Parabolic Concentrator Research Articles

Harnessing the characteristic of compound parabolic concentrators for directional concentration of emitted thermal radiation and solar shielding in building-integrated radiative cooling

Radiative sky cooling (RC) is a promising solution for meeting the growing cooling demands by passively dissipating waste heat into frigid outer space. However, current RC systems suffer from low cooling power density and limited installation flexibility, impeding their effective application as building cooling strategies. To overcome these challenges, a novel concentrated RC system coupled with a compound parabolic concentrator (CPC) is proposed and experimentally studied. The objective is to investigate the effectiveness of the CPC in enhancing the cooling capability of the RC system and the feasibility of achieving all-day RC in unfavorable working conditions when integrated with building roofs. During nighttime experiments in the humid Nottingham region, the CPC-RC system exhibited an average emitter temperature that was 5.83 °C lower than the ambient temperature, representing a 30 % and 13.6 % improvement in RC performance compared to the flat-RC system and trapezoidal-concentrated RC system, respectively. The Photopia optical software simulation indicates that when the modules are tilted to the north, the CPC functions as a solar shield, effectively limiting solar radiation reaching the emitter surface, which is advantageous for conducting daytime RC experiments. In the daytime experiment, the emitter temperature of the CPC-RC module in anti-sunward group was still 1.59 °C lower than the ambient temperature and 5.49 °C lower than that of flat-RC module. At night, the CPC-RC module of the three placement groups all showed the highest RC effect in the same group. The average emitter temperature of the CPC-RC module in the horizontal placement group is 0.6 °C lower than that of the flat RC module. This novel CPC-RC scheme presents a new energy-saving strategy for buildings and showcases its potential for achieving 24-hour RC when integrated into anti-sunward roofs.

Modeling and Energy Concentration Characteristics of Asymmetric Multi‑ Section Compound Parabolic Concentrator with Vacuum Tube Absorber

Modeling and Energy Concentration Characteristics of Asymmetric Multi‑ Section Compound Parabolic Concentrator with Vacuum Tube Absorber

Duplex solar cooker with selective evacuated tube and compound parabolic concentrator

In the present work, an indirect solar cooking proposal is shown. The proposal combines three technologies: evacuated tubes, selective absorber, and compound parabolic concentrator (CPC). The absorber used is an evacuated glass tube, with a highly selectivity inner surface. The temperature reached by the solar cooker is approximately 160°C, enough to cover the cooking needs of all types of food; Irradiance, wind speed, ambient temperature was measured, food cooking tests were carried out, using an evacuated tube and a parabolic solar concentrator; as well as evacuated tube without parabolic solar concentrator. A compound parabolic concentrator was designed with an acceptance angle of 15 degrees, the base of the solar cooker was made with acrylic, the concentrator was made with simple reflection mirrors, the clips were printed on a 3D printer, the trays were made with food grade stainless steel, food cooking tests were carried out, recording the weather variables every 15 minutes. The development of this evacuated tube duplex solar cooker project is not only important because it involves the achievement of an academic purpose, but also involves a social purpose. It is intended to provide an efficient and economical solution that is attractive to multilateral organizations capable of supporting its manufacture, industrialization and distribution to achieve the massification of the product with a real and lasting impact

Optical and thermal investigation of hyperbolic cavity receiver with secondary reflector for solar parabolic dish collector

A hyperbolic-shaped cavity-type receiver with a second stage reflection for a 40 m2 solar parabolic dish concentrator (PDC) is presented in this paper,along with optical and thermal modeling. The receiver geometry and the secondary reflector complete the hyperbolic geometrical shape of the present receiver. This study aims to estimate heat losses owing to natural convection and radiation under influential parameters associated with solar parabolic dish system. Optical modeling has been performed with verified model using ASAP® 2013 V1R1. The optical simulations have been carried out for varying receiver height (h1), height of the secondary (h2) and diameter-to-total height ratios (d/h) of 0.5, 1, and 1.5 while keeping the diameter of the plane aperture of the receiver (d) constant. The optimum receiver geometry has been selected based on the performance in terms of optical efficiency. The maximum efficiency found is 91.72% for h1 = 0.75 m and d/h = 0.5 for the mounting distance of 4.21 m. The optimized shape is further studied to determine how the receiver absorptivity and the secondary reflector's reflectivity affect the optical performance. The absorptivity and reflectivity range from 0.86 to 0.94. Obtained optimum receiver geometry from the optical investigation is further analyzed to estimate the heat transfer rate. The thermal modeling is performed for 0°, 30°, 60°, and 90° orientations of the receiver in ANSYS Fluent 2020 R1. A comprehensive comparison among the available models has been reported and validated with well-established experimental data. This work has developed free convective Nusselt number correlation. It can be a valuable addition to the existing literature.

