Monte Carlo Ray Tracing Algorithm Research Articles

Numerical investigation in an indirect concentrated solar thermal dryer incorporated with discrete mirrors

The objective of this study is to promote the production for small scale drying industries by reducing the drying time of agricultural products. Discrete mirrors are arranged in a parabolic fashion and used as reflectors to concentrate the incoming solar radiation. The available solar flux is doubled by using this discrete arrangement of mirrors. Optical simulations are performed using Monte Carlo Ray tracing algorithm and various effects were studied to select the best arrangement of mirrors. The concentrated type dryer has been numerically simulated and no-load testing is performed using ANSYS Fluent. Simulation is carried out for various inlet velocities from 0.1 to 1 m s−1. The concentrated setup operates between 0.4 and 1 m s−1 of velocity to obtain temperature in the range of 40–70 °C. The maximum and minimum increase in outlet temperature is 23.52% and 2.87%, and the Nusselt number enhancement is 18.94% and 4.15%, respectively.

Improved monte Carlo ray-tracing algorithm based on importance sampling

This paper proposes an improved ray-tracing algorithm with importance sampling (IS) to reduce the computational complexity. For multiple receiver situation, we provide improved IS including adaptive and weighted optimization.

Development of a composite model for predicting urban surface temperature distribution in the context of GIS

In this paper, we present a new model for simulating radiation heat transfer and surface temperatures in urban environments, which is a prerequisite for simulating outdoor mean radiant temperature for pedestrians. We propose a new model whose novelty lies in a new algorithm for simulating diffuse radiation by combining the Nusselt unit sphere method and Monte Carlo ray tracing algorithm. This combined use of different methods is automatically activated depending on the complexity of the scene and, in particular, the arrangement of the facets facing each other. The model is implemented in a Python-based tool, t4gpd, which combines the capabilities of geographic information science and related technologies (GIS &T) with efficient ray-casting solutions. The model is tested on a theoretical mock-up of nine virtual buildings in Nantes under summer and winter weather conditions and compared with SOLENE-Microclimat results. The view factor and solar radiation flux simulation results agree well with the reference solution, with a significant reduction in simulation computation time. However, the model has limitations due to the exclusion of vegetation evapotranspiration characteristics, wind profile model, and soil with complete stratigraphy. Overall, this new model provides an efficient tool for simulating outdoor pedestrian thermal comfort in urban environments and has potential for further development and validation.

Numerical Evaluation on the Thermal Performance of the Solar External Cylinder Receiver using Monte Carlo Ray-Tracing Algorithm

Numerical Evaluation on the Thermal Performance of the Solar External Cylinder Receiver using Monte Carlo Ray-Tracing Algorithm

Computationally efficient Monte Carlo electron transport algorithm for nanostructured thermoelectric material configurations

Monte Carlo statistical ray-tracing methods are commonly employed to simulate carrier transport in nanostructured materials. In the case of a large degree of nanostructuring and under linear response (small driving fields), these simulations tend to be computationally overly expensive due to the difficulty in gathering the required flux statistics. Here, we present a novel Monte Carlo ray-tracing algorithm with computational efficiency of at least an order of magnitude compared to existing algorithms. Our new method, which is a hybrid of the analytical Boltzmann transport equation and Monte Carlo used a reduced number of ray-tracing particles, avoids current statistical challenges, such as the subtraction of two opposite going fluxes, the application of a driving force altogether, and the large simulation time required for low-energy carriers. We demonstrate the algorithm’s efficiency and power in accurate simulations in large domain nanostructures with multiple defects. We believe that the new method we present is indeed more robust and user friendly compared to common methods and can enable the efficient study of transport in nanostructured materials under low-field steady-state conditions.

Identification of BRDF parameters with spectral measurements in the visible light spectrum towards solar irradiation evaluation in urban environment for photovoltaïc technologies

In order to incorporate real construction material reflectance properties in a Monte-Carlo ray tracing algorithm, a representative cladding material is characterised with a spectrophotometer to obtain reflectance angular distribution. These measurements are used to design a BRDF model with a reduced number of parameters that are further identified, along with their confidence intervals. Obtained results are compared to reflectance coefficients measured with an integrating sphere. The prospects of such a model is to allow for a more accurate modelling of the optical properties of materials in reflection. This knowledge can then allow a better integration of photovoltaic technologies, both in terms of energy and visual acceptance. For the particular HPL cladding material tested and despite a highly specular behavior at grazing incidence angles, we found that the specular term only amounts to 4% of reflection.

