07-07-2012, 02:40 PM
Highly Efficient Low Power Consumption Tracking Solar Cells for White LED-Based Lighting System
Highly Efficient Low Power .pdf (Size: 666.13 KB / Downloads: 113)
INTRODUCTION
SOLAR cells or photovoltaic cells are in fact large area
semiconductor diodes that convert sunlight into electrical
current to produce usable power. They have long been used in
situations where electrical power from power station is
unavailable, such as in remote area power systems. The power
output of a solar array is given in watts. In order to calculate
the energy needs of the application, a measurement in watthours
per day is often used. The output power of the solar cell
depends on multiple factors, such as sunlight intensity and
direction of the cells. In order to reach the maximum power,
the solar tracker has been added to this system to avoid time
limit of the fixed systems.
System Design
A photovoltaic module is the basic element of each
photovoltaic array. It consists of many jointly connected solar
cells. Polycrystalline photovoltaic module is used in this
system and it is designed to track the maximum sunlight by
stepping motor that is commanded by PIC microcontroller
EXPERIMENTAL RESULTS
The relationship between the average solar radiation over a
day and the power generated by the panels is largely linear,
although the fluctuations are large, due to the different actual
solar radiation levels across a day. The experimental result in
Fig. 8 compares the power generated by fixed and tracking
solar cell module. The fixed module produces the maximum
power only when there is direct sunlight to the module as
shown in the graph. What this means is that charging time
interval is limited due to sunlight direction.
CONCLUSION
In this paper, we considered the solar tracking system and
apply for lighting application based on WLED that use Pulse
Width Modulation (PWM) technique for WLED circuit
driver. The results of this study shows that maximum charging
time for tracking system is more than fixed module, so the
utilization efficiency of solar cell module will be considerably
increased. The concept and control principle of directly
connected White LED circuit driver with current limitation
resistors has low efficiency because most of energy lost as
heat at each resistor. Compared to Pulse Width Modulation
(PWM), the average output value is controlled by duty cycle
of input pulse. The output MOSFET that is directly connected
to the WLED is either on or off, so small power is wasted as
heat resulting in low power consumption and long lighting
system. As for future study, for more energy conversion we
can improve the system by using dual axis for solar module
and include maximum power point tracking.