Pathways for low carbon hydrogen production from integrated hydrocarbon reforming and water electrolysis for oil and gas exporting countries

Integrated hydrocarbon reforming processes with H2O electrolysis for H2 production have been developed to reduce greenhouse gas (GHG) emissions in oil and gas exporting countries (OGEC). The developed system includes steam methane reforming (SMR), gas-heated autothermal reforming (GH-ATR), autothermal reforming (ATR) and partial oxidation (POX). Each of these systems operates with H2O electrolysis to increase the H2 production rate and feed O2 to the reformers. The combined systems also incorporate thermophotovoltaic (TPV) units, solar cells, a wind turbine system and a Rankine cycle to convert waste heat to electricity and generate more electrical energy. Parabolic dish concentrators (PDCs) produced thermal energy for endothermic reactions. The introduction of H2 fuel cells replaced the burning of natural gas in power plants to generate electricity. The result of this study reveals that using renewable energy sources and energy recovery units to produce distilled H2O and operate other downstream units, the H2 selling price of the proposed system is expected to be <$2.9/kg. Efficiency improvement by ≥10% for each hydrocarbon reforming method operating with other units was also achieved in contrast to the current hydrocarbon reforming processes. The provided integrated method will provide a high-value chain in the H2 generation industry and promote carbon neutrality in oil and gas rich countries.

Assessment of a parabolic trough solar thermal concentrator under two-phase flow conditions

In the present work, a mathematical model is developed to describe the heat, mass, and momentum transfer of a biphasic flow during its trajectory in the absorber tube of a parabolic trough solar concentrator (PTSC) for thermal processes in a transitory simulation, showing the evolution of the parameters in a dynamic system. The working fluid is water. The numerical solution of the model is implemented in C++ code. The model is validated with the results obtained from the DISS Project experiment. The results of the numerical solution have a maximum variation in the fluid temperature profile of 6.45 % and a maximum difference of 2.02 % in the outlet pressure of the fluid with respect to the experimental results. The case study consists of the analysis of a PTSC under different radiation conditions from two different cities in Mexico, Piedras Negras and Mexico City, on an average spring day. The results obtained allow us to analyze the behavior of the fluid temperature, the quality of the steam, and pressure drop through the absorber tube and time; under the conditions studied, the concentrator reached an efficiency of 52 %. It is observed that the model is sensitive to changes in climate.

Performance of compound parabolic concentrator solar air flat plate collector using phase change material

This work involves an experimental investigation on two different new models of Compound Parabolic Concentrator (CPC) solar air flat plate collector with adding paraffin wax Phase Change Material (PCM). The first model is called involute shape model, whereas the second model is called normal shape model. To explore the best model performance, the structures of compound parabolic concentrator models have two symmetric giant parabolic mirror reflectors, similar concentration ratio of 1.7, similar flat plate receiver with 12 tubes filled by paraffin wax phase change material. The performances of both models are presented together for purpose of comparison. The tests have been performed in April and May 2023 in Mosul city/Iraq under standard conditions for around 11 h during the day. The outcomes indicated that rising in air mass flowrate leads to rise the receiver performance. The findings confirm that the thermal efficiency of normal shape is more efficient than involute shape by 7.6%, 13%, and 11.7% for 0.0085 kg/s, 0.0174 kg/s, and 0.027 kg/s, respectively. The optimum thermal performances for involute and normal shapes have been obtained equal 65.4% and 77.1% for 0.027 kg/s, respectively. For constant air flowrate, the performance of normal shape is higher than involute shape by 15.5% (14th May), 12.6% (27th April) and 11.8% (15th April). A significant temperature change has been found in involute shape as compared to normal shape. The outlet temperature of normal shape is always lower than the involute shape for all air mass flowrate. It is demonstrated that phase change material and the position of the receiver have considerable influence on the model performance. The current work provides an important information for evaluating the compound parabolic concentrator model performance for Mosul/city.

