Renewable Energy Principles Lab 2

Renewable Energy Principles 301/603

Laboratory 2B

Name, Student Number:

Bruna S. Boneberg, 17356020; Darlen P. Lovi, 16718357;

David Joynes, 16150124; Wint Wah Aung, 15448912.

Title of the experiment: Study of Electrical Characteristics of 1-Axis

Tracking Monocrystalline PV Arrays.

Laboratory group: Wed 1400-1700

Laboratory supervisor: Tahoura Hosseinimehr

Date performed: 20/03/2014

Due date: 03/04/2014

Date submitted: 03/04/2014

I hereby declare that this report is entirely my own work and has not been copied from any

other student or past student.

Student signature: --------------------------------------------------------------

2

Study of Electrical Characteristics of 1-Axis

Tracking Monocrystalline PV Arrays.

1. Introduction

A mono-crystalline photovoltaic (PV) collector is composed of many single crystal

silicon PV cells. These are made from wafers of silicon, which have been purposely cut into

quadratic cells from silicon ingots and combined to form a PV module. Mono-crystalline PV

module portrays uniform characteristics and can have commercial efficiencies of up to 85%.

The PV modules can be connected in series or parallel (depending on the preference of the

user) to form arrays.

It is often assumed that a PV array may be installed fixed to a surface and pointing in

one direction considering the financial costs. However, technology has improved to the extent

whereby there are possible solar tracking racks which the collector may be installed on. This

provides the collector with the advantage of tracking the movement of the sun throughout the

day. It increases the insolation on the surface of the photovoltaic (PV) array, and hence,

maximizing its power output after the conversion of solar energy to electrical energy.

A solar tracking axis may be of 1-Axis or Two-Axis configurations. A single axis

configuration has the ability to track the sun along a single plane to the north and the south.

On the other hand, a two-axis tracking has more advantage than the 1-axis system as it can

track the movement of the sun also to the east and the west. The latter tracking system

produces a power output greater than the 1-axis.

The experiment carried out in Lab 2B at the GEEP lab gives an insight to the electrical

characteristics of a 1-axis tracking mono-crystalline PV array. The PV array is composed of 8

modules each at 190W/36.6V/5.2A, on a single-axis tracker. There are two parts to the

experiment, and the results obtained will be used to identify and discuss the characteristics in

this report. The lab manual was used to complete the experiments.

3

2. Aim and objectives

The aim of laboratory 2B is to analyse the electrical characteristics of a 1-axis tracking

mono-crystalline PV array.

The objectives in this experiment are:

To observe and analyze the effects of tracking on insolation on the collector;

To observe and compare the changes of insolation on the collector at varying

positions;

To analyze the I-V and the P-V characteristics of a single module at highest

and lowest insolation;

To analyze the I-V and the P-V characteristics of two (2) and three (3)

modules in parallel whilst facing the direction of the highest insolation.

3. Method

The equipment utilized were:

Meter for tilt angle measurement (Inclinometer)

Compass

Optical thermometer

GEEP Client TS2

The laboratory 2B test was conducted using the GEEP Client Teaching Station 2. The 8

modules which are mounted in the tracking system are connected in series and they are

controlled at the Junction box via the switches. Since the modules are in series connection,

the optimum voltage attained from the array is equal to the open circuit voltage of each

module which is 36.6V. The tilt angle of the axis of the tracker was maintained at the local

latitude angle of 32 degrees facing north for polar mounting, throughout the experiment. The

experiment had two parts to it.

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3.1. Part 1: Effect of tracking on Insolation on the Collector

The switch on the tracker control panel was turned to manual mode and the PV array

was made to rotate towards the direction of the sun. Then the analog pyranometer was

placed on the frame of the array to record the insolation on the connected modules during

the rotation. At the highest insolation, the Sunny sensor insolation and the insolation on

the horizontal plane recorded by the weather monitor were captured using the snapshot

view of the GEEP Client. Also, the two angles y and x and the distance, as shown in the

Figure.1, were measured and recorded using the inclinometer with the assumption that the

x and the y axis of the reference corner are parallel and normal to the True North. The

procedure was repeated for 5 other positions with 2 east positions and 2 west positions of

which one measured position corresponded to the modules facing north.

