10-09-2014, 09:46 AM
Improved Structure of Solar Tracker with Microcontroller based Control
Improved Structure of Solar.pdf (Size: 1.18 MB / Downloads: 21)
Abstract
A new mechanical structure for solar tracker was
designed and presented. The structure implements two stepper
motors for free rotation on X and Y axis. The rotation is
intelligently controlled by a pre-programmed 2K
microcontroller device PIC 18F4560 which provides simple
programming strategy through C language. The designed
algorithm is based on the measurement of intensity of solar
radiation which is captured by an ultra violet sensitive device
known as Pyranometer. The system has been tested and the
results show very significant impact on the mechanical design,
controlling algorithm and also the cost of the development.
INTRODUCTION
Solar tracker has been continuously developed by many
scholars with the aim to improve the efficiency of solar
energy captured during day time. The position of the solar
panel is the most important factor that ensures the optimum
capture of solar energy. Solar panel is normally placed and
fixed at open area for long period of time with minimum
supervision. It is manned for robust application and should
not frequently breakdown which may interrupt the power
generated by the solar panel.
A solar panel receives the most sunlight when it is
perpendicular to the sun’s rays, but the sunlight direction
changes regularly with changing seasons and weather [8].
Currently, most solar panels are fixed, i.e., the solar array
has a fixed orientation to the sky and does not turn to follow
the sun. This may contribute that the energy captured is not
always maximized as the static placement of the panel limits
their area of exposure from the sun [1].The efficiency with
solar tracking methodology is 6.7 percentages higher than
that with fixed angle [2]. The oriented solar panels in the
way of sun tracking would lead to the maximum power and
increase the output by 30%-40%; significant enough to
make tracking a viable preposition in spite of the
enhancement in system cost
SOLAR TRACKER
The structures of prior designs have similar strategy [1]
[2] which often focuses on two-axis rotation. Yazidi [2]
implements two-axis rotation for the solar tracker which is
enough to ensure the maximum capture of solar energy
through out the day. It uses pulley and chain to rotate and
turn the Solar Panel facing to Sun. The structure is quite
complicated and fragile since normal PVC was used for
main weight and stand. Shadow concept is applied for Solar
Sensor which implements two LDRs. This technique is
significantly good but will face gray decision when both
LDRs not able to detect Sun. As a result, the system may
face confusion when the area is fully covered by clouds.
Another draw back is the autonomous decision is not
practical due to the process of changing is very repetitive.
Nader [9] has similar strategy where the control is done
by using motor power window. Although the author claims
the design is low cost due to the implementation on junk
motor power window, the brand new cost may not be the
same. The Solar panel is lock by stand bracket at left and
right corner. The whole structure is placed using small PVC
with the support of ring stand. Obviously the structure is
very fragile.
NEW DESIGN STRUCTURE
The new strategy for the Solar Tracker is fundamentally
focusing on bearing and gear. Small gear is used to rotate
for Y-axis while X-axis rotation is turned by shaft of stepper
motor. Fig. 1(a, b, c, d) shows the dimensions of the
structure and the concept of rotation and turning. The
weight of the Solar panel is light approximately 5 Kg which
is considerably not heavy to force the shaft of the stepper
motor. Nevertheless for safety reason and long term
operation a bearing is placed in between the weight of the
solar panel and the stepper motor so that the weight is no
longer hold by the shaft of the stepper motor. The tracking
system is powered by 12AH DC battery which is reliable
and small for quick rechargeable during daytime by the
solar panel.
NEW DESIGN STRUCTURE
The new strategy for the Solar Tracker is fundamentally
focusing on bearing and gear. Small gear is used to rotate
for Y-axis while X-axis rotation is turned by shaft of stepper
motor. Fig. 1(a, b, c, d) shows the dimensions of the
structure and the concept of rotation and turning. The
weight of the Solar panel is light approximately 5 Kg which
is considerably not heavy to force the shaft of the stepper
motor. Nevertheless for safety reason and long term
operation a bearing is placed in between the weight of the
solar panel and the stepper motor so that the weight is no
longer hold by the shaft of the stepper motor. The tracking
system is powered by 12AH DC battery which is reliable
and small for quick rechargeable during daytime by the
solar panel.
TRACKING ALGORITHM
The tracking software development is enhanced with the
support of MicroC as programming compiler and MicroICD
as debugger. MicroC uses C language which is well-known
language for engineering application. The development is
tremendously speed up compared with previous compiler
which use assembly language. MicroICD debugger is a tool
for one step debug to check the process flow of the ASM
MEASUREMENT AND RESULTS
Fig. 6 shows the result of the measurement for Ultra
Violet using pyranometer. The daily reading shows that the
intensity of ultra violet (UVA) is high started from 8.00 am
till 18.00 pm with the reading of UV is in between 0.8 to1.6
kW/m2
. After several testing process were done the tracker
algorithm shows very successful result with regard to the
correct position of the solar tracker. This shows the
pyranometer sensor is reliable and very significant for
tracking position of Sun. However the accuracy can be
improved further by reducing the horizontal turn angle
position during calibration process.
CONCLUSION
A solar tracker system with autonomous feature is highly
required. This feature is certainly essential to some
applications such as stand-alone data logger using Solar
Energy as main power supply. Three significant findings
were established from the investigation namely the
improved structure of solar tracker which has X-Y turning
position, reliable sensor for detecting intensity of UV and
functional tracking algorithm using microcontroller.