Use Of Concentrated Solar Energy Research Articles

Implications of renewable energy sources in metallurgy: Utilization of concentrated solar energy in recycling metallurgical wastes

Solar energy, when it is concentrated, can reach temperatures as high as 3000 °C and generate heat without producing pollutants such as carbon dioxide or other harmful agents. Additionally, solar energy is virtually free and can be utilized in remote areas not connected to the electrical grid. However, slags, a by-product of metallurgical industries, are not commonly used due to the cost of processing them. This manuscript proposes studying the use of concentrated solar energy to extract metals from four types of slags: basic oxygen furnace (BOF) slag, copper slag, silicomanganese slag, and ferromanganese slag, each containing important metals. Experimental work at the Odeillo solar furnace suggests that iron oxides in the BOF slag transform into magnetic phases, while copper slag experiences changes in fayalite (that partially transforms into magnetite) and copper oxides and sulfides (that also convert into metallic copper nodules). The ferromanganese and silicomanganese slags become more refractory, making the extraction of manganese more challenging. Overall, the study suggests that at least part of the metals might be collected in a usable form.

Upgrading of biomass-derived solar hydrothermal bio-oils through catalytic hydrodeoxygenation in supercritical ethanol

The use of concentrated solar energy as the heat source to perform hydrothermal liquefaction (HTL) of biomass is a promising alternative to improve the thermal efficiency of the process and reduce the environmental impact of the use of fossil fuels. However, the HTL of lignocellulosic biomass produces a bio-oil that still requires an upgrading treatment to improve its properties as fuel. In the present work, bio-oils obtained from solar hydrothermal liquefaction of Agave and corncob were upgraded for the first time by hydrodeoxygenation (HDO) in supercritical ethanol using a Mo2C catalyst supported in carbon nanofibers. The main results showed yields up to 69% of the upgraded bio-oil and a deoxygenation grade of 71%, with HHV values around 35 MJ/kg for most of the upgraded bio-oils. Moreover, it was observed that HDO treatment of the solar bio-oils can produce upgraded bio-oils with chemical properties and yields similar to those produced by conventional thermochemical methods, which opens the door to extend the use of concentrated solar technologies for the whole process: from biomass thermochemical conversion to its upgrading into drop-in fuels.

Processing of intermetallic laminates by Self-Propagating High–Temperature Synthesis initiated with concentrated solar energy

The intermetallic compounds are very interesting in a multitude of structural and functional applications, such as in turbomachines or engine parts, due to their good behaviour at high temperatures, as well as their high resistance to corrosion and oxidation. In the present work, the study of processing of the Ni-Al system intermetallics has been carried out by means of Self-Propagating High–Temperature Synthesis initiated by concentrated solar energy (SHS–CSE). Synthesis by this high-energy exothermic reaction often causes the appearance of porosity, lack of interlayer adhesion, volumetric expansion, and even the total loss of sample shape. To obtain high-quality systems, a study has been carried out on one-layer and multi-layer configurations from powder materials, considering the influence of the heating rate and time. The use of concentrated solar energy has allowed to obtain fully densified nickel parts at 1000°C in just 15 min, compared to the 1325°C and more than 12h required by conventional techniques to obtain lower relative densities (~97%). The best results in multilayer configurations have been achieved in Ni-Ni/Al-Ni system with the synthesis of intermetallic compounds type Ni2Al3, NiAl and Ni3Al. The control of volumetric expansion and porosity, full densified nickel layers perfectly adhered to the interlayer and hardness values up to 900 HV have been obtained in just 2 min. This work highlights the wide possibilities of the use of CSE in metal treatment, which allows efficient and sustainable synthesis of new systems and the improvement of the final properties of the parts.

There are hydrogen production pathways with better than green hydrogen economic and environmental costs

While the present hydrogen (H2) is mostly grey, from steam reforming of methane (CH4) with direct carbon dioxide (CO2) emission, different pathways have been proposed to produce H2 more environmentally friendly. Blue H2, adopting carbon capture and storage (CCS), has no direct CO2 emission, but the additional cost to capture and store the CO2. Thus, green H2, from the electrolysis of the water (H2O) molecule, is becoming the preferential pathway for future H2 production. Two additional pathways are proposed for reduced economic and environmental costs, both free of direct CO2 emissions, based on the use of concentrated solar energy (CSE). White H2 is produced from the catalytic solar thermochemical splitting of the H2O molecule. Aquamarine H2 is produced from solar thermochemical CH4 pyrolysis with a carbon catalyst. Here we provide an estimation of costs by 2030 of white and aquamarine H2 lower than the cost of not only green H2 but also grey H2 disregarding the CO2 emission.

