Laboratory Exercise On Solar Photovoltaic Cells Engineering Essay

Laboratory Exercise On Solar Photovoltaic Cells Engineering Essay

A solar cell or photovoltaic cell is a broad country electronic device that converts solar energy into electricity by the photovoltaic consequence. Photovoltaic is the field of engineering and research related to the application of solar cells for solar energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunshine, while the term photovoltaic cell is used when the beginning is unspecified. Assemblies of cells are used to do solar faculties or photovoltaic arrays.

Solar cells produce direct current electricity from visible radiation, which can be used to power equipment or to reload a battery. Photons from sunlight knock negatrons into a higher province of energy, making electricity. When more power is required than a individual cell can present, cells are electrically connected together to organize photovoltaic faculties or solar panels

Cells are packaged normally behind a glass sheet to protect it from the environment.

Aim/Objective

The aim/objective of this exercising was to measure the public presentation of a polycrystalline photovoltaic panel

Supporting Theory

Brief history

The term – photovoltaic is derived by uniting two Grecian words for visible radiation, exposure, with Vs, the name of electromotive force. The find of photovoltaic consequence is by and large credited to Gallic physicist, Edmond Becquerel. Many other scientists more research on PV consequence but all were extremely inefficient with less than 1 % efficiency transition of the solar energy to electricity.

The modern age of solar power engineering arrived in 1954, when Bell research lab, experimenting with semi-conductors, by chance found that Si doped with certain drosss was really sensitive to light. Rapid advancement in increasing the efficiency of PV cells and cut downing their weight and cost has been made over the past decennaries by the aerospace and electronic industries.

The PV consequence

PV cells consists of a junction between two thin beds of dissimilar semi-conducting stuffs known as P ( positive ) -type semi-conductor and N ( negative ) -type semi music directors. When these two dissimilar semi-conductors are joined together, they create a p-n junction which sets up an electric field in the part of the junction. When light falls on it, the photons from the visible radiation are transferred to some of the negatrons in the stuff thereby acquiring them to a higher energy degree. This sets up a flow of negatrons, upon excitement, to the n-region. This flow is by definition, an electric current. The electromotive force is in consequence provided by the possible difference between the beds. The power end product is given by the equation

Power produced = Voltage – Current ( Watts ) ………………..1

Efficiency

During operation the temperature and irradiance are the two variables that affect public presentation of a PV cell.

The consequence of temperature

The end product electromotive force of a solar cell decreases with temperature. The typical electromotive force lessening of a Si cell is 2.3mV/oC. The alterations in current are normally negligible.

( 2 )

A figure of cells connected together organize a panel and the end product electromotive force for a panel with, n, cells connected in series will change from the standard trial temperature by

( 3 )

Open circuit electromotive force, Voc, at a cell temperature, Tc, is given by

Voc = Voc @ trial – ( 0.0023*n* ( Tc – Tambient ) ) ( 4 )

The cell temperature can be estimated utilizing an empirical attack.

The Normal Operating Cell Temperature ( NOCT ) is found during experiment at the undermentioned conditions

NOCT is found to be 47oC for the panel under trial.

The cell temperature, Tc, runing at an ambient temperature, Ta, is found from

( 5 )

where G is the available irradiance in kW/m2

The consequence of Irradiance.

The visible radiation generated current produced by a solar cell is relative to the flux of photons. Therefore increasing the irradiance, or photon flux, generates a proportionally higher current. The fluctuation in electromotive force is much less and can be neglected.

Appraisal of solar cell power

It is besides possible to gauge what the maximal power of a panel is when working at temperatures off from the trial temperature. If it is assumed that the fill factor ( FF ) does non alter significantly so.

Pmax = Vmax * Imax = FF * Vo degree Celsius * Is hundred ( 6 )

Where

Vmax is the electromotive force measured at maximal power

Imax is the current measured at maximal power

Vo degree Celsius is the unfastened circuit electromotive force

Is c is the current measured at short circuit.

Description OF THE EXERCISE.

Description of the setup used

The setups used for this experiment are a polycrystalline solar panel, a thermocouple, a power metre, a opposition box, an formless solar panel and an unreal visible radiation beginning. See images below.

