A Unique Model of Characterization & Performance ...

Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

A Unique Model of Characterization & Performance Estimation of Various Solar Photovoltaic Cells/Modules Using Microcontroller Rakesh Naskar1

Partha Das2

Department of Electrical Engineering lIS College of Engineering Kalyani, India

Department of Electrical Engineering lIS College of Engineering Kalyani, India

I [email protected]

[email protected]

Abstract-At the end of the solar module manufacturing process,

current Imp and voltage Vmp at the maximum power point and the

Isc and Voc points, where the power will be zero and the

maximum value of power will occur between the two. The Fill Factor (FF) is essentially a measure of quality of the solar sell. When calculated the performance of the solar cell from I-V Characteristics using the conventional method, it was found that noise caused the I-V curves to zigzag slightly near the Voc and to zigzag widely near the 'knee' of the curve. Defining the exact of

solar

Module's

parameters

is

called

Module's

Characterization. So in this paper the authors are tried to minimized the noise ofI-V curve to get the highest power output using Automatic electronic load regulator and also find out a real value of Isc and Voc points from the I-V curve ploUing using ATMEGA Microcontroller. Keywords-Solar cell, I-V characteristics, Automatic Voltage Regulator, Microcontroller (ATMEGA-168).

I.

INTRODUCTION

Since the outbreak of the world economic crisis in 1973, the use of solar cells for the electricity generation has been more and more in the focus of attention. Worldwide, more than 1600 PV solar plants of smaller or greater power have been installed on the ground. Most developed countries legally regulate the possibility of generating and selling of the electrical energy generated in PV solar plants. The use of solar energy contributes to more efficient use of countries' own potentials in producing electrical and thermal energy, reduction of the greenhouse gas emission, lowering of the import rates and the use of fossil fuels, as well as to the development of the local industries and an increase in new job creation [1]. In terms of energy consumption India is one of the fastest growing countries. The country is heavily depends on fossil fuels. At present it is fifth largest consumer of energy in the world [1, 2]. It is believed that the geographical location of India allows the country to receive well over 5000 trillion kWh of pure solar energy each year [3], which is far beyond the annual power consumption of India. With the help of the solar cells and solar panels it is possible to generate electricity in areas where the exposure to sun is comparatively lesser.

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School of Energy Studies, ladavpur University Kolkata, West Bengal, India

[email protected]

The launch of lawaharlal Nehru National Solar Mission (JNNSM) has created a lot of interest in the Indian solar sector [3]. The earlier uses of photovoltaic system were mainly in the area of decentralized power generation for different purpose. Later the use of PV spread over a number of field. But the systems available in the market were neither reliable nor within the reach of common people due to its high cost. However, attempts have also been made, principally by research scholars to boost the efficiency of PV systems. But the problem is efficiency of solar cell is comparatively very low. Recent progress in the development of polymer solar cells has improved power-conversion efficiencies from 3% to almost 9%. Based on semiconducting polymers, these solar cells are fabricated from solution-processing techniques and have unique prospects for achieving low-cost solar energy harvesting, owing to their material and manufacturing advantages. Now, there are many manufacturers of solar photovoltaic cell systems of different category in the market. Therefore, there must be a unique method and standard to justifY the quality of solar cell and its suitability in different climate condition. In this paper the authors are tried to develop a unique model for characterization of SPY module by using microcontroller.

an I-V measurement is performed under different

illumination of each individual solar module to determine its

value

Ratan Mandal3

II.

SOLAR CELL EQUIVALENT CIRCUIT

Among other significant parameters of solar cells that can be extracted from the I-V curves are the equivalent series and parallel resistances [5]. The Fig-1 shows the simplified equivalent circuit of a solar cell. The value of series resistance Rs, is typically much lower than the parallel resistance Rsh. For the ideal solar cell series resistance (Rs) would be zero and parallel resistance (Rsh) would be infinite. Since the effect of Rs is negligible near open circuit condition , the slope of the I-V curve in that vicinity is an indicator of the value R,h Conversely , since the effect of Rsh is negligible near short circuit condition, the slope of the I-V curve in that vicinity is an indicator of the value Rs . If the illumination applied to the solar cell during the I-V test representative of solar radiation it receives in the field, then the maximum efficiency of the solar cell may be calculated as the ratio of Pm to the optimal power incident on the solar cell. ax

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ICONCE 2014 January 16 - 17, 2014, Kalyani,

WE,

India

Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

p �I VC I

r-

·

·· ···----------·········-----------·········---

allowing less light to reach the PV cells. Also there is a mismatch effect due to non-uniform shading [5].