Waste and Solar Energy: An Eco-Friendly Way for Glass Melting

In this work, concentrated solar energy (CSE) was applied to an energy-intensive process such as the vitrification of waste with the aim of manufacturing glasses. Different types of waste were used as raw materials: a hazardous waste from the aluminum industry as aluminum source; two residues from the food industry (eggshell and mussel shell) and dolomite ore as calcium source; quartz sand was also employed as glass network former. The use of CSE allowed obtaining glasses in the SiO2-Al2O3-CaO system at exposure time as short as 15 min. The raw materials, their mixtures, and the resulting glasses were characterized by means of X-ray fluorescence, X-ray diffraction, and differential thermal analysis. The feasibility of combining a renewable energy, as solar energy and different waste for the manufacture of glasses, would highly contribute to circular economy and environmental sustainability.

Solar synthesis of nanostructured zirconia: microstructural and thermal characterization

The use of concentrated solar energy in processing ceramic materials is an attractive route to obtain these materials with low CO2 emissions. In this work, nanostructures of monoclinic zirconia (m-ZrO2) were obtained using concentrated solar energy provided by the IER-UNAM solar furnace as a heat source. In the first stage of the process, a Zr/O/C complex was obtained by sol-gel method at a temperature of 120 °C using zirconium n-propoxide and sorbitol as precursors reagents. This complex was used in a second stage to obtain m-ZrO2 by heating it at a temperature of 1200 °C for one hour in air atmosphere. This last stage was performed in a solar furnace. Samples were analyzed by characterization techniques: FT-IR, TGA/DSC, XRD, TEM, and SEM confirming the formation of nanostructures of zirconia in monoclinic phase.

A 100 kW cavity-receiver reactor with an integrated two-step thermochemical cycle: Thermal performance under solar transients

A future sustainable economy based on hydrogen will require large-scale hydrogen production processes in a CO2 emission-free way. Within this context, solar-driven thermochemical water splitting cycles have been proposed as a promising alternative for hydrogen mass production with the use of concentrated solar energy as the principal source to provide the process heat.Numerous solar thermochemical water-splitting cycles have been investigated for hydrogen production, each with different sets of operating conditions, engineering challenges, etc. Challenges remain in the demonstration of commercially viable thermochemical cycles and reactors, in particular, efficient and robust reactor designs compatible with solar concentrating systems. A 100 kWth multi-tubular cavity reactor for hydrogen production integrated in a solar tower has been used as test bed to demonstrate the technological feasibility of a thermochemical process with incident solar transients.The work presented on this paper dealt with integration of a cavity reactor into a solar concentrating system running a ferrite based solar thermochemical water splitting cycle. This work also explores the thermal performance of a cavity reactor beyond optimal operational conditions governed by transient cloud events. These conditions emerge as a relevant matter to be considered because they have not been studied so far.

Sinter-hardening of chromium PM steels with concentrated solar energy

Abstract Cr-alloyed PM steels attract great interest in industry, especially in the automotive industry, because, due to the mechanical requirements for the parts, the parts are often subjected to hardening thermal treatments after sintering. In the present work, a sinter-hardening process was carried out in a single stage for pieces based on PM Astaloy CrA steel using concentrated solar energy. The influence of the sintering cycle and atmosphere used, as well as the content of the alloy, were studied. Among the main results obtained, it has been demonstrated that alloys based on Astaloy CrA have been successfully sintered using solar energy. Almost complete densities have been achieved, but these densities are not achieved by conventional techniques, and much shorter sintering times and temperatures (∼ 15 min of holding time at 1070 ± 10 °C) are required compared to those used in the usual processing techniques. In addition, the use of concentrated solar energy in metal treatment leads to high heating and cooling speeds that have encouraged the sinter-hardening process through the formation of bainitic and martensitic phases, which are characterized by being harder and more resistant than ferritic and pearlitic phases. Homogeneous microstructures have been obtained without the need to apply subsequent heat treatments such as tempering that it uses in the processed by conventional techniques. This research work is also intended to promote the use of concentrated solar energy in metallurgical processes that require high temperatures because it is a cheap, nonpolluting and renewable technology. Additionally, high heating and cooling speeds that often result in an improvement of the final properties of the pieces can be obtained without the need to use any external cooling medium.

