Parabolic Solar Concentrator Research Articles

Photocatalytic Advanced Oxidation Processes for Neutralizing Free Cyanide in Gold Processing Effluents in Arequipa, Southern Peru

Cyanide (CN−) from gold processing effluents must be removed to protect human health and the environment. Reducing the use of chemical reagents is desirable for small centralized and decentralized facilities. In this work, we aimed to optimize the use of ultraviolet (UV) radiation coupled with hydrogen peroxide (H2O2) to enhance the rate and extent of CN− removal in synthetic and actual gold processing effluents, from one centralized and one decentralized facility in southern Peru. Bench-scale studies conducted using H2O2 and ambient UV showed no significant effects on CN− destruction; however, experiments with higher UV intensity and H2O2 accelerated free CN− degradation. When a 1:1 stoichiometric ratio of CN−:H2O2 was tested, the highly concentrated effluent (1 g CN−/L) had a slower pseudo first-order rate constant (k = 0.0066 min−1) and took ~5 h longer to reach 99% destruction, compared with the low concentration effluent (100 mg CN−/L; k = 0.0306 min−1). Lastly, a TiO2 photocatalyst with low stoichiometric CN−:H2O2 ratios (1:0.1 and 1:0.2), in a compound parabolic solar concentrator, was tested to investigate the degradation of a high concentration effluent (1.28 g CN−/L). These results show a significant improvement to degradation rate within a 20 min period, advancing treatment options for mineral processing facilities.

Effects Of Reflectance And Shading On Parabolic Dish Photovoltaic Solar Concentrator Performance

Photovoltaic concentrating systems have recently become one of the topics of interest to researchers around the world due to the high cost of semiconductors used in the manufacture of solar cells, as well as the wide area of traditional photovoltaic panels. The target can be met by compensating for the vast areas of solar cells with smaller cell areas made of reflective or refractive materials that concentrate higher intensity solar radiation to reach a higher outward power. In this research a parabolic dish solar photovoltaic concentrator is studied theoretically. The concentration ratio at the reflecting concentrator has been studied as a function of reflectance and shading losses under five different rim angles ( 45°, 55°, 65°,75° and 85°) using equations simulated in the MATLAB software. Following that, the total absorbed solar radiation and output power provided by CPV with multi-junction solar cells. the results indicated that the concentration ratio increase linearly with reflectance, while it increases as the rim angle decrease. The best value of concentration ratio is about 172 for rim angle 45° and reflectance 95%.

Experimental investigation of a Scheffler reflector for the medium temperature applications

This research problem reveals the experimental investigation at a pressure of 1.5 bar and temperature of 120°C for the medium thermal applications utilizing the four Scheffler reflectors with 16 m2 surface area each. The Scheffler collector associated with absorber plate of mild steel of size, 0.45 m diameter, and 0.025 m thick was assessed in June 2018. The variation in solar beam radiation over the entire day was observed from 840 W/m2 to 1278 W/m2, while, the absorber plate temperature was recorded within the extent of 116–195°C, however, the maximum heating temperature was measured 129°C at the end-use. The Scheffler collectors performed appropriately in the morning and evening time with substantial heat loss factor and lower optical efficiency factor. The energy efficiency of 59.28% has been achieved which is higher as compared to the parabolic solar concentrator. The higher concentration ratio of the Scheffler collector indicates it as an efficient substitute to replace fossil fuels. The system is viable for more than 1600 kWh/m2 yearly solar potential while the cost of heating is greater than 0.05 $/kWh for them. This paper concludes that the Scheffler reflector is the most promising solar technology for the medium-temperature applications.

Solid-State Redox Kinetics of CeO2 in Two-Step Solar CH4 Partial Oxidation and Thermochemical CO2 Conversion

The CeO2/CeO2−δ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, followed by CO2 splitting, was considered in this work. This topic concerns one of the emerging and most promising processes for the recycling and valorization of anthropogenic greenhouse gas emissions. The development of redox-active catalysts with enhanced efficiency for solar thermochemical fuel production and CO2 conversion is a highly demanding and challenging topic. The determination of redox reaction kinetics is crucial for process design and optimization. In this study, the solid-state redox kinetics of CeO2 in the two-step process with CH4 as the reducing agent and CO2 as the oxidizing agent was investigated in an original prototype solar thermogravimetric reactor equipped with a parabolic dish solar concentrator. In particular, the ceria reduction and re-oxidation reactions were carried out under isothermal conditions. Several solid-state kinetic models based on reaction order, nucleation, shrinking core, and diffusion were utilized for deducing the reaction mechanisms. It was observed that both ceria reduction with CH4 and re-oxidation with CO2 were best represented by a 2D nucleation and nuclei growth model under the applied conditions. The kinetic models exhibiting the best agreement with the experimental reaction data were used to estimate the kinetic parameters. The values of apparent activation energies (~80 kJ·mol−1 for reduction and ~10 kJ·mol−1 for re-oxidation) and pre-exponential factors (~2–9 s−1 for reduction and ~123–253 s−1 for re-oxidation) were obtained from the Arrhenius plots.

