Battery Charge Regulator for a photovoltaic Battery Charge Regulator for a photovoltaic power system using microcontrollerpower system using microcontroller

ByBy::

Raed Wa’el Ennab & Raja Sa’ed AnabtawiRaed Wa’el Ennab & Raja Sa’ed Anabtawi

Supervised by :

Prof. Marwan Mahmoud

IntroductionIntroduction

Since the beginning of the oil crises, which Since the beginning of the oil crises, which remarkably influenced power development programs remarkably influenced power development programs all over the world, massive technological and research all over the world, massive technological and research efforts are being concentrated in the field of efforts are being concentrated in the field of renewable energy resources. In the solar sector for renewable energy resources. In the solar sector for electricity generation, greater attention is being given electricity generation, greater attention is being given to photovoltaic conversion. to photovoltaic conversion.

FeaturesFeatures

1- Charge any rechargeable battery 12V, 24V.1- Charge any rechargeable battery 12V, 24V.2- Supply any low dc load.2- Supply any low dc load.3- Solar-powered.3- Solar-powered.4- Displays charging status. 4- Displays charging status. 5- Polarity checking. 5- Polarity checking. 6- Current Limiting. 6- Current Limiting.

Advantages and DisadvantagesAdvantages and Disadvantages::

The advantages areThe advantages are : :

11 - -Renewable resourceRenewable resource.. 22 - -SilentSilent..

33 - -Non-pollutingNon-polluting.. 44 - -Little maintenanceLittle maintenance..

55 - -easy to installeasy to install.. 66 - -ReliabilityReliability..

And the disadvantages areAnd the disadvantages are::

11 - -Very expensive. 2- No work at nightVery expensive. 2- No work at night . .

Block DiagramBlock Diagram

Solar Panel Regulator

Lead Acid battery

PIC Load

Photovoltaic cells:

In our design, the solar panels will function as a

power supply to our circuit. It will convert the sun radiation to voltage and current.

types of photovoltaic cells:

1-mono-crystal silicon .

2-Polycrystal silicon.

3-Amorphous silicon (thin film silicon).

Regulator

Battery

Solar Panel

PIC Load

efficiency

MaterialMaterial level of efficiency in % level of efficiency in % production production

Mono crystalline siliconMono crystalline silicon 14-1714-17

Polycrystalline siliconPolycrystalline silicon 13-1513-15

Amorphous siliconAmorphous silicon 5-7 5-7

number of cells

The output voltage of a module depends on the number of cells connected in series. The module we used was 25 cell connected in series.

solar cell I-V characteristics

A Typical Current-Voltage A Typical Current-Voltage Curve for a Module at (85)c Curve for a Module at (85)c

and (25)and (25)

A Typical Current-Voltage Curve for a Module at

(1000)W/m^2&

(500)W/m^2

Photovoltaic ArraysPhotovoltaic Arrays : :

Series connection Parallel connection

Charge Regulator:

The solar charge regulator main task is to charge the battery and to protect it from overcharging and deep discharging. Deep discharging could also damage the

battery.

Kind of charge regulators:

1-Simplest switch on/off regulators.2-PWM ( Pulse Width Modulation).

3-MPPT charge regulator (Maximum Power Point Tracking).

Regulator

11 - -We are going to work on six-cell lead-acid batteriesWe are going to work on six-cell lead-acid batteries..

22 - -Voltage/cell 1.75-2.4 VVoltage/cell 1.75-2.4 V . .

33 - -Battery chargeBattery charge..

44 - -Battery efficiencyBattery efficiency..

55 - -Minimum VoltageMinimum Voltage..

Lead acidBattery

RegulatorSolar

panelPIC Load

Lead Acid Battery

Lead acid batteryLead acid battery

In our project, the circuit we built has two leds; red In our project, the circuit we built has two leds; red one and green one.one and green one.

Circuitry

circuitry+S

-S

CircuitryCircuitry

• when the voltage is lower than 14.4 V the comparator when the voltage is lower than 14.4 V the comparator (IC3) allows a high negative output signal to switch on the (IC3) allows a high negative output signal to switch on the PNP transistor (Q1)PNP transistor (Q1).

• During charging, the battery voltage increase until it reaches the 14.4 V value. At this voltage, the transistor (Q1) will be switched off.

• N1 and N2 from the IC4001 are utilized as pulse oscillators for the purpose of testing.

• In this short period, transistor Q2 will be switched on, and a current will flow from the emitter to the collector of Q2.

• Then the comparator (IC2) compares the battery Then the comparator (IC2) compares the battery voltage with the open-circuit voltage of the solar voltage with the open-circuit voltage of the solar generatorgenerator.

