Efficient Conversion Process Research Articles

Enhancing solar water evaporation with activated carbon

Fresh water production through sustainable approaches such as solar thermal sources is attracting widespread attention. One of the recently developed approaches aims at utilizing black particles to enhance evaporation and steam generation through efficient photo-thermal conversion process in direct solar thermal desalination systems. Activated carbon serves as one such material for meeting the objectives of freshwater production with negligible increments in cost of the overall system. A series of chemical and physical characterizations were performed to explore the possibility of using activated carbon as a stable carbon source. Optical characterization showed granular activated carbon to have 96.35% solar absorptance and its dispersion in water to have less than 1.5% transmittance (absorbance of 1.85) at 100 mg/L concentration. Outdoor experiments were performed at the University of California-Merced in the month of September (2019), with peak irradiation of 0.8 suns. The comparative measurements showed that the total evaporation enhancement was 38% and 100% for granular activated carbon and activated carbon dispersions, respectively, when compared to pure DI water.

Conductive-radiative heat transfer within SiC-based cellular ceramics at high-temperatures: A discrete-scale finite element analysis

Cellular ceramic materials possess many favorable properties that allow to develop efficient modern-day high-temperature thermal energy conversion systems and processes. The energy conversion within these porous media is governed by tightly coupled conduction–radiation physics. To efficiently design and optimize these systems, a comprehensive understanding of the conduction–radiation behavior within these materials becomes important. In this study, by performing large-scale numerical experiments, we analyze the conduction–radiation coupling characteristics within different (with respect to topology and porosity) silicon carbide (SiC)-based open-cell cellular ceramics surrounded by fictitious vacuum up to temperatures of 1800 K. To induct minimal approximations, our finite element simulations are based on a discrete-scale approach within which realistic discrete (pore-level) representations of the cellular ceramics are used as numerical media. The results presented in this study provide means to better understand the role of radiation in the coupled conduction–radiation physics within the ceramic samples. A detailed comparison on effectiveness of energy conversion is established for SiC-based full-scale cubic-cell, Kelvin-cell, and pseudo-random-cell ceramic structures which are at 80% and 90% porosity each. In conclusion, among the different standalone and full-scale ceramic samples, the Kelvin-cell structures at 90% porosity have proven to benefit the most from radiation coupling.

Transparent planar indium tin oxide for a thermo-photovoltaic selective emitter

Designing an efficient emitter design is an important step for achieving a highly efficient TPV conversion process. Wavelength-selective emissivity, spectra match between the emitter and TPV cells, and high thermal stability are three main characteristics that must be considered before implementing the emitter. In this work, an indium tin oxide (ITO)/sapphire emitter structure is investigated for TPV application over the temperature range from 200°C to 1000°C. A 1-µm-thick ITO layer is deposited on a 650-µm-thick sapphire substrate. In addition, 50-nm-thick SiO2 is deposited on top of the ITO to enhance the performance of emitter at high temperatures. High-temperature emissivity and absorptivity measurement of the emitter samples are obtained using FTIR and a Hitachi U-4100 spectrophotometer, respectively. The resultant SiO2/ITO/sapphire/stainless-steel planar emitter structure has selective emission with high emissivity of ∼0.8 in the 1–1.6 µm wavelength regime at 1000°C. This emission range lies at the bandgap edge of silicon TPV cells and thus can be used to harness the true potential for making a low-cost thermophotovoltaic system.

Effect of Argon Concentration on Laminar Burning Velocity and Flame Speed of Hydrogen Mixtures in a Constant Volume Combustion Chamber

Abstract Hydrogen combustion, coupled with the use of argon as a working fluid, is a promising approach to delivering clean and efficient energy from internal combustion (IC) engines. The use of hydrogen-oxygen-argon (H2/O2/Ar) mixtures in combustion aids in mitigating harmful environmental pollutants and enables a highly efficient energy conversion process. The use of argon as a working fluid decreases the NOx emissions and increases the thermal efficiency of internal combustion engines due to the high specific heat ratio of noble gases. In this study, premixed hydrogen combustion was investigated with the purpose of examining the effect of the full or partial substitution of argon for nitrogen in air on laminar burning velocity (LBV), flame speed, flame morphology, and instability. The experimental approach uses an optically accessible constant volume combustion chamber (CVCC) with central ignition; the spherical flame development was studied using a high-speed Z-type Schlieren visualization system. Moreover, a numerical model was developed to convert the experimental dynamic pressure rise data to laminar burning velocity. Coupling the model to a chemical equilibrium code aids in determining the burned gas properties. Additionally, an image processing technique has been suggested to compute the flame propagation speed. The experimental and numerical investigations indicate that increasing the concentration of argon as the working fluid in the mixture increases the laminar burning velocity and flame speed while extending the lean flammability limit.

