Developing a Mini-heliostat Array for a Solar Central Tower Plant: A Practical Experience (original) (raw)
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Heliostats Automation System For A Solar Power Tower Plant'S Efficiency Increment
2018
In this paper a System for the automatic positioning of the heliostats of the Solar Power Tower plant is presented a clod detection system and a sun position algorithm will compute the exact position of the Sun, and the clouds will be detected next to the sun in order to preserve the integrity of the power tower's system. The main purpose of this system is to achieve a maximum efficiency. Change the positions of the heliostat to away from the sun, when the clouds are about to cover the sun. In this way we can maintain the integrity of the system and to avoid damaging of the central receiver. The data that are used in the source code for the computation of the outputs from the given input parameters are also discussed. The system is successfully shock free and more efficient.
Design and Calibration of a Heliostat Prototype for Solar Energy Collections
A heliostat is a device that automatically tracks the sun as it moves across the sky and constantly reflects the sunlight to any desired location. In a large scale solar energy collection system, such as a central receiver system, heliostats are essential and cost 30 to 50 percents of the system's initial cost. This paper presents a first prototype of an on-going project of developing low-cost heliostats. The prototype has two independently rotating axes to orient the reflective mirror. Stepping motors driving worm gears are used to control these axes. The key idea to keep the cost down is to trade away accuracy but not repeatability. Repeatability allows accuracy to be recovered using an intelligent controller. This is done by estimating constant uncertainties affecting the accuracy of the system and using them to improve accuracy during actual operations. In this paper, positioning error of the heliostat in reflecting the sunlight to the target is assumed to be caused by the heliostat's installation error in orientation only. This is the dominating factor since a small orientation error can cause large error if the solar collector or the target is far away from the heliostat. This error is estimated by comparing the actual reflected lights on a screen and the desired locations using digital image processing. Two experimental results are presented. Although the results show somewhat improvement for targets inside the screen, the results are inconclusive that the proposed calibration and compensation techniques will improve accuracy.
Two Axes Sun Tracking System for Heliostat: Case Study in Algeria
Indonesian Journal of Electrical Engineering and Informatics (IJEEI), 2016
In this paper, using Proteus software, sun tracking system with two axes program has developed and simulated for site of GHARDAIA, in the south of ALGERIA. Two direct current motors have used to move heliostat in North-South and East-West axis polar, in order to tracking the sun path.In addition, the distinction between day and night has provided by light dependent resistor (LDR).An algorithm of two axes sun tracking system hab developed and simulated under Proteus software, after DC motor's parameters have verified and simulated under MATLAB software. The results show that: in the first, the development of the heliostat control requires the knowledge of the position of each heliostat relative to the tower to ensure the proper operation of the motors, and the uniformity of the reflected beam to the target.Then the choice of the drive motors is based on the useful power, including the weight of the heliostat, and all efforts affects on operation of motors in different seasons of the year, like the wind.And The position of the heliostat depends of chopper duty cycle.Finally,Conducting a power tower with mobile heliostats requires a techno-economic study on all components (heliostats, tower...) of the plant, for example weather two motors for each heliostat field.
A LOCALLY DEVELOPED 40 m 2 HELIOSTAT ARRAY WIRELESS CONTROL SYSTEM
The ability of concentrating solar power (CSP) to efficiently store thermal energy sets it apart from other renewable energy technologies. The high initial cost of CSP limits its widespread deployment. Significant cost reduction opportunities exist, especially for central receiver systems (CRS) where the heliostat field typically makes up 40-50% of total cost. CRS plants require heliostats with very high tracking accuracy. However, tracking errors occur due to manufacturing-, installation-and alignment tolerances as well as control system resolution. Typical heliostat tracking errors vary over the course of days and seasons and cannot be corrected by simple angle offsets. The objective of this research was to develop a wireless control system for Helio40, a 40m 2 heliostat array deployed on the STERG rooftop laboratory. A model based open-loop error correction method was used to minimize deterministic tracking errors over time. Individual heliostats" daily tracking error offsets were obtained periodically using a camera, calibration target and image processing techniques. Mathematical optimization was used to estimate error coefficients that best fit the measured curve. Real time error corrections were calculated for each heliostat by implementing the error model"s rotation and translation operations in reverse order and applying three adjustment coefficients to the elevation linear actuator geometry. Initial tracking results obtained with a Helio40 heliostat showed an improvement of more than a full order of magnitude in the daily open-loop RMS tracking error.
