Parabolic Trough Solar Collector System Research Articles

Thermal performance evaluation of the parabolic trough solar collector using nanofluids: A case study in the desert of Algeria

The use of Parabolic Trough Solar Collector (PTSC) is currently the best option for widespread application in industries operating at temperatures from 60 to 400 °C. Numerous studies have been conducted to enhance the thermal performance of the PTSC using synthetic oils as heat transfer fluids. In this study, the thermal performance of parabolic collectors was enhanced using Metallic Oxide Nanofluids (CuO, SiO2, Al2O3, TiO2) based on Therminol VP-1™ at 4 % volumetric concentration as heat-transmitting fluids. A thermal model was developed and validated through experimental and theoretical study, while the results showed good compatibility in the outlet temperature with an error rate of 0.184 % for experimental and 0.29 % for theoretical studies. Moreover, various theoretical models of the thermal properties of nanofluids were analyzed to determine the model that matches and simulates this study. The findings indicated that nanofluids enhanced the thermal efficiency of the PTSC system compared to pure Therminol VP-1™. Specifically, CuO/Therminol VP-1™ demonstrated the most significant improvement, increasing thermal efficiency by 1.03 %. Furthermore, the results also showed that the addition of CuO, TiO2, Al2O3, and SiO2 nanoparticles led to an increase in outlet temperature by 9.57 %, 6.04 %, 5.21 %, and 3.08 %, respectively.

The effect of adding hybrid nanoparticles (Al2O3–TiO2) on the performance of parabolic trough solar collectors using different thermal oils and molten salts

Enhancing the operational efficiency of parabolic trough solar collector (PTSC) systems is key to the advancement of solar energy technologies that enhance power generation sustainability. In the quest for efficient, environmentally friendly energy sources, solar energy systems have been a major focus of both researchers and industry. Adding hybrid nanoparticles (Al2O3–TiO2) to different base fluids of thermal oil or molten salts and then simulating the PTSC's energetic and exergetic performance is pivotal to efficiency enhancement. The focus of this paper will be on three thermal oils Syltherm-800, Therminol VP-1, and Therminol 75 that are used as base fluids with the addition of hybrid nanoparticles. Molten salts such as Solar Salt, Hitec, and HitecXL, which are considered different base fluid types, are also simulated with the same hybrid nanoparticle combination. The inlet temperature is found to be a determining factor in the choice of the base fluid. Inlet temperatures in the range of 300–650 K for thermal oils with the addition of Al2O3–TiO2 have improved the thermal and exergy efficiency of the PTSC by approximately 0.99 % and 0.59 %, respectively. Therminol VP-1/Al2O3–TiO2 has the highest average thermal efficiency among other thermal oils, with an average percentage of 71.68 %, while Syltherm-800/Al2O3–TiO2 has recorded the highest exergy efficiency of 24.1 %. At higher inlet temperatures above 500 K mixing Al2O3–TiO2 with molten salts has increased both energetic and exergetic PTSC performance by approximately 0.60 %. Solar Salt/Al2O3–TiO2 has the highest average thermal and exergy efficiency of 61.8 % and 36.1 %, respectively.

Numerical study of parabolic trough solar collector’s thermo-hydraulic performance using CuO and Al2O3 nanofluids

The current study aims to boost the thermal and hydraulic performance of a parabolic trough solar collector by modifying the absorber tube with a porous obstacle insertion. The research investigates how porous media and nanoparticles together influence the system's thermal performance, considering factors like outlet temperature, average Nusselt number, average friction factor, thermal performance factor, and thermal efficiency at different mass flow rates. To achieve better thermal performance, the base fluid, water, is substituted with Copper Oxide (CuO)-water and Aluminum Oxide (Al2O3)-water nanofluids at concentrations ranging from 3% to 7% by volume. The experiments are conducted at 800–1000 W.m-2 heat flux on the outside tube surface. The finite element method discretizes the governing equations for 3-D fluid flow simulations conducted in COMSOL Multiphysics 6.1 software. The simulation is carried out considering four altered rates of mass flow, ranging from 0.015 kg.s−1 to 0.060 kg.s−1. The findings show that at a Reynolds number of 1428 and a 7% volume concentration, the maximum thermal performance factor recorded is 1.97 and 1.99 for Al2O3 and CuO nanofluids, respectively. Additionally, the absorber tube achieves maximum thermal efficiency of up to 77.93% and 79.03%. Also, the augmentation in the average Nusselt number ratio is 26.27% and 36.74% when using Al2O3 and CuO nanofluids, respectively, with the tube height-to-diameter ratio (h/D) set at 0.42. The average friction factor ratio was reduced by 2.9% using CuO nanofluids compared to Al2O3 nanofluids. Thermal efficiency was enhanced by 7.2% using a porous obstacle insert in the parabolic trough solar collector system compared to a non-porous system.