Synthesis and characterization of tantalum carbide nanoparticles using concentrated solar energy

Tantalum carbide (TaC) nanoparticles were synthesized using the IER-UNAM (HoSIER) solar furnace, which reduces polluting gas emissions and dependence on fossil fuels through the use of concentrated solar energy. TaC synthesis was performed through a carbothermal reduction method from Ta/O/C complex, using tantalum pentachloride (TaCl5) and synthesized phenolic resin as sources of tantalum and carbon, respectively, at a temperature of 1200 °C, in a reaction time of 30 min, under argon atmosphere. A solar reactor equipped with a quartz window was used, designed to work in controlled atmospheres. Complex Ta/O/C bonds and thermal decomposition were analyzed by FT-IR and TG/DSC, respectively, while the structure and morphology of TaC were analyzed by XRD, TEM, and SEM techniques. Results showed a TaC with a cubic crystalline structure, a low amount of Ta2O5 and a near-spherical morphology. According to Debye-Scherrer, the average crystallite size was 21 nm.

Exploring the influence of solar pyrolysis operation parameters on characteristics of carbon materials

Carbon materials can be produced by different methods, one of them is solar pyrolysis, which is attaining renewed interest due to simplicity to transform biomass with environmental advantages. However, pyrolysis operation parameters are decisive factors that determine the morphological and chemical properties of carbon. This work aims to study the influence of temperature and heating rate of solar pyrolysis in the properties of carbon. Pyrolysis experiments were carried out in the 25 kW IER-UNAM solar furnace. Agave biomass was processed in a glass spherical solar reactor. Temperatures between 500 and 900 °C were utilized, as well as heating ramps between 4 and 30 °C/min. Samples were analyzed with several techniques. The results of the experiments indicate that solar pyrolysis temperature and heating rate scarcely impact the carbon composition, however the structure, surface area and electrochemical response are highly affected by both. The control of the operation conditions allows to produce carbon materials that exhibit promising properties to be used as catalyst supports for polymer electrolyte membrane fuel cells and electrolyzer cells applications. Therefore the use of concentrated solar energy represents an attractive method to obtain these valuable materials.

The use of concentrated solar energy for the reduction of CuO in H2

The reduction of copper (II) oxide was carried out under concentrated solar radiation in a stream of gaseous mixture 5/95 v/v H2/N2 in a 1.5 kW thermal power vertical axis parabolic concentrator at the PROMES-CNRS solar facility (Odeillo-Font Romeu, France). Experiments were performed using a commercial oxide in two different forms, powdered and compacted specimens. The reduction of CuO to elemental Cu was more effective for compacted specimen yielding a dendrite microstructured metallic copper with an electrochemical behavior similar to that exhibited by the commercial metal. In the case of powdered specimen, a composite metal/oxide (Cu/Cu2O) block was obtained as a macroporous material. The reduction process of CuO under concentrated solar energy tracks through the formation of Cu2O as the only intermediate phase, which was evidenced by X-ray diffraction and scanning electron microscopy.

Eco-efficient melting of glass frits by concentrated solar energy

This research aims to study the feasibility of applying real concentrated solar radiation to achieve the energy needed for melting glass frits. For this purpose, five glass compositions corresponding to different types of commercial frits were prepared. For comparison, the batches were melted by both in a solar furnace using concentrated solar energy (CSE) and in an electric furnace. The final frits were characterised by means of X-ray Fluorescence, X-ray Diffraction, Differential Thermal Analysis, Field Emission Scanning Electron Microscopy and Fourier Transformed Infrared Spectrometry. Results show that the frits prepared by CSE present short-range order, thermal behaviour and microstructure analogous to frits prepared in electric furnace. Moreover, the use of CSE for manufacturing glass frits reduces the melting time in about 80%, which leads to both lower corrosion of crucible wall and lower boron volatilization.

