Parabolic Trough Collector System Research Articles

Sensitivity of Dust Deposition for Parabolic Trough Collector Mirrors to Different Meteorological Drivers

This abstract presents a soiling forecasting tool (SFT) for assessing the deposition of dust on parabolic trough collector (PTC) mirrors and its cumulative impact on their reflectivity. The SFT was developed by the University of Patras in the frame of the Smart Solar System (S3) project (Horizon 2020 Solar-Era.net). An initial version of the model was presented at the SolarPACES 2022 conference, where the adaptation of the model to dust transport phenomena was demonstrated. The subsequent step in the evolution of the algorithm concerned the calibration of the SFT under different atmospheric conditions. In addition, the model was modified to incorporate meteorological and aerosol forecast data as inputs. The atmospheric predictions of dust and aerosol optical depth are from the global atmospheric forecasts of the Copernicus Atmosphere Monitoring Service. Regarding the meteorological data, three independent sources are used. Those are the Norwegian Meteorological Institute's meteorological forecasts (YR), the METAR meteorological observations from the closest airport, and lastly, the data from the automatic weather station at the location of the PTC system at the KEAN Soft Drinks Ltd factory in Limassol, Cyprus. The aim of this paper is to assess the impact of the three distinct meteorological input sources on the modelled reflectivity and its comparison to measurements taken during the experimental campaign.

Development of a DNI Forecast Tool Based on Machine Learning for the Smart Operation of a Parabolic Trough Collector System with Thermal Energy Storage

In the research project Smart Solar System (S3), the Solar-Institut Jülich (SIJ) developed forecast tools to predict the direct normal irradiance (DNI) in hourly resolution for the current day. The aim of the daily DNI forecast is to use it as input to enable a smart operation of a parabolic trough collector (PTC) system with a concrete thermal energy storage (C-TES) located at the company KEAN Soft Drinks Ltd in Limassol, Cyprus. The main focus in this work is on the development of a DNI forecast tool based on long short-term memory (LSTM), which is a recurrent neural network (RNN), and its comparison with a DNI forecast tool based on analytical algorithms (non-machine learning). Only the non-machine learning DNI forecast tool with hourly update was tested in real-life PTC plant operation since end of 2022. The comparisons between the three DNI forecast tools show that the potential of using machine learning is very high. Different comparisons were made including an evaluation of the accuracy of the tool (i.e. comparison of the DNI forecast data with DNI measurement data). The DNI forecast based on the LSTM network proved to be more accurate than the non-machine learning DNI forecasts when considering errors greater than ±100 W/m2. The error of the LSTM network compared to DNI measurement data was as follows: 43.6 % of the data was within ±100 W/m2, 74.8 % was within ±200 W/m2, 89.8 % was within ±300 W/m2 and 95.8 % was within ±400 W/m2.

Study of parabolic trough collector with crucial analysis on controller and estimator with variable mirror efficiency

Solar Thermal Power (STP) plants are a crucial technology for converting solar energy into electricity. Among the STP, the Parabolic Trough Collector (PTC) is one of the integral parts of STP systems for electrical power generation. Maximizing PTC performance is a challenge due to dynamic and unpredictable solar radiation and environmental disturbances, such as cloud cover and dust accumulation. The optical efficiency parameter of the PTC is critical for calculating the desired heat gain, which is difficult to measure in real-time, necessitating sophisticated control and estimation strategies for optimal heat regulation. This study introduces two control mechanisms for the PTC system and comparing their efficacy. A classical PI controller supplemented by Static Feed-Forward (SFF) control demonstrates improved performance with an optimal transfer function model. In contrast, Nonlinear Model Predictive Control (NMPC) excels in disturbance rejection and setpoint tracking, considering operational constraints. The NMPC controller notably outperforms the PI controller with SFF in performance metrics, with the Integral Time Squared Error (ITSE) decreasing by approximately 99% across case studies. Also, in the case of heat gain, NMPC controller exhibits percentage increases when compared to the PI controller. Furthermore, since the measurement of optical efficiency is essential, but due to difficulty in the measurement for various reasons, the estimator is used as a virtual sensor to estimate those optical efficiency. The unmeasured states and parameters, including optical efficiencies of the PTC, are estimated using Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) techniques, with UKF exhibiting superior accuracy. However, considering the average computation time, EKF is preferred for real-time applications.