Amorphous solar panel

Polycrystalline solar panel Resistor box

Power metre

Thermocouple

Test process:

The research lab installations needed for this experiment ( as stated above ) were already connected together. The experiment started with the measuring of the ambient temperature, Tamb, and the cell temperature, Tc, severally, utilizing the thermocouple attached to the apparatus. The unreal visible radiation beginning used in topographic point of the Sun was placed as illustrated graphically in forepart of the Solarex polycrystalline panel. The distance between the panel and the light beginning was set at 1meter.

1m

1.25m

i?±

i?±

Light

Panels

Desk

The visible radiation was switched on and the unfastened circuit electromotive force, Voc @ amb and short circuit current, Is c @ amb were instantly measured. The panel was so allowed to warm up, after which the unfastened circuit electromotive force, Vo c @ hot, short circuit current, Is hundred @ hot and cell temperature, Tc @ hot were measured once more. The opposition box was so connected. The opposition was varied and the corresponding cell electromotive force, cell current and power readings taken for each opposition.

The distance between the solar panel and the light beginning was reduced to 0.85meters and 0.5meters severally and the assorted oppositions and the corresponding cell electromotive force, cell current and power readings taking severally ( as done for the 1meter distance ) . The visible radiation was so switched off. Furthermore, the opposition box was so set to the opposition for maximal power and the maximal power at ambient temperature was measured ( Pmax @ amb_meas ) .

Consequences

The undermentioned informations shown below were obtained

Table 1

Parameter

Measurement

Unit of measurement

Number of cells

36

Cell length

0.057

m

Cell breadth

0.019

m

Area of individual cell

0.001083

M2

Entire country of cells on panel

0.038988

M2

Ambient temperature, Tamb

20

Celcius

Cell temperature, Tc @ hot,

20

Celcius

Open circuit electromotive force Voc @ amb

20.4

Volts

Short circuit current Isc @ amb

0.149

Amperes

Open circuit electromotive force Vo c @ hot ( Vs )

17.8

Volts

Short circuit current Is hundred @ hot ( As )

0.157

Amperes

Cell Temperature Tc @ hot ( oC )

50

Celcius

Table 2

Resistance ( ohms )

Cell electromotive force Vc ( V )

Cell current Ic ( A )

Power ( W )

10

1.6

0.157

0.256

20

3.1

0.156

0.494

30

4.7

0.156

0.732

40

6.2

0.155

0.960

50

7.6

0.153

1.173

60

9.0

0.152

1.373

70

10.4

0.150

1.570

80

11.8

0.148

1.742

90

13

0.145

1.892

100

14.2

0.143

2.038

110

14.9

0.138

2.053

120

15.3

0.130

1.996

130

15.6

0.122

1.918

140

15.9

0.115

1.835

150

16.1

0.109

1.751

200

16.6

0.084

1.409

250

16.9

0.069

1.163

300

17.1

0.058

0.990

350

17.2

0.050

0.857

400

17.3

0.044

0.759

450

17.4

0.039

0.679

500

17.4

0.035

0.614

1000

17.6

0.018

0.314

5000

17.8

0.003

0.065

Calculations

The estimation unfastened circuit electromotive force when the panel is hot, Vo c @ hot_est, is calculated utilizing the equation

Vo c @ hot_est = Vo c @ amb – ( 0.0023*36* ( Tc @ hot – Tamb ) ) = 20.40 – ( 0.0023- 36 – ( 50-20 ) )

Vo c @ hot_est = 17.916 Volts.

Besides, the highest value of power, Pmax, = 2.05 Watts ( from the tabular array above )

Besides, I @ max power= 0.14 Amps and V @ soap. power= 14.90Volts ( from the tabular array above ) .

Efficiency: the panel efficiency from dorsum of the panel at 25oC is calculated from the equation:

? = Pmax_panel / ( 1000-panel country ) where Pmax_panel = 4.5Watt ( from back of panel )

= 4.50/ ( 1000-0.039 ) = 0.12 or ( 12 % ) .

Besides, panel efficiency from dorsum of the panel at NOCT can be calculated from the equation

?NOCT = Pmax_panel / ( 800 – panel country ) … . Where Pmax_panel = 3.2Watt

?NOCT = 3.2 / ( 800 – 0.039 ) = 0.10 or ( 10.26 % ) .