1

r,

Isc

r",

I-V curve Shunt -

losses

g c

Max Power ---

, , ,

�

�::l

U

Fig. I. Solar cell equivalent circuit.

III.

Ise

� a; ;:

Mismatch losses', \

0 Q.

(inCl. shading)

SOLAR 1- V CHARACTERISTICS

The 1- V (current-voltage) curve of a PV string (or module) describes its energy conversion capability at the existing conditions of irradiance (light level) and temperature. Conceptually, the curve represents the combinations of current and voltage at which the string could be operated or 'loaded' , if the irradiance and cell temperature could be held constant. Figure 2 shows a typical I-V curve, the power-voltage or P-V curve that is computed from it, and key points on these curves. Referring from Figure 2, the span of the I-V curve ranges from the short circuit current (Ise) at zero volts, to zero current at the open circuit voltage (Voe). At the 'knee' of a normal I-V curve is the maximum power point (Imp, Vmp), the point at which the array generates maximum electrical power. In an operating PV system, one of the jobs of the inverter is to constantly adjust the load, seeking out the particular point on the I-V curve at which the array as a whole yields the greatest DC power.

Imp

Pmax

---

;------

Voltage (V)

In this paper the authors tried to overcome this problem using Automatic Voltage Regulator & Microcontroller. This method is a new and low cost method using automatic load regulator to estimate both voltage and current of the solar cell under different temperatures and irradiances. IV.

ON Spy MODULE CHARACTERIZATION

./

Vmp

Voe

Fig. 2. The I-V and P-V curves ofa photovoltaic device.

Under identical conditions, two healthy PV modules of a given model number should have similar fill factors. The actual magnitude of the fill factor depends strongly on module technology and design. For example, amorphous silicon modules generally have lower fill factors (softer knees) than crystalline silicon modules. Any impairment that reduces the fill factor also reduces the output power by reducing Imp or V mp or both. The I-V curve itself helps us to identifY the nature of these impairments. The effects of series losses & shunt losses and mismatch losses on the I-V curve are represented in Figure 3. There is another effect of uniform soiling, which simply reduces the height of the I-V curve by

978-1-4799-3340-2/14/$31.00 ©2014 IEEE

AUTOMATIC VOLTAGE REGULATOR (MrCROCONTROLLER)

In the photovoltaic field, manufacturers provide ratings for PV modules for conditions referred to as standard test conditions (STC). To carry out photovoltaic engineering well, a suitable characterization of PV module electrical behavior (1- V curves) is necessary. There are many methods like- Analog circuit method, Digital circuit method, Implementation of Lab view software to find out I-V curves [6, 7, 8, 9, 10 and 12]. But these processes are not efficient enough, that's why authors tried to implement a new method of characterization and performance estimation of various solar photovoltaic modules using ATMEGA Microcontroller. The Atmel®AVR® core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers. The ATmega8 provides the following features: 8 Kbytes of In-System Programmable Flash with Read-While-Write capabilities, 512 bytes of EEPROM, 1 Kbyte of SRAM, 23 general purpose I/O lines, 32 general purpose working registers, three flexible Timer/Counters with compare modes, internal and external interrupts, a serial programmable USART, a byte oriented Two wire Serial Interface, a 6-channel ADC (eight channels in TQFP and QFN/MLF packages) with IO-bit accuracy, a programmable Watchdog Timer with Internal Oscillator, an SPI serial port, and five software selectable power saving modes. The Idle mode stops the CPU while allowing the SRAM; Timer/Counters, SPI port, and interrupt system to continue functioning. The Power down mode saves the register contents

_____

Voltage

Voc

Fig. 3. Several categories oflosses that can reduce PV array output. The I-V curve provides important troubleshooting clues.