Design, simulation and experimental study of a directly-irradiated solar chemical reactor for hydrogen and syngas production from continuous solar-driven wood biomass gasification

The use of concentrated solar energy as the high-temperature heat source for the thermochemical gasification of biomass is a promising prospect for producing CO2-neutral chemical fuels (syngas). The solar process saves biomass resource because partial combustion of the feedstock is avoided, it increases the energy conversion efficiency because the calorific value of the feedstock is upgraded by the solar power input, and it also reduces the need for downstream gas cleaning and separation because the gas products are not contaminated by combustion by-products. A new concept of solar spouted bed reactor with continuous biomass injection was designed in order to enhance heat transfer in the reactor, to improve the gasification rates and gas yields by providing constant stirring of the particles, and to enable continuous operation. Thermal simulations of the prototype were performed to calculate temperature distributions and validate the reactor design at 1.5 kW scale. The reliable operation of the solar reactor based on this new design was also experimentally demonstrated under real solar irradiation using a parabolic dish concentrator. Wood particles were continuously gasified at temperatures ranging from 1100 °C to 1300 °C using either CO2 or steam as oxidizing agent. Carbon conversion rates over 94% and gas productions over 70 mmol/gbiomass were achieved. The energy contained in the biomass was upgraded thanks to the solar energy input by a factor of up to 1.21.

Applications and Contributions of Physics to the Surface Treatment Process of Materials. Part II: Other Treatments

In this second part another group of processes of surface treatment of materials in which has been employed a series of principles of the Physics are reviewed. Using technologies that employ these principles it is possible to modify the surface of materials in order to obtain improvements in their behavior, specially in regard to increasing their corrosion, wear or fatigue resistance. In particular, this work describes the processes of flame and induction hardening, surface treatments using laser beam, treatments that use concentrated solar energy and finally the processes of physical vapor deposition. All of them of industrial application, with the exception of the use of concentrated solar energy which, however, has an important potential due to the current situation of the renewable energies.

Applications and Contributions of Physics to the Surface Treatment Process of Materials. Part II: Other Treatments

In this second part another group of processes of surface treatment of materials in which has been employed a series of principles of the Physics are reviewed. Using technologies that employ these principles it is possible to modify the surface of materials in order to obtain improvements in their behavior, specially in regard to increasing their corrosion, wear or fatigue resistance. In particular, this work describes the processes of flame and induction hardening, surface treatments using laser beam, treatments that use concentrated solar energy and finally the processes of physical vapor deposition. All of them of industrial application, with the exception of the use of concentrated solar energy which, however, has an important potential due to the current situation of the renewable energies.

Titanium Alloys Thin Sheet Welding with the Use of Concentrated Solar Energy

The present study deals with the welding of titanium alloys thin sheets 1.3 mm thick, with the use of concentrated solar energy. The experimental part of the work took place at a medium size solar furnace at the installation of the Centre National de la Recherche Scientifique, at Odeillo, in Southern France, where similar and dissimilar defect-free welds of titanium Grades 4 and 6 were achieved, in the butt joint configuration. After the determination of the appropriate welding conditions, the optimum welded structures were examined and characterized microstructurally, by means of light optical microscopy, scanning electron microscopy, and microhardness testing. In addition, test pieces extracted from the weldments were tested under uniaxial tensile loading aiming to the estimation of the strength and the ductility of the joint. The analysis of the experimental results and the recorded data led to the basic concluding remarks which demonstrate increased hardness distribution inside the fusion area and severe loss of ductility, but adequate yield and tensile strength of the welds.

Biomass Gasification in an Innovative Spouted-Bed Solar Reactor: Experimental Proof of Concept and Parametric Study

Solar thermochemical gasification of lignocellulosic biomass promises a new path for the production of alternative fuels as well as storage and transport of solar energy as a convertible and transportable fuel. The use of concentrated solar energy as the external heat source for the high-temperature reaction allows producing high-value syngas with both higher energy conversion efficiency and reduced cost of gas cleaning and separation, while saving biomass feedstock. A newly designed solar reactor based on the principle of spouted bed reactor was used for continuous solar-driven gasification of biomass particles. The reliable operation of this 1.5 kW reactor was experimentally demonstrated under real solar irradiation using a parabolic dish solar concentrator. Several types of biomass particles were continuously fed in the reactor at temperatures ranging from 1100°C to 1400°C. The injected particles consisted of beech wood or a mix of resinous wood with size ranging from 0.3 mm to 2 mm. The aim of this st...