• The main objective of using the pulse generator is to control the voltage of both the solar generator and the battery continuously.

The objective of the comparator (IC5) is to control the battery voltage during the discharging mode

two MOSFET transistors were two MOSFET transistors were utilized instead of oneutilized instead of one

- -To make the prevention of the battery discharging To make the prevention of the battery discharging via the solar generator as strong as possiblevia the solar generator as strong as possible . .

- -The temperature of the two transistors, due to the The temperature of the two transistors, due to the voltage drop across them, is divided equally voltage drop across them, is divided equally between thembetween them..

- -Increasing the reliability of the controller since one Increasing the reliability of the controller since one transistor can perform the task of the other in case transistor can perform the task of the other in case of its failureof its failure..

- -This arrangement protects the controller from This arrangement protects the controller from failure whether it is connected to the solar failure whether it is connected to the solar generator first or to batterygenerator first or to battery..

Features of The Locally Features of The Locally developed Battery Control Unit developed Battery Control Unit (BCU)(BCU)

- -Protects battery against overcharging: the unit controls the Protects battery against overcharging: the unit controls the charging current via a regulated impulse, thus preventing charging current via a regulated impulse, thus preventing harmful overchargingharmful overcharging..

- -Protect the battery against deep discharging: the unit Protect the battery against deep discharging: the unit controls battery discharge by means of bistable load relaycontrols battery discharge by means of bistable load relay..

- - -If the battery charge drops bellow a predetermined If the battery charge drops bellow a predetermined voltage threshold, the relay automatically disconnects the voltage threshold, the relay automatically disconnects the load, this is indicated by a red light- emitting diode (LED)load, this is indicated by a red light- emitting diode (LED)..

- -The unit is protected against battery reverse polarity via a The unit is protected against battery reverse polarity via a diode (D4)diode (D4)..

PICPIC

Flow chartFlow chartRead the battery Voltage

Read the voltage fro

the regulator

Out to the battery

from the regulator

Out to the load from

the Regulator

Here we used the DAC to convert the digital output Here we used the DAC to convert the digital output from the PIC to Analog.from the PIC to Analog.

ResultsResults

ResultsResults

I-V Characteristic

At G=950 w/m2

Resistance (ohm)

Current (mA)

Voltage

(V)

0401.70

103841.92

20379.23.85

30370.15.12

403656.02

50360.36.9

60353.57.5

70352.28.61

80351.410.4

90350.811.3

10030515.4

>>019.1

ResultsResults

Fill factor and efficiencyFill factor and efficiency:: The Imp = 350 m A and the Vmp =15 voltThe Imp = 350 m A and the Vmp =15 voltSo the max power point = 15*.350= 5.25 wattSo the max power point = 15*.350= 5.25 watt..

The fill FactorThe fill Factor::FF= (Imp*Vmp)/ (Is.c*Vo.c)FF= (Imp*Vmp)/ (Is.c*Vo.c)

( = ( = 1515**0.3500.350( /)( /)1919.*.*44 = ) = )70%70%

The efficiencyThe efficiency:: Eff= P.opt/ A.EeEff= P.opt/ A.Ee

Eff=5.25/ 0.3*0.3*950 =6.1%Eff=5.25/ 0.3*0.3*950 =6.1% All calcu

lations a

re at G

=950 w/m

2

The results we got were:The results we got were:

Vpv (V)

Ipv

(mA)

Vbatt (V)

Ibatt (mA)

17.132812.6323

14.930212.9296

14.129813.01289.6

13.4627513.27270

Problems we have facedProblems we have faced::

11 - -The output voltage was about 15 volts, and the PIC The output voltage was about 15 volts, and the PIC accept only 5 V maximumaccept only 5 V maximum..

22 - -The radiation from the sun was different from day to The radiation from the sun was different from day to anotheranother . .

33 - -The wires we used first were the thin wires so when The wires we used first were the thin wires so when the current passed these wires got hotterthe current passed these wires got hotter . .

The applications for The applications for our projectour project

Conclusion and Conclusion and RecommendationRecommendation::

-From the technical and economical viewpoints, it can be -From the technical and economical viewpoints, it can be said that the PV technology has attained an said that the PV technology has attained an acceptable degree of operational efficiency and acceptable degree of operational efficiency and reliabilityreliability.

-Module degradation seemed to be a problem in amorphous PV technology.

-The tested amorphous PV module showed power degradation between 16.4% and 39% at the end of the first year testing period.

-if we have more time we could program the PIC with a

program that can drive a stepper motor and rotate it as the max radiation from sun and that by using photo sensors.