EXTRACTING
useable electricity from the sun was made possible by the discovery of
the photoelectric mechanism and subsequent development of the solar cell
i.e., a semiconductive material that converts visible light into a
direct current. By using solar arrays, a series of solar cells
electrically connected, a DC voltage is generated which can be
physically used on a load. Solar arrays or panels are being used
increasingly as efficiencies reach higher levels and are especially
popular in remote areas where placement of electricity lines is not
economically viable.
This
alternative power source is continuously achieving greater popularity
especially since the realization of fossil fuel’s shortcomings.
Renewable energy in the form of electricity has been in use to some
degree as long as 75 or 100 years ago. Sources such as Solar, Wind,
Hydro and Geothermal have all been utilized with varying levels of
success.
The
most widely used are hydro and wind power, with solar power being
moderately used worldwide. This can be attributed to the relatively high
cost of solar cells and their low conversion efficiency. Solar power is
being heavily researched and solar energy costs have now reached within
a few cents per kW/h of other forms of electricity generation, and will
drop further with new technologies such as titanium oxide cells. With a
peak laboratory efficiency of 32% and average efficiency of 15-20%, it
is necessary to recover as much energy as possible from a solar power
system.
This
includes reducing inverter losses, storage losses and light gathering
losses. Light gathering is dependent on the angle of incidence of the
light source providing power (i.e. the sun) to the solar cell’s surface
and the closer to perpendicular, the greater the power. If a flat solar
panel is mounted on level ground, it is obvious that over the course of
the day the sunlight will have an angle of incidence close to 90° in the
morning and the evening. At such an angle, the light gathering ability
of the cell is essentially zero, resulting in no output. As the day
progresses to midday, the angle of incidence approaches 0°, causing a
steady increase in power until at the point where the light incident on
the panel is completely perpendicular and maximum power is achieved.
As
the day continues toward dusk, the reverse happens and the increasing
angle causes the power to decrease again toward minimum again. From this
background, we see the need to maintain the maximum power output from
the panel by maintaining an angle of incidence as close to 0° as
possible. By tilting the solar panel to continuously face the sun, this
can be achieved. The process of sensing and following the position of the sun is known as Solar Tracking.
It was resolved that real-time tracking would be necessary to follow
the sun effectively, so that no external data would be required in
operation.
Many
different methods have been proposed and used to track the position of
the sun. The simplest of all uses an LDR (Light Dependent Resistor) to
detect light intensity changes on the surface of the resistor.
SOFTWARE AND HARDWARE TOOLS:
Software Tools:
- Keil compiler
- Orcad.
Hardware Tools:
- Microcontroller AT89S52.
- LCD
- L293D driver and DC motor
- LDR and ADC
- Solar panel