Monte Carlo Ray Tracing Method Research Articles

Overall performance evaluation of a novel optical truncation method for compound parabolic concentrated photovoltaic-thermal system

A variable geometric concentration ratio (VGCR) truncation method was proposed to enhance the performance of compound parabolic concentrated photovoltaic-thermal (CPC-PVT) system in this study. Based on a multi-physics field model of optical-thermal-electrical coupling, numerical investigations using Monte Carlo ray tracing (MCRT) and finite volume method (FVM) were conducted to analyze the effects of the variation rate of truncation ratio (k) and light incident angle (θin) on the overall performance (optical efficiency (ηop), instantaneous thermal efficiency (ηth), instantaneous electrical efficiency (ηele,total), instantaneous electrical power (P), instantaneous exergy efficiency (ηu,total) and economic performance) of CPC-PVT system. Also, the overall performance between the VGCR-CPC-PVT system and the full CPC-PVT (FCPC-PVT) system was compared. The results indicate that, when θin is smaller, there is little disparity in the overall performance between the two systems. However, as k increases, ηop, ηele,total, ηth and ηu,total of VGCR-CPC-PVT system monotonically increase, and the area of the high-temperature region on the PV panel surface decreases. When θin is larger, the VGCR-CPC-PVT system has a smaller shaded area, ηop, ηele,total, P and ηu,total are significantly improved compared with the FCPC-PVT system. Additionally, k has a significant impact on the overall performance of the system, and P, ηu,total and saved reflective surface area (S) are the criteria for selecting k. When using P and ηu,total as the selection criteria, the optimal k value is 0.04. For 0°≤θin≤38°, the average ηop, average ηele,total, average ηth, average P and average ηu,total of the VGCR-CPC-PVT system with k = 0.04 are relatively improved by 1.91 %, 4.59 %, 2.42 %, 3.12 % and 4.04 %, respectively, while the reflector area decreases by 17.5 %, compared with the FCPC-PVT system. The cost-effectiveness of concentrator increases significantly with k.

Design and numerical simulation of a 45 kWel multi-source high-flux solar simulator as a heating source of dielectric materials positioned in a microwave characterization cavity

This study reports the design and modelling of a high-flux solar simulator (HFSS) combined to a resonant cavity for microwave dielectric properties characterization of ceramics at very high temperatures. The HFSS comprises seven xenon arc lamps with ellipsoidal reflectors, delivering a maximal electrical power of 6.5 kWel each. Positioned on a virtual sphere of around 1600 mm radius, the lamps provide concentrated irradiation heating on a sample positioned inside the resonant cavity. The propagation of the lamp’s irradiation to the sample and the cavity is simulated using Monte Carlo ray tracing method. An ANSYS Fluent finite volume method for solving the resulting multimode heat transfer and flow indicate a radiative flux reaching 1.84 MW m−2, and a sample temperature of approximately 1470°C with 10 % non-uniformity. These results suggest that the designed heating system and resonant cavity is suitable for conducting microwave dielectric properties characterization of refracting ceramic materials at high temperatures, addressing a gap in studies focusing on temperatures exceeding 1000°C.

Determination of interparticle radiative heat transfer and radiation absorption for ellipsoidal particle beds using Monte Carlo ray tracing

The calculation of radiative heat transfer between particles in particle-based solar systems presents significant challenges in terms of computational cost and accuracy. This study addresses these challenges by employing the discrete element method to generate random particle packings and the Monte Carlo ray tracing method to investigate the influence of particle shape and volume fraction (ϕ) on interparticle radiation transfer and the absorption of incident radiation. The results reveal that, at low volume fractions, the shape and orientation of ellipsoidal particles have a pronounced impact on direct radiative transfer. Oblate particles exhibit the highest average radiation distribution factor (RDF), and the dispersion of RDF data is more prominent for oblate and elongated prolate particles compared to spheres. As ϕ increases to 0.35, the contribution of indirect transfer from neighboring particles becomes significant for oblate particles, resulting in a reduction in the dispersion of RDF data. Furthermore, when ϕ reaches 0.55, the decisive factor in determining RDF becomes the shielding effect of particles positioned between the emitting and receiving particles. The average RDF tends to converge among particles of different shapes, although oblate and elongated prolate particles still exhibit considerably larger RDF dispersion compared to spherical and near-spherical particles. Additionally, the effective absorptivity of the particle bed for incident radiation decreases as the aspect ratio of particles increases at all volume fractions. Moreover, the transmitted fraction demonstrates an exponential relationship with the depth, and beds composed of spherical particles exhibit better radiation transmittance compared to beds containing non-spherical particles.