Performance analysis and machine learning algorithms of parabolic trough solar collectors using Al2O3-MWCNT as a hybrid nanofluid

The critical importance of developing solar energy technologies for sustainable power generation places a high priority on the crucial efforts to optimize the performance of parabolic trough solar collector (PTSC) systems. This study focuses on optimizing the volume frictions of the hybrid nanofluids (1% Al2O3− 2% MWCNT/Syltherm-800, 1.5% Al2O3− 1.5% MWCNT/Syltherm-800, and 2% Al2O3− 1% MWCNT/Syltherm-800) in order to attain the most effective performance of the PTSC system. A mathematical model to investigate the PTSC performance under various volume concentrations is developed. Furthermore, this study trained three machine learning models (Decision Tree, Support Vector Machine, and Artificial Neural Network) using the generated data from the developed mathematical model to predict the PTSC outlet temperature more quickly, with the goal of achieving higher accuracy with fewer inputs. The findings of this study indicate that the PTSC system exhibits higher thermal efficiency when utilizing a combination of 2% Al2O3 and 1% MWCNT/Syltherm-800, with an average thermal efficiency of 70.54%. Moreover, the Artificial Neural Network (ANN) was the most accurate model out of the three. It performed remarkably well, showing an astounding R2 value of 99.99%, a mean absolute percentage error (MAPE) of 4.8x10−5, a root mean square error (RSME) of 0.012, and a mean absolute error (MAE) of 0.0057.

COMPUTATIONAL INVESTIGATION OF GLASS TEMPERATURE DISTRIBUTION IN PARABOLIC TROUGH SOLAR COLLECTOR RELATING TO HUMID CONDITIONS

The current work investigates the effect of humid conditions on the glass cover temperature distribution of the parabolic trough solar collector system. For the aforementioned work, a two-dimensional computational model was created and numerically examined. The simulation regime was split into two sections. The first section established the impact of moist flow and ambient temperature on the heat transfer coefficient over a cylinder with a uniform circumferential temperature distribution. The temperature distribution of the glass cover of a parabolic trough solar collector with moist airflow running across it was determined in the second step of the simulation. Studies on the temperature of the glass cover have also looked at the impact of wind speed. When the relative humidity was varied from 0 to 100%, the circumferential peak temperature decreased by 3.69, 2.9, and 1.68 K for 1, 3, and 5 m/s, respectively. Studies were also done on the impact of wind speed. When wind speed is raised from 1 to 5 m/s while relative humidity is maintained at 0 and 100%, respectively, the circumferential peak temperature decreases by 6.02 and 5.17 K, respectively.

Performance enhancement of flat-plate and parabolic trough solar collector using nanofluid for water heating application

Flat plate solar collector (FPSC) and parabolic trough solar collector (PTSC) are widely used for residential solar water heating (SWH) applications. This work studied two different solar collector systems. Nanofluid and its influence on the residential solar water heating (SWH) systems were investigated. The two SWH systems were designed, installed, tested, and compared at varying mass flow rates (mf) of 0.47, 1.05, and 1.75 kg min−1 in ambient environmental conditions. The comparative study was conducted according to thermal efficiency (ηth), useful energy gain (QU), stored energy (QS), outlet hot water temperature (To), and difference temperature (ΔT) between the cold inlet and hot outlet water from the collectors. The analysis of outcomes showed that the PTSC was more efficient than FPSC. The FPSC and PTSC systems performance were investigated using two different types of nanofluids. Carbon nanotubes in water and ethylene glycol were utilized. A remarkable improvement in the average thermal efficiency 64.1 % and 80.6 % of FPSC and PTSC systems using ethylene glycol nanofluid were obtained respectively. The total reduction in CO2 emissions was 31.26 kg/day and 39.28 kg/day for the FPSCs and PTSCs, respectively in the presence of ethylene glycol nanofluid. A significant saving in CO2 release is owing to the renewable clean energy of solar collectors.

