Acceptable Conversion Efficiency Research Articles

Valorization of process wastes from soft-wheat processing industry through biofuel production.

A substantial amount of process waste is generated during the manufacture of soft-wheat products (SWPs), such as biscuits/cookies, crackers, wafers, and cakes. A small portion of waste is reused in specific biscuits, whereas the rest is usually discarded. This study aimed to investigate the suitability of this waste for the co-production of bioethanol and fatty acid methyl esters (FAMEs or biodiesel). Two groups of waste generated in the SWP industry were included in the study: (a) the waste of low-moisture (<10%) biscuits, crackers, and wafer sheets with no fillings and/or coatings, and (b) the waste of high-moisture (>10%) biscuits, crackers, wafers, and cakes with fillings and/or coatings. The study involved extracting each sample with hexane, and the recovered fat was converted to the FAME through alkali-catalyzed transesterification. The remaining carbohydrate-rich fraction was then converted to bioethanol through amylolytic hydrolysis and yeast fermentation. A great portion (92.42%-93.17%) of the fat was extracted from the wastes and converted to the FAME with adequate yields (13.81-14.55g FAME/g waste, dm) and acceptable conversion efficiencies (85.19%-89.04%). However, bioethanol production from the defatted carbohydrate-rich fractions proceeded rather slowly, yielding only 16.54-18.02 (g ethanol per g of waste, dm), corresponding to fermentation efficiencies ranging from 43.32% to 48.29%. Upon the co-production of FAME and ethanol, a considerable amount (50.93%-53.08%) of waste solids remained in the residue fraction. These findings indicated that production of the FAME with adequate yields and conversion efficiencies is viable from the SWP industry wastes; however, bioethanol yields and fermentation efficiencies are rather limited, which warrants further investigation. PRACTICAL APPLICATION: The soft-wheat processing industry generates 1%-5% of total production as waste. The waste was studied to produce FAME and bioethanol. The fat was extracted from the waste and converted to FAME. Bioethanol yields and fermentation efficiencies are limited due to dough modifiers and antimicrobial additives used in SWP production. Further research is required to improve ethanol yield.

Influence of platinum on mordenite properties and catalytic activity towards cyclohexene epoxidation

The Pt-containing commercial mordenite catalyst that was synthesized having different Si/Al molar ratios (SAR) = 32, 40, and 50, and it was applied in the epoxidation reaction of cyclohexene. The samples were analysed and confirmed by various physicochemical techniques in powder X-ray diffraction (XRD) for identifying phases and planes, Brunauer-Emmett-Teller (BET) for determining textural properties, Fourier-transform infrared spectroscopy (FT-IR) for distinguishing functional groups, high resolution scanning electron microscopy (HR-SEM) for finding morphology, temperature-programmed desorption (TPD) to determine stability, and transmission electron microscopy (TEM) to identify microstructural details. The catalysts were tested for cyclohexene epoxidation reaction in the presence of H2O2as oxidant and acetonitrile as solvent. In this work, cyclohexene maximum conversion and selectivity is obtained with Pt/mordenite (40%) catalyst among the catalysts investigated. The conversion of cyclohexene oxidation recyclability of the Pt/Mordenite (40%) reveals reasonably acceptable conversion efficiency after six cycles, and the catalyst is found to be most suitable for an industrial production application.

Catalytic renovation of non‐edible oil to biodiesel production through sulfated Mg‐Al 2 O 3 (10) catalysts

Magnesium-alumina (Mg-Al2O3) composite was synthesized by sol-gel method. The SO42− catalyst supported Mg-Al2O3 was prepared by three different methods such as solution, hydrothermal, and vapor phase. The as-synthesized materials were characterized by different physicochemical techniques. The acid sites of Mg-Al2O3 (10) composite were enhanced by depolymerization of triglyceride (jojoba oil) to produce free FFA. Catalyst prepared by hydrothermal methods exhibits high acid sites of 3.44 mmol g−1 of NH3. Sulfidation of catalysts play a vital role in the catalytic conversion of jojoba oil by methanol activation. SO42−/Mg-Al2O3 (10) catalyst reveals 99% conversion efficiency tested under optimized conditions of jojoba oil to methyl ester (biodiesel). TGA result confirmed the S2/Mg-Al2O3 (10) catalyst is stable upto 800°C and weight loss of 19.2%. The recyclability of the S2/Mg-Al2O3 (10) catalyst reveals reasonably acceptable conversion efficiency after sixth cycle and this catalyst is found to be suitable for the industrial biodiesel production.