Figure 1 Calculate a Perpendicular to the Plane. (Lab 2 Theory document)

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3.2. Part 2: Measurement of I-V and P-V Characteristics of 1 Module

In part 2 of the experiment there were 4 different tests conducted:

3.2.1. One Module with Highest Insolation

Figure 2 Teaching Station 2 with Labelled Switches and Breakers

For initial settings, the switches and breakers on the TS2 panel were switched as

shown below:

OFF - TS2-CB1, TS2-CB2, TS2-SS2, TS2-SS3, TS2-224

ON TS2-CBE2

In this test, the capacitor bank replaced the TS2 battery bank. Through the

waveform view the voltage of the capacitor was monitored. The capacitor bank was

discharged by switching TS2-SS4 off and pressing the green button on the capacitor

bank. The zero reading on the monitor (waveform view) implied that there was no more

charge left in the capacitor. Once the zero voltage was achieved, the switch on the

junction box was set to one module and the tracker to the angle of highest insolation

achieved by the Sunny Sensor.

6

In order to capture the capacitor transient from the Waveform view, TS2_SHNT

1 and TS2_V2 were selected to display the result on GEEP Client. They represented the

measured current and voltage. After that, the green button was pressed for 5 seconds

and then TS2_SS4 was switched to bypass for two seconds only. The transient

appeared and the data was exported to excel. At times when the transient was not

captured, the capacitor had to be discharged and would start again.

The process was repeated for the three tests below. The junction box was visited

three times while working on part 2 (a, c and d) to adjust the switch (under supervision)

as required.

3.2.2. One Module with Lowest Insolation.

The procedure was similar to the above however the same module was rotated to

receive the lowest insolation.

3.2.3. Two Modules with Highest Insolation.

The 2 modules were connected in parallel via the junction box and made to face

the direction of the highest insolation. The procedure in 2 (a) was repeated.

3.2.4. Three Modules with Highest Insolation.

Lastly, 3 modules were also connected in parallel via the junction box and made

to face the direction of the highest insolation. The procedure in 2 (a) was repeated.

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4. Results

4.1. Part 1 - Effect of Tracking on Insolation on the Collector

Table 1 - Data for Part 1

Insolation y () x() Comment

940 18.9 11.9 Highest

780 18.6 8.4 East1

845 18.2 3.5 East2

928 18.6 7.9 West1

945 18.4 18.8 West2

4.1.1. Question 1

Date = 19 March 2014, n=78, Time = 2:00pm, L = -32

H t x = (12 14) x 15 = -30

= 23.45sin ((360/365) * (78 81))

= -

sin = cosLcoscosH + sinLsin

= cos(-32)cos(-1.21048)cos(-30) + sin(-32)sin(-1.21048)

= sin-1[cos(-32)cos(-1.21048)cos(-30) + sin(-32)sin(-1.21048)]

=

s = sin-1 [ cossinH / cos = cos(-1.21048)sin(-30) / cos(48.1988)]

= - ,228.5874

cos(-30) = 0.866 > tan(-1.21048) / tan(-32), Therefore

s = -

= 90 + = 90 48.1988 1.21048

= 40.59072

c = -

8

Table 2 Measurements recorded for Part 1 of Lab

Position IntrSollar (W/m2) y () y() Sol Rad (W/m

2) Tilt Angle () Ratio

west(2) 994 18.4 18.8 606 24.2208 1.64026

highest 1032 18.9 11.9 622 20.8349 1.65916

east(1) 868 18.6 8.4 617 19.0197 1.40681

west(1) 932 18.6 7.9 610 18.8267 1.52787

east(2) 893 18.2 3.5 613 17.3425 1.45677

The position of the highest insolation can be obtained by adjusting the switch

manually. The measured values of x and y were 9 and 9 respectively

From the datasheet for the PV2 module the dimensions are 1580 x 808 (mm) and

the 2 x 4 array contains 8 modules meaning dx is 3.16m and dy is 3.232m.