Energy and exergy analysis of a novel solar-based system merged with power cycle

Parabolic Trough Solar Collector (PTC) is a power generation unit that works based on solar energy. This system provides a considerable amount of thermal power but no electrical energy. Hence, the current investigation attempts to boost the outputs of the PTC system by merging this unit with the Photovoltaic (PV) module and Organic Rankine Cycle (ORC). In this regard, the outputs of the conventional PTC system under multiple operating conditions are compared with those of PTC-PV, PTC-ORC, and PTC-PV-ORC systems. These systems are three-dimensionally simulated using the steady-state approach and the influences of variation in the solar flux and concentration ratio on the energy and exergy efficiencies are scrutinized. According to the obtained data, at the base case condition, the overall energy efficiencies of the conventional PTC, PTC-PV, PTC-ORC, and PTC-PV-ORC systems are 42.75%, 47.20%, 13.43%, and 21.46%, respectively. The performance of these systems from the exergy viewpoints is 5.51%, 14.31%, 4.19%, and 13.33%, respectively. Based on the simulations, from the electrical energy and exergy viewpoints, the PTC-PV-ORC system has the highest performance followed by PTC-PV and PTC-ORC systems. Nonetheless, the thermal exergy of the ORC-based systems is remarkably lower than that of single solar units. This study shows the integration of the PTC system with the PV module and ORC boosts the output of this conventional unit.

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.

Simulation of parabolic trough solar collectors using various discretization approaches: A review

The parabolic trough solar collector (PTSC) is a medium-temperature solar system that operates in the temperature range of 60–400 ºC. This technology is utilized dominantly for heat and power generation. Recently, numerous theoretical and numerical investigations have been carried out to evaluate and enhance the performance of PTSCs. This review paper provides fundamentals of PTSC systems, mathematical models, discretization methods, and turbulence models utilized for the simulation of PTSCs. Challenges in the field and future directions are presented to provide a perspective for researchers to achieve more accurate numerical results with lower computational costs.

Numerical investigation on the thermal performance of parabolic trough solar collector with synthetic oil/Cu nanofluids

Nanofluids as the advanced heat transfer fluids, could be used in the parabolic trough solar collector system because of the enhanced thermal transport properties. In this paper, the effects of the same nanoparticles with two different base fluids on the thermal performance of the collector are numerically investigated by finite element method. Moreover, the effect of nanofluids on the cross-sectional temperature distribution of the absorber tube, which is well-known to affect the collector performance is here investigated. The numerical study is divided into two groups according to the value range of inlet velocity and inlet temperature, which represents different application scenarios of the collector. The results show that the synthetic oil/Cu nanofluids could increase the convective heat transfer coefficient under wide working conditions, but more pumping work is required because of the increase in pressure drop. The cross-sectional temperature difference of the absorber tube is greatly decreased with synthetic oil/Cu nanofluids. Furthermore, it’s found that Cu nanoparticles could trigger thermal and exergetic efficiency increment, especially at a low flow rate and high working temperature. The thermal performance improvement of these two thermal oils by Cu nanoparticles is different, and Syltherm 800 is more suitable for being the base fluid of nanofluid.

Investigation of novel turbulator with and without twisted configuration under turbulent forced convection of a CuO/water nanofluid flow inside a parabolic trough solar collector

<abstract> <p>In this study, we numerically investigated the hydrothermal performance of a parabolic trough solar collector system in which nanofluids are used to transfer thermal energy. The single-phase model has been used to evaluate the respective influences of the spherical shape of nanoparticles with a volume fraction of (φ = 3%), Reynolds number varying between 50,000 ≤ Re ≤ 250,000 and the insertion of a turbulator with and without a twisted configuration on the hydrothermal characteristics created by the turbulent forced convection of a CuO/water nanofluid. The shaped turbulator (+) inserted in the absorber tube had a length turb_L = 2.4 m, a height turb_H = 40 mm and a width turb_t = 2 mm. In the second configuration, the considered turbulator was twisted (N_twist = 5, 10 and 15 twists). The turbulator was positioned at 0.6 m from the inlet of the tube and 1 m from the outlet of the collector. The studied performances included the heat transfer characteristics, pressure drop, friction factor, thermal efficiency, temperature and velocity distribution of the outlet field. The most significant contribution of this study is the proposal of the best parameters to increase the thermal and hydraulic efficiency of parabolic troughs by adding a new turbulator with the considered twists.</p> </abstract>

Dynamic Modeling and Controller Design for a Parabolic Trough Solar Collector

The current study unveils an analytical dynamic model of a parabolic trough solar collector (PTSC) and subsequently presents the process to derive the transfer function of the PTSC system. The presented generalized transfer function derivation can be utilized to relate different operating parameters with the output temperature for any PTSC module. Presented model and derivation are applied on a PTSC module tested by Sandia National Laboratory, USA and a transfer function relating the outlet temperature of heat transfer fluid (HTF) with flowrate is derived. PID controller is designed to maintain the HTF outlet temperature by manipulating the flowrate. Controller tuning is performed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">via</i> nature-inspired algorithms (NIAs) which is rare in the context of the control systems for PTSCs. Two NIAs namely Self-adaptive Differential Evolution (SaDE) and African Vultures Optimization Algorithm (AVOA) were used for tuning with minimization of integral of time-weighted absolute error (ITAE) as an objective. It is concluded that SaDE-PID tuned controller outperforms AVOA-PID tuned controller with lower ITAE and in terms of other controller characteristics. Also, the designed controller is examined on various grounds as transient response characteristics and performance indexes. This completes the investigation of the integrity of the presented model, process, and controller.