Dual‐band CPW rectenna for low input power energy harvesting applications

A dual-frequency band low input power rectenna is proposed in this study. The rectenna is comprised of a co-planar waveguide (CPW) rectifier integrated with a rectangular split ring antenna loaded by a spiral strip line. A single diode series connection topology is used to miniaturise the losses at low input power. A spiral coil in addition to two short circuit stubs are used as a matching network for maximum power transfer between the antenna and the rectifying circuit. The proposed rectenna operates at low input power with relatively high measured RF-DC conversion efficiency up to 74 % at input power of − 6.5 dBm at the first resonant frequency f 1 = 700 MHz and 70 % at − 4.5 dBm at the second operating frequency f 2 = 1.4 GHz with a resistive load of 1.9 k Ω . The measured rectenna sensitivity (the rectenna ability to receive low power with acceptable conversion efficiency) reaches up to − 20 dBm with a conversion efficiency of 47 and 36 % at f 1 and f 2 , respectively, and a DC output voltage of 0.18 V . The measured efficiency is over 50 % from − 18 to − 3.5 dBm and from − 15 to − 1.5 dBm at f 1 and f 2 , respectively.

A Highly Stable All‐Inorganic CsPbBr3 Perovskite Solar Cell

In recent years, the instability of hybrid organic‐inorganic halide perovskite solar cells (PSCs) has been an important challenge. The issue of the destruction as well as a carrier density stability of the perovskite must be addressed to simultaneously achieve the long lifetime of PSCs and acceptable conversion efficiency. Present study aims to address these issues by using all‐inorganic CsPbBr3 perovskite as a light absorber material. Through a simulation process, the perovskite thickness was optimized yielding the highest power conversion efficiency (PCE) of a device reaching 4.04 %. After storage for 3 months at room temperature with a humidity of 20 % and under illumination of AM 1.5 G, only 35 % loss in PCE was observed, indicating a promising stability of the fabricated CsPbBr3‐based devise.

DC–DC Boost Converter With a Wide Input Range and High Voltage Gain for Fuel Cell Vehicles

In fuel cell vehicles, the output voltage of the fuel cell source is typically much lower than the voltage required by the dc bus, and also this output voltage drops significantly as the output current increases. In order to match the output voltage of the fuel cell source to the dc bus voltage, a new dc–dc boost converter with a wide input range and high voltage gain is proposed to act as the required power interface, which reduces voltage stress across the power devices and operates with an acceptable conversion efficiency. A prototype rated at 300 W/400 V has been developed and the maximum efficiency of the proposed converter was measured as 95.01% at 300 W. Experimental results are presented to validate the effectiveness of the proposed converter.

Exergy-based sustainability analysis of a low power, high frequency piezo-based ultrasound reactor for rapid biodiesel production

In this work a thermodynamic model was developed to attain enhanced process comprehensionof waste cooking oil (WCO) transesterification process in a low power, high frequency piezo-based ultrasound reactor. The reactor performance was assessed using the exergy concept to distinguish the effects of various operational variables, i.e., methanol to oil molar ratio (4:1–8:1), ultrasonic irradiation time (6–10min), and temperature (40–60°C) on the efficiency and sustainability factors. The exergetic efficiency of the developed reactor was found to be ranging from 98% to 99% and from 9% to 91% using the universal and functional definitions, respectively. The maximum functional exergetic efficiency as a decision making parameter, was found at 91% for methanol to oil molar ratio of 6:1, ultrasonic irradiation time of 10min, and temperature of 60°C. The exergetic sustainability index of the transesterification process at the selected conditions was determined at about 11. Under these conditions, the reactor efficiently converted triglycerides to methyl esters with an acceptable conversion efficiency of 97%, satisfying the ASTM standard. Overall, the outcomes of the current survey manifested that exergy analysis can be a preferred basis for decision making on the efficiency and sustainability of various biodiesel synthesizing systems.

Numerical analysis of broadband second harmonic generation using TIR-QPM in a parabolic profiled isotropic semiconductor slab

We report second harmonic generation (SHG) with a flat wide bandwidth accompanied by good conversion efficiency in an isotropic semiconductor slab with a parabolic upper profile. The concept of SHG conversion stands on the principle of total internal reflection quasi-phase matching (TIR-QPM). A simulation has been performed using GaAs as the non-linear material, in the fundamental wavelength range of 6.8–10.8μm, considering ppp polarization configuration. Optimized simulation results, after considering reflection and absorption losses, show a flatter bandwidth of 642nm in a 36mm slab in comparison to a dipped 3dB bandwidth of 770nm in an elliptically profiled isotropic slab as well as a steeper bandwidth of 187nm in a tapered isotropic slab. The present simulation shows an acceptable conversion efficiency of 1.105%.

Computer simulation of a downdraft wood gasifier for tea drying

A gasifier has been fabricated in Sri Lanka for the tea industry, but there is a lack of knowledge of the effect of certain key operating parameters and design features on its performance. Experimental testing of the design under various conditions has produced data that has then been used to calibrate a computer program, developed to investigate the impact of those parameters and features on conversion efficiency. The program consists of two sub-models of the pyrolysis and gasification zones, respectively. The pyrolysis sub-model has been used to determine the maximum temperature and the composition of the gas entering the gasification zone. The gasification zone sub-model has been calibrated using data gathered from the experiments. It was found that a wood chip size of 3– 5 cm with a moisture content below 15% (d.b.) should be used in this gasifier. Feed material with a fixed carbon content of higher than 30% and heat losses of more than 15% should be avoided. For the above parameters, the gasification zone should be 33 cm long to achieve an acceptable conversion efficiency.