Performance evaluation and optimization of solar dish concentrator in the upper Egypt region

AbstractThe goal of this study is to optimize and examine the effect of different rim angles and focus lengths on the performance of a solar parabolic dish. To achieve these goals, a solar parabolic dish concentrator was constructed with different focus point positions and tested under the climatic conditions of the Upper Egypt region in Qena city, with the location of (Latitude: 26.16°, Longitude: 32.71°). The preliminary experimental days started on 18th and lasted on 20th of September 2022, and the tested rim angles were 70°, 80°, and 60°. The results showed that the performance of the proposed solar parabolic dish concentrator was enhanced when the rim angle was between 60° and 70°, otherwise, the performance was regressed when the rim angle was between 70° and 80°. To optimize the rim angle, another available rim angle was selected to increase the performance of the solar dish fixed at 65°, and this angle was tested on 21st of September 2022. The results demonstrated that the thermal efficiency of the solar parabolic dish with rim angle of 65° was higher than that of 70°, 80°, and 60°, and the recorded thermal efficiency reached up to 79.5%, 39.4%, 5.84%, and 28.4%, respectively, under the tested rim angles.

Comprehensive investigation of a building integrated crossed compound parabolic concentrator photovoltaic window system: Thermal, optical and electrical performance

Integrating PV solar cells with concentrators into window systems can not only generate electricity for a building, but also has the potential to enhance the thermal resistance of the building's windows without a significant sacrifice of light transmittance for passive daylight. A novel system, known as the crossed compound parabolic concentrator photovoltaic window, has been recently studied for its electrical properties. However, its thermal and optical performance, particularly in terms of the overall heat transfer coefficient (U-value) and total optical transmittance when integrated into a building, remains unexamined. These factors are crucial for predicting the system's impact on a building's energy efficiency and indoor comfort. Therefore, this paper aims to investigate the U-value of this window system under various temperature scenarios and the optical transmittance of the window at different incident angles. The thermal conductance was assessed through numerical simulations using a computational fluid dynamics model, which was validated by experimental measurements conducted in a large climate chamber. The optical transmittance was investigated using a validated 3D ray-tracing model. The total optical transmittance and electricity generation were calculated for typical sunny days in winter and summer under London's climate conditions. Additionally, alternative designs were developed to explore the impact of pitch between adjacent optics on the thermal conductance and optical transmittance of the window. The results showed that the window with a configuration of Dx = Dy = 5 mm (where Dx and Dy represent the horizontal and vertical pitches, respectively, between two adjacent solar optics) achieved the lowest U-value (2.566 W/m2·K). This U-value is slightly lower than that of the original window design, which has a U-value of 2.575 W/m2·K. The original window configuration with Dx = Dy = 1.77 mm produces the highest power output. Specifically, it generates 499.25 Wh/m2 on a typical sunny day in winter and 162.73 Wh/m2 on a typical sunny day in summer. However, it exhibits the lowest transmittance (14.6 % on a typical sunny day in winter and 25.2 % on a typical sunny day in summer, respectively), indicating that it is more suitable for buildings with a higher window-to-wall ratio to ensure an adequate amount of natural light. For buildings with a lower window-to-wall ratio, the CCPC-PV window should be designed with a larger horizontal pitch, such as 15 mm and 30 mm, to meet indoor illuminance requirements while also providing enhanced thermal performance and additional power output.

Design of a Scheffler Mosaic Mirror by Optical Raytracing and CAD Software

The Scheffler reflector is a parabolic metal concentrator, typically applied in solar thermal systems with receiver fixed to the ground. The Scheffler mirror is deformed during the year to optimize its solar light collection. For practical reasons it is useful to manufacture such a curve reflector as mosaic mirror. This study develops a configuration of the mosaic mirror type starting from the continuous mirror, trying to indicate how the reflector can be designed. Combining a CAD software tool with raytracing simulations, the optical performance of the Scheffler mosaic mirror is compared with a continuous Scheffler collector. The CAD software reproduces the mechanical deformations of a real Scheffler reflector; while the raytracing software simulates the image that the Scheffler reflector concentrates on the receiver. However, the characteristics of the final composed reflector must be revised depending on the receiver requirements. Moreover, the sizing of the elementary mirrors must be chosen considering the final receiver and it also depends on economic considerations.