Monte Carlo Ray-Tracing Simulation of a Cassegrain Solar Concentrator Module for CPV

The concentration ratio is one of the most important characteristics in designing a Cassegrain solar concentrator since it directly affects the performance of high-density solar energy applications such as concentrated photovoltaics (CPVs). In this study, solar concentrator modules that have different configurations were proposed and their performances were compared by means of a Monte Carlo ray-tracing algorithm to identify the optimal configurations. The first solar concentrator design includes a primary parabolic concentrator, a parabolic secondary reflector, and a homogenizer. The second design, on the other hand, includes a parabolic primary concentrator, a secondary hyperbolic concentrator, and a homogenizer. Two different reflectance were applied to find the ideal concentration ratio and the actual concentration ratio. In addition, uniform rays and solar rays also were compared to estimate their efficiency. Results revealed that both modules show identical concentration ratios of 610 when the tracking error is not considered. However, the concentration ratio of the first design rapidly drops when the sun tracking error overshoots even 0.1°, whereas the concentration ratio of the second design remained constant within the range of the 0.8° tracking error. It was concluded that a paraboloidal reflector is not appropriate for the second mirror in a Cassegrain concentrator due to its low acceptance angle. The maximum collection efficiency was achieved when the f-number is smaller and the rim angle is bigger and when the secondary reflector is in a hyperboloid shape. The target area has to be rather bigger with a shorter focal length for the secondary reflector to obtain a wider acceptance angle.

Parametric analysis and optimisation of porous volumetric solar receivers made of open-cell SiC ceramic foam

In recent years, research on the usage of porous materials as volumetric thermal receivers in concentrated solar power plants is growing significantly. This interest is due to their capabilities to improve the efficiency of solar radiation conversion into thermal energy. In this work, detailed parametric analysis and optimisation of the thermal and hydrodynamic performance of porous volumetric receivers are performed using a detailed numerical model. The transport and absorption of solar radiation is modelled through a Monte Carlo Ray Tracing algorithm, while the governing equations of fluid flow and heat transfer are solved using a Computational Fluid Dynamics model. The mean temperature of the fluid at the outlet, thermal efficiency and pressure drop across the receiver are investigated through a parametric analysis and optimisation for different values of porosity, pores size and inlet fluid velocity. The receiver of choice should have high thermal efficiency without greatly increasing the pressure drop and not decreasing the mean fluid temperature at the outlet. Results show that these conditions are achieved for receivers with high porosity (0.8−0.9) and pores size (4.5−3 mm). For a given receiver porosity, there is a pores size value that maximises thermal efficiency, being this value lower for high porosity.

RAMP: A prototype for massively parallelized Monte Carlo raytracing

Simulated optimization of neutron instrumentation via Monte Carlo raytracing (MCR) has played a vital role in instrument design in recent decades. With the increasing complexity of modern instruments, however, optimization is becoming more computationally demanding. Graphics processing unit (GPU) acceleration is a promising strategy to reduce the hardware cost and execution time of simulations, thanks to the massively parallelizable nature of the MCR algorithm. In this proceedings, we present RAMP, a prototype MCR package employing GPU acceleration through the OpenCL application program interface (API). Our preliminary results demonstrate the potential to run simulations on a typical workstation which previously would have required access to a cluster.

Bulk luminescent solar concentrators based on organic-inorganic CH3NH3PbBr3 perovskite fluorophores

In this paper, we report characterization and performance results of lead bromide perovskite luminescent solar concentrator. CH3NH3PbBr3 fluorophores are synthesized by sonication method and examined by their X-ray diffraction pattern and scanning electron microscopy. Synthesized perovskite shows excitonic absorption at 524 nm and PL emission peak located at 532 nm with a Stokes shift around 8 nm. Micron-sized fluorophores are dissolved in prepared solutions and uniformly embedded in PMMA host with 0.006–0.120%wt concentration. Then, Fabricated devices are cut into 50 × 30 × 5 mm cuboid shapes and placed in a mirror surrounded configuration with an attached photovoltaic cell. Fabricated device is put under standard AM1.5 illumination and the output spectrum from the concentrator is acquired. Re-absorption in the samples is also measured by variable optical path method, showing red-shifts up to 13 nm in the output spectrum. Spatially resolved photoluminescence maps and optical efficiencies are also presented for each sample. Plus, a Monte-Carlo ray tracing algorithm is developed to assist better understanding the experimental results. Stability of fabricated samples are evaluated under high intensity UV illumination, reporting efficiency reduction around 15% after 24 h. Finally, Comparing current-voltage characterization of the attached photovoltaic cell reveals optimized efficiency enhancement in the 0.04%wt sample above 65%.

