2. To develop a small scale solar powered system that will power a DC load, which incorporates power management techniques, DC-DC conversion and a user interface.

3.  Renewable energy source  Non-polluting  Reliable  Can work anywhere sun is shining  No major mechanical parts  Relatively no maintenance  Noise Free  Last decades

4. Solar Panel DC-DC Converter Load Controller Back-up Battery

5.  Silicon cells combined in series or parallel  Converts solar energy into electricity  Cell Technologies › Copper Indium Selenide (CIS) and Amorphous › Monocrystalline and Polycrystalline  Current varies with cell size and light intensity

6. Rp Rs IphD Id Vo Ip

7.  Peak Power of 10 Watts  Vmpp = 15.6 V  Impp = 0.64 A Shell ST10  Voc = 22.9 V  Isc = 0.77 A The solar panel was tested with different resistances under a constant light source + - V

10. Two MPPT algorithms were considered:  Incremental Conductance Method › By comparing incremental conductance with instantaneous conductance.  Perturb & Observe Method › By periodically perturbing the PV array voltage and comparing the output power with that of the previous cycle. The operating point oscillates around the MPP since the system is continuously perturbed.

11.  Algorithm was implemented using LabVIEW  Solar panel read via a NI-USB 6009  The voltage was measured across a high power resistor to read current  Duty cycle output on NI USB 6009 digital output line Start Set Duty Out Read V, I P_new = V*I P_new > P_old Duty = Duty(-) Duty = Duty(+) P_old  P_new

12.  Used to implement P&O algorithm › ‘G’ programming  Also used to generate a user interface through the front panel › Waveforms showing voltage and current of solar panel › Numeric indicator showing power › Duty cycle displayed › ‘Stop’ button to end program

13.  Data acquisition tool  Read data in, and generate digital signals out  Does not have a hardware counter, cannot generate digital outputs at high frequencies  Solution M series

14.  DC-DC converter needed for two reasons › To implement the MPPT algorithm › To bring the DC voltage to an acceptable level to power the load  Buck converter was chosen and designed

15.  The most important components are the inductor and capacitor  Use Vo = DVi to deduce ideal duty cycle range (0.3 – 0.5)  Using both of these values for D, and the ΔI equation two values for the inductor were calculated (2.8 mH & 1.6 mH)  Using the Δ V equation the capacitor value was determined (21.3 μF)

16. Vin 2.2 mH 22 uF LOADLOAD + - + - D PWM

17.  Solar panels only generate power when there sun available  Storage element is recommended  Various rechargeable battery cell chemistries › Lead Acid › Nickel-Cadmium › Nickel-Metal-Hydride › Lithium Ion

18.  Up to 99% efficiencies  Highest weight to energy ratio  Average voltage of one Li-ion cell is 3.6- 3.7 Volts  A Li-ion battery pack with a capacity of 4 AH would be enough to store all energy generated on the longest day of the year at maximum power  Safety issues

19.  Overvoltage  Over discharging can cause short circuit  Battery packs usually include protective circuit › Limits input voltage › Limits discharge voltage  Li-ion charger IC is recommended to implement charging profile

20.  Initially it was thought a mobile phone charging algorithm would have to implemented  Research showed that the charging algorithm is employed on the phone  To prove this, a commercial Nokia car cigarette lighter charger was disassembled  A ‘ma34063a’ DC-DC converter was found  To charge a mobile an appropriate constant voltage is needed, along with some circuitry protection

21.  Solar cell equivalent circuit, characteristics and various cell technologies  Maximum power point tracking techniques  LabVIEW – ‘G’ programming and user interface  DC-DC converter design including choosing appropriate components and simulation in Pspice  Rechargeable Batteries