Parabolic Trough Solar Concentrator Research Articles

Testing of a 3D-Printed Solar Micro-Reactor for Hydrogen Production via Natural Gas Reforming

This paper presents the design, fabrication, and successful real-condition testing of a solar micro-reactor for hydrogen synthesis via steam methane reforming (SMR). This micro-reactor integrates all the sub-processes necessary for SMR in a network of small three-dimensional channels, making it well-suited for implementation on the commercially available parabolic trough solar concentrators. Additive manufacturing was used to create an operational prototype of this micro-reactor. The prototype was integrated to a parabolic mirror for solar concentration, and tested in real conditions. Complete methane conversion to syngas was obtained with an absorbed solar radiation equivalent to 240 suns, which demonstrates the feasibility of solar SMR at moderate solar concentration.

Experimental performance investigations on various orientations of evacuated double absorber tube for solar parabolic trough concentrator

The parabolic trough concentrator is a widely used concentrator to harness and concentrate on the solar energy. The performance of the parabolic trough concentrator depends upon its various parameters like reflecting surface, mass flow rate, concentration ratio, heat transfer fluid, rim angle, tracking of system, evacuation of absorber, and absorber tube. An absorber tube or receiver is the most important parameter that has an effect on the enhancement of heat transfer which was further specified by its material, surface coating, length, diameter, type of flow through it, number of absorber tube, various orientations of double tube, internal flow obstructions like twisted tape, different shape insertion in it etc. Different researchers had worked on different modifications of the absorber tube to increase the effective heat transfer. In this present experimental work, an investigation of the evacuated double tube absorber with its various orientations carried out for the designed and developed prototype of PTC.

Thermal Evaluation of a Parabolic Trough Solar Concentrator Using Three Different Receivers

Energy demand, global warming from the fossil fuels and attempt to reduce greenhouse gas emission have placed the centre of attention on how to utilize an alternative sources of energy such as renewable energy technology This work presents the design, fabrication, and evaluation of the performance of Parabolic Trough Solar Concentrator (PTSC) as a source of heat energy. The PTSC is built, having the Supporting stand made of mild steel and reflector is made of the segmented mirror having a reflectivity of 0.85, a rim angle of 90 o and aperture area of 2.5 m 2 and with a concentration ratio of 11.7. The receiver pipes are made of three different materials; copper, aluminum, and stainless steel. The effects of shifts in focal lengths on the performance of the PTSC with three different receivers were investigated. The results reveal copper as a receiver tube conducts heat to the heat transfer fluid better than aluminum and stainless steel receivers. The focal length of 30 cm gave the best results compared to other values of 27 and 35 cm with a maximum temperature of 114.4 o C. The experimental results revealed that useful heat gained, overall heat loss coefficient, collector efficiency factor, heat removal factor, collector and thermal efficiency were 147.8 J, 5.04 W/m 2 K, 0.05, 15.05, 0.032% and 15.5% respectively. The study shows that the Parabolic Trough Solar Concentrator as a source of heat energy gives a promising performance. This concentrator will reduce the dependence on the electric power supply, and it controls pollution emanating from fossil fuel, thereby reducing environmental problems. Keywords : Parabolic Trough Solar Collector, Segmented Mirror, Efficiency, Receivers. DOI : 10.7176/JETP/9-5-03 Publication date :June 30 th 2019

Geometric, optical and thermal analysis for solar parabolic trough concentrator efficiency improvement using the Photogrammetry technique under semi-arid climate

The investment of renewable energy, especially the solar energy, seems to be the real alternative and the potential solutions for the classical fuel energy due to its pollutant and limited source. Therefore, the cost and performance are the main criteria to assess a solar power plant. The purpose of this work is to evaluate the optical and thermal efficiencies of a solar Parabolic Trough Concentrated (PTC) installed in the Green Energy Park (GEP) research platform in Benguerir, Morocco. In order to improve the optical efficiency of the system, an optical qualification is necessary because of the difficulties of handling the glasses and the deformations from the ideal design. In this sense, an experimental study was carried out using the robust Photogrammetry measurement technique to perform the geometrical and optical errors of the solar concentrating system. Slope error, misalignment error, and receiver position error has been identified and analyzed. Moreover, the intercept factor and the optical efficiency of the PTC system according to the experimental measurements given by the Photogrammetry technique were determined. Finally, the thermal efficiency of the PTC according to results obtained and the weather conditions climate of Benguerir city extracted by an accurate meteorological station have been performed and analyzed. The results obtained show the relevant impact of the optical efficiency on the thermal energy and the plant performance.