Study on the effect of conical and parabolic solar concentrator designs on hybrid solar dryers for apricots under variable conditions: A numerical simulation approach

ABSTRACT The main objective of this paper is to present a numerical model and simulation of coupled heat and mass transfer of solar dryer with various solar concentrator shapes considering the thermo-physical properties of apricot and climatic conditions of Nancy France. The resolution of the model will permit the prediction of the temperature and humidity of the solar air heater at the collector and drying chamber and also determine the moisture profile during the drying process. The thermal performance of each concentrator design was compared for best performance. A solar dryer with a non-coaxial conical concentrator presented for drying of apricot under the variable external conditions was used for the validation of the model. The numerical results showed a good agreement with experimental data determined for Elazig town Turkey. Numerically the global results were satisfying for moisture content and air temperature for the solar dryers. Parabolic concentrator had comparatively poor drying kinetics when compared with conical concentrators while co-axial design outperforming the non-coaxial design for drying kinetics. When applied in Nancy France environment to dry 30 kg of apricot with an initial moisture content of 3.5 kg/kg (db), lower energy consumption of 8.143 MJ per kg of water removed was determined for non-hybrid drying with non-coaxial conical concentrator while intermittent deployment for 2 MW electrical power consumed more energy with the higher energy of 18.668 MJ per kg of water extracted. For simulation on the environmental condition of Nancy France under the winter, summer, autumn and spring periods drying kinetic were better for drying with 1 MW continuous drying, while drying with 2 MW discontinuous drying performed better in the autumn period. Generally, non – hybrid drying performed poorly compared to others but is more energy utilization efficient compared to others.

Performance and determination of Concentration Ratio for a parabolic solar concentrator using a thermographic technique

This work addresses the methodology to determine the exact concentration ratio (CR) for a parabolic solar concentrator (PSC) using thermographic imaging. The value of CR is commonly given in terms of the area of the receiver and not in terms of the area of the image produced by the concentrator on the receiver surface. With thermographic analysis, it is possible to know the real image generated by the PSC on the receiver, which helps to have a precise calculation of CR. It is important to measure the real CR not only for manufacturing purposes but also for the maintenance of solar concentrators, since its miscalculation lowers their energy efficiency or lifespan. In experiments, the real image on the receiver is divided into 4 regions, stratified with an equal temperature difference for each one. With this consideration, CR varied from 20 to 151. To complete the analysis, the energy efficiency is calculated. Since heating is a non-stationary process, thermal efficiency fluctuated during the time of experimentation, having a peak of 25% and a mean value of 15.3%. The irregularities of curvature in the concentrators significantly deteriorate the uniformity of the radiation flux and the energy efficiency due to unused areas of concentration.

A design method for optimizing the secondary reflector of a parabolic trough solar concentrator to achieve uniform heat flux distribution

Non-uniform solar flux distribution in a parabolic trough concentrator (PTC) causes large temperature gradients on absorber tube surface, making the PTC inefficient and damaged. To solve the problem, a novel method is proposed for designing the additional secondary reflector (SR) in a PTC to improve uniform heat flux distribution on absorber tube surface. In the design, the heat flux between upper and lower surfaces of absorber tube is well balanced by optimizing the location of absorber. Then, the SR with segmented broken-line type composed of multiple plane mirrors is delicately designed with local heat flux compensation strategy. Two case studies are conducted to compare the performances of the newly designed SRs with other existing SR designs. It is shown that the uniformity of heat flux distribution can be improved to over 90% for present SR design, much higher than those for other existing SR designs. Also, the optical efficiency of the PTC with present SR design is also increased as compared with other designs. The results indicate that this proposed method is competent for designing SR in a PTC with uniform heat flux distribution.