Silicon porous disc featured parabolic trough collector functioned with paraffin: Thermal performance study

The advancement of renewable solar energy has potential for industrial heat exchanger applications, and its performance is enhanced by using nanofluid. Besides, the losses of heat during the energy transfer from solar to heat exchanger limit thermal performance and lead to reduced thermal efficiency. The conventional solar system functioning with nanofluid needs to be upgraded with an advanced thermal management system to limit energy loss and enrich the thermal performance of the overall system. The investigation aims to enrich the thermal performance of a parabolic trough solar collector (PTC), which features silicon porous discs and phase change material (PCM-paraffin). During the investigation, the flow of fluid ranged from 100 to 200 LPH with an interval of 50 LPH. Influences of silicon porous disc and phase change material melting phase on fluid temperature, temperature, energy stored, and thermal efficiency of the present system are experimentally investigated, and its values are related to conventional absorber performance without porous material and phase change material. The output results prove the significance of silicon porous and phase change material related to conventional absorber systems. The parabolic solar collector functioned with silicon porous material with phase change material phase on 200LPH spotted superior thermal performance including fluid temperature, PCM temperature, energy stored by phase change material, and average thermal & exergy efficiency of 84.2 °C, 98.5 °C 599.7 kJ, and 73.8 % & 15.1 %. These findings underscore the promising potential of porous medium absorbers in significantly elevating the efficiency of parabolic trough collector systems.

Modeling and Evaluation of a Solar Trigeneration System With Thermal Energy Storage

In the present study, an on-demand solar combined cooling, heating, and power (CCHP) system with parabolic trough collector (PTC) and solid-state thermal energy storage (TES) is investigated, which will be demonstrated on-site in 2024 at the Administration Building of the Lavrio Technological and Cultural Park (LTCP) in Attica, Greece, covering the energy needs of the building in form of heating and electricity in winter and cooling during summer. The system is based on a combined Organic Rankine Cycle and an Ejector Cooling Cycle (ORC-ECC), which is modeled and simulated in a steady-state manner while the PTC and TES systems are modeled dynamically, i.e., they are influenced by the thermal inertia of the components, the variable weather conditions of the location, and the defined operating strategies. The ORC-ECC simulation results show an efficiency of up to 14.20 % for the ORC system and a Coefficient of Performance (COP) of 0.10 for the ECC system under defined conditions. The dynamic simulations for the specified operating strategies indicate that on typical sunny days up to 100 % of the consumers' electricity consumption can be covered by the system.

Thermo-economic investigation on organic Rankine cycle based solar integrated ejector-trigeneration system (EORC-CCHP) for Indian climate

A novel solar integrated ejector-based combined cooling, heating, and power (EORC-CCHP) system based on an organic Rankine cycle is proposed to provide sustainable multiple outputs to meet energy demand. A comprehensive energy and exergy analysis is performed to evaluate the system's performance using six different environment-friendly refrigerants, such as R1233zd, R245fa, R236fa, R142b, R600a, and R124. A parabolic trough collector (PTC) distributes the solar energy to the boiler as a heat source. To study the system's performance at sub-zero evaporator temperatures, the primary flow from the ORC turbine's first-stage expansion is extracted and sent through an ejector refrigeration cycle for the required cooling effect. The remaining refrigerant is expanded across the turbine with a targeted power output of 5 kW and is sent for heat recovery across the heater. Among the refrigerants studied, R600a, R124, and R1233zd demonstrated the highest refrigeration COP of 0.58, system COP of 1.69, and exergy efficiency of around 68.26%. However, due to the lower critical condenser temperatures of R124 and R1233zd makes them obsolete due to negative pressure, R600a is observed as the optimal working fluid. The PTC system demonstrates diurnal variations, with a combined peak energy output of 31.3 kW in May for the Hyderabad climate. Exergy analysis shows that the primary sources for exergy destruction are the PTC system, boiler, and ejector, with destruction rates of 51%, 20.1%, and 22.1%, respectively. The boiler is the main source of exergy destruction cost, with a cost of 0.18 $/h, and the condenser and PTC exhibit the highest total cost rates. The environmental impact of the PTC system is assessed, with July showing the highest environmental effect to unit useful exergy of 71.54 mPts/GJ.

