SolTrace Software Research Articles

Optical and Thermal Modeling of a Cylindrical– Hemispherical Receiver

Receiver geometry optimization is a crucial domain in enhancing the efficiency of parabolic dish concentrators. This optimization necessitates thoroughly scrutinizing the receiver's optical and thermal characteristics. The present study engages in a cylindrical-hemispherical receiver's optical and thermal modeling. Set at an aperture of 0.150m, the receiver's height varies between 0.150m to 0.160m. Sol-Trace software is employed for the optical modeling to analyse the total amount of heat flux absorbed by the receiver that has been concentrated using parabolic dish. The diameter of the is taken as 3m, and the receivers placement is varied between 1.55m and 2.05m from the dish concentrator to obtain the optimal distance for absorbing maximum heat flux. From the results optimal distance has been observed as 1.8m from the dish concentrator. Maximum heat flux of 6664.56W has been absorbed by the receiver surface at this position. Additionally, thermal modeling using CFD has been conducted to calculate convective heat losses from the receiver under different wind conditions, such as varying wind direction and wind velocity. The maximum convective heat loss observed under head-on wind conditions is 772.73W, while under back-on wind conditions, it is 606.84W

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.

Numerical investigation to optimize the modified cavity receiver for enhancement of thermal performance of solar parabolic dish collector system

The concentrated parabolic dish collector (PDC) systems are widely utilized for the purpose of generating high-temperature heat by receiving and converting solar energy efficiently into thermal energy. Cavity receivers including spiral coils have a common use in PDC system for optimal thermal performance. Therefore, to enhance the thermal performance of a PDC system, the present study investigates different cavity receiver configurations, such as cylinder and conical shaped receivers with flat and spherical absorber surface as well as the effect of spiral coil arrangement. To identify the most optimal spirally coiled cavity receiver, the comparison is conducted based on outlet temperature, heat exchange rate, thermal efficiency, effectiveness, and thermal performance capability (TPC). The investigations were conducted using the ANSYS Fluent CFD simulation software package. The SolTrace software package was utilized to compute the maximum heat flux incident on the absorber surface of the receiver, and peak heat flux data was used as input parameter at the absorber surface of the receiver. Furthermore, to select the suitable working fluid in PDC system, different heat transfer fluids, such as Syltherm 800, Xceltherm 600, ParathermHR™ and water, respectively were studied. From the thermal analysis of various proposed receiver geometries, the receiver with conical shape and spherical absorber surface is more efficient over other configurations. It provides 50 % higher heat transfer rate thancylindrical receiver with flat absorber surface. Moreover, receiver's thermal performance could modestly be improved by modifying the spiral coil pitch (variable pitch). In terms of pumping power consumption, readily availability, low viscosity, and high specific heat, water is suggested as working fluid for receiver of PDC system.

New Evacuated Tube Solar Collector with Parabolic Trough Collector and Helical Coil Heat Exchanger for Usage in Domestic Water Heating

Buildings represent approximately two-thirds of the overall energy needs, mainly due to the growing energy consumption of air conditioning and water heating loads. Hence, it is necessary to minimize energy usage in buildings. Numerous research studies have been carried out on evacuated tube solar collectors, but to our knowledge, no previous study has mentioned the combination of an evacuated tube solar collector with a parabolic trough collector and a helical coil heat exchanger. The objective of this paper is to evaluate the thermal behavior of an innovative evacuated tube solar collector (ETSC) incorporated with a helical coil heat exchanger and equipped with a parabolic trough collector (PTC) used as a domestic water heater. To design the parabolic solar collector, the Parabola Calculator 2.0 software was used, and the Soltrace software was used to determine the optical behavior of a PTC. Moreover, an analytical model was created in order to enhance the performance of the new model of an ETSC by studying the impact of geometric design and functional parameters on the collector’s effectiveness. An assessment of the thermal behavior of the new ETSC was performed. Thus, the proposed analytical model gives the possibility of optimizing ETSCs used as domestic water heaters with lower computational costs. Furthermore, the optimum operational and geometrical parameters of the new ETSC base-helical tube heat exchanger include a higher thermal efficiency of 72%. This finding highlights the potential of the heat exchanger as an excellent component that can be incorporated into ETSCs.

A novel technique of schedule tracker for parabolic dish concentrator.