A fundamental investigation on supercritical carbon dioxide energetic, exergetic and entropy behavior in parabolic trough solar collector

Supercritical carbon dioxide (s-C O2) has been gaining prominence among researchers due to its ability to operate at high temperatures and overcome the current state-of-the-art parabolic trough solar collector system's limitation. This research aims to investigate the energetic, exergetic and entropy performance of the PTSC under a wide range of operating and climatic conditions in detail. Using a modified LS-3 PTSC as a model, a 1-D mathematical model was validated with previous works and solved by using EES under a steady-state condition. The results showed that the system's primary energy efficiency is greatly affected by pumping power requirement while the impact is less prominent on exergetic efficiency. When the system was tested under actual climatic conditions, its energetic performance showed consistent results with fixed conditions, but contrary results were observed for exergetic efficiency. The most important observation was that the performance of Tin = 550K noticeably outperformed Tin = 750K & 850K, which contradicted previous studies with fixed climatic conditions. Besides that, at low DNI levels, the results showed that s-C O2's primary thermal and exergetic performance at high temperatures (750K & 850K) was greatly reduced. For entropy analysis, the dominant reason for entropy generation is primarily due to exergy destruction for the two most important inlet temperatures (550K & 650K). The overwhelming reason for entropy generated due to exergy destruction is between the sun and the receiver with a ratio of ≥95%. Whereas the dominant cause of exergy loss is primarily due to optical loss.

Optical performance investigation on flat receiver for parabolic trough solar collector based on the MCRT method

Parabolic trough solar collector (PTC) system with a flat receiver is widely used in concentrating photovoltaic/thermal (CPV/T) systems, where the flat receiver and PTC are the key components to exchange the solar radiation into heat or electricity. The optimal design and geometric structure of PTC using a flat receiver are essential to achieve high efficiency and energy yield for CPV/T systems. In this paper, a mathematical model of PTC with the flat receiver was developed to investigate and evaluate optical properties based on Monte Carlo Ray Tracing method, whose feasibility and reasonability was verified by the comparison between the model and published literature's results. An innovative method was proposed to calculate the minimum width by vectoring. The optimal geometric design for the same geometrical focusing ratio was derived through simulations based on MATLAB. The influence of geometric parameters and errors were discussed, which showed that the optical performance has large variations in local concentration ratio (LCR) at the center of the flat receiver and is superior at rim angles of 75°–90° under ideal conditions with the same geometric focusing ratio. The errors were found to have a significant effect on the optical performance, especially on the peak LCR.

A hybrid parabolic trough solar collector system integrated with photovoltaics

It is challenging to reduce the massive radiation heat loss from the parabolic trough solar receiver and enhance the solar utilization efficiency of the parabolic trough collector (PTC) system. On the basis of the negative thermal-flux phenomenon discovered in the PTC system, a novel PTC system integrated with photovoltaic (PTC-PV) panels is proposed in this study to effectively enhance the thermal performance and solar utilization efficiency of the PTC system. Four modes of the hybrid PTC-PV system are put forward for catching the optimum configuration. The mathematical models of the hybrid PTC-PV system in terms of photothermal and photoelectrical conversions are established. Additionally, a test rig of the hybrid system is built, and the experiments are carried out in an indoor laboratory with a solar simulator. Comparisons between the experimental and simulated results show that the model has an excellent prediction ability. Furthermore, a 12 m-length PTC-PV system using molten salt as heat transfer fluid is studied to validate its thermal, exergy, and overall performance. The results show that the hybrid PTC-PV system exhibits dramatic superiority in overall performance over the PTC prototype system. The heat loss of the solar receiver in the hybrid PTC-PV system is significantly reduced by 44.0 %, and the photoelectrical efficiency of the PV panel in the PTC-PV system is drastically enhanced by 118.3 % compared to that installed on the ground. Moreover, the overall and exergy efficiencies of the PTC-PV system can be improved by 14.3 and 13.7 %, respectively, at the inlet fluid temperature of 580 °C.

