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Abstract—
In this work we propose an innovative system for
tracking the sun which is based on the use of a commercial web
cam as the sensor element. An experimental electro-mechanism
was designed and developed to evaluate its accuracy and
efficacy in tracking the sun under different weather conditions.
The impact on the system performance caused by intermittent
cloud cover and temperature changes were also analyzed. The
system showed an accuracy of 0.1º and high immunity to
temperature variations. It demonstrated to be able to relocate
the sun, as well as extrapolate its position when it cannot be
observed for a period of time.
Index Terms—Solar tracking system, sun tracker, webcam
as a sensor.
I. INTRODUCTION
Solar collector systems require high-precision solar
trackers to increase their photovoltaic or thermodynamic
efficiency [1]. The trackers currently in use apply discrete
elements such as light dependent resistors or photodiodes to
establish the approximate position of the sun [2]-[4]. One of
the main disadvantages of using this type of sensor is its
high sensitivity to weather conditions such as temperature
and humidity [5]. To overcome this disadvantage, solar
tracking systems which currently present a better
performance and accuracy depend on sophisticated control
systems [6], [7] and complex electronic circuitry. Moreover,
their installation and maintenance costs are usually very
high [8]. Very few alternative solutions have been proposed
[9]-[11].
The use of low cost webcams as sensing elements in solar
tracking systems has not been explored previously.
Webcams provide a highly developed technological
platform that can be easily adapted to any type of solar
tracking mechanism.Worth mentioning that in most of the
solar concentrators, computers are frequently used to
monitor and registering information regarding the amount of
energy obtained, so that in most cases a computer is
available and it does not imply any additional inversion
[12].
Manuscript received March 25, 2010. This work was supported in part
by Centro de Investigación y Estudios Avanzados del Instituto Politécnico
Nacional (CINVESTAV IPN) and by Consejo Nacional de Ciencia y
Tecnología (CONACYT).
Minor. M. Arturo is with the Department of Electrical Engineering.
Centro de Investigación y Estudios Avanzados del Instituto Politécnico
Nacional (CINVESTAV). México, D.F. 07360.
García. P. Alejandro is with the Department of Electrical Engineering.
Centro de Investigación y Estudios Avanzados del Instituto Politécnico
Nacional (CINVESTAV). México, D.F. 07360. phone: 555-747-3800; fax:
555-747-3981; e-mail: agarciap[at]cinvestav.mx.
II. MATERIALS AND METHODS
A commercial plug and play webcam was used (Genius
312S), it offers an image resolution of 640 x 480 pixels. A
polarized filter of welding mask was fitted to the webcam to
prevent saturation of the charge-coupled device (CCD)
when solar radiation is very intense. The filter was also
found useful to develop a real time pre-binarization of the
image, see Fig.1. This pre-binarization speeds up the process
of locating the sun.