Control and optimal management of a heliostat field for solar power tower systems
2019 IEEE 23rd International Conference on Intelligent Engineering Systems (INES), 2019
The competitiveness of Concentrated Solar Power (CSP) plants over conventional ones still has to be improved. For CSP systems based on Central Receivers (CRS), one of the challenges to face is the optimal management of the aim points of the heliostats which form the collector field. The flux distribution that the field projects on the receiver must be carefully controlled to get an adequate form and to avoid dangerous flux peaks that might damage the receiver. Phenomena such as cloud transients can result in pronounced temperature gradients that reduce the life expectancy of receivers. Therefore, it is necessary to develop a control system which ensures that the critical parameters of the receiver (e.g., temperatures, solar radiation, pressure, mass flow) are always within the allowed range. This work presents an automatic control system connected to an optimization method based on a genetic algorithm which theoretically configures the field to obtain any desired flux distribution. It is a heuristic feedback controller that minimizes the error between the flux distribution theoretically computed and that obtained over time. The control logic tries to reduce the effect of perturbations as well as modeling and optimization errors that might have affected the genetic optimizer when computing the initial operating state.
Solar Energy, 2004
This paper presents the development of a simplified and automatic heliostat positioning offset correction control system using artificial vision techniques and common CCD devices. The heliostats of a solar power plant reflect solar radiation onto a receiver (in this case, a volumetric receiver) placed at the top of a tower in order to provide a desired energy flux distribution correlated with the coolant flow (in this case air mass flow) through the receiver, usually in an open loop control configuration. There exist error sources that increase the complexity of the control system, some of which are systematic ones, mainly due to tolerances, wrong mirror facets alignment (optical errors), errors due to the approximations made when calculating the solar position, etc., that produce errors (offsets) in the heliostat orientation (aiming point). The approximation adopted in this paper is based on the use of a B/W CCD camera to correct these deviations in an automatic way imitating the same procedure followed by the operators. The obtained images are used to estimate the distance between the sunbeam centroid projected by the heliostats and a target placed on the tower, this distance thus is used for low accuracy offset correction purposes. Basic threshold-based image processing techniques are used for automatic correction.
Selection of Sensors for Heliostat of Concentrated Solar Thermal Tower Power Plant
Engineering Proceedings, 2021
As the energy demand of the world is rising, more and more efforts are being made to harness different forms of energy available. Current pollution due to fossil fuels has directed the world to shift to cleaner renewable energies, such as solar. Photovoltaic, as well as concentrated solar technologies, are developed to harness solar energy. The concentrated solar tower power plant is an emerging technology and is under development having vast areas of improvement. The efficiency of the concentrated solar tower power plant depends upon the accuracy of the tracking system of the heliostats placed all around the central tower of the plant. A closed-loop tracking system a feedback method is a need. In addition, to check the accuracy of the system, a calibration system is required. This system uses different types of sensors. In this study, an effort is made to enlist different types of sensors available and their use in the tracking system of the solar thermal tower power plant. In addi...
2022
A recent assessment of a pilot concentrating solar power plant in Ghana noticed the failure of the tracking system to accurately align the multifaceted heliostats toward the sun and focus the sunbeams onto the target. A further review of solar tracking systems revealed the limitation of concentrated solar power tracking systems to simultaneously improve accuracy and reduce operational cost. In this paper, a computer vision-based solar tracking system, comprising a vision controller, webcam, light sensor, Arduino microcontroller, two stepper motors, a stick, and a transparent plate, is proposed and implemented. The light sensor indicates the presence or absence of sunlight, the webcam captures the image of the stick's shadow on the plate and the vision controller reads this data from the webcam and processes it to extract the solar angles. The angles are sent to the microcontroller which uses them to orient the heliostat appropriately through the stepper motors. The proposed system is location independent and can be installed in each heliostat or a group of heliostats. the preliminary tests show it tracks the sun accurately and exhibits minimal operation cost.
Heliostat Array Wireless Control System
2014
The ability of concentrating solar power (CSP) to efficiently store thermal energy sets it apart from other renewable energy technologies. The high initial cost of CSP limits its widespread deployment. Significant cost reduction opportunities exist, especially for central receiver systems (CRS) where the heliostat field typically makes up 40-50% of total cost. CRS plants require heliostats with very high tracking accuracy. However, tracking errors occur due to manufacturing-, installationand alignment tolerances as well as control system resolution. Typical heliostat tracking errors vary over the course of days and seasons and cannot be corrected by simple angle offsets. The objective of this research was to develop a wireless control system for Helio40, a 40m 2 heliostat array deployed on the STERG rooftop laboratory. A model based open-loop error correction method was used to minimize deterministic tracking errors over time. Individual heliostats‟ daily tracking error offsets were...