Developing a multipurpose sun tracking system using fuzzy control

The present work demonstrates the design and simulation of time controlled step sun tracking systems that include: one axis sun tracking with the tilted aperture equal to the latitude angle, equatorial two axis sun tracking and azimuth/elevation sun tracking. The first order Sugeno fuzzy inference system is utilized for modeling and controller design. In addition, an estimation of the insolation incident on a two axis sun tracking system is determined by fuzzy IF-THEN rules. The approach starts by generating the input/output data. Then, the subtractive clustering algorithm, along with least square estimation (LSE), generates the fuzzy rules that describe the relationship between the input/output data of solar angles that change with time. The fuzzy rules are tuned by an adaptive neuro-fuzzy inference system (ANFIS). Finally, an open loop control system is designed for each of the previous types of sun tracking systems. The results are shown using simulation and virtual reality. The site of application is chosen at Amman, Jordan (32° North, 36° East), and the period of controlling and simulating each type of tracking system is the year 2003.     

The effect of using sun tracking systems on the voltage–current characteristics and power generation of flat plate photovoltaics

An experimental study was performed to investigate the effect of using different types of sun tracking systems on the voltage–current characteristics and electrical power generation at the output of flat plate photovoltaics (FPPV). Four electromechanical sun tracking systems, two axes, one axis vertical, one axis east–west and one axis north–south, were designed and constructed for the purpose of investigating the effect of tracking on the electrical values, current, voltage and power, according to the different loads (variable resistance). The above mentioned variables were measured at the output of the FPPV and compared with those on a fixed surface. The results indicated that the volt–ampere characteristics on the tracking surfaces were significantly greater than that on a fixed surface. There were increases of electrical power gain up to 43.87%, 37.53%, 34.43% and 15.69% for the two axes, east–west, vertical and north–south tracking, respectively, as compared with the fixed surface inclined 32° to the south in Amman, Jordan.     

Measured and modelled improvement in solar energy yield from flat plate photovoltaic systems utilizing different tracking systems and under a range of environmental conditions

This work is performed to investigate the effect of using different sun tracking mechanisms on the flat plate photovoltaic system performances and the main parameters affecting the amount of their electrical energy output as well as those affecting their gains compared to the traditional fixed photovoltaic systems. To this end, five configurations of sun tracking systems and two traditional fixed panels have been considered. The sun tracking systems effect on the PV system performances is improved by using the hourly data collected over 18 days for different seasonal sky conditions. The daily cumulative electrical energy produced by the different systems have been quantified separately for each sky state and the corresponding electrical gains have then been compared to those experienced with two traditional fixed photovoltaic systems. It is found that for a completely clear day, the highest obtained gains are those related to the two-axis sun tracker systems, which decrease gradually from the inclined to the vertical rotating axis when the same optimum slope is applied and from the seasonal to the yearly optimum slope if the same rotating axis is considered. On the other hand, for the partially clear days, the gain amounts are mainly dependant on the clearness index and on the seasonal variation of day length values. For a completely cloudy day, the results show that all considered systems produced closely the same electrical energy and the horizontal position of the photovoltaic panel presented the best performance.     

Multi-axes sun-tracking system with PLC control for photovoltaic panels in Turkey

In the present study, the azimuth and solar altitude angles of the sun were calculated for a period of 1 year at 37.6° latitude in the Northern hemisphere, where Turkey is located, and according to these angles, an electromechanical system which tracks the sun on both axes and which is controlled via a programmable logic control (PLC) and an analog module was designed and implemented.After the mechanical control unit of the designed system was started, the performance measurements of the solar panel were carried out first when the solar panel was in a fixed position and then the solar panel was controlled while tracking the sun on azimuth and solar altitude angles and the necessary measurements were performed. It was observed that the control system operated without a problem. Besides, when the data obtained from the measurements were compared, it was seen that 42.6% more energy was obtained in the two-axes sun-tracking system when compared to the fixed system.     

Performance of Cylindrical Parabolic Collector with Automated Tracking System

Parabolic solar collector collects the radiant energy emitted from the sun and focuses it at a point. Parabolic trough collectors are the low cost implementation of concentrated solar power technology that focuses incident sun light on to a tube filled with a heat transfer fluid. However, the basic problem with the cylindrical parabolic collector without tracking was the solar collector does not move with the orientation of sun. Development of automatic tracking system for cylindrical parabolic collectors will increase solar collection as well as efficiency of devices. The main aim of this paper is to design, fabricate and analyze the performance of parabolic collector with automated tracking system. The automated tracking mechanism is used to receive the maximum possible energy of solar radiation as it tracks the path of sun. The performance of the parabolic trough collector is experimentally investigated with the water circulated as heat transfer fluid. The collector efficiency will be noted.     