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ICONCE 2014 January 16 - 17, 2014, Kalyani,

WE,

India

Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

but freezes the Oscillator, disabling all other chip functions until the next Interrupt or Hardware Reset. In Power-save mode, the asynchronous timer continues to run, allowing the user to maintain a timer base while the rest of the device is sleeping. The ADC Noise Reduction mode stops the CPU and all I/O modules except asynchronous timer and ADC, to minimize switching noise during ADC conversions. In Standby mode, the crystal/resonator Oscillator is running while the rest of the device is sleeping. This allows very fast start-up combined with low-power consumption. The pin diagram of proposed microcontroller is given below. (RESET) PCS

1

(INTO) PD2 (INTl) P03 (XCKlTO) PD4 VCC

D

PC5 (ADCSlSCL)

DDCCOODD (\

PC4 (ADC4ISDA)

(RXO) POO

(TXO) POl

. f .

PC3(ADC3) PC2(ADC2)

4

5 6

PCl (ADC1) PCo(ADCO) GND

7

GNO (XTAllITOSC1) PBS

8 9

(XTAl2ITOSC2) PB7

10

(11) PD5 lAINO) P06

19

AREF AVCC

PB5(SCK)

18 17

PB4 (MISO) PBS (MOSV0C2)

15

PB1 (OC1A)

16

Fig. 6. Block Diagram ofATMEGA microcontroller with Solar Module.

PB2(�lB)

B. Experimental Results

The experimental results I-V Characteristics of both of these components is observed in the graph.

Fig. 4. Pin diagram ofATMEGA Microcontroller.

A. Experimental Methodologies

l'

i.�

.j I

I

"

Fig. 5. Experimental set-up.

Fig.7. the I-V curves ofa photovoltaic Module using ATMEGA microcontroller at radiation of430 W/m'

In this paper the authors have tried to improve the I-V characteristics. The block diagram of the electronic circuit developed to trace the 1- V characteristics electronic components is shown in figure below. Voltage Reading for DUT (device under test) is carried out by connecting the supply to the ADC channel 0 input of the microcontroller. Microcontroller converts this analog value in digital format i.e. 0-1023 for 10 bit operation. Again the readings are converted to the voltage by multiplying with the factor of (511024) for 5 volts of operating range. These conversions are directly carried out using floating point library found in C compiler. Results are buffered and shown to the display in volts level. A predefined voltage sweep is programmed like for example, a voltage increasing from 0 to 10 V in steps of 1v. For measurement of current a series shunt resistor is connected to the device and the voltage drop is measured which is equivalent to the current drawn by OHM' s law (I=v/r). But since the voltage drop is quite small to be measured by the ADC of the circuit it is then amplified by the non inverting amplifier constructed with the LM358 FET based OPAMP IC with gain of 3X (1+RFIRI), where RF is 20 k and Rl is 10k respectively[lO, 11].

978-1-4799-3340-2/14/$31.00 ©2014 IEEE

J-

+

After using the ATMEGA microcontroller the performance of the solar cell from I-V Characteristics , we found that noise caused the I-V curves to zigzag slightly near the VDC and to zigzag widely near the 'knee' of the curve is reduced largely and now it is nearly equal to the ideal characteristics of I-V curve of solar module. And also from author's desired mode, the starting point and ending point of the characteristics are found out successfully. The authors have taken data on a 3Wp poly crystalline solar module at 420 W/m2 solar radiation intensity. For this experiment 1-255 ohm resistor (shift and clock type register) at one ohm step variation with increasing order is used for automatic control purpose. V.

CONCLUDING REMARKS

A microcontroller based electronic circuit has been presented in this paper for analyzing the electronic component by tracing their I-V characteristics. Op-Amp is used in non inverting mode for current to voltage conversion. A programmable voltage supply is deduced using the PWM (Pulse Width Modulation) over the microcontroller.