Design and Implementation of an Automatic Control for Two Axis Tracking System for Applications of Concentrated Solar Thermal Power

The present work presents design and implementation of an automated two-axis solar tracking system using local materials with minimum cost, light weight and reliable structure. The tracking system consists of two parts, mechanical units (fixed and moving parts) and control units (four LDR sensors and Arduino UNO microcontroller to control two DC servomotors). The tracking system was fitted and assembled together with a parabolic trough solar concentrator (PTSC) system to move it according to information come from the sensors so as to keep the PTSC always perpendicular to sun rays. The experimental tests have been done on the PTSC system to investigate its thermal performance in two cases, with tracking system (case 1) and without tracking system (case 2). The experimental results showed that the average solar radiation falling on the PTSC prototype in the two cases during the same time was 854 and 701 watt/m2, respectively, which means an increase in the solar radiation about 21.8 % when using tracking system. It was found that the average useful heat gain output of solar collector was equal to (376.2, 252.6 watt) for the two cases, respectively, so there was an increase of about 48.9 % when using the tracking system. Also, the average thermal efficiency of the PTSC was found to be (20.7, 26.5 %) for the two cases, respectively, which means an increase in the average efficiency by 28% with use of tracking system compared to the fixed case.

Dynamic simulation, control, and performance evaluation of a synergistic solar and natural gas hybrid power plant

Solar power is considered among the leading renewable energy technologies. Abundant supply, flexibility of installation, and decreasing cost makes it an interesting renewable energy resource. However, there are challenges associated with the reliability of solar power due to its intermittent nature. This work demonstrates the synergies that exist in integrated hybrid systems, where a dispatchable fuel is used in conjunction with concentrated solar power. In this simulation-based study, a parabolic trough solar concentrator is used to collect solar energy. The heat collected from the solar field is used to generate steam in a Rankine cycle. The system also utilizes natural gas combustion in the steam generator to provide supplemental steam when the solar intensity is reduced due to cloud cover or at night. Natural gas is also used for superheating the steam, which allows the system to produce higher temperatures and achieve increased thermodynamic cycle efficiencies. This flexible design produces 100 MW at nominal conditions, while it is capable of producing a maximum of 140 MW when sufficient solar energy is available. The novel contributions of this work include a complete, systems-level, dynamic model of a hybrid solar plant. The model is complete with a control system that smoothly transitions the plant from pure natural gas mode at night to solar hybrid mode during the day. It evaluates innovative design features such as flexible fuel operation, steam superheating to boost efficiency, and preheating by solar or waste heat. Furthermore, this work demonstrates that by hybridizing a solar system with a dispatchable energy source, both the reliability and efficiency of the solar power production are increased. The annual solar-to-electric efficiency increases from 15.2% to 26.13% with hybridization, which indicates that utilization of the solar energy is effectively increased.

Thermal stress in bimetallic receiver of solar parabolic trough concentrator induced due to non uniform temperature and solar flux distribution

The absorber-tube of the parabolic trough collector (PTC) witnesses compression and tension while operation due to the thermal gradient developed over the cross-section of the tube. While the researchers have proposed a number of receiver models to improve the energy collection by heat transfer fluid inside the absorber-tube, the stress developed that forms the essential frameworks for the tube’s and glass-envelope’s safety has not been modelled for real life scenarios where the absorber is held at a number of pillars. The current study models the stress due to compression and tension in a double-layered absorber (held at pillars) having a high conducting material’s layer to mitigate the risk of stress significantly. The pillars are movable that ensure the smooth elongation of the absorber-tube under stress. The pillars are equipped with ball-joints that help the tube to rotate in longitudinal plane. The verification of the proposed model has been carried out against the reported results. The impact of placing the high conductive material as inside or outside layer of the double-layered absorber, width and focal-length of PTC, HTF’s rate of flow, and the geometrical imperfections on the normal-stress are found out. The performance of the modelled double-layered absorber is observed in contrast with the single-layered one. It is concluded that (i) the single-layered absorber witnesses stress of −127 MPa/+101 MPa due to compression/tension. The one with double-layer undergoes lesser respective stress of −78 MPa/+59 MPa when the high conductivity material is placed on the inner side. Besides, the use of high conductivity material as outside layer reduces the stress further to −38 MPa/+35 MPa. Thus, for minimum stress, the outside layer should always be made up of high conducting material, (ii) increasing the HTF’s rate of flow from 0.4 kg/s to 1.4 kg/s results in the reduction of stress from −127 MPa/+101 MPa to −86 MPa/+66 MPa for single-layered absorber. For double-layered absorber, stress comes down from −38 MPa/+35 MPa to −29 MPa/+26 MPa and (iii) an appropriate focal-length of around 0.7 m results in the reduction of stress to almost negligible value of 3 MPa for 3rd generation Luz PTC.

