1. Development of a MPPT System for Solar Lighting Applications
T.C. Peiris1, D.U.J Sonnadara2 and T.R. Ariyaratne2
1Arthur C Clarke Institute for Modern Technologies, Moratuwa
2Department of Physics, University of Colombo, Colombo 3

2. Solar lighting systems
In Sri Lanka, 65% of the electricity is generated using a variety of diesel fuel and 35% through hydro resources .
Since Sri Lanka is situated close to the equator, solar radiation over the island does not show high seasonal variability. The average solar radiation remains at roughly 5.0 kW-hr/m2/day, and thus, substantial potential exists for harvesting solar energy.
Renewable sources of energy such as solar power is an economical and sustainable alternative source to promote medium term electricity generation to the rural population.

3. What is a charge controller?
Solar
Panel
Charge Controller
Battery
Regulation
Efficiency
Battery life time

4. Importance of a charge controller
Solar panels output voltages much higher than battery voltages. Hence, if there is no regulation, the batteries may be damaged from overcharging.
The efficiency at which the system is able to capture and store depends on the performance of the quality of the panels and the batteries. In order to obtain maximum power from the solar panel to charge a battery, an efficient charge controller is required.
In addition, the charge controller should offer enhanced protection and increase life time to the battery by preventing damages.

5. Typical characteristics of a Solar panel
Conventional battery charge controllers regulate the charging voltage at maximum battery voltage

6. Temperature & irradiation variations
FIG 01
FIG 02

7. MPPT Process
Duty Cycle
Power
Pmax P1

8. Hardware: charge controller
Microcontroller
Duty Cycle adjustment for MPPT
PWM
Control
DC/DC Converter
Charging Current
&
Output Voltage
Battery
PV Array
A/D
PIC16F877A
PWM
PV Array
Switch
Battery Voltage
Rsense
Charging Current
Voltage

9. Hardware: light controller
Three lamps constructed with white LEDs were used
Switching priority was decided according to the charge level of the battery
Microcontroller was programmed to continuously monitor the battery voltage

10. PV-powered lighting system

11. Performance of the system

12. Performance on Sunny days

13. Performance on Cloudy days

14. Conclusions
MPPT process has increased the charging current. The increase in the charging current compared to the 12.5 V regulation is about 112%.
Low Amp Hour Battery & small PV array is sufficient.
The lighting system designed in this work is more suitable for rural houses in remote areas which can manage with three sets of lights.
No power outages even under the worst weather conditions.
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