But Irradiance, G, is calculated from the equation

G = Pmax_measured / ( ?NOCT – Panel country – 1000 ) ( kW/m2 )

= 2.05 / ( 0.10 – 0.039 – 1000 ) = 0.53 kW/m2 or 525.64 W/m2.

The cell temperature estimation, Tc @ est, was calculated from the equation

where NOCT = 47oC and G = KW/m2

Re-arranging the equation, we have

Tc @ est = Tamb + [ { ( 47-20 ) / 0.8 } * G ] = 20 + ( 33.73 – 0.53 ) = 37.89oC

Besides, the Fill factor ( FF ) was calculated from the equation

FF = Pmax / ( Vo c @ hot – Is hundred @ hot ) = 2.05 / ( 17.80 – 0.157 ) = 0.73.

The estimated maximal power of the cell at ambient, Pmax @ amb_est, is given by the equation

Pmax @ amb_est = FF – Vo c @ amb – Is hundred @ amb = 0.73 -20.40 -0.149 = 2.23W.

Amorphous panel

The efficiency of the panel was gotten from the equation

G = Pmax_measured / ( ?NOCT – Panel country – 1000 )

Re-arranging the equation, we have

?NOCT = Pmax_measured / ( G – Panel country – 1000 ) ,

Where panel country = 0.10m and G = 525.64 W/m2

= 0.59 / ( 525.64 – 0.10 ) = 0.011 or 1.12 %

Table 3 ( Calculated consequences )

Parameter

Calculated consequence

Unit of measurement

Vo c @ hot_est

17.916

Volts

Pmax

2.05

Watts

, I @ max power

0.14

Amperes

V @ soap. power

14.90

Volts

?

12 % .

%

?NOCT

0.10 or ( 10.26 % ) .

%

Gram

0.53

KW/m2

Tc @ est

37.89

Celcius

FF

0.73

Pmax @ amb_est

2.23

Watts

Pmax @ amb_meas

2.60

Watts

Amorphous panel

Parameter

Calculated consequence

Unit of measurement

Panel country

0.10

M2

Pmax

0.59

Watts

?NOCT

1.16

%

Graph 1

Graph 2

Discussions

The photocurrent developed by a photovoltaic cell is dependent on the strength of the light incident on it and on the wavelength of the incident visible radiation. Therefore, the strength and wavelength of the unreal visible radiation beginning affected the consequence, as a different and more realistic consequence would hold been obtained if the light beginning was different or the Sun. Furthermore, changing the panel temperature besides consequences in alterations in the end product electromotive force of the solar panel. On the efficiency of both the polycrystalline panel and formless panel, it was observed that the polycrystalline solar panel has a better efficiency than that of the formless panel which is in conformity with established theories.

It can be inferred from the consequences obtained that the estimated unfastened circuit electromotive force when the panel was hot, Vo c @ hot_est, is somewhat higher than the existent ( measured ) unfastened circuit electromotive force, Vo c @ hot. Besides, the estimated cell temperature at hot status, Tc @ est, is lower than the measured cell temperature, Tc @ hot, , by 12.2oC. The estimated maximal power at ambient, Pmax @ amb_est, is besides lower than the measured maximal power at ambient, Pmax @ amb_meas. This means that the panel gets more power out when it is cold hence, more efficient.

Furthermore, for the experiment to be improved, a more realistic visible radiation beginning should be used in topographic point of the present beginning in usage.

The possible beginning of mistake in the experiment comes mostly from the undependability of the light beginning used as its beams were frequently disrupted by motion around its way.

Finally, the intent the Fill Factor ( FF ) is that it is used to work out the maximal power of the system.

Decision

This experiment has shown that the public presentation of a photovoltaic cell is truly dependent on the strength of the light incident on it and its wavelength. It besides has been able to demo that the polycrystalline photovoltaic cells are more efficient than the formless cells ( regardless of possible beginnings of mistake that exist, which affected their efficiencies ) .

With improved efficiency, the polycrystalline solar panel can be yet another beginning of presenting clean and sustainable energy to mankind and the environment.