final year project presentation

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.

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

SolarPanel

DC-DC ConverterLoad

Controller Back-upBattery

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

Rp

Rs

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pdph IIII

p

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satph R

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IdVo

Ip

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 withdifferent resistances under aconstant light source

+

-V

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.

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

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

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

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

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 ΔV equation the capacitor value was determined (21.3 μF)

Vin

2.2 mH

22 uF

LOAD

+

-

+

-

D

PWM

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

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

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

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

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