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ICONCE 2014 January 16 - 17, 2014, Kalyani,

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Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

Voltage

Experimental results obtained with a known resistance, diode, transistor, and wet soil fabricated electronic components demonstrates the operational suitability of the electronic circuit developed for the present work. Also the authors aim that this model is not implementing only for 3watt peak different type modules but also want to implement for Characterization of different rating module using ammeter shunt and voltmeter multiplier method in future.

[7]

REFERENCES

[8]

[1]

2009, IEEE conference publication on 5-8 Nov, 2009, pp 1-24 1-28.

standalone

"A new application of duty cycle sweep based

[9]

PV

Photovoltaic

Specialist

R.

Swenson,

System

Design

Conference

"A

and

and

Real

World

Performance",

Exhibition,

IEEE

U. Umapathi, and G. G. Das, "Simple techniques to improve panel

efficiency

using

a

microcontrol1er

or

SOC",

Experimental

Analyses

of

Photovoltaic

Systems

with

'98/99. Photo

-

IIth July 2012, Terengganu, Malaysia.

[12] Ratan MandaI & Rakesh Naskar, "An Unique Method of Characterization & Performance Estimation of various Solar

2078-0273,

PHOTOVOLTAIC Cel1slModules using microcontrol1er:

November, 2010.

A

review." 978-93-82359-56-2/13/@2013HlTK (Proceedings of

R. Khezzar, M. Zereg, and A. Khezzar, "Comparative Study of

NATCONIC-2013), Feb, 26-27, 2013.

Mathematical Methods for Parameters Calculation of Current-

978-1-4799-3340-2/14/$31.00 ©2014 IEEE

on LabView Monitoring using Data

11th International Annual Symposium on Sustainability Science

salinity and temperature and pol1ution monitoring", Journal of ISSN:

Based

and Management 09th

S P Kosta, J Gupta et aI., "Sea-water electronic circuits for Sciences,

Voltaic

Acquisition System at Universiti Malaysia Terengganu", UMT

1350-2360, Jan. 2004.

[6]

Parker and

of

[11] A. Zakaria, A.F. Ayob and W.B. Wan Nik, "Characterization of

static voltage stability limit of a power system" pp 1-7, ISSN:

Biomedical

T.

December 2002. Panasonic, Solar Cel1s Technical Handbook

Haque, M.H., "Use of V-I characteristic as a tool to assess the

and

and

IEEE Transactions on energy conversion, vol. 17, NO. 4,

I-V Characteristics oJPhotovoltaic

23th to 25th March, 2010.

Medicine

IEEE

Test

Voltage- and Current- Based Maximum Power-Point Tracking",

Energies and Power Quality (ICREPQ'10) Granada (Spain),

[5]

Gregg,

Examination

and

Modules and Strings", International Conference on Renewable

[4]

Third

[10] Md. A. S. Masoum, H. Dehbonei, and E. F. Fuchs, "Theoretical

Vicente Leite and Faustino Chenlo, "An Improved Electronic the

the

Design,

Published in Low Power Design, July, 2011.

802, 2008, ISSN: 1816-949X. Tracing

A.

solar

Soil Electronic Device- Transistor and Ats application Circuit",

for

of

Electronic

Florida USA.

pp1-6, print ISBN: 978-1-4224-1705-6,

S P Kosta, Y M Dubey, A Gaur, Y P Kosta, and S Kosta, "Wet

Circuit

Proceedings on

conference publication on January 3-7, 2005, Lake Buena Vista,

Journal of Engineering And Applied Sciences 3(10): pp 798[3]

systems,"

Workshop

Applications (DELTA'06), 2005.

Apr. 2008. [2]

PV

International

on microcontrol1er to obtain the I-V characteristic curve of photovoltic Modules",

A. S. Kok Bin, S. Weixiang, O. Kok Seng, S. Ramanathan and L. I-Wern, "Development of a LabVIEW-based test facility for

Duran E., Galan J., Sidrach-de-Cardona M., Ferrera M.B., Andujar J.M.,

Characteristic of Photovoltaic Module", International

Conference on Electrical and Electronics Engineering, ELECO

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