For P (in the direction of the positive y axis),

b= 3.05 , c = 0.66

And for Q (in the direction of the positive x axis)

d= 2.98, f = 1.02

= 32.3

= -32.3

9

The collector altitude angle

= 53.09

The measured tilt angle for when the PV modules received the maximum

insolation is then

effective = 90 +

= 90 53.09 + (-1.21048) = 35.69

The collector azimuth angle (-35.69) for maximum insolation is also less than the

calculated suns azimuth angle (-48.5874) which indicates the PV array is facing a

more north-west direction to receive maximum insolation.

The incidence angle of direct beam on the PV modules

cos = coscos(s - c)sin + sincos

= cos(48.19)cos(-48.5874 (-32.3))sin(35.69) + sin(48.19)cos(35.69)

= 0.978

= 11.84

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4.1.2. Question 2

Figure 3 Plot of Insolation recorded on PV Modules for Monocrystalline Array

The main reason for the difference between sunny sensor and weather station

monitor recorded insolation values is due to the weather station monitor mounted

parallel to the horizontal plane The suns rays will never be directly overhead which is

required if the collector is on the horizontal plane and to receive the best possible

insolation. From the graph in figure 2, the sunny sensor will receive greater insolation

as the 1-axis tracking PV array rotates throughout the day. The time period of the day

must also be taken into consideration where the measurements were recorded just after

solar noon when the sun is the highest in the northern sky. Therefore appropriately

tilted modules will have a higher chance for the suns rays to strike the collector normal

to the surface which results in a greater amount of insolation than horizontally tilted

modules at this location.

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4.1.3. Question 3

In order to identify how much more insolation would be received by the 1-axis

polar mount tracking array compared to a fixed PV north facing array.

For 1-axis polar mounting:

Insolation on collector, Ic=IBC+IDC+IRC

Where:

Beam radiation, IB=A*e-km

Beam component of radiation, IBC=IB*cos

Diffuse component, IDC=C*IB[ + /2]

Reflected Component, IRC * IBH+IDH)*[(1-cos / ]

Where IBH=IB*sin and IDH=C*IB

Apparent extraterrestrial flux, A=1160+75*sin[(360/365)*(n-275)] W/m2

Optical depth, k=0.174+0.035*sin[(360/365)*(n-100)]

Air-mass ratio, m /sin

C=0.095+0.04*sin[(360/365)*(n-100)

Data: c = 68.06, = 20.72 , c = . , s = - 8. 8 , = 22.68 , n=78

Total amount of radiation calculated = 1009.273 W/m

Fixed PV north facing array:

Insolation on collector, Ic=IBC+IDC+IRC

Ic=Ae-km[cos*cos(s- c)*sin+sin*cos+C((1-cos /2)+* sin+C *((1-

cos / ]

Data: c = 68.06 , = 20.772, c = 0 , s = - 8. 8 , = 6. 8 , n=78

Total amount of radiation calculated = 1003.753 W/m

Percentage insolation received = (1009.273 1003.753) / 1009 = 0.55 %

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4.2. Part 2: Measurement of I-V and P-V Characteristics of 1 Module

Figure 4 Excel Data for I-V and P-V Characteristics

-2

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50

Cu

rren

t (A

)

Voltage (V)

PART A - Highest 1 mod

PART B - Lowest 1 mod

PART C - Highest 2 mod

PART D - Highest 3 mod

Figure 5 Current vs Voltage of 1-Axis Tracking Monocrystalline Array

Figure 6 Power vs Voltage of 1-Axis Tracking Monocrystalline Array

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4.2.1. Question 1

The output current increases with increasing number of modules in parallel. The

initial current (short circuit current) of three modules in parallel is approximately three

times the value of the single module short circuit current. The short circuit current for 2

modules in parallel is approximately twice the value of the single module short circuit

current. We know that each module is essentially an independent current source and

each module is essentially equal. Hence:

I1 I2 I3

And from our previous studies we know that current sources in parallel sum

together. Hence;

1 module parallel: IT = I1

2 module parallel: IT = I1 + I2 = I1 + I1 = 2I1

3 module parallel: IT = I1 + I2 + I3 = I1 + I1 + I1 = 3I1

The above equations confirm what was seen in our results.