Prediction of Circumsolar Irradiance and Its Impact on CSP Systems under Clear Skies

In this work, a model to estimate circumsolar normal irradiance (CSNI) for several half-opening angles under clear skies was developed. This approach used a look-up table to determine the model parameters and estimate CSNI for half-opening angles between 0.5° and 5°. To develop and validate the proposed model, data from five locations worldwide were used. It was found that the proposed model performs better at the locations under study than the models available in the literature, with relative mean bias error ranging from −13.94% to 0.70%. The impact of CSNI for these different half-opening angles on concentrating solar power (CSP) systems was also studied. It was found that neglecting CSNI could lead to up to a 7% difference between the direct normal irradiance (DNI) measured by a field pyrheliometer and the DNI that is captured by CSP systems. Additionally, a case study for parabolic trough concentrators was performed as a way to estimate the impact of higher circumsolar ratios (CSR) on the decrease of the intercept factor for these systems. It was also concluded that if parabolic trough designers aim to reduce the impact of CSNI variation on the intercept factor, then parabolic troughs with higher rim angles are preferred.

Design, Fabrication and Performance Evaluation of Hybrid Parabolic Dish Solar Concentrator for Cooking and Heating of Water

Design, Fabrication and Performance Evaluation of Hybrid Parabolic Dish Solar Concentrator for Cooking and Heating of Water

Performance enhancement of compound parabolic concentrating vaporized desalination system by spraying and steam heat recovery

This paper employs the compound parabolic concentrator to heat the thermal conduction oil as working fluid to a higher temperature. The feed water is sprayed and obtains heat from the working fluid in evaporation chamber. The spraying of feed water enhances heat and mass transfer and increases the vaporization intensity. The latent heat of steam is recovered to preheat the feed water which improves energy utilization. Multivariate orthogonal experiments were conducted to obtain the optimized nozzle arrangement in the evaporation chamber. Numerical simulations were performed to evaluate the effect of nozzle parameters on liquid film thickness and water production performance. In system performance experiments, the heat loss, heat recovery performance, fresh water production and gain output ratio in sunny weather were achieved. The daily fresh water production of the system was 15.1 kg with a maximum rate of 4.32 kg/h. The nozzle group arrangement optimization increases the fresh water production by 28.12 % and the maximum rate was 8.48 %. The heat recovery unit increases fresh water production by 13.18 %, with an average heat recovery efficiency of 0.85.

A novel solar disk chamber reactor for agricultural waste recycling and biochar production

The quality and properties of biochar are generally influenced by the nature of the raw materials and pyrolysis techniques. To assess the quality of sesame biochar production, a disc chamber reactor set on a solar parabolic dish concentrator was proposed as a modified slow pyrolysis technique. To evaluate the physicochemical characterizations of the produced biochar, two pyrolysis settings were used: 470 °C for 1 h (T1) and 440 °C for 2 h (T2) to produce biochar from sesame stalk feedstock (SS) using the proposed solar disk chamber reactor. Ash content, mass fraction of elements (C, H, and O%), pH, surface area, zeta potential, Fourier transform infrared (FTIR), and scanning electron microscope (SEM) were investigated. The results showed that the mass of T1 biochar decreased by 5% when compared to T2, while ash content, pH, fixed carbon, and volatile gases for both biochars were relatively close. The H/C and O/C molar ratios were below 1.00 and 0.4, respectively, indicating a loss of degradable polar contents and the formation of aromatic compounds. The surface area of T2 biochar was three times the surface area of T1, with the opposite trend in mean pore diameter. Two biochars showed the same FTIR peaks and SEM data, with small differences in their characteristics, demonstrating that pyrolysis time and temperature had a tight relationship. Both biochars showed approximately similar properties. The reactor’s efficiency is mainly affected by solar energy and atmospheric conditions during operation, which influence the average surface temperature. In Egypt, climatic conditions would be more favorable in the summer to improve the efficiency of parabolic solar dish concentrators for producing high-quality biochar.Graphical abstract

