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 - 8th International Conference on Sustainable Energy TechnologiesAachen, Germany. August 31st to 3rd September 2009

Jeju Nat’l Univ.Jeju Nat’l Univ.

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1. INTRODUCTION

2. CALCULATION OF SOLAR POSITION

3. COMPONENTS & FABRICATION

4. MOTION APPLICATION

5. RESULT

Contents


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Kyoto is intended to cut global emissions of greenhouse gases

INTRODUCTION


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Solar energy reliable and cost-effective , no pollutant into environment systems without a solar tracking system → lower output

Solar tracking system orienting a day-lighting reflector, solar photovoltaic panel or concentrating solar reflector or lens toward the sun. works best when pointed directly at the sun, increasing the effectiveness over the non-tracking systems.

The accuracy of the solar trackers depends on the types of application: 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.

Systems are either a single-axis or two-axes devices.

Large power plants or high temperature facilities may employ multiple ground-mounted mirrors and an absorber target with or without secondary concentration.

INTRODUCTION


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Solar Energy Uses

INTRODUCTION


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Existing programC-language and Visual Basic are often usedManufacturers have supplied their systems with libraries for these algorithms. The problem is that it is difficult for a user to integrate such codes into the one main program.

LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) a platform and development environment for a visual programming language from National Instruments. The graphical language is named "G“.Block diagram, Front panelEasy-to-use, high-performance,extensive application

Motion Control by LabVIEW

INTRODUCTION


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Optical method :

“closed loop system”

it uses several feedback sensors ; a photo-sensor and a position sensor and a comparator.

Drawback in a cloudy day without an extensive algorithm.

Astronomical method : employs the longitude and latitude data of a location

simple programming

high degree accuracy and less error

starting position of tracker to be always same from day to day

operating motors are easily subject to the “backlash”

Method of Solar Tracking Systems


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Calculations of Solar Altitude and Azimuth

The tracker device must be positioned horizontally to implement the altitude and azimuth angles along with the hour angle

the Solar altitude(h) : the angle between a line that points from the site towards the centre of the sun, and the horizon

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.

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

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.

coseSin Sin Sin Cos CosH a

e

Cos SinHSinCos

CALCULATION OF SOLAR POSITION


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Calculations of Solar Altitude and Azimuth

Block diagram for calculating solar altitude and azimuth



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Calculations of Sunrise and Sunset Time

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.

Why is “sunrise and sunset time” necessary?

(0.06571 ) 6.622T H t

((18 ln ) / 24)t N gHour For Sunrise,

For Sunset,

lng

TH

Hour

Time of Sunrise or SunsetHour angle

Right ascension(Longitude)/15

((6 lng ) / 24)t N Hour



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Calculations of Sunrise and Sunset Time

Block diagram for calculating the time of sunrise and sunset



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Application Software

Motion Controller

Amplifier or Drive

Mechanical Elements

Feedback device or Position sensor

COMPONENTS & FABRICATION


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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



Amount of Clouds1

243

Cover for making shadow

CdS Sensor ⅹ4ea

5

Working principal of system by feedback sensorsSensor(1) > Sensor(2) : Rotate downSensor(2) < Sensor(2) : Rotate upSensor(3) >Sensor(4) : Rotate leftSensor(3) < Sensor(4) : Rotate rightSensor(1) = Sensor(2) or/and Sensor(3)= Sensor(4) : StopSensor(5) lower than a specific value : transfer to open loop




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Motion Application



Motion Application


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-100

-80

-60

-40

-20

0

20

40

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Solar Elevation

계산식한국천문연구원

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Solar Azimuth

계산식한국천문연구원

RESULTS

cCalculation

KASI

cCalculation

KASI


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Conditions value

Location Jeju city, Jeju do, Koea

Longitude Long. 126˚15΄60˝ E

Latitude 33˚ 30΄ 30˝ N. Lat.

Date 1st of January, 2009

Time 00:01~24:00

Error Altitude Azimuth

Maximum[°] 0.0371at 4am

0.0823at 1 am

Minimum[°] 0.0006 at 10am

0.00012at 5pm


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Closed loop system


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Open loop system


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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


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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.

Education

A Study on the Development of High Accuracy Solar Tracking Systems