Solar Furnace Research Articles

Development of an optical method to align a high-flux solar furnace

Development of an optical method to align a high-flux solar furnace

Production of calcium and magnesium titanates using concentrated solar energy

Solar energy is an adequate technology for different processes in metallurgy, materials processing, recycling, or ceramic-refractory materials, because of the high temperatures attained which are reached when the solar radiation is concentrated. This growing interest has also emerged from the obtaining of such temperatures without releasing pollutants such as carbon dioxide, SOx, NOx, or dioxins. Other benefits associated with concentrated solar energy are that this energy source is virtually free and the possibility of operating in places isolated from the electrical grid. Therefore, this research proposes the integration of concentrated solar energy in the production of calcium and magnesium titanates, which are materials with increasing demand in the field of electric components. Experimental work was carried out in the Odeillo solar furnace located in Font-Romeu-Odeillo-Via (France) using a 1.5-meter parabolic concentrator and mixtures of CaO and TiO2 and MgO and TiO2 in 1:1 molar ratio. Mixtures were subjected to values of incident radiation exceeding 900 W/m2 without using any special atmosphere and in very short times, which did not surpass 10 minutes. X-ray diffraction technique was employed to confirm the formation of the CaTiO3 and MgTiO3 perovskites. Therefore, concentrated solar energy might be a novel, fast, and environmentally sustainable manner of producing calcium and magnesium titanates.

Thermal energy storage behaviour of 3D ceramic/molten salt structures under real concentrated solar radiation

Molten salts, phase change materials commonly employed in thermal energy storage (TES) systems, are widely known to enhance the efficient use and storage of solar energy in concentrated solar power (CSP) plants. Here, three-dimensional TES (3DTES) have been manufactured from highly porous (up to ∼90 %) 3D printed patterned vermiculite (V) and alumina (Al2O3) supports, which have been infiltrated with molten sodium nitrate salt (nn) and solar salt (ss). These 3DTES have been validated under real concentrated solar radiation in a parabolic solar furnace. Among the different 3DTES, those based on V-nn exhibits the best efficiency for the conversion of the incident solar radiation into heat; whereas Al2O3-nn transfers the heat more efficiently and allows a faster charging-discharging cyclability due to its higher thermal conductivity. This study confirms the benefits of additive manufacturing to develop a new class of innovative TES for CSP applications.

Compositionally complex AlB2-type diborides in dissociated air plasma

Multi-metal compositionally complex (CC) AlB2-type diboride solid solutions (SS) containing IV-V-VI group elements are garnering a steadily growing research interest. The present work explores the composition dependence of oxidation resistance on nominally equiatomic (Hf,Me,Ta,Ti,Zr)B2 SS, Me = Nb or Cr, exposed to a dissociated air plasma (total pressure of about 1 kPa): specimens were exposed for 5 min at some selected set points between 1800 K and 2500 K using a solar furnace. The CC diboride with Nb showed superior resistance to oxidation compared to that with Cr. The experimental results showed good agreement with predictions based on a thermodynamic assessment.

Numerical simulation and structural optimization of the diffusion furnace for crystal silicon solar cells

The diffusion furnace is an important device for crystalline silicon solar cell production. Given the rapid evolution of solar cell technology, large-scale, high-efficiency and mass-produced diffusion furnaces are required by the market. This puts forward higher requirements for the diffusion furnaces. In this study, a large-scale 3D model is established and validated by measured data in practical diffusion furnace. Its internal temperature, velocity and gas concentration fields are analyzed. The silicon wafer temperatures are found to be high at the top but low at the bottom. The temperature uniformity at both ends of silicon wafer groups is poor. To solve these problems, three structural optimization methods, namely the inlet pipe optimization, adding uniform-flow plates and the quartz boat optimization, are proposed and analyzed. The average mass fraction in the diffusion furnace is improved by 6.311% using the two-tube forked intake pipe. The uniform flow plates with evenly distributed pores on the lower half effectively improve the gas concentration uniformity on silicon wafer surfaces. The optimized quartz boat can improve the temperature uniformity of silicon wafers, though its deformation slightly increases by 0.338%. The silicon wafer temperature differences after quartz boat optimization are 13.77–50.27% smaller than those before optimization, which are conducive to reducing the thermal stress, the risk of thermal damage and the failure during manufacture and utilization of silicon wafers. Results in this study give guidelines for design and utilization of crystal silicon solar cell diffusion furnaces, some of which have been successfully used in Trina Solar Energy Co., China.

