Solar Cell Report Mendoza-Pineres

8/10/2019 Solar Cell Report Mendoza-Pineres

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ENERGY PRACTICE

REPORT SOSE 2014Experiment 1: Solar Cells

Diego Felipe Mendoza Osorio;Luis Daniel Pieres [email protected]; [email protected]


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Contents

1. Introduction................................................................................................................................2

2. Experimental Set-up..................................................................................................................2

3. Results and Discussion.............................................................................................................4

3.1 Basic Circuits: Parallel Connection. ..................................................................................4

3.2 Basic Circuits: Series Connection. ....................................................................................5

3.3 Basic Circuits: Shading Influence......................................................................................7

3.4 Incident Angle. ...................................................................................................................9

3.5 Temperature Properties...................................................................................................10


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1. Introduction

Since their development in 1954, when solar cells were produced by Bell laboratories, this

technology has experience a strong increase in efficiency and applications. Nowadays

with efficiencies reaching 25 % under laboratory conditions, silicon solar cells became areliable renewable energy source. Although the moderate costs for producing solar cells,

this technology offers the highest versatility among other energy technologies, mainly due

to the modularity. The generator sizes could be realized from a milliwatt range for pocket

calculators for example, up to the megawatt range for public electricity supply.

In this practice the main objective is to have a better understanding of the influence of

different operating conditions on the parameters of solar cells. In a first step, the

arrangement of the solar cells (series and parallel connection) was modified and

properties such as short circuit current, open circuit voltage and maximum power point

(MPP) were measured. Secondly, with a fixed set-up of solar cells in parallel, the behavior

of the parameters was analyzed adjusting the incident angle between the light source andthe cells arrangement. Finally, a temperature dependency test of current, voltage and

power on a single solar cell was performed.

2. Experimental Set-up

There were 3 different setups for this experiment. In the first set-up, solar cells connected

in series with different combinations (2, 4, 6, 8 cells) were tested to get the characteristic

curves of each setup. In the same way were tested the same solar ce lls but connected inparallel with the different combinations (2, 4, 6, 8 cells). In the figure 1 and 2, the electric

diagrams of the setups are shown.

DC DC DC DC DC DC DCDC

A

V

DC

8

6

4

2

L

Figure 1. Series Connection Configuration.


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DC DC DC DC DC DC DCDC

A

VL

DC

2 4 6 8

Figure 2. Parallel Connection Configuration.

The Ammeter, Voltmeter and load were incorporated in the testing device, therefore they

were not able to be manipulated in any sort of way. The results were acquired by software

in a .Lab file.

For the second set up, an arrangement of 8 cell in parallel was used to perform an incident

angle test. In the test bench, the board that embeds the solar cell arrangement could be

turned to a fixed angle as can be observed in the figure 3.

0 1 0 2 0 3 0 4 0

50

60

70

80

90

Figure 3. Test Bench for Incident Angle Measurement.


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The circuit configuration used to test the system was the same as shown in figure 2, taking

into account that the whole set of solar cells were plugged (8 cells).

For the third set up, the test bench was changed in order to probe the temperature

dependency of a single solar cell. The temperature on the cell was measured andcontrolled electronically. Different cell temperatures were achieved to get the

characteristic curves. The same software and file extension were obtained as a result from

each test.

3. Results and Discussion

3.1 Basic Circuits: Parallel Connection.

From the figure 4, it could be observed that the short circuit current is directly proportional

to the number of cells connected in parallel, while the open circuit voltage remains

unchanged. The maximum power point, indicated as black dots in the graph, is slightly

shifted to the left side (low voltage side) but highly shifted upwards (high current side),

showing a directly proportional power to the number of cells connected in parallel.

Figure 4.I-V Characteristic curves for different solar cell parallel distributions (arrangement).

0

0,1

0,2

0,3

0,4

0,5

0,6

0 0,1 0,2 0,3 0,4 0,5 0,6

Current(A)

Voltage (V)

I-V Characteristic curve

2 cells in parallel

4 Cells in parallel

6 Cells in parallel

8 Cells in parallel


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Figure 5.P-V Characterist ic curves for different solar cell parallel distributions (arrangement).