Tracking is important in a system that harnesses solar energy. Single axis tracking mechanism is cheaper and simple to develop but because of the limitation of tracking axis, this system is less efficient than dual axis. Dual-axis tracking systems necessitate a large number of equipment, sensors, motors, and a lengthy computer program to function properly. Therefore, in the present study, a novel method of solar tracking has been discussed where each tracking point has the impact of both the azimuth and altitude angle at a single point. This method is an average axis tracking method (AATM). HelioScope software was used to extract the hourly solar altitude and azimuth angles for each day and month for the site of Bhopal, India. The average method was then used to get the hourly average solar tracking angle (ASTA) for each month. The parabolic dish concentrator was designed in SolidWorks to apply and simulate the newly developed tracking points on SolTrace software. The graphical analysis was presented along with proper validation of the proposed method, and the single and dual axes were compared with AATM. The graphical study shows that the average axis tracking points have a smoother slop of wave than the single axis. From June to September, the proposed method's error was estimated between 0.85 and 0.95. It can be concluded that by making slight adjustments to the seasonal angle, this error could be minimized and the concept could be successfully applied to a parabolic dish or a solar PV system.

Optical modeling of a cylindrical-hemispherical receiver for parabolic dish concentrator

Among all sub-systems of a solar thermal energy system, the receiver plays a significant role when it gets heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy that the receiver collects and other optical parameters like focal length, aperture diameter, surface absorptivity, and slope error. The present paper discusses the optical analysis of a cylindrical-hemispherical receiver coupled with a parabolic dish concentrator having 3-m diameter. The study has been carried out using the SolTrace software by varying the parameters like receiver aperture diameter (Da) ranging from 0.125 to 0.162m, surface error of the concentrator varying from 1.7453 to 34.907 mrad, and also surface absorptivity (α) changing from 75 to 95% for different receiver distances (H) ranging from 1.7 to 1.95m. The simulation results show that the optical efficiency is maximum when the receiver with 0.150-m aperture diameter is placed at a distance of 1.85m from the concentrator. An increase in slope errors from 1.7453 to 17.453 mrad decreases the average optical efficiency by almost 50% for all receiver diameters. It is also noticed that uniform heat flux distribution can be achieved when the receiver's position is maintained at H = 1.85m from the concentrator for 0.150-m receiver diameter and 95% absorptivity of the receiver surface. The simulated results of heat flux intensity on the receiver surface are then compared and validated by the experimental results available in the literature. The simulated optical efficiency of the present receiver is found to be 8% higher when compared with a conventional cylindrical receiver with similar dimensions.

DESIGN AND CFD ANALYSIS OF CONICAL CAVITY RECEIVER FOR SCHEFFLER DISH

In the present paper, a conical cavity receiver is designed and analyzed for a 16 m<sup>2</sup> Scheffler dish concentrator. The optimum aperture diameter of conical cavity receiver is estimated using ray-tracing SolTrace software. The optimum aperture diameter of the conical cavity receiver for 16 m<sup>2</sup> Scheffler dish was found to be 0.4 m. Also, thermal and fluid flow analysis is performed using computational fluid dynamics (CFD) software, Ansys Fluent. The different parameters such as receiver temperature, heat losses, pressure drop, Nusselt number, and pumping power are analyzed. The maximum thermal efficiency was found to be 64% at receiver surface temperature 85°C and ambient temperature 25°C. Also, maximum pumping power required to circulate a flow through the receiver is found to be 1.03 W for 0.04 kg/s flow rate.

Efficient distributed concentrating solar power system with ammonia-based chemical heat pump

Recently, distributed renewable energy system has become a flexible, reliable and environmentally friendly alternative to the conventional large-scale centralized power plant. This paper proposed a distributed concentrating solar power system coupled with an ammonia-based chemical heat pump. The proposed system is able to upgrade the solar thermal energy absorbed from 450 °C to 650 °C. To design a concentrated solar module, consisting of a Linear Fresnel Reflector field and a Compound Parabolic Collector, for the proposed system, a three-dimensional optical model is developed with SolTrace software. Moreover, the optical model has been validated by comparing the model predicted results with the data from the reference. As for the ammonia decomposition membrane reactor in the system, a three-dimensional reactor model is developed with COMSOL software, which is capable of simulating both ammonia decomposition and hydrogen permeation processes under solar irradiation. With an experimental prototype of the membrane reactor, experiments have been conducted to validate the reactor model. With the validated model, the effects of the reactor length, reactor inlet temperature and ammonia flow rate on the thermochemical conversion efficiency of the reactor have been investigated parametrically. The results show that the reaction conversion increases with the reactor length increasing, while thermochemical conversion efficiency decreases. The thermochemical conversion efficiency increases with reactor inlet temperature and/or ammonia flow rate increasing, which reaches the maximum of 34.9 % in our study. By integrating an ultra-supercritical double reheat power cycle, the system with a low concentration ratio of ∼ 24 can achieve a high solar to power efficiency of ∼ 18.3 %, which surpasses the peak efficiency of a typical concentrating solar power plant with a concentration ratio of ∼ 30.