Valorization of acai bio-residue as biomass for bioenergy: Determination of effective thermal conductivity by experimental approach, empirical correlations and artificial neural networks

Current concerns about the depletion of fossil fuels and global warming led to new policies put into place for the use of agro-industrial residues as biomass for thermochemical conversion. Acai berry residues are large-scale agro-industrial by-products that can be used in the production of bioenergy. Biomass effective thermal conductivity is one of the parameters that affect efficiency in the bioenergy process. Once research about acai berry residues as biomass for bioenergy is in its initial stages, prior determination of thermal conductivity may help future optimization studies towards high process efficiency and low operating and capital costs. In this work, it is shown that a simple experimental approach, together with a simple neural model, may allow initial assessment regarding reactor throughput and process cost. This is the main contribution of this work. Results from physical characterization, thermogravimetric analysis, and differential scanning calorimetry of the biomass were reported and discussed. Effective thermal conductivity as a function of moisture content and heating rate was experimentally determined by the line heat source method and predicted by artificial neural networks, empirical correlations proposed by literature, and multiple linear regression analysis. Four values of biomass moisture content were studied, 30.97%, 25.94%, 18%, and 11.86% (wet basis) and two values of heating rate, 4.16 and 16.74 W⋅m−1. The experimental values lay in the range 0.136–0.325 W⋅m−1·K−1, typical for common biomass and insulation materials. Such low values are not interesting for reactor design purposes since the dynamics of the thermochemical conversion is less effective. This leads to lower reactor throughput, which must be compensated by increasing reactor effective volume, translating to high capital and process costs. The findings obtained in this work have shown that thermal conductivity can be simply improved by increasing the heating rate. The developed neural model, which was superior to empirical correlations and multiple linear regression, accurately predicted experimental values outside the database. Simulation results have shown that artificial neural networks are a potential tool to provide means for understanding the influence of biomass properties and process conditions on a reactor design parameter like thermal conductivity. A simple neural model may contribute to the optimization and design studies towards efficient thermochemical conversion processes of acai berry residues, which may help to provide a proper destination to those by-products.

Power-to-chemicals: Low-temperature plasma for lignin depolymerisation in ethanol

Lignin valorisation into renewable fuels and platform chemicals is desirable but still encounters major challenges due to lignin’s recalcitrant structure, and the lack of cost-, energy-, and material efficient conversion processes. Herein, we report a low-temperature plasma-based route to lignin depolymerisation at mild conditions. The discharge over ethanol surface locally creating a high-energy and reactive environment rich in free electrons, energetic H radicals, and other reactive species, is well suited for lignin depolymerisation. Furthermore, assisted with a Fenton reaction (by adding Fe2O3 and H2O2) to sustain a more oxidative environment, the lignin conversion yield increases from 42.6% to 66.0%. Thus-obtained renewable chemicals are rich in aromatics and dicarboxylic acid derivatives. The proposed strategy on intensifying reactive chemistry by high-power plasmas enables an effective power-to-chemicals conversion of lignin and may provide useful guidelines for modern biorefineries.

Plasma frequency demand for mode conversion processes from slow Z-mode to LO-mode waves in an inhomogeneous plasma

The mode conversion process responsible for radio wave generation has been studied for several decades; however, the properties of the condition required for an efficient conversion process are still unknown. The aim of this study is to determine the value of plasma frequency required for an efficient mode conversion process from slow Z-mode to left-hand ordinary (LO)-mode waves in the matching cases, where the two branches of the dispersion relation of the two modes are perfectly connected. We derive the dispersion relations for electromagnetic wave propagation in an inhomogeneous plasma considering Snell’s law and investigated them in detail. We quantify the minimum variation of plasma frequency required for the efficient mode conversion process, which we call “the plasma frequency demand.” We show that the condition required for the efficient mode conversion can be satisfied by waves propagating first toward the high-density region and then returning toward the low-density region before reaching the region where the wave frequency matches the cutoff frequency; therefore, a large inhomogeneity is not always required. We show that the angle between the background magnetic field and the density gradient has a significant effect on the plasma frequency demand.

Reddish GaN:ZnO photoelectrode for improved photoelectrochemical solar water splitting.