Characterization of New Excimer Pumped UV Laser Dyes 3. P-Quinqui-, Sexi-, Octi- and Deciphenyls

The spectroscopic and lasing characteristics of a series of 308 nm pumped p-oligophenylenes with five or more phenyl rings have been studied. Quantitative comparisons of the absorption spectra of these dyes with numerous other dyes in this class of compounds can be made by defining a parameter, theta, as the sum of the number of phenyl rings and the number of ring-bridges. Statistically good linear regressions result from the correlations of molar extinction with theta and from wavelength of absorbance with the reciprocal of theta. We find that these correlations provide good predictive information in deciding which dyes to attempt to synthesize for testing. The lasing characteristics of the dyes studied show that these dyes are amongst the best dyes in this class of dyes. Some of these dyes have exceptionally long lifetimes coupled with acceptable conversion efficiencies.

Developmental experiments on large-area silicon solar cells

A comprehensive design/material/technological study was conducted with the aim of obtaining high-efficiency back-surface-field- (BSF-) type bifacial solar cells with reproducible parameters on large-area n- and p-silicon wafers. Practical ways of attenuating the severe limitations imposed by different kinds of areal inhomogeneities on the electro-optical performance of large-area BSF single-crystal silicon solar cells are described and tested experimentally. Various procedures leading to a substantial increase of both the emitter and the base contributions to the generated photocurrent are implemented and discussed in detail. The p+-n-n+ and n+-p-p+ cells were processed as bifacial devices and tested under both front and backside AM1 illumination. The trial devices were fabricated on 2-in and 3-in. commercially available lower-grade silicon and the minimization of the cell cost was one of the sought-after objectives. The combination of simple design/technological approaches described in this work has ultimately led to the development of low-cost, high-efficiency (17%–18%) large-area silicon solar cells with good overall electro-optical performance as bifacial devices. The results of this work show clearly that simple, but adequately designed/processed cells fabricated on an industrial scale on large-area silicon wafers could possess parameters similar to those of sophisticated laboratory samples elaborated on small-area silicon. With the design/technological approaches outlined in this work, the use of even cheaper, i.e., lower-grade single-crystal silicon, could still yield 2- and 3-in. cells with fairly acceptable conversion efficiencies.

Design/technological experiments on low cost, BSF-type, bifacial solar cells fabricated on large-area silicon wafers

A comprehensive design/material/technological study was conducted with the aim of obtaining high-efficiency, back-surface-field (BSF)-type bifacial solar cells with reproducible parameters on large-area n- and p-silicon wafers. Practical ways of attenuating the severe limitations imposed by different kinds of material (areal) inhomogeneities on the electro-optical performance of large-area BSF single-crystal silicon solar cells are described theoretically and tested experimentally. Various procedures leading to a substantial increase of both the emitter and the base contributions to the generated photocurrent are implemented and discussed in detail. Both p + −−n + and n +−p−p + cells were processed as bifacial devices and tested under both front and backside AM1 illumination. The test devices were processed on 2-in. commercially-available silicon and the minimization of the cells' cost was one of the sought-after objectives. The combination of simple design/material/technological approaches described in this work has ultimately led to the development of low-cost, high-efficiency (17–18%) 2-in. silicon solar cells with good overall electro-optical performance as bifacial devices. The results of this work show clearly that simple, but adequately designed/processed cells fabricated on industrial scale on large-area (2-in.) silicon wafers could possess parameters similar to those of sophisticated laboratory samples elaborated on small-area silicon chips. With the outlined design/technological approaches, the use of even cheaper, i.e., lower-grade, single-crystal silicon could still yield 2-in. cells with fairly acceptable conversion efficiencies.

Monolithic Integration of a Dielectric Millimeter-Wave Antenna and Mixer Diode: An Embryonic Millimeter-Wave IC

A monolithic silicon integrated circuit consisting of a mixer diode and an all-dielectric receiving antenna has been built and tested at 85 GHz. Radiation is coupled into the device optically with a coupling loss of 2.7 dB. No external metal structure is required for coupling. The design can be used efficiently at considerably higher frequencies, and can be elaborated into more complex integrated circuits. From measurements of video responsivity the losses of various parts of the device are estimated. A simple theory of conversion efficiency is found to agree well with experiment this theory is then used to predict the performance of improved versions of the device. The conversion efficiency obtained with this demonstration device is low; it is shown, however, that acceptable conversion efficiencies can be obtained with a more advanced diode fabrication technology using epitaxial Si or GaAs. Integrated millimeter-wave receivers of this kind should be suitable for short-path terrestrial communications, in applications where compactness and low cost are required.

High-Efficiency Selenium Photovoltaic Solar Cells

Selenium thin layer solar cells have been fabricated in an ITO–Se structure. The cells exhibit an acceptable conversion efficiency of about 2.5 percent under AMI illumination, with an open-circuit voltage of 0.5 V, a short-circuit current density of 10 mA/cm2, and a fill factor of 0.5. The photovoltaic performance makes a very good comparison with that of ordinary selenium cells.