Numerical analysis using SolTrace software to determine the size and position of a central receiver for ganged heliostat system

Concentrated solar power (CSP) technology has become a promising technique for harnessing the sun’s energy. Ganged heliostat system, also called as central receiver system (CRS), a type of CSP system that uses a field of radially distributed heliostats (mirrors), which track the position of the sun in two axes and focus the sunlight on the centrally placed receiver. Heliostats are used to concentrate solar rays on the receiver, producing a huge amount of energy which can later get converted into electricity or heat. The receiver is kept at a sufficient height to absorb maximum reflected rays. In the present work, a numerical analysis method is used to optimize receiver design parameters such as receiver size, its position in horizontal and vertical planes, and to predict the heat flux intensity at the receiver surface. However, there is no direct method to decide these parameters and often results in a loss of time while optimizing them. In this research paper, a simple methodology has been proposed to design a central receiver for CRS consisting of ganged heliostat system using SolTrace 3.1.0 software. This method is effective in determining the size, the position of the receiver and heat flux distribution at the receiver surface in the initial phase of receiver system design.

Optimum Height and Tilt Angle of the Solar Receiver for a 30 kWe Solar Tower Power Plant for the Electricity Production in the Sahelian Zone

This work investigated the prediction of the optimum height and tilt angle of the solar receiver of a 30 kWe solar tower power plant for the electricity production in the Sahelian zone. Initially, the solar field is sized to determine the total reflecting surface area of the mirrors and the number of heliostats. A PS10-like radially staggered heliostat field is used to design the heliostat layout in the field using a Matlab code. The concentrated solar flux at the input of the receiver was determined using Soltrace software by the Monte Carlo ray tracing (MCRT) method. The sizing results show that the total reflecting surface area is 350 m2 for an optical efficiency of 76.4% and a reference DNI of 600 W/m2. The solar field layout indicates 175 heliostats of 2 m2 surface area and 1.5 m height each. The simulation results show that the optimum height and tilt angle of the solar receiver are 26 m and 65°, respectively.

Design and Three-Dimensional Simulation of a Solar Dish-Stirling Engine

Design and three-dimensional simulation of a solar Dish-Stirling (SDS) engine is currently performed. The design starts with the GPU-3 Stirling engine, which is originally built to generate power from the fossil fuel exclusively. The design is conducted through three subsequent phases. Firstly, several parabolic dishes with different rim angles and number of facets are investigated to optimally design the dish concentrator. Secondly, different relative positions of the receiver aperture to the dish focal plane are tested to reach the optimal position. The optical simulation of the solar concentration process is carried out using SolTRACE software. Finally, an optimal design for a cavity receiver that involves a new structure of the heater tubes is performed. The simulation of the engine with the designed receiver is implemented using the commercial CFD code ANSYS FLUENT. Having finished the design, a comprehensive energy analysis of the designed SDS engine is carried out. The results show that a nearly uniform temperature distribution of the heater tubes throughout the cycle is achieved. The overall thermal efficiency of the designed SDS engine is about 31.8 % at a DNI of 1000 W/m2.

Numerical investigation of the optical efficiency of a parabolic trough collector at different concentration ratios

ABSTRACT The Concentration Ratio (CR) is one of the first parameters defined before starting a Parabolic Trough Collector (PTC) construction project as it can easily provide access to the operating temperature and the determination of geometric dimensions. Few studies have been conducted to highlight the importance of the CR. Hence, this work aims to numerically analyze three models of PTC, A, B, and C, with different concentration ratios to perform a comparative analysis of impacts of this parameter in the size and optical efficiency of the models. We used the Monte Carlo Ray Tracing (MCRT) method through the SolTrace software to perform this study. From the results, we conclude that the CR has a considerable effect on the size and optical efficiency of the PTC. On average, the results presented showed that for every gain in PTC optical efficiency, it would be necessary to increase the concentration rate by . However, it is noticed that these gains are not linear and decrease as the concentration rate increases. Also, the increase in the CR leads to an increase in the rim angle, in the collector aperture width, and in the solar energy flux density around the absorber. Finally, the results we found were investigated and validated, presenting excellent agreement with other works in the literature.