Efficient light harvesting is one of the key prerequisites in improving the solar conversion efficiency for photoelectrochemical water splitting. As classic semiconductors for water splitting, the solid state solution GaN:ZnO based photoanodes exhibit poor water splitting efficiency mainly limited by its light absorption. To overcome this bottleneck, here we report that phosphorus modification shifts the absorption edge of GaN:ZnO from 480 nm to the red end of 650 nm and also leads to one order of magnitude increase of the carrier concentration. Further, taking the surface phosphate groups as anchors, cobalt can be adsorbed, leading to the in situ formation of cobalt phosphate as a cocatalyst for water oxidation, which results in drastically improved photocurrent density and stability. This work highlights the significance of phosphorization treatment in extending the light harvest and changing the surface reaction kinetics for an efficient solar conversion process.

The Potential of Non-thermal Plasmas in the Preparation of Supported Metal Catalysts for Fuel Conversion in Automotive Systems: A Literature Overview

The worldwide growing demand for energy and the extensive use of fossil fuels have resulted in severe environmental problems such as air pollution and the accumulation of greenhouse gases in the atmosphere. In this scenario, both new energy sources and more efficient energy conversion processes have been deeply studied. Heterogeneous catalysis is currently widely used for hydrogen production due to its higher selectivity and conversion compared to other processes. Although the use of catalysts is fundamental for green chemistry, their production through traditional methods is not. Nonetheless, in order to obtain more efficient supported metal catalysts, the interest of using non-thermal plasma as a pretreatment or synthesis technique is increasing. Thus, the present article aims at summarizing and briefly discuss the relevant research results on this subject, elucidating the advantages and disadvantages of using non-thermal plasmas in the preparation of supported metal catalysts. Aspects such as morphology, the chemical composition of the catalytic surface, crystallographic phases, average size and dispersion of crystallites, specific surface area and metal-support interaction were analyzed. The use of plasma assisted techniques contributes to the synthesis of supported metal catalysts with smaller, more dispersed and strongly bonded active particles, resulting in higher catalytic activity, conversion rate, selectivity and durability. In addition, the plasma allows to enhance the synthesis of supported metal catalysts, by reducing the process time, the use of hazardous substances and the temperature required.

Motion Planning for Convertible Indoor Scene Layout Design

We present a system for designing indoor scenes with convertible furniture layouts. Such layouts are useful for scenarios where an indoor scene has multiple purposes and requires layout conversion, such as merging multiple small furniture objects into a larger one or changing the locus of the furniture. We aim at planning the motion for the convertible layouts of a scene with the most efficient conversion process. To achieve this, our system first establishes object-level correspondences between the layout of a given source and that of a reference to compute a target layout, where the objects are re-arranged in the source layout with respect to the reference layout. After that, our system initializes the movement paths of objects between the source and target layouts based on various mechanical constraints. A joint space-time optimization is then performed to program a control stream of object translations, rotations, and stops, under which the movements of all objects are efficient and the potential object collisions are avoided. We demonstrate the effectiveness of our system through various design examples of multi-purpose, indoor scenes with convertible layouts.

A Bifunctional Electroactive Ti4O7-Based Membrane System for Highly Efficient Ammonia Decontamination

Herein, an electroactive filtration system, consisting of a Ti4O7 anode and a Pd-Cu co-modified nickel foam cathode, was developed and applied for the decontamination of ammonia from water. When assisted with an external electrical field, ClO• was generated on the surface of the Ti4O7 anode, which then reacted selectively with ammonia to generate N2. The anodic byproduct, NO3−, could also be reduced efficiently at the functional cathode to produce N2 as well. Electron paramagnetic resonance technique and radical scavenging tests synergistically verified the essential role of ClO• during the highly efficient ammonia conversion process. Relative to conventional batch systems, the developed flow-through design demonstrated enhanced ammonia conversion kinetics, thanks to the convection-enhanced mass transport. The proposed technology also showed desirable stability across a wide environmental matrix. This work provides new insights for the development of advanced and affordable continuous-flow systems towards effective decontamination of ammonia.

Thermal conversion of biomass: a comparative review of different pyrolysis processes

Biomass has been worldwide seen as a promising solution for meeting the increasing energy demands of a growing population, replacing fossil fuels in whole or in part, and achieving sustainable development. The use of biomass as an energy source is done through various conversion routes such as combustion, gasification and pyrolysis. Pyrolysis is a simple and efficient thermochemical conversion process to obtain energy from biomass and generate high energy density products. These technologies used for energy utilization are distinguished according to the characteristics of the biomass and product, process efficiency, amount of oxidant used, temperature and rate of heating, among others. The technical and scientific knowledge of biomedical thermochemical conversion options is a fundamental step both for academic researchers who aim to investigate these technologies to improve and optimize these processes, and for entrepreneurs who aim to implement biorefineries in the market. In this context, this work aimed to review the latest pyrolysis technologies, discussing the characteristics and the main variables of this technology.