Solar technology for the production of Bi/Pb superconducting ceramics and its properties

Based on the experience of isostoichiometric and isostructural oxides production using solar energy, the prospects for synthesizing of Bi/Pb superconducting ceramics are shown. The principle of technology in the Large Solar Furnace (Parkent), the influence of gradient conditions on the formation of the oriented structure of crystallites-nuclei, and the connection of the innate properties of precursors with the lamellar morphology and phase composition of massive ceramics are described. The homophase composition of Bi/Pb ceramics was determined. Graphs of resistance and voltage of BSCCO in the temperature range 80-320K are presented. Anomalous of resistance and magnetic susceptibility in bismuth cuprates synthesized by solar energy were observed. Experimental graphs in resistance and magnetic susceptibility changes represent dependencies characteristic of the potential superconducting transitions. The manifestation of the Meissner effect at room temperature and normal atmospheric pressure and daylight, and under the influence of light is shown. The properties of Bi/Pb ceramics are explained by the connection with the innate properties of precursors obtained by concentrated solar energy.

Energetic and Exergetic Analyses of a Double-Pass Tubular Absorber for Application in Solar Towers

Abstract The present research integrates the concept of double-pass (DP) flows with high-temperature solar receivers to introduce an innovative design aimed at minimizing heat losses and optimizing performance. The new DP system was developed using a tubular absorber derived from billboard solar tower technology and operated with air as the heat transfer medium. Computational fluid dynamic models are developed based on an experimental campaign conducted at a solar furnace facility. The computational analyses indicated that employing the DP design instead of single-pass (SP) absorbers results in an average enhancement of energy and exergy efficiency by 35% and 225%, respectively, across all test conditions. However, this enhancement is accompanied by an average increase in pressure drop of ∼60%. The detailed exergy analysis also revealed the contribution of each term in the exergetic performance, identifying the exergy destruction between the sun and the absorber as the primary source, accounting for an average of ∼65% of the total inlet exergy for both SP and DP absorbers. Consequently, the DP presents itself as a promising alternative design for future solar tower configurations, offering improved Nu numbers up to ∼50% in air-based solar systems.

Sun tracking control technology of solar furnace

Sun tracking control technology of solar furnace

Design solutions and characterization of a small scale and very high concentration solar furnace using a Fresnel lens

The use of Fresnel lenses for solar energy concentration technology dates back to the 1950 s. These lenses feature a plano-convex optical design with a series of discontinuous convex grooves. Typically made from materials like polymethyl methacrylate, Fresnel lenses are lightweight, resistant to sunlight, thermally stable, and cost-effective.This study presents a novel Fresnel lens-based solar furnace configuration installed at the Eduardo Torroja Institute for Construction Science in Madrid, Spain. The novelty of this work lies in the exceptional performance and operability of the facility. Experimental characterization revealed a record peak irradiance over 7 MW m−2 for an incident target power exceeding 800 W. Comparison with ray tracing simulations shows good agreement with experimental results. This setup enables high temperature experiments up to 2000 °C with rapid execution times. A fixed receiver, a shutter system and a closed-loop heliostat tracking control system allow for flexible operation up to 5000 suns and straightforward maintenance. The concentrator element costs less than 300 USD (2022) m−2, offering an economical solution to solar-powered high concentration and temperature applications. This innovative design overcomes previous operational challenges, providing a robust and economical method for high-temperature material processing and other industrial applications.