Evaluating energy efficiency and economic effect of heat transfer in copper tube for small solar linear Fresnel reflector

An experimental and numerical investigation of a small linear Fresnel for water heating application has been carried out in Blida, Algeria. The numerical simulation with a 1D modeling in transient mode was performed by using the finite difference method. The thermal evaluation is based on the energy assessments characterized by the differential equations of pure water with a flow mass rate equal to 0.015 kg s−1 and copper absorber tube temperature. Moreover, the Fluent code has been developed in order to conduct the CFD modeling at the absorber tube of the solar collector. SolTrace software has been used to determine the optical behavior of the linear reflector. The average optical efficiency of the device is about 42.97%, but the average value of the experimental thermal efficiency reached 29.21% for 22/01/2015 and 29.20% for 19/02/2015. The average value of pure water temperature for 22/01/2015 is 67.28 °C, while its value for 19/02/2015 is 70.99 °C. This solar experimental setup will reduce the consumption of liquefied natural gas by 88.9 m3, which will reduce the CO2 emission by 187.93 kg. In addition, its manufacturing cost will be recovered 16 years from the date of use of this heater.

Sensitivity analysis of parabolic trough concentrator using rectangular cavity receiver

The objective of this work is the investigation of a parabolic trough concentrator (PTC) with a linear cubical cavity receiver which operates with thermal oil as the working fluid. The solar collector is investigated in order to achieve maximum thermal efficiency. The PTC is investigated optically in Sol Trace software, while the thermal modeling is conducted by a code in Maple software. The developed model is validated with experimental data from the literature. Finally, a good agreement has been found between the measured thermal efficiency and the calculated thermal efficiency based on the presented model. Different geometrical dimensions of the cavity receiver were investigated based on sensitivity analysis including cavity position, cavity aperture, cavity height and cavity tube diameter. Also, the system is examined for different operating conditions. According to the results, the lower tracking and optical errors lead to higher optical performance. The best cavity depth is equal to the cavity aperture width. It was found that the higher concentrator aperture increases the absorbed energy. Moreover, it is found that the cavity has to be located in the focal line of the parabola. The highest absorbed heat and thermal efficiency of the solar system calculated was equal to 618.09 W, and 77.26% respectively for the cavity tube diameter of 5 mm.

A novel optical-thermal modeling of a parabolic dish collector with a helically baffled cylindrical cavity receiver

In solar energy conversion and utilization in a parabolic dish collector (PDC), the accurate modeling of the system and also the appropriate selection of adjustable operational parameters, are so important. In this work, a helically baffled cylindrical cavity receiver in a PDC system was studied experimentally and theoretically. For optical and thermal modeling of the system, a novel combining method was used. The real solar flux distribution on the receiver internal walls was obtained by using SolTrace software and then, the real fluxes were employed in ANSYS Fluent software to increase the accuracy of CFD modeling of the system. The model was verified and validated with the experimental data, and a good agreement was observed with a maximum deviation of about 2%. The effect of some geometrical and structural parameters such as receiver aperture distance to the focal point ratio, receiver aspect ratio and system geometrical concentration ratio and also, some operational parameters such as Heat Transfer Fluid (HTF) inlet temperature, mass flow rate and solar irradiation intensity on the thermal performance of the system were investigated. The results show that the optimal selection of the mentioned parameters can enhance the thermal performance of the system up to 65%.

Performance study and comparative analysis of traditional and double-selective-coated parabolic trough receivers

Based on the simulated non-uniformity solar radiation flux distribution of the absorber by the Soltrace software using the Monte Carlo Ray-Trace Method, an innovative parabolic trough solar receiver that employs two solar selective coatings with different properties on the outer surface of the absorber is proposed. The concentration ratio and absorber temperature that influence optimal cut-off wavelengths of the solar selective coatings are quantitatively analyzed to optimize the property of the coating. The optimal cut-off wavelength increases with the concentration ratio, but drops with the increasing absorber temperature. The heat transfer process of receivers is numerically simulated to predict the thermal performance of evacuated receivers based on spectrum parameters heat transfer model. Heat loss simulation results show that: the double-selective-coated receiver can reduce heat loss and boost the collecting efficiency significantly compared with PTR70 receiver. When the temperature of absorber is 500 °C, the double-selective-coated receiver can reduce heat loss by 157.8 W/m and increase the collecting efficiency from 64.7% to 68.1%. The System Advisor Model annual simulation results indicate that double-selective-coated receivers can decrease the levelized cost of electricity of concentrating solar plants by 2.78%–7.34%, and increase electricity production by 2.94%–8.21% compared with traditional PTR70 receivers.