Experimental study of concentrated thin-film receiver with phase change material

A Scheffler type parabolic dish solar concentrator (PDSC) of 16 m2 aperture area was used to concentrate the incident beam radiation onto a solar thin receiver. Magnesium chloride hexahydrate (Mgcl2.6H2O) phase change material (PCM) was incorporated into the thin receiver based on the availability, thermophysical properties and cost. The average energy efficiency of the thin receiver was 26.37%, 39.56% and 54.20% without PCM and 29.47% and 44.20% and 59.10% with the PCM for flow rates of water of 0.01 kg/s, 0.02 kg/s and 0.03 kg/s respectively.

Design and Fabrication of Stirling Engine for Solar Power Application

Abstract This paper showcases the designing, fabrication, and performance evaluation of 90-deg alpha-type Stirling engine. The diameters of the hot and cold cylinder are 50 mm and 44 mm, respectively, with a stroke length of 70 mm. The computer-aided design (CAD) model is developed by keeping in mind the ease of manufacturing, maintenance, bearing replacements, and lubrication. After fabrication, the engine is tested by heating the hot cylinder with air as a working fluid. The engine delivered peak power of 155 watts at the temperature of 1123 K and 968 K for hot and cold cylinders, respectively. This developed prototype can be commissioned with the solar parabolic concentrator in the future based on the smooth operation while delivering power.

Modelling and Simulation of a Combined System Geothermal Binary Plant and Parabolic Solar Concentrator

Modelling and Simulation of a Combined System Geothermal Binary Plant and Parabolic Solar Concentrator

Improvement of the performance of parabolic trough solar concentrator using freeform optics and CPV/T design

<abstract> The developmental tendency of parabolic trough collector (PTC) is larger aperture area for energy harvest and novel optical design for higher solar concentration. Larger aperture faces a higher demand in tracking accuracy and lower tolerances with respect to wind loads, quality of mirrors, control, and mounting imprecisions. With the increase of reflection angle, the divergence size of concentrated focal spot gets enlarged on receiving surface, forming a Gaussian distribution. Receiving more energy and making best use of the concentrated solar power have become a key problem. In current study, a novel trough free-form solar concentrator (TFFC) has been developed by extending the aperture size with the aid of freeform optics and combined PV/thermal utilization. The structure model is composed by traditional parabolic trough with thermal tube, and extended freeform reflector with solar panel in slope configuration. The free-form surface is generated by geometric construction method for the sake of uniform heat flux distribution. The optical characteristics are validated by ray tracing method. The advantages will be revealed by compared with traditional system. The sensitivity analysis and error factors would be discussed as well. The initial results are promising and significant for the enhancement of trough type solar concentrator systems. </abstract>

Modeling and Simulation of a Parabolic Trough Solar Concentrator

This work consisted of the mathematical modeling of a parabolic trough concentrator. To this end, a heat balance has been established for the different parts of the parabolic trough concentrator, which are the heat transfer fluid, the absorber and the glass. This allowed us to establish a system of equation whose resolution was done by the finite difference method. This digital resolution made it possible to obtain the temperatures of the different parts of our parabolic trough concentrator, namely, the heat transfer fluid, the absorber and the glass. The simulation of the heating process of the fluid is done in time steps of one hour, from six hours to eighteen hours. The results obtained show that the temperature difference between the inlet and the outlet of the solar collector is very large. A computer program has been developed to simulate the temperatures of the heat transfer fluid, the absorber tube and the glass as a function of time and space. These results were obtained for a typical day with regard to the variation of the temperatures of the heat transfer fluid, the absorber and the glass, as well as the powers and efficiency of the parabolic trough concentrator and various factors for the sake of improve the performance of our prototype.

The experi̇mental thermal analysis of aluminum metal melting with concentrated solar energy

The concentrated solar energy which is one of the renewable energy sources, is examined in metal melting which requires high temperatures. The study is carried out for the first time in an environment where total solar radiation of 1394 kWh m−2-year and sunshine duration of 2132 h-year at the sea level in Trabzon province at 41° latitudes and 39° longitudes. In the present work, a single concentrator model of solar furnace system is presented. Parabolic dish with a diameter of 1.42 m was used for the first time with high reflection rate chromium nickel foil in the concentration of the solar rays. To store the concentrated solar beams, a metal melting furnace is designed, manufactured and tested. Total heat loss analysis of the furnace according to measured experimental values is performed for the designed solar furnace. The melting process of the aluminum metal was realized in the furnace. In the experiment, the efficiency of the system was calculated based on the measured temperatures and solar radiations. The system efficiency which consists of the parabolic solar concentrator and the solar furnace was found to be approximately 46% at the average focal temperature of 1023 K. In the melting process, the efficiency of the furnace is calculated as the ratio of stored energy to the absorbed solar energy on the surface. The total thermal efficiency 22% is calculated for the first time in the aluminum melting process and mass flow rate is 0,0667 g s−1 at this time.