Particle swarm optimization algorithm for optical-geometric optimization of linear fresnel solar concentrators

Abstract In this work we propose the application of the particle swarm optimization (PSO) method to Optical-geometric optimization of linear Fresnel reflector solar concentrators (LFR). The optical-radiative behavior of the system is modeled based on the Ray tracing-Monte Carlo algorithm that calculates the optical performances and the radiative energy collected by the absorber tube. For this system, the application of particle swarm optimization method for optical optimization has not been studied yet. For this reason, testing this method and developing its strategy of implementation in the case of Fresnel concentrator system is one of other objective of this work. In that sense, we present mainly the coupling strategy between the Monte Carlo-ray tracing algorithm and the particle swarm optimization method. In first, the PSO optimization algorithm established is validated by comparison with a deterministic method results. Then, we demonstrated the ability of the method to resolve optimization problem with high number of decision parameters and complex objective function. Subsequently, the various guidelines allowing the rational use of this method in the case of linear Fresnel systems optimization are proposed and discussed. Subsequently, the optimization algorithm is applied to the case of linear Fresnel concentrator module designed in the framework of SIROCCO project.

Mathematical framework for predicting the thermal behaviour of spectrally selective coatings within an industrial near-infrared furnace

AbstractA transient finite difference thermal model based on the heat equations is developed, valid for spectrally selective surface coatings on any substrate material within a near-infrared (NIR) furnace. Spectral radiative heat transfer equivalent to a blackbody provides the heat source. Both radiative and natural convective cooling are accounted for. A Monte Carlo ray tracing algorithm is formulated and used to determine the radiation view factor. The variance of the algorithm in relation to mesh resolution and sample size is tested against published exact solutions. The radiative flux is divided into absorbed and reflected bands using hemispherical reflectance spectra measured within the 250–15,000 nm wavelength range, enabling the model to predict the thermal build-up of coatings with very different radiative properties. Results show that the transient temperature distribution of spectrally selective surface coatings within an NIR furnace can be modelled, with good agreement observed between experime...

Influence of receiver surface spectral selectivity on the solar-to-electric efficiency of a solar tower power plant

The spectral selectivity results in increasing the absorption of the incident solar flux and decreasing the radiative losses due to emission of heated walls. This study investigates the influence of the spectral selectivity on power generation efficiency of a central receiver solar concentrating system (solar power tower). A parametric study is conducted to quantify the potential efficiency gain that may result from spectral selectivity with the solar absorption, the cutoff wavelength, the infrared emissivity, the wall temperature and the receiver geometry (plane or cavity) as parameters. The model used to compute the receiver efficiency is based on a Monte Carlo ray-tracing algorithm for the radiative losses, the Clausing model for the convective losses and the Chambadal–Novikov–Curzon–Ahlborn approach for thermodynamic efficiency. The two tested receiver geometries are a plane receiver and a cubic cavity having the same cross section area of the aperture. State-of-the-art (metal alloys) and promising ceramic materials were studied such as SiC, ZrB2, ZrC and TaC. In the latter cases the native measured optical properties of carbides are considered. Finally, an intrinsic spectrally selective material such as TaC demonstrates promising results with global facility efficiency close to the maximum when solar absorptivity is enhanced by microstructuration, for example. As a conclusion, it is shown that spectral selectivity may result in an increase of overall solar power plant efficiency by about 6% (or 28% in relative value) with current state-of-the-art.

Computation of Effective Radiative Properties of Powders for Selective Laser Sintering Simulations

Selective laser sintering (SLS) is an additive manufacturing technique for rapidly creating parts directly from a computer-aided design (CAD) model by using a laser to fuse successive layers of powder. However, better understanding of the effect of particle-level variations on the overall build quality is needed. In this work, we investigated these effects computationally by considering the role of the particle size distribution and variations in the powder bed depth to mimic the part complexity found in overhangs and protrusions. In addition, the results from these studies can be distilled to obtain better effective material properties such as laser absorptivity and laser extinction coefficient that are needed for continuum models of the process. We implement a Monte Carlo ray-tracing algorithm within the discrete element model in the open-source simulation software MFiX. Random, loose-packed, particle bed structures are generated, and effective absorptivity and extinction coefficients are calculated. Results are compared against previous computational and experimental measurements for free, monodisperse, and deep powder beds, with good agreement being obtained. Correlations along with uncertainties are developed to allow the effective absorptivity and extinction coefficient as a function of various particle and operational parameters to be accurately set in SLS macroscale models.

Design of a free-form lens for LED light with high efficiency and uniform illumination.