Thermal Performance Analysis of Parabolic Trough Solar Concentrator with Helical Tube Receiver

In this paper, the experimental thermal performance for a parabolic trough solar concentrator (PTSC) combined with helical tube receiver and directed by two axes solar tracking system at different amount of water flow rates has been analyzed. The experimental test results of thermal performance with regard to temperature rise of water, useful heat gain and collector thermal efficiency for the PTSC prototype at controlled water flow rates (2.3, 22.5 and 29.4 L/h) are collected. The results show that the increase of water mass flow rates causes decrease in the average water output temperature as (120.8, 63.82 and 46.08oC), respectively, the maximum outlet temperature becomes (160.5, 76, 47) oC, respectively, and thus, the average useful heat gain will be (1249.4, 732, 732.5W), respectively and the average thermal efficiency decreases as (73.021, 49.51 and 44.31 %), respectively. The experimental results show that decrease the water mass flow rate by 74.4%, causes an increase in the thermal efficiency of the PTSC by 64.7%.

A tool for fast flux distribution calculation of parabolic trough solar concentrators

Parabolic trough concentration (PTC) systems are widespread technologies for the large-scale exploitation of solar energy. The flux density on the wall of the absorber of a PTC is non-uniform and complicated, and the calculation of flux distribution is key for estimating the optic performance of a PTC and analyzing the flow characteristic of the fluids in the tubular absorber. Traditional 3D ray-tracing methods for the calculation of flux distribution consume many computational resources and involve long CPU running time. This paper presents a 2D method for the fast calculation of the flux distribution of a PTC based on a descending dimension algorithm. By converting the PTC optical model from 3D space to 2D space, the calculation consumption required by the presented 2D method shrinks by two orders of magnitude compared to traditional 3D ray-tracing methods. Upon assessment, the method demonstrates a capacity to work out the flux density distribution within 0.22 s, compared to approximately 40 s required by traditional 3D ray-tracing methods, using a standard personal computer with a level of good accuracy, with a standard deviation of approximately 0.3 suns. Mathematical proof of this method was also provided. The numerical results were compared with those from the literature and a good agreement was observed, with the average standard deviation of 0.359 suns under different incident angles, proving the reliability of the method presented here. Based on this 2D method, a software tool was developed to facilitate the analysis of characteristics of solar PTC systems.

An integrated program of a stand-alone parabolic trough solar thermal power plant: Code description and test

Solar thermal systems produce steam after being energized by solar parabolic trough concentrators, are incorporated with a steam turbine-generator assembly to produce electricity. This study presents a code for prediction of performance, while under-taking preliminary plant-sizing for a variety of parabolic trough solar fields operating under nominal conditions. The code, named as PTPPPP (Parabolic Trough Power Plant Performance Predictor) consists of four blocks. The code allows prediction of variables including: heat loss coefficient, UL, aperture effective direct normal irradiance, I, heat gain, Qgain, and the thermal efficiency of stand-alone parabolic trough solar thermal power plant in commerce, ηp. The conceptual design of the stand-alone parabolic trough solar involves: selection and sizing of system components, power generation cycles, working fluid types, and power block sizing. The input weather parameters and the operational parameters to the code have been acquired from in-situ measurements. The prediction results of the code have been found in good agreement with literature data with mean error of 0.18% in prediction of output power. In addition, this code is able to provide a flexibility in terms of temperature, heat transfer, and pressure range.