Properties of a general azimuth–elevation tracking angle formula for a heliostat with a mirror-pivot offset and other angular errors

The solar field of a central receiver system (CRS) is an array of dual-axis tracking heliostats on the ground beside or around a central tower, with each heliostat tracking the sun to continuously reflect the solar beam onto the fixed tower-top receiver. Azimuth–elevation tracking (also called altitude–azimuth tracking) is the most common and popular tracking methods used for heliostats. A general azimuth–elevation tracking angle formula was developed previously for a heliostat with a mirror-pivot offset and other typical geometric errors. The angular error parameters in this tracking angle formula are the tilt angle, ψ_t, and the tilt azimuth angle, ψ_a, for the azimuth axis from the vertical direction, the dual-axis non-orthogonal angle, τ₁ (bias angle of the elevation axis from the orthogonal to the azimuth axis), and the non-parallel degree, μ, between the mirror surface plane and the elevation axis (canting angle of the mirror surface plane relative to the elevation axis). This tracking angle formula is re-rewritten here as a series of easily solved expressions. A more numerically stable expression for the mirror-center normal is then presented that is more useful than the original mirror–normal expression in the tracking angle formula. This paper discusses some important angular parametric properties of this tracking angle formula. This paper also gives an approach to evaluate the tracking accuracy around each helistat rotational axis from experimental tracking data using this general tracking angle formula. This approach can also be used to determine the heliostat zero angle positioning errors of the two rotational axes. These supplementary notes make the general azimuth–elevation tracking angle formula more useful and effective in solar field tracking designs.     

Experimental analysis of a two‐axis tracking system for solar parabolic dish collector

In this paper, an attempt has been made to develop a two‐axis tracking system for solar parabolic dish concentrator and experimentally evaluated the performance of the tracking system. In this proposed design, the sensor design uses the illumination produced by the convex lens on the apex of a pyramid to align the dish in‐line with the sun. The change in incident angle of the solar rays on the lens surface shifts the area of illumination from the apex of the pyramid towards its faces. Photodiodes placed on the faces of the pyramid are used as the sensitive elements to detect the movement of the sun. The sensor output is fed to a microcontroller‐based system to drive the stepper motor on the basis of the programmed algorithm such that it receives normal incidence of sunlight on the sensor. To evaluate the performance of the proposed system, a conventional available 1‐W photovoltaic (PV) panel is placed at the focal point to measure the short circuit current and open circuit voltage. With respect to the conventional solar PV panel, it is observed that the positioning accuracy of the proposed tracking system enhances the short circuit current of 0.11 A by 86%. Thus, the proposed tracking system can be used in a stand‐alone parabolic dish with concentrating PV module as the focal point for further studies.     

太阳自动跟踪系统的研究与设计

为提高太阳能的转换效率,设计了基于四象限探测器的太阳跟踪装置,采用视日运动轨迹跟踪与光电跟踪相结合的方式对太阳进行跟踪,利用光电二极管检测作为反馈实现两种跟踪方式间的转换.设计了一套能自动使太阳能电池板与太阳光线保持垂直的跟踪系统,实现了最大效率的太阳能利用.试验结果表明,该系统跟踪精度高,可实现各种天气状况下全天候全自动跟踪,跟踪器稳定,效果满意.     

General formula for on-axis sun-tracking system and its application in improving tracking accuracy of solar collector

Azimuth-elevation and tilt-roll tracking mechanism are among the most commonly used sun-tracking methods for aiming the solar collector towards the sun at all times. It has been many decades that each of these two sun-tracking methods has its own specific sun-tracking formula and they are not interrelated. In this paper, the most general form of sun-tracking formula that embraces all the possible on-axis tracking methods is presented. The general sun-tracking formula not only can provide a general mathematical solution, but more significantly it can improve the sun-tracking accuracy by tackling the installation error of the solar collector.     