Experimental study of parabolic trough collector in series having a concentric copper tube in evacuated tube for air heating

ABSTRACT Currently, the utilization of solar energy for domestic purposes, particularly in applications such as space heating and hot water, is constrained to flat plate collectors and evacuated tubes due to its compact size, absence of tracking mechanisms, low maintenance, and cost-effectiveness. The objective of this study is to evaluate the practical effectiveness of a locally developed parabolic trough collector system through experimentation. In this configuration, two parabolic trough collectors with one-ended evacuated tubes and inner concentric copper tubes for double pass airflow were connected in series, exhibiting an average air temperature within the range of 130.22°C to 166.72°C, which indicates its potential for use in industrial and domestic applications. Solar intensity, thermal performance, and pressure drop were determined after the first evacuated tube (intermediate point) and after the second evacuated tube. The experiments were carried out on six separate days, with three distinct airflow rates of 0.0056 kg/s, 0.0038 kg/s, and 0.0021 kg/s. Results discovered that the maximum air temperature reached was 210.5°C. The maximum thermal efficiency observed was 39.31%, with an overall average thermal efficiency of 30.56%. Further, the maximum pressure drop achieved was 510 Pa at 0.0056 kg/s.

Hybrid solar hydrothermal carbonization by integrating photovoltaic and parabolic trough technologies: Energy and exergy analyses, innovative designs, and mathematical Modelling

Hydrothermal carbonization (HTC) is an excellent process for transforming biomass into solid fuels. Evaluating HTC's environmental benefits requires addressing substantial energy needs for reactant heating. In this regard, two innovative solar systems for powering HTC were investigated: a parabolic trough collector (PTC) that heats a heat transfer fluid (HTF) circulating through a heat exchanger surrounding a batch reactor and photovoltaic panels (PV) that powers a heating collar. Experimental results reveal that the PV system efficiently attains subcritical conditions, whereas the PTC system faces challenges. Exergetic analysis identifies heat transfer as a primary irreversibility factor, resulting in a recorded maximum entropy of nearly 100 W/K. This caused the exergy efficiency to decrease to a minimum of 0.07, dropping the accumulated exergy below 82 W. To address this issue, a validated mathematical model was employed to investigate three optimized configurations: an immersed heat exchanger, a jacketed system, and a hybrid system combining both. The results demonstrated achieving desired HTC conditions at mixing temperatures of 185 °C, 195 °C, and 230 °C, respectively. In contrast, the PV system rapidly attains 220 °C and 40 bar in 70 min. This study proposes innovative solar HTC designs for sustainable hydrochar production using PV and PTC technologies.

Photo-Thermal Optimization of a Parabolic Trough Collector with Arrayed Selective Coatings

This work aims at enhancing the photo-thermal performance of a parabolic trough collector (PTC) system by implementing multiple coatings arrayed along the receiver tube. For this purpose, a lumped-parameter model was developed in the radial direction of the receiver tube to compute absorber tube wall temperature and heat losses at various heat transfer fluid (HTF) temperatures. The HTF is a mixture of molten salt (60%wt. NaNO3 + 40%wt. KNO3). The lamped-parameter model was exploited by a 1D model developed in the axial direction to determine the HTF temperature profile along the tube. The 1D model was employed to calculate photo-thermal efficiency at different HTF temperatures considering six selective coating formulations. Consequently, the most photo-thermally efficient configuration of the PTC system was determined, encompassing three HTF temperature ranges characterized by three different selective coating formulations. These temperature ranges were 290–436 °C (low temperature), 436–517 °C (medium temperature) and 517–550 °C (high temperature). The respective tube lengths were computed to be 792 m, 566 m and 293 m, considering the reference operational conditions. The optimal configuration enhanced the overall photo-thermal efficiency by 0.5–1.9% compared to the single-coated configurations. Furthermore, receiver cost could be reduced because of the employment of the more expensive coating only at the final segment.