Development of sustainable approaches for converting the organic waste to bioenergy

Dependence on fossil fuels such as oil, coal and natural gas are on alarming increase, thereby causing such resources to be in a depletion mode and a novel sustainable approach for bioenergy production are in demand. Successful implementation of zero waste discharge policy is one such way to attain a sustainable development of bioenergy. Zero waste discharge can be induced only through the conversion of organic wastes into bioenergy. Waste management is pivotal and considering its importance of minimizing the issue and menace of wastes, conversion strategy of organic waste is effectively recommended. Present review is concentrated on providing a keen view on the potential organic waste sources and the way in which the bioenergy is produced through efficient conversion processes. Biogas, bioethanol, biocoal, biohydrogen and biodiesel are the principal renewable energy sources. Different types of organic wastes used for bioenergy generation and its sources, anaerobic digestion-biogas production and its related process affecting parameters including fermentation, photosynthetic process and novel nano-inspired techniques are discussed. Bioenergy production from organic waste is associated with mitigation of lump waste generation and its dumping into land, specifically reducing all hazards and negativities in all sectors during waste disposal. A sustainable bioenergy sector with upgraded security for fuels, tackles the challenging climatic change problem also. Thus, intensification of organic waste conversion strategies to bioenergy, specially, biogas and biohydrogen production is elaborated and analyzed in the present article. Predominantly, persistent drawbacks of the existing organic waste conversion methods have been noted, providing consideration to economic, environmental and social development.

Green and efficient two-step degradation approach for converting Powder River Basin coal into fuels/chemicals and insights into their chemical compositions

A green and efficient two-step degradation approach, including supercritical CO2/ethanol degradation and oxidation in aqueous hydrogen peroxide solution, was reported to convert Powder River Basin coal into fuels/chemicals. In total, 43.5 wt% liquid tar and 23.3 wt% oxidation products were obtained from the two-step degradation. The liquid tar was facilely separated into light oil and asphaltene, with yields of 27.3 wt% and 16.5 wt%, respectively. The first-step degradation has high energy recovery (50%) and low energy consumption ratio (minimum 0.17), indicating an energetic net energy gain. The light oil is a promising feedstock as clean liquid fuels due to its high H/C ratio (1.58) and heating value (34.56 MJ/kg). The asphaltene with lower H/C and O/C ratios but higher aromaticity (0.83) could be a good precursor for carbon materials. The light oil can be upgraded into clean liquid fuels by hydrodeoxygenation or used as feedstock for producing oxygenated chemicals because it is rich in oxygenated components. Phenols and aliphatic esters account for 74.2% of the volatile components in the light oil. High resolution mass spectrometric analysis revealed that the O1–O4 class species are dominant components with relative abundance of 71% in the light oil. Valuable carboxylic acids with total yields of 19.7 wt%, especially alkanedioic and alkanetricarboxylic acids, were produced from oxidation of the scCO2/ethanol degradation residue, which is a promising second-step degradation to utilize the residue. This study provides an efficient coal conversion processes for producing fuels/chemicals and reducing energy consumption and environmental impact.

Three-dimensional numerical simulation of hydrogen production from coke oven gas reformer

The non-catalytic partial oxidation process is a simple and efficient gasification furnace conversion process. In this paper, a three-dimensional numerical simulation of a coke oven gas reforming furnace is carried out. This calculation uses the component transport model to simulate the combustion reaction in the furnace. The reason for the reactor is GRI-Mech 3.0. The calculation results show that when the syngas stays in the furnace for a short period of time, the increase of pressure is beneficial to the conversion of methane, and the H2/CO ratio will increase slightly with the increase of pressure.

Molecular design of novel indacenodithiophene‐based organic dyes for efficient dye‐sensitized solar cells applications

AbstractIndacenodithiophene (IDT)‐based high‐efficiency photovoltaics have received increasing attention recently. This paper reports a density functional theory investigation of the electronic and optical properties of three IDT‐based organic dyes together with the dye/(TiO2)46 interface. In order to enhance the photoelectric properties of IDT dyes, this paper considers two methods for the structure modification of the experimentally reported dye DPInDT (J. Org. Chem. 2011, 76, 8977): the extension of the conjugation length by dithienothiophene as well as the heteroatom substitution of the bridging atoms by electron‐rich nitrogen atoms. Our calculations show that both methods obviously affect the distributions of the molecular orbitals and notably red shift the absorption peaks of around 20 nm, with the former method demonstrating enhanced light harvesting efficiency. The structure modifications proposed also enhance the emission spectrum properties for IDT‐based organic dyes. The calculated ultrafast injection time of electrons from the excited state of IDT dyes to the (TiO2)46 belongs to the femtosecond order of magnitude, and is ideal for efficient photoelectric conversion process in dye‐sensitized solar cells (DSSCs) applications. The IDT dyes designed in this paper have good electronic and spectroscopic properties. This study is expected to provide useful guidance for the development of novel IDT dyes for applications in DSSCs.