Design of Solar Lime Kiln

Calcium oxide (CaO), commonly known as quicklime is a key ingredient of cement. It is produced by thermal dissociation of limestone (CaCO3) in a calcination reaction. The process of converting limestone to quicklime involves heating limestone to a temperature of 1200-1400K. This thermal dissociation reaction produces carbon dioxide (CO2). The heat required for the process is habitually supplied by the combustion of coal or, oil in the lime kiln. The combustion of these fuels produces additional CO2 emission which represents around 40% of the cement plant CO2 emissions. This emission can be reduced by switching to fuels, like natural gas, biomass or waste-derived fuels. The use of concentrated solar energy as the source of process heat is an energy efficient alternative. This paper presents the design of a mini, scalable solar lime kiln which was designed from first principles. The kiln is designed to calcine small-grained (1-5 mm diameter) limestone particles. A solar dish collector is proposed to supply the required heat energy at the desired temperature. The heat is focussed on a heating element located centrally in a tilted rotary kiln driven by chain drive. The carbon dioxide emitted from the calcination reaction is released to prevent re-carbonation of limestone. The heating element can easily be replaced with another heat source such as electrical heating. The design procedure and design simulation are detailed in the paper.

Carbo‐ and Methanothermal Reduction of Tungsten Trioxide into Metallic Tungsten for Thermochemical Production of Solar Fuels

AbstractThe WO3/W redox pair is proposed as an alternative option for the production of solar fuels due to high reactivity and selectivity in two‐step thermochemical redox cycles. This study addresses the high‐temperature solar step involving the use of carbonaceous materials (carbon or methane) as reducing agents to lower the temperature of the reduction step in the WO3/W cycle, which makes the process compatible with the use of concentrated solar energy as the source of process heat. The carbothermal reduction of tungsten trioxide to tungsten by using carbon in the form of graphite, carbon black, and activated carbon was investigated with a thermobalance and a packed‐bed tubular reactor, whereas methanothermal reduction was studied by using a solar‐driven thermogravimetric reactor. The WO3/C powder reactivity was analyzed as a function of temperature, carbon type, and stoichiometry of the reactant mixture. The reaction was complete upon heating to 1280 °C when using excess carbon in the mixture, with metallic tungsten and carbon monoxide as the main products. A high specific surface area of carbon favored the solid–gas reaction mechanism, whereas a small carbon nanoparticle size favored the solid–solid mechanism, along with the formation of carbides. Methanothermal reduction of WO3 started from 850 °C and yielded mainly W and WC at 1000 °C with WO3 conversion above 80 %. This study thus indicates that carbo‐ and methanothermal reduction of tungsten trioxide can be used to produce metallic tungsten powder efficiently.

Solar Convective Furnace for Metals Processing

Metals processing operations, primarily soaking, heat treatment, and melting of metals are energy-intensive processes using fossil fuels, either directly or indirectly as electricity, to operate furnaces at high temperatures. Use of concentrated solar energy as a source of heat could be a viable “green” option for industrial heat treatment furnaces. This paper introduces the concept of a solar convective furnace which utilizes hot air generated by an open volumetric air receiver (OVAR)-based solar tower technology. The potential for heating air above 1000°C exists. Air temperatures of 700°C have already been achieved in a 1.5-MWe volumetric air receiver demonstration plant. Efforts to retrofit an industrial aluminium soaking furnace for integration with a solar tower system are briefly described. The design and performance of an OVAR has been discussed. A strategy for designing a 1/15th-scale model of an industrial aluminium soaking furnace has been presented. Preliminary flow and thermal simulation results suggest the presence of recirculating flow in existing furnaces that could possibly result in non-uniform heating of the slabs. The multifarious uses of concentrated solar energy, for example in smelting, metals processing, and even fuel production, should enable it to overcome its cost disadvantage with respect to solar photovoltaics.