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4.2.2. Question 2

From the power against voltage graph we can determine the maximum power for

each test and the voltage at which this occurs.

Figure 7 Identifying Maximum Power for Each Configuration

Power vs Voltage of 1-Axis Tracking Monocrystalline Array

We can then use the voltage found above to mark on the current/voltage graph

where the maximum power occurs and the current at which this power occurs.

Figure 8 Identifying the Current of Maximum Power for Each Configuration

Current vs Voltage of 1-Axis Tracking Monocrystalline PV Array

15

The maximum power and the voltage and current at which it occurs can be

summarised in the table below:

Table 3 - Summary for Maximum Power Output

Configuration Maximum Power (W) Current (A) Voltage (V)

1 - Full Insolation 140.6 4.71 29.84

1 Low Insolation 137.4 4.50 30.57

2 parallel Full Insolation 252.8 8.47 28.86

3 parallel Full Insolation 364.9 12.04 30.30

4.2.3. Question 3

From the data sheet we can find the area for different number of modules in

parallel. The insolation values are the highest and lowest values from part one of the

experiment that were recorded. From these values and taking the voltage and current

from the maximum power, the average energy conversion efficiency can be determined.

Table 4 Area for Different Number of Modules

Area 1 Modules 1.27664 m2



Table 5 Calculating Conversion Efficiency

Configuration Maximum

Power (V,I) S Area

1 - Full

Insolation (29.84,4.71) 1032 1.27664 m

2 0.10667

1 Low

Insolation (30.57,4.50) 928 1.27664 m

2 0.11611

2 parallel Full

Insolation (28.86,8.47) 871 2.55328 m

2 0.10991

3 parallel Full

Insolation (30.30,12.04) 871 3.82992 m

2 0.10936

Average Conversion Efficiency 0.1105375

Looking at the data sheet for the PV cell, it is stated that the cell has a maximum

efficiency of 14.4%. This indicates that our efficiency 11.054% is quite accurate.

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4.2.4. Question 4

Voc is calculated by finding the largest output voltage from the current/voltage

graph. Isc is calculated by taking the values corresponding to the initial flat section of

the current voltage graph and finding the average value. An example of this process is

shown below.

Figure 9 - Example Calculation for Isc

As can be seen in the table below, the average fill factor Value was calculated to

be 70.6%. From this we can assume that our results were accurate as a typical fill factor

for a crystalline silicon PV cell is around 70-75%.

Table 6 Calculating Fill Factor

Configuration Maximum

Power (W)

Voc

(V)

Isc

(A) FF =

1 - Full Insolation 140.6 40.175 4.75 73.67%

1 Low Insolation 137.4 40.04 4.72 72.70%

2 parallel Full Insolation 252.8 40.15 9.10 69.19%

3 parallel Full Insolation 364.9 40.50 13.48 66.84%

Average Fill Factor 70.6%

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4.2.5. Question 5

Table 7 Calculating % Error in Isc

Configuration Measured Isc Theoretical Isc % error

1 - Full Insolation 4.75 5.62 15.48%

1 Low Insolation 4.72 5.62 16.01%

2 parallel Full Insolation 9.10 11.24 19.04%


Average % Error in Short Circuit Current 17.74%

Table 8 - Calculating % Error in Voc

Configuration Measured Voc Theoretical Voc % error

1 - Full Insolation 40.175 45.2 11.12%

1 Low Insolation 40.04 45.2 11.42%



Average % Error in Open Voltage Circuit 11.03%

Table 9 Calculating Temperature of the Module

Configuration Ambient

Temperature S NOCT

1 - Full Insolation 29.111111 0.662 45 48.55

1 Low Insolation 28.722221 0.592 45 47.22

2 Parallel Full Insolation 27.888889 0.538 45 44.70

3 Parallel Full Insolation 27.888889 0.538 45 44.70

Average Cell Temperature 46.28

Table 10 Calculating % Error in Temperature of Module

Configuration

Tcell Theoretical % Error

1 - Full

Insolation 48.55 40.13 17.32%

1 Low

Insolation 47.22 39.03 17.34%

2 Parallel Full

Insolation 44.70 40.03 10.45%

3 Parallel Full

Insolation 44.70 40.03 10.45%

Average % Error Cell Temperature 13.89%

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Table 11 - % Error Maximum Power