Development and performance evaluation of an active solar distillation system integrated with a vacuum-type heat exchanger

Industrialization and growth in the world's population have increased the demand for fresh water. Solar desalination systems are energy consuming and therefore using solar stills in the remote locations is more feasible and affordable. In the present study, a solar distillation system integrated with a solar parabolic trough concentrator and a vacuum-type heat exchanger with falling film technique has been developed and experimentally evaluated during five sunny days in October 2015 between 10am to 2.30pm. During the evaluation period, the environmental parameters of solar radiation, air temperature, and wind speed were recorded in every 15min. Then, the effect of these environmental parameters on the daily productivity of the distillation system through the performance evaluation of both solar concentrator and heat exchanger. Then, the energy and exergy efficiencies of the heat exchanger, as the central part of the system, were calculated based on the recorded environmental and operational parameters during the experiments. The obtained results showed that the solar radiation has the dominant effect on the thermal performance of the concentrator which delivers hot oil to the heat exchanger. Moreover, it has been investigated that the vacuum pressure of the heat exchanger has a significant effect on the vapor productivity of the system. The maximum distillate production of the distillation device was recorded to be 1.5kg/m2/day with the average solar radiation of 1227.68W/m2 under the heat exchanger vacuum pressure of 0.5bar. According to the results obtained from the energy and exergy analysis, the highest energy and exergy efficiencies were obtained as 60.98% and 56.80% respectively.

Small Organic Rankine Cycle Coupled to Parabolic Trough Solar Concentrator

In this paper, the design and performance of small Organic Rankine Cycle (ORC) coupled to parabolic trough solar collector (PTC) are showed. The system is analyzed using the first and second laws of thermodynamics. This small ORC is designed to provide 10 kWe for almost 18 hours every day and also energy to heat water. The main components of this system are: a) parabolic trough solar concentrators (PTC), b) thermal storage system and c) ORC system, which uses R245fa as working fluid and a radial turbine as expander. The ORC system is designed to operate in Temixco, city located at the central region of México. The solar radiation database of Temixco was used to compute the estimated performance of the proposed ORC system. Simulation was carried out using Matlab and CoolProp. The ORC power and efficiency were computed. The mass flow and thermal load stored for the PTC loop are shown.

Validation of reverse Hartmann test for mirror shape measurement of parabolic trough concentrator.

A method for the surface shape qualification of a parabolic trough solar concentrator, based on the reflection of sinusoidal fringes in the mirror surface and their distortions due to the surface deviations from ideal geometry, has been developed. Without complex calibration, accurate surface slope data were collected and reduced by using sixteen-step phase shifting methods. As the gradient data may not be ideally available for the entire surface, surface deviations and geometrical parameters were obtained through Zernike slope polynomials iterative fitting and the Southwell integration algorithm. Additionally, an absolute reference measurement for calibration of the measurement accuracy using three standard mirrors is presented. It is shown that the proposed method can easily test the surface shape and concentration efficiency of a solar concentrator with high slope measurement accuracy (less than 0.05 mrad in the x-direction) and high spatial resolution (more than 2.5 × 106 points per mirror facet).

Modeling and designing of the solar thermal parabolic trough concentrator and its environmental effects

Concentrating solar power (CSP) system is a favorable application because of its potential to constantly generate large‐scale electricity. Today, there are many CSP plants in the world. Therefore, the aim of this study is to analyze these systems in detail. To measure the efficiencies of these systems, a model is created and a microsystem is experimentally tested. As a result, the gas boiler modeled in this study generates a monthly amount of 3.222,317 kWh, and the collector generates a monthly amount of 1.709,8 kWh. In addition, we also analyzed the CO2 emission status, and CO2 emission reduction was calculated as 5.279,6 kg, demonstrating the environment‐friendly nature of the system. This study introduces a model of CSP plant prior installation. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 967–974, 2017

Sliding Mode Control of a Water-Displacement Based Mechanism Applied to the Orientation of a Parabolic-Trough Solar Concentrator

In this paper the problem of guiding a parabolic trough solar concentrator through a system based on a water displacement mechanism is addressed. The actuator mechanism consists of a set of four on/off electrovalves in ”H-bridge” configuration, a small water pump, a sun sensor and two containers half-filled with water, installed on the side ends of the concentrator. To guide and balance the concentrator, a sliding mode controller (SMC) to enable / disable the opening and closing of the valves that control the direction and flow of water between the two containers is proposed. The validity of the implementation of the proposed law of control applied to the actuator mechanism is verified with stability analysis and simulation results.

