application value for providing assisted electronic component cooling in the nighttime. Full article

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11 pages, 2866 KB

Open AccessArticle

Hydrothermal Synthesis of Three-Dimensional Perovskite NiMnO₃ Oxide and Application in Supercapacitor Electrode

by Hyo-Young Kim, Jeeyoung Shin, Il-Chan Jang and Young-Wan Ju

Energies 2020, 13(1), 36; https://doi.org/10.3390/en13010036 - 19 Dec 2019

Cited by 66 | Viewed by 8847

Abstract

Supercapacitors are attractive as a major energy storage device due to their high coulombic efficiency and semi-permanent life cycle. Transition metal oxides are used as electrode material in supercapacitors due to their high conductivity, capacitance, and multiple oxidation states. Nanopowder transition metal oxides [...] Read more.

Supercapacitors are attractive as a major energy storage device due to their high coulombic efficiency and semi-permanent life cycle. Transition metal oxides are used as electrode material in supercapacitors due to their high conductivity, capacitance, and multiple oxidation states. Nanopowder transition metal oxides exhibit low specific surface area, ion diffusion, electrical conductivity, and structural stability compared with the three-dimensional (3D) structure. Furthermore, unstable performance during long-term testing can occur via structural transition. Therefore, it is necessary to synthesize a transition metal oxide with a high specific surface area and a stable structure for supercapacitor application. Transition metal oxides with a perovskite structure control structural transition and improve conductivity. In this study, a NiMnO₃ perovskite oxide with a high specific surface area and electrochemical properties was obtained via hydrothermal synthesis at low temperature. Hydrothermal synthesis was used to fabricate materials with an aqueous solution under high temperature and pressure. The shape and composition were regulated by controlling the hydrothermal synthesis reaction temperature and time. The synthesis of NiMnO₃ was controlled by the reaction time to alter the specific surface area and morphology. The prepared perovskite NiMnO₃ oxide with a three-dimensional structure can be used as an active electrode material for supercapacitors and electrochemical catalysts. The prepared NiMnO₃ perovskite oxide showed a high specific capacitance of 99.03 F·g⁻¹ and excellent cycle stability with a coulombic efficiency of 77% even after 7000 cycles. Full article

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13 pages, 4228 KB

Open AccessArticle

Binder-Free Centimeter-Long V₂O₅ Nanofibers on Carbon Cloth as Cathode Material for Zinc-Ion Batteries

by Lyn Marie De Juan-Corpuz, Ryan Dula Corpuz, Anongnat Somwangthanaroj, Mai Thanh Nguyen, Tetsu Yonezawa, Jianmin Ma and Soorathep Kheawhom

Energies 2020, 13(1), 31; https://doi.org/10.3390/en13010031 - 19 Dec 2019

Cited by 48 | Viewed by 6027

Abstract

Recently, rechargeable aqueous zinc-ion batteries (AZBs) have attracted extensive interest due to their safety, abundance, low cost, and low toxicity. However, aqueous electrolytes require a polymeric binder to prevent dissolution of the active material in addition to its binding properties. This study highlights [...] Read more.

Recently, rechargeable aqueous zinc-ion batteries (AZBs) have attracted extensive interest due to their safety, abundance, low cost, and low toxicity. However, aqueous electrolytes require a polymeric binder to prevent dissolution of the active material in addition to its binding properties. This study highlights binder-free, centimeter long, single-crystal, V₂O₅ nanofibers (BCS-VONF) on carbon cloth, as the cathode material for AZBs synthesized via a simple one-step hydrothermal process. BCS-VONF in 3.0 M Zn(OTf)₂ exhibit promising electrochemical performance with excellent capacity retention. Even in the absence of a binder, BCS-VONF were found to be very stable in 3.0 M Zn(OTf)₂. They will not yield to the dissolution and detachment of the active material on the current collector. The novel strategy described in this study is an essential step for the development of BCS-VONF on carbon cloth, as a promising cathode material for AZBs. Full article

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8 pages, 1584 KB

Open AccessArticle

Cost/Performance Analysis of Commercial-Grade Organic Phase-Change Materials for Low-Temperature Heat Storage

by Tomáš Hásl, Ivo Jiříček, Michal Jeremiáš, Josef Farták and Michael Pohořelý

Energies 2020, 13(1), 5; https://doi.org/10.3390/en13010005 - 18 Dec 2019

Cited by 14 | Viewed by 3697

Abstract

Alkanes are widely used as phase change materials (PCMs), especially for thermal energy storage (TES), due to their high thermal capacity, stability, availability, and non-corrosiveness. However, the drawbacks of alkanes are low heat conductivity and high cost. Our aim was to explore alternative [...] Read more.

Alkanes are widely used as phase change materials (PCMs), especially for thermal energy storage (TES), due to their high thermal capacity, stability, availability, and non-corrosiveness. However, the drawbacks of alkanes are low heat conductivity and high cost. Our aim was to explore alternative organic PCMs for TES and to compare such compounds based on the relationship between their performance and cost. For this purpose, we analysed several commercially available products, including long chain alkanes, alcohols, monocarboxylic acid, amines, ethers and esters in high purities. Differential scanning calorimetry and thermogravimetry (DSC and TGA) were used to measure the melting point, melting enthalpy and thermal stability of these compounds. The materials were classified according to their melting temperature. In order to compare the compounds, we calculated from the measured enthalpies and the price list provided by producers a coefficient that represents factors in both the performance and cost of the material. This method was used to identify the most suitable organic compound for thermal energy storage in each temperature range. As the main result of this work, it has been revealed that various organic compounds can be considered as a vital alternative to the alkanes in temperatures from −10 to 50 °C. On top of that, alcohols and carboxylic acids can cover the temperature range from 50 to 75 °C, which cannot be covered by alkanes. Full article

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11 pages, 3202 KB

Open AccessArticle

Adhesion-Increased Carbon Nanowalls for the Electrodes of Energy Storage Systems

by Hyeokjoo Choi, Seokhun Kwon, Hyunil Kang, Jung Hyun Kim and Wonseok Choi

Energies 2019, 12(24), 4759; https://doi.org/10.3390/en12244759 - 13 Dec 2019

Cited by 11 | Viewed by 3553

Abstract

Carbon nanowalls (CNWs), which are used as electrodes for secondary batteries in energy storage systems (ESSs), have the widest reaction surface area among the carbon-based nanomaterials, but their application is rare due to their low adhesion with substrates. Indium tin oxide (ITO), a [...] Read more.

Carbon nanowalls (CNWs), which are used as electrodes for secondary batteries in energy storage systems (ESSs), have the widest reaction surface area among the carbon-based nanomaterials, but their application is rare due to their low adhesion with substrates. Indium tin oxide (ITO), a representative transparent conducting oxide (TCO) material, is widely used as the electrode for displays, solar cells, etc. Titanium nitride (TiN) is a well-used material as an interlayer for improving the adhesion between two materials. In this study, ITO or TiN thin films were used as an interlayer to improve the adhesion between a CNW and a substrate. The interlayer was deposited on the substrate using a radio frequency (RF) magnetron sputtering system with a four-inch TiN or ITO target. CNWs were grown on the interlayer-coated substrate using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system with a mixture of methane (CH₄) and hydrogen (H₂) gases. The adhesion of the CNW/interlayer/substrate structure was observed through ultrasonic cleaning. Full article

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Advanced Materials for Energy Conversion and Storage Devices

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