Enhancing optical and thermohydraulic performance of linear Fresnel collectors with receiver tube enhancers: A numerical study

Linear Fresnel collector system is a type of solar thermal utilization installation. It is mainly used to focus solar radiation on the receiver tube to generate high temperature thermal energy which can be applied in many aspects. This study investigates five different types of receiver tube models using water as the flowing medium, which leads to improving heat transfer performance by means of being equipped with enhancers. The optical results and thermohydraulic performance of the Linear Fresnel collector system are evaluated through Monte Carlo Ray Tracing and Computational Fluid Dynamics (CFD) simulation methods. The obtained optical results reveal that the distribution of energy flux density concentrating on the receiver tube surpasses that of the parabolic trough collector system. In order to maintain an energy reception rate of 90.0% or higher, the installation height range of the receiver tube should be between 1468–1532 mm. When the sun-tracking error increases from 0.0° to 1.0°, the overall optical efficiency of the Linear Fresnel collector system decreases from 98.9% to 79.7%. The thermohydraulic performance shows that the enhancers can generate a swirling flow as its main feature, which effectively promotes the homogenization of the temperature field and destroys the boundary layer near the receiver tube wall, thus greatly improving the convective heat transfer in the receiver tube. However, the introduction of the enhancers also means that the pressure drop loss of the receiver tube increases. Furthermore, the impact of the Kenics mixer's enhancer on heat transfer and flow characteristics is further amplified as the rotation rate decreases, owing to its alternating and complex structure. Through a comparative analysis of the influence of different receiver tube models on Nusselt number (Nu), Frictional resistance coefficient (f) and comprehensive evaluation criterion (PEC) under four rotation rate conditions (y = 6.3, 8.1, 11.34, 18.9), the conclusions present that the receiver tube with an enhancer at a low rotation rate has a larger Nu than that at a high rotation rate, while the Frictional resistance coefficient changes little at different rotation rates. Therefore, the PEC is higher when the receiver tube is equipped with a low-rotation-rate enhancer. Moreover, the receiver tube equipped with a Kenics mixer at a rotation rate of 6.3 was found to be the overall optimum case, with the PEC value varying from 1.47 to 1.73.

Comparative Analysis of Solar Tower and Parabolic Trough Systems for Solar Heat in a Steel Industry

Concentrated Solar Thermal (CST) systems emerge as a promising alternative to replace fossil fuels used in industrial thermal processes due to their high energy density and dispatchability. In this study, a comparative analysis of two CST systems, Solar Tower (ST) and Parabolic Trough Collector (PTC), has been made to replace natural gas used in the steam generation process in Türkiye's largest steel production plant, located in the Mediterranean Region of Türkiye. Both the ST and PTC systems were placed in a field area of approximately 0.4 km2. The results have shown that, on a monthly basis, the PTC system could exceed the plant's thermal energy for two-thirds of the year, while the ST system could meet the plant's energy requirements for one-third of the year. This could reduce CO2 by about 12.7 and 19.1 kilo-tones for ST and PTC at LCOH of about 68.9 and 36.9 EUR/MWh, respectively.

Optimal energy collection with rotational movement constraints in concentrated solar power plants

In concentrated solar power (CSP) plants based on parabolic trough collectors (PTC), the sun is tracked at discrete time intervals, with each interval representing a movement of the collector system. The act of moving heavy mechanical structures can lead to the development of cracks, bending, and/or displacement of components from their optimal optical positions. This, in turn, diminishes the overall energy capture performance of the entire system. In this context, we introduce two combinatorial optimization problems of great interest to PTC plants. The minimum tracking motion (MTM) problem is aimed at detecting the minimum number of movements needed while maintaining production within a given range. The maximal energy collection (MEC) problem seeks to achieve optimal energy production within a predetermined number of movements. Both problems are solved assuming scenarios where the energy collection function contains any number of local maximums/minimums due to optical errors of the elements in the PTC system. The MTM and MEC problems are solved in O(n) time and O(n2mω∗) time respectively, where n is the number of steps in the energy collection function, m the maximum number of movements of the solar structure, and ω∗ the maximal amplitude angle that the structure can cover. The advantages of the solutions are shown in realistic experiments. While these problems can be solved in polynomial time, we establish the NP-hardness of a slightly modified version of the MEC problem. The proposed algorithms are generic and can be adapted to schedule solar tracking in other CSP systems.