As a power increase was observed in the figure 4, in the P-V curves could be verified.

Higher maximum power could be obtained with lesser voltages. Although this setup

keeps the voltage constant in a low level, higher currents could be achieved, increasing

distribution (ohmic) losses.

3.2 Basic Circuits: Series Connection.

The figure 6 shows the I-V characteristics of 2, 4, 6 and 8 solar cells connected in series.

As it is expected from the literature, the voltage of the system increases with an increasing

number of cells connected in series, starting from an open circuit voltage of 1.1 V for 2

cells (0.55 V per solar cell) in series up to a of nearly 4.4 V for 8 solar cells with the

same configuration. As it could be seen there is only and slightly change in the short circuit

current for the different connections from 0.048 A to 0.05 A respectively, it is due to the

fact that in a series system the current remains constant independent from the voltage ofthe elements connected to this.

0

20

40

60

80

100

120

140

160

0 0,1 0,2 0,3 0,4 0,5 0,6

Power(mW)

Voltage (V)

P-V Characteristic Curves

2 Parallel Cells

4 Parallel Cells

6 Parallel Cells

8 Parallel Cells


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Figure 6.I-V Characteristics for Solar cells series connection

The figure 7 displays the P-V characteristic curve for 2, 4, 6 and 8 solar cells connected

in series with the maximum power point (MPP) pointed with a marker. It is noticed that the

power of the system increases with an increasing number of solar cells connected inseries. The MPP is shifted to the right of the graph and the increase of power is mainly

due to an increase in voltage with each new cell connected, hence the current remains

almost constant. The maximum power output for 2 cells connected in series was about

37.5 mW, this value increases according to the number of cells in the system, up to a

value of about 150.7 mW for 8 solar cells in series.

0

0,01

0,02

0,03

0,04

0,05

0,06

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

CurrentI(A)

Voltage (V)

I-V Curve Solar Cells Series Connection

2 Solar Cells 4 Solar Cells 6 Solar Cells 8 Solar Cells


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Figure 7.Power output for solar cells in series connection

3.3 Basic Circuits: Shading Influence.

As part of the experiment, it was intended to show the shading behavior of a solar cell.

The figure 8 depicts the I-V Characteristic curves for 8 solar cells connected in series and

the same characteristics for the 8 solar cells with one of them shaded. As it could be

noticed, the shading strongly influences the power output of the system, due to a critical

decay in the short circuit current of the system, it is reduced nearly 5 times from 0.05 A to

0.008 A. The current is more sensitive to changes in series connections, in this case the

whole system takes the minimum current of all the solar cells connected to it, that is, the

current of the solar cell shaded. The voltage of the array is just slightly reduced and not

highly affected by the shading condition.

150,69

109,24

73,61

37,48

0

20

40

60

80

100

120

140

160

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

Power(mW)

Voltage (V)

P-V Curve Solar cells Series Connection

2 sollar cells 4 Sollar Cells 6 Solar Cells 8 Solar Cells


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Figure 8. I-V Characteristics for 8 Solar cells series with and without shading.

The figure 9 shows the difference between the I-V curves of the parallel setup uncovered

and the parallel setup with one cell covered. As displayed in the figure, the power is slightlydecreased under the presence of shadowing. If the result of this setup is compared to the

result of shadowing on series connected cells, the loss of power is considerably lower in

the parallel setup, due to the fact that in a parallel setup the shadowed cell is not dominant

in the behavior of the system and thus, assuming a fully covered cell, the power delivered

by the system is the same as if one cell is disconnected (Open circuit).

0

0,01

0,02

0,03

0,04

0,05

0,06

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

CurrentI(A)

Voltage (V)

I -V Characte r ist ic Curve Covered Cell Serie s

One Cell covered Cells Uncovered


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Figure 9.I-V Characteristic curves of the 8-cells parallel setup under shading.

