Good afternoon . Everyone my name is seung jin from jeju national university of korea. Today, I would like to present a study on the development of high accuracy solar tracking systems. Our Solar tracking system is intended for concentrating solar light for solar cell and indoor lighting and other solar energy applications.
The outline is as follows
Ok , let me stat with some graph related with greenhouse gases. These graph show the global trends in major greenhouse gases through the year 2002. These five gases, carbon dioxide, mthane, ntrous oxide, cfc-12, cfc-11 account for about 97% of the direct climate effect. So we have to decrease these greenhouse gases by using clean energy and new technology.
Solar energy is reliable and cost-effective compared to other energy source and it has no pollutant into environment. However, solar energy systems without a solar tracker has lower output. So, we can increase the efficiency of these systems if we adpat the high accuracy solar tracking system And the accuracy depends on the types of application For example, conentrators for solar cells, espescially multi-junction solar cell, and day-lighting system would require ~ Because the concentrated sun rasys must be directed at the focal point. So solar tracking system could be either a single-axis or two-axes devices, two axes device is more effective than a single –axiss system. And
We can classfy solar energy systems inteo five systems by its applciation; pv system solar collector, solar thermal power generation, Daylinghting system, photocatalyst system. So as I before mentioned , all those system require a high accuracy solar tracker for increasing it efficiency.
So.. One of the most inportant compoenet is sorftware for motion controlling. And We developed motion control program using labview. Actually, until now, So the labview we used in this study, is powerful program for motion ctrolling I.. nd it has block diagram in which we can easily code what we want, and frontpane in which we can control many funtions visually
There are two methods available for solar tracking; optical method and astronomical method Optical method is also called “closed loop system” Because it used several feedback sensors such as a photo-sensor and a position sensors. However, this method has a drawback, i.e., it cannot track the sun in a cloudy day without an extensive algorithm. And astronomical method uses the longitude and latitude data of a location in which solar tracker systems is installed
For calculating solar altitude and azimuth, we need some important values such as declination, hour angle, year And these two equations show how to
This is the block diagram for calculation From the left side, the local time and longitude and latitude input into this loop. and once this loop runs, the many variations are calculated in the loop, finally the altitude and azimuth are output from the loop
And the solar tracking system must be returned to the initial position after the sunset and It must begin to track the sun after sunrise. That is why we need to calculate the time of sunrise and sunset and this equation is for sunrise time, and this equation is for sunset time
this loop also runs like the loop for solar altitude.
Our solar tracking system consists of application software, motion controller. This figure shows The principle of working of the solar tracking system. At first , The application calculate the solar position as well as sunrise and sunset time and determine the steps of step motors to transfer the signal to Motion Controller. Motion Controller transfers the signal relevant to the each axis to two step motors by step drive . If the error signal occurs at the feedback sensor, the application will set up the steps and compensate the position of solar tracker. And these are hardware we used in our system
And our system has 2-axis. Bout x and y axis are roated by step motors. The concentraotr we also deveolped is 30cm in diameter and 2 nd mirr is 3cm in diameters
We used five cds sensors for closed loop system. Number fiive seons is for determining which loop is the system use by checking the amount of clouds. Alnd number 1 to number 4 sensors are for checking theshoadow. If all output of sensors are same the system works in openloop sysetm Otherwise, it works in closed loop system.
And this is the second model of concentrator and 2 nd mirror In ther first model , we installed the 2 nd mirror using beam.
And this is the our 2 nd solar tracking system. It is more light and compactive.
And this picuture shows the two solar tracking systems. You can see right one is more smaller.
And this picture show the indoor lighting from the solar trackier . The illuminace of center is about 1,0000 lux .
And this is the final motion application software.
And this is fornt panel It has many cotroll buttons . So we can also control the system manually.
These two figures show the results We compared the calculated the solar altitude and azimuth with those of korea astonomy & space science institute And this table show the conditions for calculations As you can see two lines are almost same, The maximum error of altitude is 0.0371 degree at 4am. And minimum error was 0.0006 degree at 10am. For the azimuth, the mximum error is 0.0823 degreee at about 1 pm, and minimum error was 0.00012 degree at about 5 pm We can see the both mximum errors were occurered at dawn , but this has not effect on the reusults And the sunrise an sunset was calculated for the month of january, this year and comapred with those of kASI. And we found that the average error was less than 1 second.