A free-form secondary lens is proposed to optimize an LED light. Based on Snell's law, energy conservation law, and a Monte Carlo ray-tracing algorithm, the surface contour of the free-form lens can be determined according to the requirements of an LED light. Optical experimental results show that an optical efficiency of 95.69% can be achieved by the lens, of which the illumination uniformity 0.317 is higher than the commercial illumination uniformity 0.259. The lens does not need the help of a white ring holder, so the cost of the LED light can become effective.

Selection of thermotropic materials for overheat protection of polymer absorbers

Thermotropic materials offer the potential to provide passive overheat protection for polymer solar absorbers. These materials are comprised of a matrix in which a second material, referred to as the scattering domain, is dispersed as small particles. Overheat protection is provided by a change in transmittance and reflectance at elevated temperature. The magnitude of this change depends on the change in the relative refractive index between the matrix and the scattering domain, the volume fraction and size of the dispersed particles, and the thickness of the material. To predict the effect of these parameters on the normal-hemispherical transmittance and reflectance, thermotropic materials are modeled as a non-absorbing slab comprised of discrete, anisotropic scattering, spherical particles embedded in a matrix material. A Monte Carlo ray tracing algorithm predicts the transmittance and reflectance of the slab. The model predictions are compared with: the analytical solution for a slab of non-absorbing, non-scattering media, and the measured transmittance of 0.3mm thick polymer samples containing 400nm particles. A parametric study of the effects of the design parameters on the transmittance is presented to identify potential material combinations which will produce a thermotropic composite capable of providing overheat protection for flat plate solar collectors. Relatively short chain alkanes or low molecular mass polyethylene in a matrix of polycarbonate are identified as promising materials.

Design considerations of conventional angle diversity receivers for indoor optical wireless communications

Abstract A conventional angle diversity receiver uses multiple receiving elements that are oriented in different directions, where each element employs its own filter and nonimaging concentrator, such as a compound parabolic concentrator (CPC) or hemispheric lens. In this paper, a study of the design of a conventional receiver structure using angle diversity that offers improved performance with respect to the infrared channel characteristics is presented. To this end, a recently proposed model for the effective signal collection area of a conventional angle diversity receiver that more closely approximates real behaviour than the ideal model is used. The inclusion of this model in a Monte Carlo ray-tracing algorithm allows us to investigate the effects of conventional receiver parameters on the main infrared channel parameters, such as path loss and rms delay spread. Furthermore, in order to determine the number of receiver elements, the outage probability and the average error probability are also considered. Based on the results, a conventional angle diversity receiver composed of seven elements is proposed, with one of them oriented towards the ceiling, and six angled at a 56° elevation with a 60° separation in azimuth. For each element, a CPC with a 50° field of view must be used.

Reading lamp-based visible light communication system for in-flight entertainment

This paper explores the use of a reading lamp as an access point for a Visible Light Communications (VLC) downlink channel. We have established an infrared uplink channel based on a network adapter, supporting both a VLC receiver and an infrared emitter. The optical signal power distribution over the passenger area has been also studied using a Monte Carlo Ray-Tracing algorithm. The hardware implementation and testing results are also presented.

Simulation of impulse response for indoor visible light communications using 3D CAD models

In this article, a tool for simulating the channel impulse response for indoor visible light communications using 3D computer-aided design (CAD) models is presented. The simulation tool is based on a previous Monte Carlo ray-tracing algorithm for indoor infrared channel estimation, but including wavelength response evaluation. The 3D scene, or the simulation environment, can be defined using any CAD software in which the user specifies, in addition to the setting geometry, the reflection characteristics of the surface materials as well as the structures of the emitters and receivers involved in the simulation. Also, in an effort to improve the computational efficiency, two optimizations are proposed. The first one consists of dividing the setting into cubic regions of equal size, which offers a calculation improvement of approximately 50% compared to not dividing the 3D scene into sub-regions. The second one involves the parallelization of the simulation algorithm, which provides a computational speed-up proportional to the number of processors used.

Parallelization of a Monte Carlo Ray Tracing Algorithm for Channel Modelling in Underwater Wireless Optical Communications

In this paper, an algorithm to calculate the underwater wireless optical impulse response is presented. It is based on a modified Monte Carlo Ray Tracing algorithm and takes into account the most significant phenomena of the underwater channel. In order to reduce the simulation time, two parallelization schemes are proposed, one based on a multiprocessor architecture and other based on the use of GPU (Graphics Processing Unit). Several simulation results are presented, including scenario channel simulations and calculation of time computation complexity for each algorithm implementation.