Configuration (V,I,TCell)

Measured

Pmax %Error

1 - Full

Insolation 29.84, 4.71, 48.55 123.99 140.6 11.81%

1 Low

Insolation 30.57, 4.50, 47.22 122.28 137.4 11.04%

2 Parallel Full

Insolation 28.86, 8.47, 44.70 220.37 252.8 12.83%

3 Parallel Full

Insolation 30.30, 12.04, 44.70 328.87 364.9 9.97%

Average % Error 11.41%

Table 12 Calculating % Error In Energy Conversion Efficiency

Configuration Measured, Theorical % Error

1 - Full Insolation 0.10667 0.1414 24.54%

1 Low Insolation 0.11611 0.1414 17.89%

2 Parallel Full Insolation 0.10991 0.1414 22.27%

3 Parallel Full Insolation 0.10936 0.1414 22.70%

Average % Error 21.85%

4.2.6. Question 6

Following the steps outlined in the theory, we can determine the parallel and

series resistances of the PV module. As can be seen below, adding a trend line to the I-

V graph for the single module at lowest insolation, we can more accurately determine

suitable points. Taking 3 points will allow the results to be averaged for a more

accurate calculated value for resistances. For simplicity, we will take points for current

values of 1,2 and 3 amps.

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Figure 10 Current vs Voltage of Lowest 1 Mod

1-Axis Tracking Monocrystalline PV Array

From previous questions, Isc2 = 4.72.

Table 13 Variation of I

Point (V2,I2) I Isc2 I2

P1 (35.2,3) 1.72

P2 (37.1,2) 2.72

P3 (39.1,1) 3.72

Now we must take the I values and use them to determine the I values on the

I-V graph of 1 module at full insolation. The Isc1 for this graph is 4.75 as show

previously.

Table 14 Values of I1

I I1 = Isc1 - I

1.72 3.03

2.72 2.03

3.72 1.03

We can determine the V1 values by plot the I1 currents on the I-V graph of 1

module at full insolation.

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Figure 11 Current vs Voltage of Highest 1 mod

1-Axis Tracking Monocrystalline PV Array

Using the points above we can now calculate series resistance Rs.

Table 15 Series Resistance

Point (V1,I1) Point (V2,I2)

P1 (35.7,3.03) P1 (35.2,3) 0.03 6 6

P2 (37.5,2.03) P2 (37.1,2) 0.03 3 33

P3 (39.2,1.03) P3 (38.8,1) 0.03 3 33

Average Series Resistance

To calculate the parallel resistance we need to determine the slope of the initial

flat section of the I-V graph. To do this we will find the average values of the flat

section closest to the where the curve starts to decrease. For simplicity we will find the

average current for a voltage of 25, as after the 25 volts the I-V graph appears to start

decreasing. This can be seen below.

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Figure 12 Average of Current

Table 16 Parallel Resistance

Point (V1,I1) Isc

1 Module Full Insolation (25.1,4.69) 4.75 33

1 Module Low Insolation (25.0,4.65) 4.72 3

Average Parallel Resistance 3

Theoretically the series resistance is neglible compared to the parallel shunt

resistance. Our results support this with the series resistance being only 3.7% of the

parallel resistance value. The circuit with these parameters can be seen below.