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.

Performance evaluation of a partially-filled porous foam cylindrical tubular receiver realizing Ni foam material reduction

The optimization of metal foam structure parameters is crucial for enhancing the heat transfer and pressure drop performance of cylindrical tube heat exchangers. In this study, thermal output performance of 16 different nickel foam-filled solar receivers with varying thicknesses and positions is numerically simulate. An optical-thermal conversion model is established using the Monte Carlo ray tracing (MCRT) method and user-defined functions. The influences of foam filling thickness and position on heat absorber, wall hot spot distribution, heat loss type, thermal efficiency, pressure drop, thermohydraulic performance, exergy loss, and outlet temperature were analyzed. Furthermore, a multi-objective optimization algorithm called non-dominated sorting genetic algorithm II (NSGA II) is used to generate the best trade-off solutions between improvement of thermal efficiency and pressure drop. The results show that enhancing the thickness of the filled foam within the CTR tube enhances thermal efficiency and elevates pressure drop. However, optimizing the length and filling position of the foam can effectively mitigate excessive pressure drop caused by longer foam, without compromising thermal efficiency. This approach results in a reduced pressure drop while maintaining optimal performance. The optimal solution of multi-objective optimization is that the 123 mm thickness foam is filled at 0 mm from the inlet of the tube, and the pressure drop and thermal efficiency of the solar receiver are 830.2Pa and 83.1 %, respectively, when the mass flow rate is 0.01 kg/s.

Exploring potential of quantum dots for high power solid-state lighting protected by transparent ceramics

When quantum dot diffusion plates (QDDPs) are used as phosphor conversion materials for high-power lighting, transparent ceramics (TCs) can be used to prevent thermal damage of QDDPs. The spectral, suitable for diverse lighting environments, can be precisely calibrated by modifying their ratio. The temperature dependent photoluminescence spectra, fluorescence lifetime, Huang Rhys factor and activation energy of TCs were studied in detail. It was evident from the results that the intensity of TCs remained above 89% even at 423 K, while fluorescence lifetime remained stable, nearly 64 ns. Huang-Rhys factor and activation energy were consistently measured at 1.81 and 0.13 eV, respectively. The extraordinary luminescent stability of TCs revealed their integral role in providing reliable protection for QDDPs. The spectra of LEDs/LDs were successfully predicted using Monte Carlo ray tracing method. The service condition under high-energy laser was studied using finite element method. White light with Commission Internationale de l'Eclairage (CIE) of (0.38, 0.39) and (0.31, 0.34) and luminous efficiency of 58 and 150 lm/W were prepared by combining QDDPs/TCs with LEDs/LDs, and the Color Rendering Index (CRI) reached a remarkable 88.4 and 78.8. A detailed exploration of the proficient thermal management was accomplished using finite element analysis, with the simulated outcomes matching closely with the experimental results.

Calculation of optical efficiency of the heliostat field based on Reverse Projection Box Counting Model

A more accurate and reasonable calculation model is proposed for the calculation of total optical efficiency, shadow blocking efficiency, cosine efficiency, atmospheric transmittance, collector truncation efficiency and output thermal power of heliostat field in tower solar photovoltaic power plant. In this paper, under the condition that the relevant parameters of heliostat field are determined, the Monte Carlo Ray Tracing method is used as the basis for the calculation of each optical efficiency. At the same time, the innovative Reverse Projection Box Counting Model is established to accurately identify whether there is a shadow blocking problem or not, and the differential idea is used to effectively solve the problem of repeated calculation of the blocking shadow area and the irregularity of the blocking area difficult to be calculated caused by one heliostat being blocked by multiple heliostats, so as to estimate the shadow blocking efficiency of the heliostat field more accurately. Finally, the heliostat field in Gansu, China, is taken as an example for calculation, and the results are compared with those of other scholars and the real value of the heliostat field to prove the superiority of the model constructed in this paper and the accuracy of the solution results.