Temperature Control in Solar Furnaces Using Nonlinear PID-based Control Approaches

Temperature Control in Solar Furnaces Using Nonlinear PID-based Control Approaches

Experimental assessment of the effect of reflectors on the thermal behavior of box-type solar furnaces

Solar ovens are eco-friendly ovens that use solar energy, a clean, sustainable and above all free source of energy. In the context of the economic and environmental crises facing the world today, solar cookers are considered a good alternative to electric cookers or those based on wood combustion. Several types of solar cooker have been developed in recent years. However, the box type remains the most efficient and simplest. To this end, an experimental study of three types of box-type solar cookers (triangle, trapezoid and rectangle) was carried out in this work. For each type of solar cooker, the effect of the number of reflectors added to the Cookers system was examined. The experimental tests were carried out in August 2023 under the climatic conditions of Morocco's eastern region. The evaluation of the systems studied is based on the hourly evolution of air, absorber and load temperatures for each type of solar furnace in different cases. Thermal photos were also taken using a Dia-Cam thermal imaging camera to visualize temperature distribution and analyze the thermal behavior of the systems. The obtained results show that the thermal behavior of three solar furnaces and the evolution of the absorber temperature depend on the load used. In addition, a significant improvement in absorber temperature and water boiling time was observed with the addition of solar reflectors. For example, the absorber temperature was increased by up to 40 °C and the water boiling time was reduced by more than 120 min in the case of triangle-type furnaces.

Enhancing solar furnace thermal stress testing using an adaptive model and nonlinear predictive control

Solar furnaces rely on renewable energy for thermal tests using concentrated solar direct irradiance. To address the complex dynamics and constraints of these systems, a novel control approach is introduced based on an adaptive model strategy. The proposed adaptive model representation with an Adaptive Practical Nonlinear Predictive Controller (A-PNMPC) strategy is employed in the solar furnace SF60 at Plataforma Solar de Almería (Spain), demonstrating enhanced model prediction that culminates in a finer control performance. A Recursive Least Squares solution for model adaptation adjusts the model dynamics to the actual behavior of the solar furnace. Then, the predictive control strategy uses the updated model to calculate optimal control actions that lead the sample temperature to the desired reference. Simulation studies demonstrated the superior performance of the A-PNMPC in temperature control and prediction compared to the constant parameter model PNMPC strategy. The proposed A-PNMPC was compared to the conventional PNMPC in simulations, showing up to a 5% improvement in control performance and an 80% in large model predictions. Additionally, the A-PNMPC was tested on the actual system for various temperature profiles, achieving a mean error of less than 10 °C in sample temperature ramp tracking

Developing a sustainable energy model for solar nixtamalization of native maize from Michoacán, Mexico

In Mexico, corn and the nixtamalization technique hold immense culinary and economic significance. Thus, optimizing and offering alternatives for this process is critical. This research proposes a solar-driven nixtamalization method customized for native maize varieties in Michoacán, Mexico. The objective is to present a technique that is energy-efficient, environmentally friendly, socially acceptable, and cost-effective. We devised a straightforward yet effective nixtamalization process utilizing the HSMC solar furnace. This method encompasses:•Field research to understand the practices and traditions regarding nixtamalization and the most consumed maize varieties.•Thermal determination and profiling of the solar oven to be used for each case study.For the rural areas of Michoacán, solar nixtamalization presents a practical and eco-sustainable alternative in both energy usage and economic terms. However, those interested in its local application must consider that the duration may vary due to differing climatic conditions and maize types.

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.