Figure 13 Equivalent Circuit

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4.2.7. Question 7

Figure 14 Average of Pmax

Table 17 Extra Power Generated

Point (V1,I1) Measured Pmax Average Pmax Difference

Pmax Measured - Pmax Theorical

1 Module Full Insolation

(25.1,4.69) 140.6 132.94 7.06

1 Module Low Insolation

(25.0,4.65) 137.4 130.33 7.07

Average of Extra Power at maximum power point 7.065

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5. Discussion

From the experimental results, there were some great variations in expected results and

there were others which proved relevant to the theories. It is important to note that this

experiment like any experiment is prone to inaccuracies.

In part 4.1, the effect of solar tracking on the collector was examined. From the

recorded data, the highest insolation was 940 W/m2 and it was achieved at y=18.9 and

x=11.9. As the tracking continued, different insolation values were recorded by the

pyranometer as shown in Figure 3. As the collecter was tilted towards the east, the insolation

on the collector decreased. In contrast, the insolation increased towards the east. The effect of

tracking increases the solar radiation on the surface of the collector. Hence, the output power

should increase proportionally.

The altitude angle and the azimuth angle were calculated to be -1.21 and -48.59

respectively. Effective tilt angle of the collector was 40.69 and its azimuth angle was equal

to that of the suns, at the highest insolation When comparing the effective tilt with that of

that measured, it showed that the measured value was 50% less than the calculated value.

Also, the incidence angle of the beam was calculated to be 11.83.

From the analysis of the insolation and ratio against the tilt angle, there are two facts to

state. Firstly, the weather monitor is mounted parallel to the horizontal plane and therefore it

results (Solar Rad) indicates that there is minimal variation of insolation on the horizontal

module. Secondly, the sunny sensor it attached to the rotating PV array therefore it can

measure the insolation variation when the collector is tracking the sun. It is recommended

that modules be installed with a tilted angle at the GEEP laboratory to improve insolation on

the collector.

By using the results, the percentage of surplus insolation (that would be received by a

1-axis polar mount tracking array) was compared between when positioned to receive the

highest and the lowest insolation. It has been found that the highest insolation was

1009.273W/m2, and the least was 1003.753W/m

2. The percentage surplus insolation was only

0.55%.

24

In part 4.2, the transients for the single-module to the 3-parallel modules shows

characteristcs similar to the theories for photovoltaic modules. Our results successfully prove

that the total current supplied for modules conneted in parallel is equal to the sum of the

currents passing through each parallel string. It is also important to note that adding modules

in series will increase voltage for a given current.

Also, the maximum power points along plotted curves were determined through the

method of hill climbing on the knee of the P-V curve. It was observed from the results that

the 3-modules in parallel could produce the highest insolation. This is possible as the output

power of the module is directly proportional to the current produced. This is an important

finding as real life solar farms also have modules connected in parallel to increase output

power. Another benefit is that modules that are shaded in parallel produce less current but do

not affect the other modules. Where as a shaded module in series will reduce the total current

of the whole string.

From calculations, results shows that the collector has an efficiency of 11.05% which is

a slightly reduced figure to the 14.14% expected efficiency of the monocrystalline module.

This means power is being lost in the module. A likely cause of this is that some sunlight that

has enough energy to jump electrons over the bandgap of the semiconductor are being

absorbed and turned into heat instead. Another cause could be the air mass ratio being

slightly different to the standard testing conditions of AM 1.5 and the parallel resistance and

series resistane which are discussed later.

The average fill factor was only 70.6% which is within the typical range of 70-75% for

crystalline silicon solar collectors. This indicates that our results are accurate in determining

the fill factor. The fill factor is a ratio of the power output of the module(s) at the maximum

power point on the P-V curve and the resulting product of the open circuit voltage and short-

circuit current, and hence, characterizes the performance of the module.

25

As we can see from the table for % errors in cell temperature, as the temperature has

decreased so has cell temperature. As the Cell temperature decreases our results show that Isc

% error has increased (Isc is not as large as it should be). This confirms our knowledge that

current decreases with decreasing temperature. This is a significant finding as it means all our

results that were taken last (3 module in parallel) and involve calculations using the current

will also have increasing errors. What we learn from this is that the experiment should be

performed fast as possible as the decresing temperature throughout the day starts to affect the

efficiency of the module.