ビームダウン式太陽集光装置のための機械撹拌式顕熱蓄熱装置の開発

One of the merits of a solar thermal utility is that the cost of heat storage is lower than that of an electrical battery. Furthermore, a power generation system using solar thermal energy with heat storage equipment is capable of stabilizing its output. For a parabolic trough solar concentrator, molten salt is adopted as the heat storage material using latent heat. However, molten salt is applicable only up to 600 °C; this temperature is not sufficiently high for adaptation to a solar central receiver system. Therefore, we designed and produced sensible heat storage equipment for a beam down solar concentrator (a central receiver system) to offer higher temperature storage. Heat storage materials in this device are mechanically mixed, and receive the concentrated sunlight on the focal plane of the solar concentrator. First, the radiation flux distribution under CPC (Compound Parabolic Concentrator) was measured using thin film heat flux sensors to obtain the input energy for the storage equipment. Next, an experiment was carried out using the storage equipment and the beam down solar concentrator. The maximum temperature was found to reach 1070 °C at the center of the heat storage tank in this experimental conditions, and the stored energy was approximately 14 % of the incident energy.

Modeling and optimization of a solar parabolic trough concentrator system using inverse artificial neural network

In this paper, an artificial neural network inverse (ANNi) model is applied to optimize the thermal performance (η) of parabolic trough concentrators. A feedforward neural network architecture is trained using an experimental database from parabolic trough concentrators operations. Rim angle (φr), inlet (Tin) and outlet (Tout) fluid temperatures, ambient temperature (Ta), water flow (Fw), direct solar radiation (Gb), and the wind velocity (Vw) were used as main input variables within the neural network model to estimate the thermal performance with a correlation coefficient of R2 = 0.9996 between experimental and simulated values. The sensitivity analysis is carried out to verify the effect of all input variables. The optimal operation conditions of parabolic trough concentrators are established using artificial neural network inverse modeling (ANNi) to achieve optimal operation conditions of parabolic trough concentrators. The results indicated that ANNi is a feasible tool for Parabolic Trough Concentrators optimization.

Fabrication and Performance of Solar Parabolic Trough Concentrator With and Without Coating on Receiver Tube

Fabrication and Performance of Solar Parabolic Trough Concentrator With and Without Coating on Receiver Tube

A novel design concept for a reflector of parabolic trough concentrator based on pure bending and correction principle

It is cost effective to manufacture a reflective surface of a solar parabolic trough concentrator in a parabolic cylinder shape by pure bending of a flat sheet. However, the surface manufactured by such an elastic bucking is only a coarse approximation of a parabola, which is not precise enough for meeting the demand of a high quality concentrator. A novel design concept was proposed to remove this error by applying an external force on both edge of a sheet, together with two additional forces: the edge torsion force and the pressing force. The optimal position and magnitude of two additional forces were figured out among various conditions, thereby a theoretically maximal concentration ratio up to 115 was found. Prototypes and engineering realizations of this method were also presented. This method provides a very attractive approach for low cost and high efficiency solar energy solutions.

Novel process for performance enhancement of a solar continuous adsorption cooling system

Adsorption cooling is regarded as one of promising clean technologies since it constitutes a rational way for the use of low-grade thermal energy (industrial waste, excess production, etc.) and renewable energy sources. The current paper provides fresh ideas on the relevant issues associated with the intermittence and low performance, which are considered among the main drawbacks of solar-driven adsorption cooling systems. Its primary aim is to design and analyze a solar continuous adsorption cooling system whose design consists mainly of combining a two-tank thermal energy storage system with two adsorbent beds. The operating process is based on storage of excess thermal energy, supplied by means of a solar parabolic trough concentrator, and on its subsequent recovery for producing an additional amount of cold.The simulation results indicate that, under the system conditions (design, working and weather), the solar coefficient of performance and daily cooling production are considerably improved when a latent heat storage unit is integrated with the system. The study reveals also that, thanks to this novel process, the number of refrigeration cycles achieved per day could be significantly increased, which means that the intermittence disadvantage could widely be overcome.