Antioxidant and phytoestrogenic activities of puffed black soybeans (Glycine max)

Black soybeans are generally consumed after steaming, boiling or roasting. They have also been consumed after puffing, which is a thermal processing using high temperature and high pressure. However, limited information is available on bioactive constituents of puffed black soybeans. Therefore, antioxidant and phytoestrogenic activities of puffed black soybeans were investigated. The puffing pressures used were 490, 588, 686, and 784 kPa. Raw and autoclaved samples were designated as “raw” and “control”, respectively. In case of isoflavones, decarboxylation and demalonylation of malonylglucoside isoflavone, deacetylation of acetyl glucoside isoflavone as well as deglycosylation of glucoside isoflavone were occurred by puffing and autoclaving resulting in transformation of malonylglucoside isoflavones to acetylglucoside and glucoside isoflavones. Glycitein was only detected after puffing over 490 kPa, and acetylglycitin and acetyldaidzin were detected after puffing. Antioxidant activities, total reducing capacity, total flavonoid contents, and browning increased with increasing puffing pressure with some exception (decreased TFC and browning at 784 kPa). Anthocyanins were degraded into phenolic acids by puffing. Consequently, puffing is an efficient process for conversion of specific phytoestrogenic compounds, such as glycitein, and novel processing for improvement of antioxidant activity of black soybeans.

Combined Selective Hydrogenation and Catalytic Cracking Process for Efficient Conversion of Heavy Cycle Oil to High Octane Number Gasoline

Heavy cycle oil (HCO) is difficult to be converted into gasoline via fluid catalytic cracking (FCC) or hydrotreating. Abundant polycyclic aromatic hydrocarbons in HCO lead to condensation coke and ...

Addressing Challenges in Converting Grant-Funded Infrastructures to Broadly Used Research Resources.

The NCI invests heavily in research resources to serve the research community, including datasets, biospecimen banks, and networks of institutions in which clinical trials and other human subjects research are conducted. These resources often begin as grant-funded infrastructure initiated by scientists based on their own scientific interests, with a subsequent recognition of additional scientific uses. Although converting existing project-specific research activities into research resources may appear efficient in terms of time and financial investment, challenges can arise that undermine this efficiency and jeopardize future use. Here, we describe three challenges in the conversion process: (i) project-based infrastructure versus a research resource for a broader research community; (ii) complexity versus ease of use; and (iii) individual professional goals versus research resource priorities. We use our experience with the NCI-funded Cancer Research Network, particularly the Virtual Data Warehouse, to illustrate each challenge, concluding with strategies to mitigate each one. As studies grow in size and complexity, an ever-increasing volume of data, biospecimens, and human subjects research networks will be available for conversion to resources for scientific questions beyond those originally proposed. Addressing likely challenges thoughtfully can result in a more efficient conversion process and ultimately greater scientific impact.

Sustainable Electrochemical Conversion of Lignin to Renewable Chemicals with Simultaneous Hydrogen Production Via a Continuous Flow Electrochemical Reactor

Lignin is the most abundant renewable source of aromatic compounds which can be utilized to generate fuels, chemicals, and polymers, however, due to the lack of an efficient lignin conversion process, it is usually burned as a low-grade fuel in the pulp and paper industry [1,2]. The key issue for commercial application of lignin is to develop an efficient depolymerization process to produce lower molecular weight aromatic compounds at relatively low cost. Several methods including photocatalytic degradation, hydrogenolysis, thermolysis, oxidation, biodegradation, and electrocatalytic degradation have been used to convert lignin to other value-added chemicals. Among them, electrochemical valorization of lignin is likely a promising method for commercial application due to occurring in moderate reaction conditions. Lead dioxide is one of the common active catalysts for electrochemical lignin oxidation [3]. However, due to the toxicity of lead which causes environmental and health issues, developing the lead-free electrocatalysts is greatly needed. Accordingly, we investigated the rate of lignin conversion and hydrogen production on different lead-free electrocatalysts developed in this study using a flow electrochemical reactor. Gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography (HPLC), and fourier transform infrared spectroscopy (FTIR) were employed to evaluate molecular weight distribution of lignin and characterize the functional groups.