A Study on the Development of High Accuracy Solar Tracking Systems
A Study on the Development of High Accuracy Solar Tracking Systems Department of Nuclear & Energy Engineering, Jeju National University OH, SEUNG JIN SET2009 - 8 th International Conference on Sustainable Energy Technologies Aachen, Germany. August 31 st to 3 rd September 2009 Jeju Nat’l Univ. SET2009
1. INTRODUCTION 2. CALCULATION OF SOLAR POSITION 3. COMPONENTS & FABRICATION 4. MOTION APPLICATION 5. RESULT Contents Jeju Nat’l Univ. SET2009
Kyoto is intended to cut global emissions of greenhouse gases INTRODUCTION
<ul><li>Solar energy </li></ul><ul><li>reliable and cost-effective , no pollutant into environment </li></ul><ul><li>systems without a solar tracking system -> lower output </li></ul><ul><li>Solar tracking system </li></ul><ul><li>orienting a day-lighting reflector, solar photovoltaic panel or concentrating solar reflector or lens toward the sun. </li></ul><ul><li>works best when pointed directly at the sun, increasing the effectiveness over the non-tracking systems. </li></ul><ul><li>The accuracy of the solar trackers depends on the types of application: </li></ul><ul><li>Concentrators for solar cells and day-lighting systems would require higher degree of accuracy, ensuring the concentrated sun rays are directed at the focal point. </li></ul><ul><li>Systems are either a single-axis or two-axes devices. </li></ul><ul><li>Large power plants or high temperature facilities may employ multiple ground-mounted mirrors and an absorber target with or without secondary concentration. </li></ul>INTRODUCTION
<ul><li>Existing program </li></ul><ul><li>C-language and Visual Basic are often used </li></ul><ul><li>Manufacturers have supplied their systems </li></ul><ul><li>with libraries for these algorithms. </li></ul><ul><li>The problem is that it is difficult for a user </li></ul><ul><li>to integrate such codes into the one main program. </li></ul><ul><li>LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) </li></ul><ul><li>a platform and development environment for a visual programming language from National Instruments. </li></ul><ul><li>The graphical language is named "G“. </li></ul><ul><li>Block diagram, Front panel </li></ul><ul><li>Easy-to-use, high-performance, </li></ul><ul><li>extensive application </li></ul>INTRODUCTION Motion Control by LabVIEW
INTRODUCTION <ul><li>Optical method : </li></ul><ul><li>“ closed loop system” </li></ul><ul><li>it uses several feedback sensors ; a photo-sensor and a position sensor and a comparator. </li></ul><ul><li>Drawback in a cloudy day without an extensive algorithm. </li></ul><ul><li>Astronomical method : </li></ul><ul><li>employs the longitude and latitude data of a location </li></ul><ul><li>simple programming </li></ul><ul><li>high degree accuracy and less error </li></ul><ul><li>starting position of tracker to be always same from day to day </li></ul><ul><li>operating motors are easily subject to the “backlash” </li></ul>Method of Solar Tracking Systems
The tracker device must be positioned horizontally to implement the altitude and azimuth angles along with the hour angle <ul><li>the Solar altitude(h) : the angle between a line that points from the site towards the centre of the sun, and the horizon </li></ul><ul><li>The solar azimuth(A) : the angle between the line from the observer to the sun projected on the ground and the line from the observer due south. </li></ul><ul><li>The declination(δ) : The declination(δ) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle </li></ul><ul><li>The hour angle(H) : the angle between the half plane determined by the Earth axis and the zenith (half of the meridian plane) and the half plane determined by the Earth axis and the given point. </li></ul>CALCULATION OF SOLAR POSITION Calculations of Solar Altitude and Azimuth
Block diagram for calculating solar altitude and azimuth CALCULATION OF SOLAR POSITION Calculations of Solar Altitude and Azimuth
<ul><li>The solar tracking system must be returned to the initial position after the sun disappears below the horizon, otherwise it must be started to track the sun after the sun appears above the horizon. </li></ul>Why is “sunrise and sunset time” necessary? For Sunrise, For Sunset, Time of Sunrise or Sunset Hour angle Right ascension (Longitude)/15 CALCULATION OF SOLAR POSITION Calculations of Sunrise and Sunset Time
Block diagram for calculating the time of sunrise and sunset CALCULATION OF SOLAR POSITION Calculations of Sunrise and Sunset Time
<ul><ul><li>Application Software </li></ul></ul><ul><ul><li>Motion Controller </li></ul></ul><ul><ul><li>Amplifier or Drive </li></ul></ul><ul><ul><li>Mechanical Elements </li></ul></ul><ul><ul><li>Feedback device or Position sensor </li></ul></ul>COMPONENTS & FABRICATION
COMPONENTS & FABRICATION Performance of step-motor and gear ratio • Step- motor step angle : 0.0144˚ • Step- resolution : 25,000 • X-axis gear ratio 2:1 -> Azimuth • Y-axis gear ratio 2:1 -> Altitude
COMPONENTS & FABRICATION Amount of Clouds 1 2 4 3 Cover for making shadow CdS Sensor ⅹ4ea 5 Working principal of system by feedback sensors Sensor(1) > Sensor(2) : Rotate down Sensor(2) < Sensor(2) : Rotate up Sensor(3) >Sensor(4) : Rotate left Sensor(3) < Sensor(4) : Rotate right Sensor(1) = Sensor(2) or/and Sensor(3)= Sensor(4) : Stop Sensor(5) lower than a specific value : transfer to open loop
Conditions value Location Jeju city, Jeju do, Koea Longitude Long. 126˚15 ΄60˝ E Latitude 33˚ 30΄ 30˝ N. Lat. Date 1 st of January, 2009 Time 00:01~24:00 Error Altitude Azimuth Maximum[°] 0.0371 at 4am 0.0823 at 1 am Minimum[°] 0.0006 at 10am 0.00012 at 5pm
In this study, the solar tracking system was fabricated and has achieved high accuracy for the tracking of the sun rays. Our tracker system is cost effective and the algorithm is relatively simple , combining the advantages of both the optical and the astronomical methods. A series of studies with the solar tracker yield the following results. 1)The calculated solar altitude and azimuth for the 1st of January, 2009 were compared with those of KASI, and the average errors are less than 0.018 degrees during the day . 2)The calculated sunrise and sunset times for the month of January, 2009 were compared with those of KASI, and the average errors are found to be less than 1 second. 3)The solar tracking system is found to be accurate and cost-effective and it can be used in many fields such as data-processing, concentrated PV, the photocatalyst generation of hydrogen , and contributing to the harnessing of the solar energy . CONCULSION
This work is supported by the grant (No.R33-2008-000-10166-00) of the World Class University (WCU) programme of the Korea Science & Engineering Foundation.