Design of a new three-degree of freedom spherical motor for photovoltaic-tracking systems

Photovoltaic (PV) panels directly convert the solar energy to electrical energy. The amount of electrical energy converted by PV panels mainly depends on incident solar radiation. Sun tracking systems can be used to maximize energy production since they ensure keeping the photovoltaic panels perpendicular to the incoming solar radiation. Spherical motors, which have the linear and circular movement ability in three independent dimensions, can be used for precisely tracking the sun as a solution. In this study, a spherical motor controlled by a micro-controller is designed for a PV-tracking system with the ability to move on two axes. Performance of PV-tracking system over a fixed tilted one is evaluated for the climate condition of Denizli, Turkey. The designed sun tracking system is observed to be improving this performance apparently using the output voltages obtained for one day.     

Development and performance analysis of a two‐axis solar tracker for concentrated photovoltaics

This study presents a two‐axis solar tracking system equipped with a small concentrator module for electricity generation through a multijunction solar cell. The system can accurately track the sun without the need of calibration for an extended period and operate as a stand‐alone system. High‐precision solar tracking was achieved by a combination of open‐loop and closed‐loop controls. A camera tracking sensor was introduced as a feedback device in closed‐loop control. Two different types of solar concentrator modules were designed and fabricated. Their concentration ratios were analyzed against solar tracking errors by means of ray tracing software. One is made up of a paraboloidal primary concentrator and a paraboloidal secondary reflector, whereas the other has a paraboloidal primary concentrator and a hyperboloidal secondary reflector. Both modules showed an almost identical concentration ratio of 610 provided that the solar tracker is pointing perfectly at the sun. However, their performance differs considerably when tracking error is present. The maximum power output was obtained near solar noon with multijunction cells, whose average solar conversion efficiency was 21%, much higher than that of conventional photovoltaic systems. Copyright © 2015 John Wiley & Sons, Ltd.     

一种高精度的太阳跟踪方法

为提高太阳能利用率,提出了同时使用视日跟踪和光电跟踪的太阳跟踪新方法。为提高视日跟踪精度,对常见的太阳位置算法仿真比较,得到实用的太阳位置高精度混合算法;同时,设计了特制的四象限硅光电池,对视日跟踪进行误差修正,从而实现了太阳精确跟踪。理论分析和设计表明,该方法能够实现高精度、全天候地自动跟踪太阳,易于推广应用。     

飞雕太阳能收集与高温储能技术装置制作

太阳能热开发利用中有三个需要同时解决的问题:精确简洁地自动跟踪太阳,实时以最大面积采光;将收集到的太阳能转移到固定的地方;实现高温高效的储存或利用。目前的太阳灶或太阳能热发电系统都是在其中某个问题上存在较大的缺陷。为此设计并试制了装置:通过自动跟踪系统分别对太阳的两个运动方向进行相对独立的精确简洁的跟踪,实现凹面镜保持实时以最大采光面积采光;利用光能传输管在系统跟踪太阳的同时定向输出光能;最终光能在储热容器中转换为热能进行高温储存或利用。根据样机的制作结果及试验,该装置可同时有效解决上述三个问题,集成了太阳灶与太阳能热水器的功能,也可用于规模化的太阳能热发电。     

A high precision tracking system based on a hybrid strategy designed for concentrated sunlight transmission via fibers

This paper investigates a high precision tracking system that adopts the coordinate calculation algorithm and a photosensitive sensor. This system is designed to satisfy the precision requirement in sun tracking for a concentrated sunlight transmitting system via optical fibers. This system is based on a two-stage tracking process, which consists of a coarse adjustment based on the coordinate calculation algorithm and a fine adjustment using a specially designed photosensitive sensor. The core of the photosensitive sensor is a photodiode matrix that could exactly detect the position of the sunlight focal spot via lens focusing. A predictive control process based on the running trend of sun traces will begin once the fine adjustment is completed. The tracking process is steady and accurate because of the predictability of sun traces based on the coordinate calculation algorithm and the acuteness of the photodiode matrix. The highest tracking precision depends on the compactness of the photodiode matrix and has no limits in the accuracy of the coordinate calculation algorithm. The proposed system can track the sun's focal spot with a position precision of less than 0.3 mm, which is the space between the adjacent photodiodes. The tracking angle precision is determined by the ratio of the position resolution of the photodiode matrix to the focal length, and reaches 0.1°.     

Maximum solar flux concentration achievable with axicon collectors

The concentration characteristics of co-axial cone axicon concentrators using the sun as the radiation source are examined. By employing a ray tracing approach and the known concentration result for rays entering strictly parallel to the axicon axis, it is shown that the concentration remains finite and that the maximum achievable value is C₀ = 273 at the optimum reflector cone angle of 90°. All radiation entering the solar tracking collector will strike the central absorber cone as long as the vertex angle of this cone exceeds the angular size of the sun.     