Experimental Study on Performance of a Solar Thermal-Driven Vapor Absorption System Integrated with Hot Thermal Energy Storage for Milk Chilling

Abstract Solar-powered vapor absorption system has proven to be a feasible and viable cooling source. However, most reported installations for milk chilling applications are equipped with an auxiliary heater that consumes significant electricity/gas, making it economically unviable. In this study, the experimental investigation of the performance of a solar-powered vapor absorption chiller has been reported for milk chilling applications as per standard ISO 5708 – 2 II. It has been identified that the performance of the vapor absorption chiller is quite uncertain and underperforming while operated with the heat directly fed through the evacuated tube compound parabolic concentrator solar field due to diurnal and seasonal variations of solar radiation intensity. Therefore, a hot thermal energy storage integration has been studied and analyzed in this study. The performance of the vapor absorption chiller has improved significantly with the use of hot thermal energy storage in the solar circuit as the coefficient of performance of the vapor absorption chiller improved up to 0.4, which was earlier around 0.25. Further, hot thermal energy storage provides better thermal management to increase the productivity and performance of the vapor absorption chiller, and the cooling time for the first milking is 2 hours and 45 minutes. The energy efficiency ratio has a maximum value of 6.1 with an average of 4.3, whereas the thermal COP has an average of 0.35 and a maximum value of 0.52 when run with thermal energy storage alone.

Solar side-pumped Nd-doped fiber laser based on a doughnut-shaped hollow reflector

A high-power solar side-pumped Nd-doped fiber laser based on a doughnut-shaped hollow reflector (DHR) is proposed. The primary concentrator consists of twelve off-axis parabolic mirrors. The DHR coupled with an array of three-dimensional compound parabolic concentrators (3D-CPCs) functions as the secondary concentrator, inside which many cycles of Nd-doped fiber is coiled. After being reflected by the off-axis parabolic mirrors, the sunlight is launched into the DHR through the twelve 3D-CPCs, and experiences multiple-times reflection by the DHR, and finally is absorbed by the Nd-doped fiber for laser oscillation. Ray tracing shows that 173-W of solar power can be absorbed by the fiber. By solving the rate equations and power transmission equations, laser output power, slope efficiency and optical-to-optical conversion efficiency of 10.3 W, 6.12% and 5.94%, respectively, are realized. This kind of solar-pumped fiber laser thus offers a new route for achieving high-power solar-pumped laser sources.

Comparison of the cumulative exergy demand of phase change and reverse osmosis desalination plants with environmental impacts approach

In the scope of the current study, an investigation into the cumulative exergy demand index was conducted for freshwater production across multiple distillation technologies. These technologies encompassed Waterfall Cascading Distillation with Linear Parabolic Solar Concentrator (WCDLPC), Distillation with Linear Parabolic Concentrator and Vacuum Pump (DLPCVP), Distillation with Stand-Alone Point-Focus Parabolic Solar Concentrator (DSPPC), Reverse Osmosis with Non-renewable Energy (RONRE), and Reverse Osmosis with Solar Renewable Energy (ROSRE).The functional unit was established as the production of one ton of freshwater using various desalination technologies. The Outcomes of the analysis pertaining to the cumulative exergy demand in diverse saline water desalination technologies revealed notable findings. Specifically, in the Reverse Osmosis Desalination System with the Conventional System as well as in other desalination technologies (ROSR, WCDLP, DLPCVP and DSPPC), the electricity factor and the photovoltaic panel factor respectively exhibited the most substantial contributions to the cumulative exergy demand. Remarkably, it was observed that the RONRE technology exhibited the highest cumulative exergy demand, reaching 107.04 MJ, while the ROSRE technology demonstrated the lowest demand at 5.98 MJ. Furthermore, the integration of renewable solar energy in lieu of non-renewable electricity within the reverse osmosis technology exhibited a remarkable reduction in cumulative exergy demand, achieving a reduction of 17.90 times. Similarly, the substitution of the waterfall cascade system with a vacuum system in the WCDLPC technology resulted in a 2.69 times reduction in cumulative exergy demand.