Designing a novel small-scale parabolic trough solar thermal collector with secondary reflector for uniform heat flux distribution

This paper presents a new stepwise approach to design a medium-temperature solar parabolic trough collector with a secondary reflector, which is the fastest growing technology among concentrated solar power technology. The goal of the design is to have a homogeneous concentrated solar flux distribution with maximal output power over the receiver tube. Tonatiuh, a Monte Carlo ray-tracing based optical simulation software, has been used to conduct the ray-tracing analysis of the secondary reflector. Response surface methodology has been used to examine and select the desirable configuration of the solar collector system, and the findings have been analysed using the analysis of variance. It is found that the use of secondary reflector improves the uniformity of heat flux distribution to 0.58, whereas it is 1.0836 for the solar collector without the secondary reflector. For a target output power of 5.5 kW, the most attractive configuration has a maximum desirability value of 0.974. The computational fluid dynamics analysis has been performed in the configuration with better uniform heat flux and the collector without a secondary reflector, using the flux distribution acquired from the ray-tracing analysis. Results show that the use of secondary reflector significantly reduces the thermal gradient, and the heat flux distribution is found to be homogenous. By determining configurations with the best heat flux distribution against a specific output power, the approach provided in this paper lays the groundwork for future research on the design of parabolic trough solar collector systems with secondary reflectors.

Selective Absorber Coatings and Technological Advancements in Performance Enhancement for Parabolic Trough Solar Collector

Parabolic trough solar collector systems are the most advanced concentrating solar power technology for large-scale power generation purposes. The current work reviews various selective coating materials and their characteristics for different designs in concentrating solar power. Solar selective absorbing coatings collect solar radiation and convert it to heat. To promote higher efficiency and lower energy costs at higher temperatures requires, this study aims to analyse the fundamental chemistry and thermal stability of some key coatings currently being used and even under investigation to find reasons for differences, information gaps and potential for improvement in results. In recent years, several novel and useful solar absorber coatings have been developed. However, qualification test methods such as corrosion resistance, thermal stability testing and prediction of service life, which have essential technical value for large-scale solar absorbers, are lacking. Coatings are used to enhance the performance of reflectors and absorbers in terms of quality, efficiency, maintenance and cost. Differentiated coatings are required as there are no uniformly perfect materials in various applications, working conditions and material variations. Much more knowledge of the physical and chemical properties and durability of the coatings is required, which will help prevent failures that could not be discovered previously.

Investigation of the behavior of a heating system coupled to parabolic trough solar collector system

The objective of this work is to study the thermal behavior of a solar heating system using an active layer, integrated in a wall and supplied with hot water by a parabolic trough solar collector (PTC). The prototype includes a PTC collector with a surface area of 1.8m2, a tank and an active layer integrated in a wall. A complete simulation model using the TRNSYS 16 simulation software has been established. Simulation tests under the climatic conditions of the city of Errachidia located in southeastern Morocco show the temperature variations in the different components of the installation as well as the useful energy gained during the three coldest months (December, January and February). In addition, an evaluation study of the system's performance with effect of different values of the reflectivity of PTC collector mirror was carried out. The results obtained show that the PTC efficiency increased from 0.41 to 0.63 when the reflectivity of the collector mirror increased from 0.6 to 0.9 for the three heating months.

Analysis of heat transfer performance of the absorber tube with convergent-divergent structure for parabolic trough collector

In order to effectually improve the performance of parabolic trough solar collector system and homogenize the temperature distribution on the absorber tube, an innovative convergent-divergent tube was designed as the absorber tube of PTR. The finite volume method (FVM) and the Monte Carlo ray tracing method (MCRT) are combined to simulate the heat transfer process in parabolic trough collector. The average relative error between the numerical results and the experimental results conducted in the Spanish DISS test facility is 1.103%, which confirms the reliability of the simulation results in this paper. The heat transfer characteristics and flow characteristics of PTR and convergent-divergent PTR are compared in the inlet velocity range of 0.05-0.75m/s, and the effect of the number of zoom sections(N) for CD-PTR performance is also studied. The simulation results show that the parabolic trough collector with convergent-divergent tube has significantly enhanced heat transfer capability. The average Nu of CD-PTR increases as the number of zoom sections increases, and is always higher than that of PTR. When Re=86400 and N=25, the average Nu increased by 66%.

Using artificial neural networks and multiple regression models to generate economic solar thermal energy

Optimizing parabolic trough solar collector systems to create more mature, reliable and cost-efficient solar energy