Performance evaluation of a parabolic cylinder collector applying the Monte Carlo ray tracing method

The purpose of this article is to evaluate the performance of a prototype parabolic trough collector for three proposed scenarios, where geometric designs with optical characteristics are tested according to the appropriate technological paradigm; low cost of maintenance and implementation, intensive local labor, materials and resources of the implementation area. The device was developed by the Energy, Automation and Control Systems Research Group GISEAC of the Unidades Tecnológicas de Santander for low-cost water heating; using materials and labor for its fabrication easily available locally. Monte Carlo ray tracing methodology was applied using the open-access software SolTrace and Tonatiuh. To select the geometric scenario to be simulated, the edge angle and the width of the primary reflection system of the device were varied. The results obtained showed that the aperture of the parabola has a direct impact on the drop in the concentration ratio (CR) percentage value and the performance of the prototype.

Efficiency Calculation of Solar Concentrator Field Based on Monte Carlo Ray Tracing Method

Efficiency Calculation of Solar Concentrator Field Based on Monte Carlo Ray Tracing Method

The performance evaluation of the free-falling particle solar receiver with a novel zigzag mass-flow controlled particle release pattern

A free-falling particle receiver is a promising technology to be used in concentrating solar power plants. In this study, an optical-thermal coupled model is established by combining a Monte Carlo ray-tracing method with a finite volume method to simulate the energy transfer processes in a solar power tower system employing a cavity receiver. Using the developed model, a novel particle release pattern, zigzag mass-flow controlled pattern, is proposed and compared with three other patterns, straight-line, zigzag, and mass-flow controlled patterns. First, the effects of the amplitude of the zigzag particle release slots on the receiver performance are analyzed. Then, the variations of the solar energy entering the receiver at different times on the vernal equinox is studied. Moreover, a new particle release pattern, zigzag mass-flow controlled pattern, is proposed and evaluated. The results demonstrated that the thermal performance of the zigzag mass-flow controlled particle release pattern was found to be superior to the other three patterns, allowing an increase in the thermal efficiency of 2.90 %. This allows for achieving effective thermal performance improvements while employing cost-effective designs in the free-falling particle receiver.

Developing optical and thermal models with experimental validation of parabolic trough collector for moroccan industrial heat applications

This work presents the development of advanced optical and thermal models for parabolic trough collector systems (PTCs) through an extensive experimental study utilizing a PTMx-24 collector from Soltigua company, installed at Green Energy Park (GEP) research facility. The optical model leverages Tonatiuh software, employing the Monte Carlo Ray Tracing (MCRT) method. Moreover, a MATLAB script was adjusted to account for Incidence Angle Modifier (IAM) fluctuations in the optical analysis, while incorporating receiver thermal parameters for the thermal analysis. This study assesses the potential of PTCs in the territory of Solar Heat for Industrial Processes (SHIP) over various seasons within a semi-arid climate, offering invaluable insights for sustainable energy utilization. The validation of the models was conducted across four distinct days characterized by diverse meteorological conditions. The optical model demonstrates a remarkable correlation of 97.04 % between the MATLAB script and experimental results. Additionally, results from Tonatiuh software exhibited an important accuracy of 95.92 %. The thermal model showcased outstanding precision, revealing a correlation of 98.5 % compared to experimental results, signifying its adaptability to collectors of varying geometries and parameters. These findings highlight the predictive potential of these models, aiding in the decision-making process to determine the system's performance on specific days with specific meteorological conditions.