Solar-pumped dual-rod Ce:Nd:YAG laser with 58W continuous-wave output power and 5.1° tracking error compensation width.

The pursuit of high-power solar laser systems with high efficiency and capacity for large tracking error compensation is determinant for the applicability of this renewable technology. A side-pumped dual-rod Ce:Nd:YAG solar laser was developed and tested at the focus of a 2 m diameter parabolic concentrator. Maximum continuous-wave total solar laser power of 58 W was measured. To the best of our knowledge, this is the highest laser power from a Ce:NdYAG solar laser. Moreover, wide tracking error compensation width of 5.1° in the azimuthal direction was reached, being 4.25 times higher than the previous measurement without solar tracking assistance.

Experimental study on a concentrating solar photovoltaic/thermal system using different fluid spectral beam filters

Spectral splitting photovoltaic/thermal technology is the leading field in the area of extremely efficient utilization of solar energy. Due to its complexity, experimental research on spectral splitting photovoltaic/thermal devices is relatively limited, mainly focusing on the laboratory scale energy efficiency test or calculation process verification. These studies do not provide intuitionistic guidance for the actual operation of engineering systems. In this paper, a fluid filter-based compound parabolic concentrator solar photovoltaic/thermal system with engineering application dimensions is designed and experimentally studied under actual outdoor environments. Different fluid filters are prepared and used to regulate the spectral splitting characteristics of the proposed system, including the deionized water, silver/water nanofluids and silver-cobalt sulfate/water nanofluids. When the environmental parameters are relatively stable, the method of adjusting the composition of the fluid filter is used to obtain the dynamic operating characteristics of the system. The results show that silver nanoparticles and cobalt sulfate can improve the spectral absorptivity of the deionized water. Compared with the deionized water, when the silver/water nanofluids is used as the fluid filter, the thermal efficiency of the system increases, the electric efficiency and overall exergy efficiency of the system both decrease, and the three efficiencies are 56.0%, 8.5% and 19.6%, while for the silver-cobalt sulfate/water nanofluids, the efficiencies are 58.0% 8.0% and 20.0%. Moreover, the results reveal that for the photovoltaic/thermal system with a low solar concentration ratio, by enhancing the absorptivity of the fluid filter, the fill factor of the photovoltaic module can increase, but the output electric power will decrease. When the silver-cobalt sulfate/water nanofluids is used, the fill factor and maximum output power of the proposed system are 0.633 and 69.2 W. For a unit consisting of four sets of the proposed photovoltaic/thermal systems, the emission reductions of CO2, NOx, SO2 and dust for the whole lifetime are approximately 7794.19 kg, 181.48 kg, 191.95 kg and 111.68 kg, respectively.

Reduction of Aflatoxin contamination in coconut oil using concentrated solar radiation

Global demand for edible coconut oil has a rapid growth due to its health benefits. However, the susceptibility to carcinogenic mold contamination, aflatoxin, poses a significant global health concern. Concentrated solar radiation was used in this study as a new initiative to investigate the more efficient elimination of aflatoxin in coconut oil. Samples were collected from the Colombo district, Sri Lanka, as branded (n = 3) and unbranded (n = 5). The initial aflatoxin content was determined using High-Performance Liquid Chromatography (HPLC-FLD) system with AflaStarTM FIT immunoaffinity columns. They were exposed to concentrated solar radiation for 10 (T-1), 20 (T-2), and 30 (T-3) minutes respectively, using a parabolic proto-type solar concentrator. The remaining aflatoxin content was re-determined after each treatment. Following each treatment (T-1, T-2 and T-3), the maximum allowed total Aflatoxin and Aflatoxin B1 (AFB1) content of all coconut oil samples were lower than the set European Union (EU) limits (4.2 µg/kg) with a mean total Aflatoxin reduction of 94.00 ± 6.48 %, 98.67 ± 2.80 %, 100.00 ± 0.00 % respectively. T-1 and T-2 treatments at mean concentrated solar radiation levels (W/m2) of 971 ± 29 and 945 ± 65.4 were recognized as the most efficient at removing total and AFB1 aflatoxin tainted in coconut oil at higher levels.