We can also see that this decrease in cell temperature has slightly increased Voc. Which

in turn slightly reduces the error between measured and theoretical Voc values.

The average error in maximum power is 11.41%. This is very similar to the efficiency

error of 11.05%. This is to be expected as the efficiency is derived from the maximum power.

The reasons for error in the power are the same as the reasons for errors in the efficiency that

were discussed earlier.

In theory, the series resistance is very small and it is as demonstrated by the results as

being only 3.7% of the parallel resistance at . The parallel resistance is large at

3 It is a shunt resistance and the current caused by the reverse biased mode of the

diode (when Isc=0) is diverted to it to minimize damage. However, it contributes to the losses

in the output voltage as the current is dissipated through it when the resistance is not large

enough. This is most evident when the insolation is the lowest as most of the light generated

current would flow through the shunt resistance.

However, our results do not show this as the insolation values for 2 and 3 modules in

parallel at highest insolation are lower than the lowest insolation values. This has arisen from

taking too long to complete the experiment and further emphasizes the need to perform the

experiment quickly.

26

Another finding was the output power difference between 1 module at highest and at

lowest insolation was only 7.065W. From the I-V characteristic graphs, the two plots are

practically ontop of each other. This indicates that while the 1 module at lowest insolation

had lower power than 1 module at highest insolation, it is very unlikely that this was infact

the absolute lowest insolation level. In future we should ensure we are recording the actual

lowest insolation value. This would push the two plots on the I-V graphs further apart. This

would make calculating the series and parallel resistances much easier as the points would

not be practically on top of each other and the values calculated would be more accurate.

The limitations that may have contributed to inaccuracies in the results would be human

error in taking measurements and recording them when using the equipments or the GEEP

Client. There were times when the procedures were repeated due to communication

breakdown and reflex errors in exporting data. Also, the non ideal air mass ratio needs to be

taken into account when perform calculations. As well as the affect on the operation of the

module due to decreasing temperature.

By exploring this aspects of the monocrystalline PV array, it broadens the knowledge

on the characteristic of power systems and its components. It also gives an insight to the

needs of making comparisons of theoretical data with the practical data to determine the

discrepancies between them. In that way the efficiency of the equipment may be determined.

Then different approaches may be applied to try improve the efficiency to near optimum,

which in turn reduces the system losses.

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6. Conclusion

Throughout the experiment the results recorded were well within reasonable variance of

the theoretical expected values which indicates that the laws and rules that were being

investigated hold true. This is demonstrated in the percentage error calculations which were

all between 10-20%. Some of our confirmed findings include :

1-axis tracking can be manually adjusted to different tilt angles along the north-

south axis. It has a mechanism which allows the collector to track the sun from

east to west.

A PV array with a tracking system recieves large amounts of insolation on the

collector surface compared to a horizontal or fixed PV array.

Solar tracking gives the PV collectors the advantage of maximizing its daily

power output.

Increasing modules in parallel increases output power

Total current for modules in parallel is equal to the sum of the currents in each

branch

Decreasing temperature decreases current and slightly increases Voc

The series resistance is neglible compared to the parallel resistance

Higher insolation means higher power

The tested module has a stated maximum efficiency but in realilty the module

will not always operate at this efficiency

To improve the accuracy of our results in the future, we should work faster to ensure

that the results taken are from a small section of the day. As our results indicated an increase

in error for results taken later in the day. We should also ensure that the lowest insolation is

the actual lowest value possible. This would of allowed for easier calculations and improved

accuracy.

28

7. References

G M Masters, Renewable and Efficient Electric Power Systems, 1st ed. Hoboken, NJ:

John Wiley & Sons, 2004.

REP 603 Lab 2B Manual, Renewable Energy Principles 603, Student Blackboard 2014

REP 603 Lab 2B Theory Document, Renewable Energy Principles 603, Student Blackboard

2014

REP 603 Lecture Notes, Renewable Energy Principles 603, Student Blackboard 2014

Suntech Power, STP 90S- /Ad+, PDF, Suntech: Revised 0

Documents

Renewable Energy Principles Lab 2