3.4 Incident Angle.

The aim of this procedure was to vary the angle of incidence of the light coming from the

halogen lamp on the system. The figure 10 displays the short circuit current against the

angle of inclination of the plate where the solar cells are connected. The 8 solar cells were

connected in parallel and the plate supporting them was tilted. It is expected to have a

maximum power output and a maximum current of a module when the sunlight reaches

the solar cells with an angle of 90, which is equivalent to 0 of inclination of the plate.

As it could be noticed, the short circuit current decays with an increasing angle of

inclination of the plate (decreasing angle of incidence). From the theory it is expected to

have a lower current output with lower angle of incidence. It could be explained because

the direct irradiation on the cells is reduced when the angle of incidence decreases, hencethe short circuit current, which is proportional to the irradiation will also drop.

0

0,1

0,2

0,3

0,4

0,5

0,6

0 0,1 0,2 0,3 0,4 0,5 0,6

Current(A)

Voltage (V)

I-V Characteristic curves under shading

8 Parallel Cells Uncovered

8 Parallel Cells-1CellCovered


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Figure 10.Comparison of short circuit current against inclination angle.

3.5 Temperature Properties.

As it is shown in the figure 11, the Cells voltage is clearly dependent on the temperature

(from 0.45 V to 0.6 V) while the current is not so affected by the change of temperature

(from 0.060 A to 0.064 A). The Maximum power point was only shifted on the Voltage

component (P=I*V). A graph of the P-V characteristic curves is shown in the figure 12.

0

0,1

0,2

0,3

0,4

0,5

0,6

0 20 40 60 80 100

ShortcircuitcurrentIsc

(A)

Inclination Angle of the plate (degrees)

Short circuit current vs angle

Isc (A)


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Figure 11.I-V Characteristic Curves for variations on cells temperature.

Figure 12.P-V Characteristic Curves from a single solar cell under changes of temperature.

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7

Current(A)

Voltage (V)

I-V Characteristic Curves( Temperature Dependency)

10C

20C

15C

25C

30C

35C

40C

45C

50C

55C

60C

65C

70C

0

5

10

15

20

25

30

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7

Power(mW)

Voltage (V)

P-V Characteristic Curves (Temperature Dependency)

10C

20C

30C

40C

50C60C

70C


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It can be observed from the figure 13 that the maximum power point could be

approximated as a linear function of the temperature. From the results of the tests

measurements, several graphs could be drawn to show the temperature dependency of

the power, voltage and current. This charts are displayed in the figures 13, 14 and 15, and

the values were tabulated in the table 1.

Table 1. Characteristics of a Cell for temperature changes

Temp (C) Voc (V) Isc (A) Pmax (mW)

10 0,595 0,0639 23,895

15 0,5775 0,0624 22,44

20 0,5675 0,0604 21,371

25 0,555 0,0603 20,91

30 0,545 0,0613 20,46

35 0,5375 0,0608 19,92

40 0,5275 0,0619 19,46

45 0,5125 0,0625 19,09

50 0,4975 0,0623 18,15

55 0,4875 0,0634 17,25

60 0,48 0,0638 17,08

65 0,465 0,0634 16,14

70 0,4525 0,0638 15,65

Figure 13. Graph of the temperature dependency of the maximum power point.

y = -0,1259x + 24,406

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80

Power(mW)

Temperature (C)

Pmax Temperature dependency


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Figure 14.Graph of the temperature dependency of the shot circuit current.

Figure 15.Graph of the temperature dependency of the open circuit voltage.

y = 3E-05x + 0,061

0,06

0,0605

0,061

0,0615

0,062

0,0625

0,063

0,0635

0,064

0,0645

0 10 20 30 40 50 60 70 80

Current(A)

Temperature (C)

Isc Temperature dependency

y = -0,0023x + 0,6149

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0 10 20 30 40 50 60 70 80

Voltage(V)

Temperature (C)

Voc Temperature dependency


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Due to the fact that most of this variables are linear dependent on the temperature, the

typical temperature coefficients for each variable could be computed. Linear trendlines

were used to achieve a linear function that approximates the behavior of the variables.

From this trendlines equations, the Temperature coefficients were approximated as

follows:

= 0,1259

= 0,0023

= 3,0 10

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