Performance analysis of a novel direct absorption parabolic trough solar collector with combined absorption using MCRT and FVM coupled method

Direct absorption parabolic trough solar collector (DAPTSC) using nanofluid absorber has been demonstrated as an efficient technology for exploiting solar energy at high temperature. However, most mono nanofluids are unable to achieve broadband absorption and hybrid nanofluids are unstable at high temperature. In this work, the mono nanofluid and optical glass combined absorption is proposed for the DAPTSC. In which the absorption glass (HB850) and an outer glass tubes form an annular space for indium-tin-oxide (ITO)/Therminol VP-1 nanofluid flowing. Monte Carlo Ray-Tracing and Finite Volume Method (MCRT-FVM) coupled model is developed and validated for system investigation. The results show that the novel collector with the combined absorber exhibits obvious enhancement in thermal performance compared to Therminol VP-1 or ITO/Therminol VP-1 nanofluid. The DAPTSC with concentric annular tube (CAT) has a significantly superior thermal performance to that of the single tube collector, with 45.91 % higher achievable temperature gain and 1.15 % more achievable exergy efficiency. Finally, an eccentric annular tube (EAT) is proposed for further improvement. To quantify the performance improvement of the DAPTSC with EAT, a comparison has been made to that of a DAPTSC with CAT. The results indicate that EAT configuration shows 1.96 % enhancement in the exergy efficiency.

Performance analysis of a nanofluid spectral splitting concentrating PV/T system with triangular receiver based on MCRT-FVM coupled method

Optimizing system structure is one promising way to enhance the spectral beam splitting concentrating photovoltaic/thermal (SBS CPV/T) system performance. In this study, a linear Fresnel CPV/T system incorporated with triangular cooling duct and Ag@SiO2/ethylene glycol (EG) nanofluid filter is designed to enhance the overall performance of the system. To quantitatively reflect the heat generation of Ag@SiO2/EG nanofluid filter and silicon PV modules under inhomogeneous solar flux distributions, a coupled method combining Monte Carlo ray tracing (MCRT) method with Finite Volume Method (FVM) is employed. After validating the coupled method, the performance of the system with triangular receiver is discussed under various operating conditions. The results demonstrate that the nanofluid outlet temperature and PV module temperature present 316.3 K and 306.8 K at nanofluid inlet temperature of 298 K, respectively. The high mass flow rate and low inlet temperature allow high thermal and total efficiencies, while they present slight effect on electrical efficiency. To quantify the achievable enhancements with the triangular receiver, a SBS CPV/T system with flat-plate receiver is also discussed. It is found that the total efficiency of the triangular receiver is higher than that of the flat-plate receiver, with a maximum enhancement of 7.9%.

A study on the model of solar radiation transfer in multi-layer glass facade with attached droplets

To obtain the optical properties of the spray cooling double skin façade (SC-DSF), a solar radiation transfer model of the multi-layer glass system with attached droplets is proposed in this study. The solar radiation is segmented into direct and diffuse radiation, and the monte carlo ray tracing method and angle discretization method are used to obtain the optical properties of the single layer glass with attached droplets. And then, the energy balance equation of the multilayer glass system is established based on the net-radiation method, and the transmittance, reflectance and absorptance of the multilayer glass system are calculated. The effectiveness of the proposed method is verified by the experimental results, which shows the numerical results are in good agreement with the experimental data. In addition, some important influence factors are analyzed and discussed, including the solar incidence angle, the droplet contact angle, the droplet coverage rate, and the average droplet diameter. It is found that there is little influence on the system transmittance when the incidence angle is smaller than 40°. However, the transmittance decreases with the increase of the incidence angle when the solar incidence angle is greater than 40°. When the droplet contact angle is small (less than 40°) or large (larger than 140°), its influence on the transmittance of the system is negligible. Subsequently, with the increase in the droplet contact angle within 40–140°, the transmittance firstly decreases and then increases. Adjusting the droplet coverage rate and droplet size is an effective measure to decrease transmittance and solar heat gain.