Development and Economical Analysis of Innovative Parabolic Trough Collector Integrated Solar Still

Experimental setup of the integrated parabolic trough collector (PTC) with solar still was developed. PTC was designed considering the solar geometry and the physical laws of parabolic shape and the concentrators. Test were conducted at the location with latitude 19.9975ON and longitude 73.7898OE. Theoretical analysis was done using ray tracing and engineering equation solver (EES) software while designing the system. PTC system was developed with dimensions of 1.5 m length, 1 m width and a concentration ratio (CR) of 21.22. Theoretical thermal efficiency was predicted as 48.1% whereas experimental average thermal efficiency is observed as 42.76%. The observed temperature difference between the vapor and the glass cover is about 17 °C and between ambient air and vapor is about 24.4 °C. Maximum water temperature in the conventional solar still was 64.6 °C where as for the PTC coupled solar still was 74.4 °C. PTC coupled solar still is having averagely 37% higher production rate. This has definitely added an advantage because of the higher energy absorption rate compared with the conventional solar still. PTC coupled solar still system has nearly 35% more heat absorption. Total embodied energy of the system is around 896.875 kWh. Total capital cost of the system is Rs. 41300/-. Total annual output of pure water is around 3 L/Day. Estimated energy payback period is around 2.29 years and the total carbon credit earned is Rs. 2165.38 per year.

Hybrid Solar Thermal Energy System for District Heating Application

Solar district heating (SDH) systems can be good alternatives to conventional systems when they are optimized with hybrid configurations and thermal energy storage (TES). In this scope, a hybrid renewable thermal energy system (RTES) model has been built combining flat plate collector (FPC) solar system with parabolic trough collector (PTC) system via a heat exchanger and coupled with TES. To undertake the hybridization of the system, System Advisor Model (SAM) software was modified, which allowed control over configurations and more accurate modelling of heat transfer between the collectors. The model is first compared to an existing hybrid solar district heating systems (DHS) system in Taars, Denmark. The results showed a good correlation with an overestimation of only 6.4% compared to most recent heat output. Then the same system configuration was modeled in different geographic locations to investigate the impact of changes in direct normal irradiance (DNI) to the heat sink thermal output of the hybrid system. The results showed that the annual net thermal power output in California, USA can be three times more than the annual net thermal power output in Taars, Denmark. Finally, multiple hybrid configurations with varying solar field sizes were simulated based on the heat demand of two different university campuses DHS. The results showed that, retrofit applications of this hybrid DHS system coupled with TES could reduce the natural gas consumption of the existing systems between 25% and 41%. The use of hybrid RTES highlighted in this paper can be extended to many more opportunities.

DNI Forecast Tool for the Smart Operation of a Parabolic Trough Collector System With Concrete Thermal Energy Storage

This work presents a basic forecast tool for predicting direct normal irradiance (DNI) in hourly resolution, which the Solar-Institut Jülich (SIJ) is developing within a research project. The DNI forecast data shall be used for a parabolic trough collector (PTC) system with a concrete thermal energy storage (C-TES) located at the company KEAN Soft Drinks Ltd in Limassol, Cyprus. On a daily basis, 24-hour DNI prediction data in hourly resolution shall be automatically produced using free or very low-cost weather forecast data as input. The purpose of the DNI forecast tool is to automatically transfer the DNI forecast data on a daily basis to a main control unit (MCU). The MCU automatically makes a smart decision on the operation mode of the PTC system such as steam production mode and/or C-TES charging mode. The DNI forecast tool was evaluated using historical data of measured DNI from an on-site weather station, which was compared to the DNI forecast data. The DNI forecast tool was tested using data from 56 days between January and March 2022, which included days with a strong variation in DNI due to cloud passages. For the evaluation of the DNI forecast reliability, three categories were created and the forecast data was sorted accordingly. The result was that the DNI forecast tool has a reliability of 71.4 % based on the tested days. The result fulfils SIJ’s aim to achieve a reliability of around 70 %, but SIJ aims to still improve the DNI forecast quality.

