Advanced Energy Conversion Materials

Evaporated Chalcopyrite Thin Films for Indoor Photovoltaic Applications

Cecilia Guillén — Tue, 05 Dec 2023 00:00:00 +0800

The feasibility of capturing indoor artificial light using chalcopyrite photovoltaic absorbers has been analyzed. For this purpose, various chalcopyrite compounds (CuInSe₂, CuInS₂ and CuGaS₂) were prepared by evaporation and then measured to obtain their main structural, morphological and optical characteristics. On the other hand, several artificial light sources were selected (incandescent, halogen, fluorescent, high-pressure sodium, metal halide and LED lamps) and represented by their respective spectral radiance. The absorption characteristics of CuInSe₂ and CuInS₂ are optimal for collecting light from fluorescent lamps and warm or cool white LEDs, requiring only a small film thickness of about 0.6 μm to capture 90-100% of the light radiance. Otherwise, the efficiency of CuGaS₂ is found to increase as the color temperature of the LED lamp increases, being always lower and more dependent on the film thickness than for the other evaporated compounds. The worst performances (collection of less than 50% of the light radiance) correspond to incandescent and halogen lamps, which have a significant emission in the infrared region outside the absorption range of the evaporated chalcopyrite films. These results provide guidelines for the design of chalcopyrite-based photovoltaic devices suitable for operation under different indoor lighting conditions.

Evaluation of Avocado Peels Dye as Sensitizer in Dye-Sensitized Solar Cells by Experiment and Computational Intelligence

Mon, 04 Dec 2023 00:00:00 +0800

This work was designed to evaluate the unmodified and modified natural dye obtained from a sensitizer in dye-sensitized solar cells using experimental and computational approaches. Natural dye (APPE) was extracted from Avocado pear (Persea Americana) peels and chemically modified into nanocomposite by a one-pot reaction with silver nitrate. The modified dye was characterized by UV-Vis spectroscopy, X-ray diffraction (XRD) spectroscopy, Energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The APPE and APPE-AgNPs composite show maximum wavelength of light absorption at 542 nm and 493 nm respectively. Both APPE and APPE-AgNPs were evaluated as sensitizers for dye-sensitized solar cells (DSSC). The APPE-AgNPs dye afforded a higher power conversion efficiency of 0.93% compared to 0.44% for APPE. Current-voltage responses and photo-electrochemical properties were determined at one sun illumination. The electronic properties of the major phyto-compounds in the dye, namely perseorangin and cyanidin associated with light harvesting and sensitization were modeled using a quantum chemical computational approach. The power conversion efficiency of APPE-AgNPs obtained from this study compares with other plant-based dye sensitizers and hence could be deployed for practical application.

Improvement of Polypropylene (PP)-Chitosan Nanoparticles (CNP) for Advanced Bio-Composite

Oluwaseun Adekoya Adelaja, Babafemi Raphael Babaniyi, Daniel Udorah — Thu, 25 Apr 2024 00:00:00 +0800

This study delves into the augmentation of polypropylene (PP) with chitosan nanoparticles (CNP) to develop bio-composites tailored for multifaceted applications, particularly in the context of environments. The investigation focuses on characterizing these composites concerning their structural, thermal, degradation, and electrochemical properties. Commercial polypropylene waste obtained from the Federal University of Technology, Akure (FUTA), underwent meticulous processing, converting it into pellets of varying sizes. Chitosan nanoparticles were derived from chitin, procured from a Lagos-based seafood company. These fillers were judiciously chosen for their ability to confer heightened conductivity, cost-effectiveness, biodegradability, and availability. The synthesis involved the preparation of nano-chitosan (CNP) through a method wherein chitosan powder underwent dissolution and subsequent reaction with Sodium Tri-Poly-Phosphate (TPP). Composite blends with different weight percentages of PP and CNP were formulated using a solvent casting method. Fourier Transform Infrared Spectroscopy (FTIR) was employed to discern surface functionalities in the PP/CNP bio-composites. The results revealed significant alterations in functional groups upon the introduction of chitosan nanoparticles into the PP matrix, suggesting chemical modifications within the composite structure. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) elucidated the thermal behavior of the composites, indicating a decrease in thermal stability with increasing CNP content. Water absorption tests displayed variances in absorption rates, with higher CNP content leading to escalated water absorption capabilities due to the hydrophilic nature of chitosan. Soil biodegradability assessments unveiled a direct correlation between chitosan content and degradation rates, evidencing enhanced biodegradability with higher concentrations of chitosan nanoparticles. Electrochemical measurements via Cyclic Voltammetry depicted a marked increase in specific capacitance with 30% CNP inclusion, signifying improved charge storage capabilities in the composite.