Fungible, Multiyear Solar Thermochemical Energy Storage Demonstrated via the Cobalt Oxide Cycle

Abstract We present a proof of concept demonstration of solar thermochemical energy storage on a multiple year time scale. The storage is fungible and can take the form of process heat or hydrogen. We designed and fabricated a 4-kW solar rotary drum reactor to carry out the solar-driven charging step of solar thermochemical storage via metal oxide reduction–oxidation cycles. During the summer of 2019, the solar reactor was operated in the Valparaiso University solar furnace to effect the reduction of submillimeter cobalt oxide particles in air at approximately 1000∘C. A particle collection system cooled the reduced particles rapidly enough to maintain conversions of 84–94% for feed rates of 2.9−60.8gmin−1. The solar-to-chemical storage efficiency, defined as the enthalpy of the reduction reaction at 1000∘C divided by the solar energy input, reached 20%. Samples of the reduced cobalt oxide particles were stored in vials in air at room temperature for more than 3 years. The stored solar energy was released by reoxidizing samples in air in a benchtop reactor and by electrochemically reoxidizing samples to produce H2. Measurements of the oxygen uptake by the reduced metal oxide confirm its promise as a medium to store and dispatch solar energy over long durations. Linear sweep voltammetry and bulk electrolysis demonstrate the promise of H2 production at 0.55 V relative to the normal hydrogen electrode, 0.68 V below the 1.23 V potential required for conventional electrolysis.

Modeling and control strategy optimizing of solar flux distribution in a four quadrant and adjustable focusing solar furnace

The solar furnace is key equipment for the thermochemical reaction research which uses focused solar energy to drive the reactor, and the solar flux distribution on the reactor surface plays a decisive role in the regulation of the thermochemical reaction process and formation of target products. In this paper, a reflective solar furnace with a thermal power of 30 kWth in Yanqing, Beijing, is taken as the research objective. Firstly, the Monte Carlo Ray Tracing (MCRT) method is used to establish the mathematical model for the optical calculation, and the distribution characteristics of solar flux are deeply analyzed. The accuracy of the model is verified through the comparison with the SolTrace software and experimental measurements respectively. Secondly, an improved four-quadrant and adjustable focusing solar furnace experimental equipment is developed, and a new solar flux distribution regulation strategy is proposed by using the inward crossover and outward expansion offset of the four-quadrant focusing points coupled with the heat-absorbing platform movement. The results show that the non-uniform factor and the peak value of the solar flux distribution in the set target area can be optimized by selecting an appropriate inward crossover offset and movement of the heat-absorbing platform, respectively. Moreover, when the DNI varies between 480 W/m2 and 800 W/m2, through the optimized control strategy, a non-uniformity factor with the value of less than 0.10 can be achieved in the target area of a square reactor surface with a side length of 10 cm, and the peak flux can also be controlled in the range from 3000 kW/m2 to 3300 kW/m2 with a fluctuation range of less than 10.0% as set by the thermochemical reaction. The optimized control strategy can effectively meet the uniformity and stability requirements of solar flux distribution in solar thermochemical reaction and finally achieve the goal of regulating the target products.

Optimizing capacitance performance: Solar pyrolysis of lignocellulosic biomass for homogeneous porosity in carbon production

This work compares the effect of using a solar reactor against a conventional electrical furnace to obtain carbon materials by pyrolysis of a lignocellulosic precursor. The solar reactor is directly irradiated and includes modifications to improve the control of the process and the reproducibility of solar experiments. A bagasse of agave creole was selected as the lignocellulosic precursor or biomass to obtain carbon materials at temperatures of 700 °C. Comparing carbons produced by conventional and solar pyrolysis, higher crystallinity and lower hydrophilicity are evident in the former. Moreover, conventional pyrolysis tends to promote a more homogeneous porous structure in comparison to solar pyrolysis. However, within the spectrum of solar carbons produced, the morphology of biomass plays a crucial role in influencing the chemical composition and porosity properties. Specifically, the use of fibers instead of powders to produce carbons through solar pyrolysis results in a more homogeneous porosity, attributed to an enhanced volumetric absorption of solar radiation. This modification leads to a significant improvement in capacitance, increasing from 125 F/g to 175 F/g at 5 mV/s in aqueous electrolytes. The carbons from the solar furnace are reproducible, underlying the potential of the proposed process towards a sustainable alternative. To achieve a theoretical reference, the pyrolysis process was mimic trough Reactive Molecular Dynamics calculations modeling the initial structural conditions of agave biomass with its corresponding lignocellulosic components and considering analogous thermal conditions. The resulting carbon structures at the end of the simulations showed structural properties that are consistent with those observed in the pair distribution functions obtained from XRD and the pore size distribution from physisorption analyses. This combined experimental–theoretical approach offers the potential to elucidate porous carbon structures derived from pyrolysis processes powered by solar radiation . This method can help in the design and identification of lignocellulosic structures in biomass, with the resulting carbon materials suitable for energy storage applications.