Enhancing tubular solar still performance using novel PCM-tubes

The present study developed a novel PCM-tubes geometry to be used inside a tubular solar still with parabolic solar concentrator. Paraffin wax is filled inside 12-aluminum tubes working as a PCM material. Copper rods are installed inside the paraffin wax to enhance thermal properties. Parabolic concentrator solar tracking system is used to intensify solar radiations on the tubular solar still. Experimental work was executed under the climatic conditions of Ha'il city (27.64 °N, 41.75°E) 965 m above sea level in Saudi Arabia. The 12‑aluminum tubes were black painted and placed inside the trough. Results show a great enhancement of the freshwater productivity and device performance with relatively low production cost. Using PCM-tubes enhances the productivity and efficiency of the developed device by 40.51% and 38.25% respectively. The yield, efficiency and cost per liter are 5.55 L/m2day, 44.1% and 0.00782 USD for device with PCM-tubes compared to 3.95 L/m2day, 31.9% and 0.0163 USD for device without PCM-tubes. The developed device was able to reduce the freshwater production cost by 21.8% achieving a very competitive cost compared to the available solar desalination techniques. Further development of the tubular solar still is required in the future research effort.

Determination of the parameters for photocatalytic degradation from Chromium hexavalent to Chromium trivalent in a solar parabolic cylindrical concentrator in a simulated sample from tanning

The purpose of this study is to determine the efficiency of photocatalytic​ reduction (UV/TiO 2 ) from Hexavalent Chrome to Trivalent Chrome using a solar parabolic cylindrical concentrator for a simulated effluent sample from the tanning processes. For this purpose, a model of the solar parabolic cylindrical reactor was used, which was considered the most suitable for the capture of radiation and for its mobilization. The independent variables of the simulated liquid effluent sample were pH, temperature (T), flow (Q), hexavalent chrome concentration and dependent variables were the efficiency of the results, solar radiation and titanium dioxide concentration [TiO 2 ]. The optimum processing values were: pH= 3.75; Q= 8.2; T= 30; [TiO 2 ]= 30g. The results of the simulated samples were decreasing from 0.183 mg/L to the values of the maximum permissible limits (MPL) of 0.4 mg/l. In the results carried out before the photocatalytic treatment of the actual tannery sample from the Rio Seco Industrial Park, 326.95 mg/L was obtained, the concentration of hexavalent chromium was 173.28 mg/L. After the photocatalytic treatment, 58.85 mg/L and 25.89 mg/L were obtained respectively, with a reduction of the efficiency from 3 to 1. It is feasible to perform the photocatalytic​ treatment using the Parabolic Cylinder Reactor on a semi-industrial scale for the reduction of Cr + 6 to Cr + 3 . The research solves the current problems of the tanning companies in Arequipa. The optimal operation conditions are an exposure time of 4 h, between 10 am and 2.00 pm, with a radiation intensity of 875 W/m 2 . • Control parameters of photocatalytic degradation from CR VI to CR III are determined. • Solar parabolic cylindrical reactor model is used for radiation and mobilization. • Control parameters of photocatalytic degradation from Cr +6 to Cr +3 are determined. • Parameters like pH, temperature, solar radiation and TiO 2 concentration are focused.

Passive performance enhancement of parabolic trough solar concentrators using internal radiation heat shields