Cupric oxide nanofluid influenced parabolic trough solar collector: thermal performance evaluation

ABSTRACT The availability of solar radiation has potential for energy applications, and recently, the parabolic trough collector (PTC) plays a crucial role in heat exchanger applications. The conventional system lacked thermal performance, reducing heat transfer coefficient and thermal efficiency. With this, the main goal of the research is to attempt to enrich the overall thermal capacity of the PTC system by introducing triangular copper fins and CuO nanoparticles (10–20 nm). During the experimental evaluation, the different concentrations (0.1, 0.2, and 0.3%) of CuO blended with water (nanofluid) are permitted to circulate the receiver boundary configured with PTC setup 3.5 m2 at the flow rate of 0.12 kg/s. Effects of CuO nanofluid concentrations on heat gain, heat transfer coefficient, and thermal and exergy efficiency of the system are measured and spot the optimum heat gain of 689.9Wm enriched heat transfer coefficient of 172.3 W/m2K, maximum thermal and exergy efficiency of 70.9% and 37.2% respectively.

Thermal performance evaluation of an indigenously designed small-scale solar parabolic trough collector for manufacturing Indian milk products

ABSTRACT A small-scale solar parabolic trough collector system coupled with a jacketed vessel was designed and evaluated for its performance and quality of the products manufactured in it. The prototype having a 7.026 m2 aperture and 88.38° rim angle was installed in Mehsana, Gujarat, India. The study was conducted in May–June 2022 at different flow rates of sigma therm-k. The useful heat rate ranged from 567.82 W to 861.25 W. The daily average thermal efficiency was obtained in the range of 9.81–14.61% and maximum thermal efficiency achieved during the milk trials was 31.51%. Similarly, maximum absorber temperature achieved during stagnation was 193.4°C and during absorber fluid flow condition was 146.5°C. The maximum convective heat transfer coefficient of 49.5 W/m2K was calculated at Reynold number 1822 and Nusselt number 24.12. It was found that the quality parameters of manufactured milk products were at par with domestic food safety standards. Direct normal irradiance was found to be the most influencing factor followed by the initial milk load. The present system is a potential substitute for various small-scale Indian traditional heat-desiccated milk products, where higher thermal efficiency is not the primary requirement and emphasis is more on the importance of ease of operation.

Design and evaluation of solar parabolic trough collector system integrated with conventional oil boiler

Design and evaluation of solar parabolic trough collector system integrated with conventional oil boiler

Design, fabrication and thermal analysis of parabolic trough collector

Parabolic trough collector (PTC) is considered environmentally friendly and one of the green technologies with net-zero emissions. In this study, performance evaluation of a developed solar PTC system is performed by conducting a series of experimentation. The study focuses on the design, development, and thermal evaluation of a PTC prototype, under hot and humid climatic conditions of Islamabad, Pakistan. Thermal efficiency of the solar PTC system is determined and effect of solar irradiance on thermal efficiency and heat gain is evaluated. Energy and exergy efficiency of the PTC systems are determined 66%, and 38%, respectively.

Enhancing the efficiency of solar parabolic trough collector systems via cascaded multiple concentration ratios

Solar parabolic trough collector (PTC) technology is clean and economical. However, PTC technology suffers from relatively low optical and thermal efficiencies at high operating temperatures and concentration ratios (CRs). In this work, a novel strategy for cascadingly using solar collectors with multiple concentration ratios in one collector loop is proposed to reduce optical losses and improve the overall performance of the PTC system. Two systems were studied for implementation of the proposed strategy: an ideal system employing multiple optimal CRs in distinct collector loop sections and a multisection system employing multiple practical CRs. An integrated optical model and two-dimensional heat transfer model based on finite volume and radiation heat transfer methods were developed in this study. These models proved to be highly accurate in estimating the thermal properties of solar collectors. At operating temperatures between 293 and 393 °C, the optical efficiency of the multisection system was 6.7% higher than that of a conventional system with a single CR. Under the same conditions, the thermal efficiency was improved by 4.5%. This work is anticipated to provide a reference for solar collector design and a new avenue for enhancing the overall efficiencies of PTC systems.