Design and Characterization of the New FAHEX100 Concentrator of PSA's SF60 Solar Furnace

The facets of the old Mc Donnell Douglas concentrator of Plataforma Solar de Almería –PSA- SF60 solar furnace were degraded after thirty years of service, which had a great influence on its thermal response and efficiency, as the reflectivity decreased significantly due to the reflective surface being corroded and scratched. That is why, it was decided to replace them by new facets with higher reflectivity and better optical conditions.
 This paper describes the new facets, as well as the new support structure and the assembly and alignment of the concentrator facets. Finally, the technical characteristics of the new concentrator, and the power, size and flux distribution on the focus, are presented.
 For the new facets we selected a thin, hexagonal-shaped mirror bonded to an aluminum plate.
 Therefore, new facets with improved optical conditions were designed and manufactured and, for the assembly a new tubular structure was used to conform the new FAHEX100 concentrator
 To anticipate the behavior of the new FAHEX100 concentrator, a model was built in Tonatiuh, for which a geometric analysis of the facets was previously performed by means of photogrammetry.
 Once the facets were mounted on the concentrator, they were aligned by the Reverse Ilumination Method -RIM–, and the flux distribution on the focus was measured with a CCD camera.
 The performance of the SF60 solar furnace was improved significantly with the new FAHEX100 concentrator, including power, peak concentration, flux distribution on the focus, focus diameter and optical error σopt.

HYDROGEN ABSORBERS BASED ON POROUS CERAMICS SYNTHESIZED IN A SOLAR FURNACE

In this study, we investigated the processes of hydrogen absorption in porous ceramic materials sythesized in a solar furnace. We used burning additives inserted into ceramic materials and melted in a solar furnace in a high-density stream of concentrated solar radiation (200 W/cm<sup>2</sup>). The melt was cooled by pouring it into water at a cooling rate of 10<sup>3</sup>-10<sup>4</sup> degree/s. The castings were characterized by a fine-grained microstructure (in which the grain size did not exceed 10 µm). The crushed and molded samples were fired at a temperature of 1150°C for 2 hours. Thr results obtained showed that the sodium aluminosilicate zeolite ceramic porous material based on a mixture of aluminum powder, quartz sand, and polyvinyl alcohol exhibited high hydrogen absorption-up to 13% (at temperature = 250°C and pressure = 13 atm).

SYNTHESIS OF A SILICON CARBIDE FROM NATURAL RAW MATERIAL IN A SOLAR FURNACE

In this study, the processes involved in synthesis of silicon carbide (SiC) from a natural mineral raw material (diatomite mixed with coke) were investigated. The initial material mixture was placed in a graphite crucible installed on the focal zone of a large solar furnace. High-temperature heating was carried out using a stream of concentrated high-density solar radiation (200-300 W/cm<sup>2</sup>). After irradiating the material sample with the concentrated solar radiation, the crucible was cooled arbitrarily for 30 minutes. The synthesized material contained three phases: β-SiC with a cubic crystalline lattice and lattice parameter of 0.436 nm; α-SiC with a hexagonal crystalline lattice and lattice parameters of a = 0.307 nm and c = 1.511nm; and graphite with a hexagonal crystalline lattice. The SiC material obtained in the solar furnace in a freshly sintered state showed high refractoriness (up to 1650°C), while the material fired at 1550°C showed refractoriness up to 1580°C.