Prompt: Probability-conserved cross section biasing Monte Carlo particle transport system

An open source software package for simulating thermal neutron propagation in geometry is presented. In this system, neutron propagation can be treated by either the particle transport method or the ray-tracing method. Supported by an accurate backend scattering physics engine, this system is capable of reproducing neutron scattering experiments in complex geometries and is expected to be used in the areas of instrument characterisation, optimisation and data analysis.In this paper, the relevant theories are briefly introduced. The simulation flow and the user input syntax to control it are provided in detail. Five benchmarking simulations, focusing on different aspects of simulation and scattering techniques, are given to demonstrate the applications of this simulation system. They include an idealised total scattering instrument, a monochromatic powder diffractometer, a neutron guide, a chopper and an imaging setup for complex geometries. Simulated results are benchmarked against experimental data or well-established software packages when appropriate. Good agreements are observed. Program summaryProgram Title:PromptCPC Library link to program files:https://doi.org/10.17632/337frmp9ky.1Developer's repository link:https://gitlab.com/cinema-developers/promptLicensing provisions:Apache-2.0Programming language:C++, C and PythonExternal routines/libraries:NCrystal, VecGeom, MCPL, PyVistaNature of problem: It is challenging for traditional neutron ray-tracing simulation methods to consider multiple scatterings in complex geometries, hence the accuracy and precision of the simulated neutron scattering experiments are limited.Solution method: A hybrid system of Monte Carlo particle transport method and ray-tracing method is proposed.

Effect of novel vortex generator on parabolic trough solar collectors using ionic liquid

In order to improve the overall thermal performance of parabolic trough solar collector systems, numerical simulation with different forms of vortex generators inserted in the absorber tube using [EMIM][BF4] ionic liquid is presented. The absorber tubes with eight vortex generators are compared with smooth absorber tubes and verified from the field synergy principle by combining the finite volume method and the Monte Carlo ray trace method. The thermal efficiency, Nusselt number, friction factor, performance evaluation criterion factor, and exergetic efficiency with varying parameters like Reynolds number, structure, and arrangement of vortex generators are discussed. The results show that the Nusselt number of common flow up double winglet pair structure increases by almost 77% when the Reynolds number is 5000, and its thermal efficiency and exergetic efficiency improvements are both the highest, which are 2.68% and 1.51%, respectively.

Performance assessment of compound parabolic concentrating photovoltaic system based on optical-thermal-electrical-environmental coupling

Based on established optical-thermal-electrical-environmental coupling model and proposed method for calculating electrical efficiency, the effects of tilt angle (θ) on the optical performance, thermal performance and electrical performance of compound parabolic concentrating photovoltaic (CPC-PV) system were numerically investigated by using the coupled Monte Carlo ray tracing (MCRT) and finite volume method (FVM). The results show that with the increase of θ, the peak irradiation flux on the PV panel surface increases sharply. When θ is larger than the critical angle, the shadow area appears and the distribution uniformity of irradiation flux decreases rapidly. Under natural convection condition, increasing θ reduces the distribution uniformity of temperature on the silicon elements with a maximum temperature difference of 120.93 °C at the same position. While, the air average flow velocity around PV panel and reflector surfaces decreases, and the maximum flow velocity appears on reflector surface. Radiative heat loss is dominant in CPC-PV system, and convective heat transfer on the glass surface has a greater impact on the combined heat transfer than that on the TPT surface. From the aspects of values and variation trends, the electrical efficiency calculated by using traditional empirical formula defies the facts. The regional discrete integral method proposed in this study accounts for the effects of shaded areas and non-uniform temperatures on electrical performance. The maximum difference between the electrical efficiency calculated by using the present method and the traditional empirical formula is 10.59 %.