Numerical Study and Optimization of Parabolic Trough Solar Collector Receiver Tube

In this study, the parabolic trough collector's (PTC) performance is analyzed. In order to achieve this goal, the adopted procedure comprises two main steps. In the first step, the concentrated solar heat flux densities in the solar concentrator focal zone are calculated by soltrace software. In the second step, computational fluid dynamics (CFD) simulations are carried out to analyze and to optimize the thermal performance of the tube receiver. The calculated heat flux densities by soltrace software are used as wall heat flux boundary conditions for the receiver tube. The effect of the receiver tube diameter variation on the PTC thermal performance is studied. A new type of receiver tube is tested. This latter is covered with a metallic thickness. The performance of tube receiver covered with a metallic layer for different diameters is compared to those of the same diameters without the addition of metallic thickness. It has been found that increasing tube metallic thickness enhances the performance of PTC system comparing to the tubes of the same diameter and crossed by the same flow rates.

Thermal Stress Analysis of Absorber Tube for a Parabolic Collector under Quasi-Steady State Condition

The design of parabolic trough collectors is based on the concentration of solar heat flux on its absorber tube. This may be subjected to high thermal stresses which could cause deflection of the absorber tube and failure of its cover glass tube. Investigation of earlier studies on thermal gradient and thermal stresses demonstrates that so far, the issue is considered for steady state condition based on the assumption of constant solar heat flux distribution during the day hours. However, in practice, solar heat flux distribution on the receiver tube has continues changes with respect to time and deformation is basically transient. Due the low speed of sun during a day and for specific time intervals, the average solar radiation could be considered constant for thermal stress and deflection analysis. Hence, in this study, thermal gradients as well as thermal stresses in the absorber tube are numerically investigated in quasi steady condition. Due to the wide changes of solar radiation during a year, computations are performed for four specific days of Spring Equinox, Summer Solstice, Autumnal Equinox and Winter Solstice. To compute solar heat flux distribution, SolTrace software is used and three dimensional heat flux distribution is applied as an external boundary condition to calculate temperature distribution in the absorber tube. By using Von-Misses theory, maximum equivalent of total stress is computed. Maximum deflection is evaluated for various different inlet temperatures and hot oil mass flow rates in the common range of solar thermal power plants for atypical parabolic trough collector which is under construction in Shiraz, Iran.

Sensitive Analysis for the Efficiency of a Parabolic Trough Solar Collector Based on Orthogonal Experiment

A multitude of the researches focus on the factors of the thermal efficiency of a parabolic trough solar collector, that is, the optical-thermal efficiency. However, it is limited to a single or double factors for available system. The aim of this paper is to investigate the multifactors effect on the system’s efficiency in cold climate region. Taking climatic performance into account, an average outlet temperature of LS-2 collector has been simulated successfully by coupling SolTrace software with CFD software. Effects of different factors on instantaneous efficiency have been determined by orthogonal experiment and single factor experiment. After that, the influence degree of different factors on the collector instantaneous efficiency is obtained clearly. The results show that the order of effect extent for average maximal deviation of each factor is inlet temperature, solar radiation intensity, diameter, flow rate, condensation area, pipe length, and ambient temperature. The encouraging results will provide a reference for the exploitation and utilization of parabolic trough solar collector in cold climate region.

Solar flux distribution on central receivers: A projection method from analytic function

This paper presents a methodology to project the flux distribution from the image plane into the panels of any central receiver in Solar Power Tower plants. Since analytic functions derived from the convolution approach are conveniently defined on the image plane, its oblique projection solves the distorted spot found in actual receivers. Because of its accuracy describing the flux distribution due to rectangular focusing heliostats, we make use of the analytic function on the image plane by Collado et al. (1986). Based on the projection method, we have developed a computer code successfully confronted against PSA measurements and SolTrace software, either for flat plate or multi-panel cylindrical receivers. The validated model overcomes the computation time limitation associated to Monte Carlo technique, with a similar accuracy and even higher level of resolution. For each heliostat in a field, the spillage is computed besides the rest of optical losses; parallel projection is used for shading and blocking. The resulting optical performance tool generates the flux map caused by a whole field of heliostats. A multi-aiming strategy is investigated on the basis of the radius of the reflected beams, estimated from error cone angles.