Energy Consumption Pattern and Performance Indices of Federal Medical Center, Jalingo, Nigeria

Muhammad Ahmad, Laaye Koliya, Ibraheem Shehu Diso — Tue, 19 Dec 2023 00:00:00 +0800

Energy audit in buildings is an effective energy management tool that seeks to identify all the energy end-users within the buildings under investigation, estimate how much energy is used by each end-user, and determine the amount of energy used in relation to the budgeted or designed values which leads to significant energy and cost saving in addition to direct benefits such as extending equipment life, reducing maintenance costs, increasing comfort, safety and productivity, all leading to enhanced profit and improved efficiency. This study carried out a walk through energy audit for electricity energy consumption from two sources, electricity from the national grid and diesel generators at the Federal Medical Centre Jalingo, Taraba State Nigeria, and covers a period of 10 years (2008-2017). The hospital has a total floor area of 163,823 square meters with a total bed capacity of 425 beds. It is located between latitude 8.8932° N and longitude 11.3590° E. Jalingo climate is typically hot and cool with distinct wet and dry seasons. The mean annual temperature is about 27.9 ℃, mean monthly ranges of maximum temperature range between 25.9 ℃ in December/January and over 36.7 ℃ in the hottest months (April/May). A study of energy consumption, with special consideration on the operation of the air conditioning systems, lighting, electrical equipment and medical equipment was carried out. The consumption pattern showed distinct seasonal variation indicating peak electricity demand during the hot humid summer months from April to August resulting in significant air conditioning requirements. 52.21% of electricity consumed was contributed by the burning of automotive gas oil (AGO) in the diesel power generator showing a greater contribution over that of electricity from the national grid of 47.79% and this is the general trend in most buildings/facilities in Nigeria. 40.44% of electricity was consumed by air conditioners due to high or significant air conditioner requirements, office equipment with 23.49% consumption rate, while medical machine and equipment, and lighting with 28.83% and 7.24%, respectively. The building yearly energy performance index determined for the whole hospital, operating theatres, outpatient department, and inpatient department was 229.726 kWh/m²/year, 412.349 kWh/m²/year, 160.790 kWh/m²/year, and 181.313 kWh/m²/year respectively. If all the proposed Energy Conservation Measures (ECMs) were implemented, it would give a total of 20.58% energy saving of the annual energy consumption.

Exploring the Interface Between Two Nanoclusters: Insights from Computational Methods

Divya Maldepalli Govindachar, Ganga Periyasamy — Tue, 19 Dec 2023 00:00:00 +0800

Aggregation of gold nanoclusters (GNCs) with desired properties requires detailed knowledge about the inter-cluster interface and its properties. The stability of [Au₆]₂ dimeric cluster configuration has been confirmed based on molecular dynamic simulation at 298 K temperature, 1 atm pressure, and water as solvent. The structural and electronic properties of series of monomeric and dimeric [Au₆]₂, [Au₆H]₂, [Au₆CH₃]₂, [Au₆C₂H₅]₂, [Au₆C₅H₉]₂, [Au₆C₆H₁₁]₂, [Au₆C₆H₅]₂, [Au₆C₆H₄CH₃]₂, [Au₆C₆H₄CH₃]₂, [Au₆C₂H]₂, [Au₆C₂CH₃]₂ and [Au₆C₂C₆H₅]₂ clusters were studied using three different functionals in density functional theoretical methods by considering three different interfaces. The dimerization was found to alter the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap depending upon the interface between the clusters. The computation predicts that the presence of ligand-ligand (ML-LM) and ligand-metal (ML-ML) interfaces in ligated cluster dimers were found to decrease the HOMO-LUMO gap while the metal-metal (LM-ML) interface leads to larger cluster formations. The change in electronic structures is found to be the reflection of symmetry in the eigenfunctions. The vertical plane of symmetry at the ML-LM interface leads to a smaller HOMO-LUMO gap as a result of degenerate orbitals between the monomeric units. The distortion from the reflection symmetry at the ML-ML interface removes the degeneracy by splitting the orbitals which increases the HOMO-LUMO gap in the ligated clusters. Among the studied ligated nanoclusters, experimentally realized [Au₆C₂C₆H₅]₂ possesses a small HOMO-LUMO gap. All the interfaces are found to behave similarly in the presence of various uniform electric fields. The consequences of HOMO-LUMO gaps were observed in redox parameters, and absorption properties and have been explained using molecular orbital plots.