Characterization and Deviation Analysis of a High-Flux Solar Simulator With Metal-Halide Lamps

Abstract Utilizing highly concentrated solar power for thermochemical processing as one of the extraterrestrial in situ resource utilization (ISRU) applications has been highlighted as an essential technique to support deep-space exploration in the future. Multi-source high-flux solar simulators (HFSSs) are widely employed to provide stable irradiance for indoor solar thermal experiments. Meanwhile, numerical modeling that can characterize the radiation transport mechanisms within the solar thermal system has been developed for performance evaluation before field trials. However, significant differences between simulated and measured flux distributions were shown for existing models developed based on the Monte-Carlo ray-tracing (MCRT) method, which has been attributed to only one or two specific reasons. In this paper, we proposed a comprehensive analysis of the concentration characteristics of a 42 kW metal-halide lamp HFSS, developed at Swinburne University of Technology, considering the effect of five aspects. The flux distribution, uniformity, and vector distribution under different configurations were compared to quantify the influence of these factors on receiving irradiance. The suitable arc size, reflector shape, and reflector surface properties of the existing HFSS have also been numerically determined to improve the model and reduce the root mean square error (RMSE) for the lamp array from 38.2% to 8.3%. This research provides a potential pathway to numerically predict the radiation transfer performance of HFSSs and determine the suitable configuration for desired solar thermochemical applications.

Critical review and experimental validation of radiative transfer models for semitransparent media containing large gas bubbles

Many materials manufacturing, photobiochemical, and photoelectrochemical processes involve radiation transfer through foams and bubbly fluids. Controlling and optimizing these processes require accurate predictions of radiation transfer through semitransparent media. Previously developed models treated the heterogeneous media as homogeneous plane-parallel slabs with some effective radiation characteristics while radiation transfer was governed by the one-dimensional radiative transfer equation (RTE). Unfortunately, their accuracy and range of validity remains unclear for lack of comparison with one another or against the same set of experimental data. This study aims to critically review and assess the validity of these models both numerically and experimentally. First, predictions of the transmittance and reflectance of heterogeneous slabs containing large randomly distributed bubbles were compared with those obtained from Monte Carlo ray-tracing (MCRT) method based on geometric optics. A new hybrid model was proposed that predicts the effective scattering coefficient and asymmetry factor using the Lorenz–Mie theory and the effective absorption coefficient as the volume-weighted sum of the bubbles and medium absorption coefficients and solves the RTE using the Monte Carlo method. Its predictions showed excellent agreement with those by the MCRT method for a wide range of bubble volume fractions (0%–30%) as well as slab thicknesses (2–40 mm) and medium absorption coefficients (0.1–100 m−1). Second, microcomputed X-ray tomography scans were performed on a fused silica sample containing bubbles with mean radius of 480 μm to retrieve the exact locations, diameters, and total volume fraction of bubbles. Here also, predictions of the hybrid model using the retrieved data agreed well with experimental measurements of the spectral normal-hemispherical reflectance and transmittance of the sample for wavelengths between 0.4 and 3 μm when silica ranges from weakly absorbing to absorbing.

Investigation into the effect of multiple line dipoles magnetic field through LS-3 parabolic trough solar system

This paper simulates the LS-3 parabolic trough solar collector with Monte Carlo Ray Tracing and computational fluid dynamics methods. The heat flux is non-uniform around the absorber tube. Therefore, multiple line dipoles magnetic field location can effect on solar collector performance. There is no article that has investigated the effect of this parameter in the parabolic trough solar collector. Also, this collector is simulated for the first time for June 21 and December 21, and the heat flux distribution for it is provided by the Monte Carlo Ray Tracing method. The multiple line dipoles magnetic field leads to a decrease in the maximum temperature of the absorber tube wall by 2.3 %. The magnetic field intensity also affects the solar collector's performance. If the magnetic flux density is equal to 100 G, 75 G and 50 G, then the value of Performance Evaluation Criteria is equal to 1.47, 1.43 and 1.39, respectively. Finally, the magnetic field location affects the Nusselt number but does not affect the Darcy friction factor. For example, if the multiple dipoles magnetic field are placed at angles of 0, 30, 60, and 90°, then the Nusselt number ratio is 1.50, 1.42, 1.44, and 1.65, respectively.