Measurements of solar flux density distribution on a plane receiver due to a flat heliostat

An experimental facility is designed and manufactured to measure the solar flux density distribution on a central flat receiver due to a single flat heliostat. The tracking mechanism of the heliostat is controlled by two stepping motors, one for tilt angle control and the other for azimuth angle control. A x-y traversing mechanism is also designed and mounted on a vertical central receiver plane, where the solar flux density is to be measured. A miniature solar sensor is mounted on the platform of the traversing mechanism, where it is used to measure the solar flux density distribution on the receiver surface. The sensor is connected to a data acquisition card in a host computer. The two stepping motors of the heliostat tracking mechanism and the two stepping motors of the traversing mechanism are all connected to a controller card in the same host computer. A software “TOWER” is prepared to let the heliostat track the sun, move the platform of the traversing mechanism to the points of a preselected grid, and to measure the solar flux density distribution on the receiver plane. Measurements are carried out using rectangular flat mirrors of different dimensions at several distances from the central receiver. Two types of images were identified on the receiver plane—namely, apparent (or visible) and mirror-reflected radiation images. Comparison between measurements and a mathematical model validates the mathematical model.     

Experimental validation of an optical and thermal model of a linear Fresnel collector system

This paper describes the design and validation of a mathematical model for a solar Fresnel collector. The function of the model is to simulate the optical and thermal dynamics of a Fresnel system for heating water. The model is validated using real data gathered from a cooling plant with double effect absorption chiller located in the School of Engineering University of Seville, Spain (Experimental cooling plant is also described in the paper). Comparison of calculated and plant measured data shows that the error is lower than 3% in the optical model and within 7% in the thermal model.The model uses a new approach to include a solar tracking mirror mechanism in one axis. This tracking has been designed to maximise the reception of available solar radiation by the absorption pipe. The thermal model used is based around classical models for solar receivers and it is validated with real operating data gathered from a supervisor system.The Fresnel model has been designed with sufficient flexibility to consider different geometries and thermal parameters, and may be used to simulate the performance of a proposed Fresnel collector system at any location.     

Cost comparative study for new water distillation techniques by solar energy using

The aim of this work is to compare the extra added cost of different new water distillation techniques to the cost of extra collected distilled water. The comparison is between; a traditional single slope solar still, a solar still with installed reflecting mirror, a solar still with replacing the flat water with step wise basin, a solar still with a single axis sun tracking system and a solar still with sun tracking system and replacing the flat water basin with step wise basin. It was found that all cases of modifications have an economical effect except one which is the system with sun tracking. The most feasible system is the step wise design, which gave the shortest pay back period of 2.1 years, followed by the system with sun tracking and step wise, which gave the payback period of 3.6 years, followed by the system with reflecting mirrors, which gave the payback period of 4.6 years.     

Cascade closed-loop control of solar trackers applied to HCPV systems

High concentration photovoltaic (HCPV) modules require a high precision tracking system for reaching their highest conversion efficiency. One way to accomplish this goal is by using a closed-loop mechanism and a sun sensor to track the sunlight. This paper proposes a cascade control algorithm capable of achieving a sun tracking error of 1′ for its application in high concentration photovoltaic systems. The algorithm follows an inner loop-outer loop topology. The inner loop employs a Nonlinear Proportional-Proportional Integral (NP-PI) controller and the outer loop resorts on a Proportional Integral (PI) controller. A tuning procedure for setting up the cascade controller is also described. Experiments on a laboratory prototype compare the performance of the proposed cascade controller with a PI controller not resorting on an inner loop. These outcomes show that the proposed control law provides improved tracking accuracy with less actuator wear.     

Application of one-axis sun tracking system

This paper introduces design and application of a novel one-axis sun tracking system which follows the position of the sun and allows investigating effects of one-axis tracking system on the solar energy in Turkey. The tracking system includes a serial communication interface based on RS 485 to monitor whole processes on a computer screen and to plot data as graphic. In addition, system parameters such as the current, the voltage and the panel position have been observed by means of a microcontroller. The energy collected is measured and compared with a fixed solar system for the same solar panel. The results show that the solar energy collected on the tracking system is considerably much efficient than the fixed system. The tracking system developed in this study provides easy installation, simple mechanism and less maintenance.