Boosting the optical and thermal efficiencies of parabolic trough concentrators is gaining renewal global interest for improving the overall concentrating solar power plant efficiency and reducing the specific costs of power generation. Using internal radiation heat shields in the annular space of the heat collection element is an attractive passive solution that is not well-addressed in the literature. This study is a first attempt to analyze and map both energetic and exergetic performances of parabolic trough concentrators in terms of the configuration of the radiation heat shield and the operating conditions of the concentrator. A 3D model based on Monte-Carlo ray tracing and computational fluid dynamics is developed, validated, and used to examine 420 combinations of design and operating parameters. The proposed design outperformed the conventional one in the whole spectrum of operating conditions, except for a narrow range of low operating temperatures and high flow rates. Floating radiation heat shields with small diameters and large shading angles enhanced the temperature uniformity of heat collection element and showed the highest enhancement ratios of both energy and exergy efficiencies, which were up to 15.4 and 14.4%, respectively. A radiation heat shield with a diameter of 75 mm and a shading angle of 150° was found the best performing configuration for most operating conditions. Increasing the shield’s emissivity (0.06) to that of the absorber tube (0.14) reduced the energy and exergy efficiencies by up to 33.75 and 29.06%, respectively. The effectiveness of the modified design was more pronounced at lower solar irradiance levels. The enhancements of energy and exergy efficiency decreased by 85.76 and 86.40% as the irradiance increased from 200 to 1000 W/m2. However, the modified design was still more efficient at all considered values of emissivity and solar irradiance.

Theory of concentration distribution over the surface of axisymmetrical receiver in cylindrical parabolic mirror solar energy concentrator

This work is devoted to develop the theory of concentration distribution of radiation over the receiver surface in cylindrical parabolic concentrator of radiation with axisymmetrical (cylindrical) radiation receiver has been studied. The results will make it possible to estimate concentration distribution over the radiation receiver surface and to associate output characteristics of concentrator unit for various combinations of design parameters at the stage of engineering, to choose the best combination of such parameters and to optimize reflecting surface and radiation receiver. Photovoltaic module with cooling or without it, solar collector, photovoltaic thermal module, etc. may be applied as radiation receivers. Mathematical physics equations have been deduced that describe the specifics of incident radiation flux reflection from the concentrator’s surface and falling onto that of radiation receiver. Concentration distribution has been estimated, for various concentrator design parameters and various positions of receiver axis in relation to the focus of reflecting surface, on the symmetry plane. The most effective concentrator designs characterized by 100% optical efficiency correspond to options where the focus of concentrator’s reflecting surface is located inside radiation receiver. Analysis of design options using the developed theory is shown on examples for given values of average concentration ratio (2, 6, 8, 10, 15, 20, 50), as well as radius of radiation receiver, half concentrator aperture and distance between the focus line and the symmetry axis of radiation receiver in cross-section.

Solar thermal and electricity. A state of the art

The objective of this contribution is to provide a state-of-the-art on research in solar thermal electricity systems. This objective is achieved using Scopus, and the softwears “Publish or Perish” and “VOSviewer”. The results of the research show the behavior of scientific productivity in this area. As well as the most productive thematic areas. Nations that lead the research in the generation of electric power on a large scale, using solar thermal energy. Network of scientific collaboration among nations, referring to the research of electricity generation through solar thermal energy. Correlation network among the most productive authors, in this subject within the Scopus directory. Most cited articles by each of the main journals that disseminate this theme. Conceptual bases of the generation of electricity with solar thermal energy. Properties of thermal energy storage technologies (TES) in power plants with parabolic solar concentrators or solar concentration towers. Current technologies and trends. Technological trends. Trends in the global energy market.

Solar gasification of grape marc for syngas production: Solar-dish-coupled reactor basic engineering and optimization

In this paper, a new 5.8 kW solar biomass gasification reactor design is proposed. It is meant for energetic exploitation of grape marc, a residue of the wine-making industry. The design couples the reactor with a 3.0 m diameter Parabolic Dish Solar Concentrator, and contemplates controlling its temperature by manipulating the biomass inlet rate. This work aims to establish an upper limit on the reactor syngas yield under actual solar and environmental conditions, to determine the optimal dimensions of the reactor, and to evaluate the feasibility of the temperature control system. Also, a process is proposed for industrial application and practical implications are considered. The performance of the reactor was numerically simulated employing 1-min solar irradiance data, heat transfer models, reaction models and enthalpy balances. The reactor dimensions that maximize syngas production were determined. Simulation results showed an upper limit of 73 gdry basis/min for the grape marc inlet rate (stationary regime), and of 3180 Nm3 (36.68 GJ) for the total syngas yield on the grape marc production season. Solar irradiance peaks were compensated, which supports the proposed temperature control system. Several design aspects were found to have substantial impact on the reactor performance, which contributes towards prototype manufacturing.

The Influence of Some Important Parameters on the Performance Efficiency of the Compound Parabolic Solar Concentrator

The Influence of Some Important Parameters on the Performance Efficiency of the Compound Parabolic Solar Concentrator