Study on Structural Stability of ZrO₂ and YSZ: Doping-Induced Phase Transitions and Fermi Level Shift

Mon, 20 Nov 2023 00:00:00 +0800

This work summarizes the results of structural stability, electronic properties and phonon dispersion studies of biocompatible ZrO₂ compound in its cubic (c-ZrO₂), tetragonal (t-ZrO₂) and monoclinic (m-ZrO₂) phases. The authors found that the monoclinic phase of zirconium dioxide is the most stable among the three phases in terms of total energy, lowest enthalpy, highest entropy, and other thermodynamic properties. The presence of rather weak frequencies for m-ZrO2 also confirms the monoclinic phase as a stable conformation of zirconia. Our analysis of the electronic properties showed that during the m-t phase transformation of ZrO₂, the Fermi level first shifts by 0.125 eV toward higher energies and then decreases by 0.08 eV in the t-c cross-section. The band gaps for c-ZrO₂, t-ZrO₂, and m-ZrO₂ are 5.140 eV, 5.898 eV, and 5.288 eV, respectively. Calculations to study the effect of 3.23, 6.67, 10.35 and 16.15 mol%Y₂O₃ on the structure and properties of m-ZrO₂ showed that the enthalpy of m-YSZ decreases linearly and accompanies further stabilization of zirconium dioxide. Doping-induced phase transitions of ZrO₂ were discovered under the influence of Y₂O₃ doping, due to which the position of the Fermi level changes and the band gap decreases. It has been established that, not only for pure systems but including those doped with Y₂O₃, the main contribution to the formation of the conduction band is made by the p-states of electrons.

Development of Recycled Aluminum Alloy for the Manufacture of an Electrical Current-Conducting Tape

Wed, 13 Mar 2024 00:00:00 +0800

This research aimed to develop an electrical current-conducting tape using secondary aluminum (Al) obtained from recycled beverage cans. The gravity casting process was used, and Cu and Mg were added to assess the properties of the alloys. The evaluated alloys were from three groups of samples: (A) secondary Al; (B) Al-Cu; (C) Al-Cu-Mg. A homogenization process was applied to reduce the segregation of the heterogeneous structure of the cast ingots and to reduce the thickness of the tape to 0.5 mm, the cold rolling process was carried out. The samples were characterized by Vickers microhardness, tensile tests, hardening, anisotropy and electrical conductivity. After four lamination passes a reduction of 85.4% of the initial thickness was observed, reaching (0.59 ± 0.04) mm of final thickness. Subsequently to each lamination pass, the annealing process was applied to restore the material’s properties. The electrical conductivity presented results between 45.96 and 47.67 International Annealed Copper Standard (IACS), with a reduction of only 1.82% after lamination. Therefore, a tape with electrical conductivity and 0.59 mm thickness was obtained from recycled beverage cans aluminum. In addition, the characterization presented for the 3 samples will allow for the study of applications for these alloys and respective electrical conductive tapes.

Phase Engineering and Impact of External Stimuli for Phase Tuning in 2D Materials

Shahab Khan — Wed, 06 Dec 2023 00:00:00 +0800

Two-dimensional (2D) materials have captured the imagination of the scientific community for their remarkable properties and potential applications. To further harness the full spectrum of their capabilities, researchers have turned to phase engineering as a powerful tool. Phase engineering involves controlling and manipulating the structural and electronic phases of 2D materials, leading to a wide array of novel and tunable properties. In this comprehensive review, we investigate the exciting world of phase engineering in 2D materials. We start by providing detailed background on the emergence of 2D materials, highlighting their exceptional electronic, mechanical, and optical properties. We then explore the concept of phase engineering, elucidating its principles and significance in tailoring the behavior of 2D materials. Advanced field applications of 2D materials, such as sensing, water desalination, energy storage, and detection were also considered in this review article.