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VALIDATING THE OPTIMUM TILT ANGLE FOR PV
MODULES IN THE HIGHVELD OF SOUTH AFRICA FOR
THE SUMMER SEASON
Motlatsi Cletus Lehloka
Department of Electrical and Mining Engineering, University of South Africa, Christiaan de Wet Road and
Pioneer Avenue, Florida, Roodeport, (South Africa).
E-mail: lehlomc@unisa.ac.za ORCID: https://orcid.org/0000-0002-0901-9731
Arthur James Swart
Department of Electrical, Electronic and Computer Engineering, Central University of Technology,
Bloemfontein, (South Africa).
E-mail: aswart@cut.ac.za ORCID: http://orcid.org/0000-0001-5906-2896
Pierre Eduard Hertzog
Department of Electrical, Electronic and Computer Engineering, Central University of Technology,
Bloemfontein, (South Africa).
E-mail: pertzog@cut.ac.za ORCID: http://orcid.org/0000-0002-3396-6050
Recepción:
21/01/2020
Aceptación:
03/04/2020
Publicación:
30/04/2020
Citación sugerida Suggested citation
Lehloka, M. C., Swart, A. J., y Hertzog, P. E. (2020). Validating the optimum tilt angle for PV modules in
the highveld of South Africa for the Summer season. 3C Tecnología. Glosas de innovación aplicadas a la pyme.
Edición Especial, Abril 2020, 137-157. http://doi.org/10.17993/3ctecno.2020.specialissue5.137-157
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ABSTRACT
Energy supply is a major problem in today’s world due to increase in demand, depleting
of fossil fuels and increase in global warming due to carbon emission. The need for an
alternate, overall ecient and environment-friendly energy system has ascended globally.
Photovoltaic (PV) systems can be used to harness solar energy that is considered to be one
of the most promising alternative energy sources. However, its eciency is aected not
only by varying environmental conditions but also by the installation of its PV modules.
The purpose of this paper is to empirically validate the optimum tilt for PV modules in the
Highveld of South Africa. Three xed-axis PV modules installed at optimum tilt angles of
Latitude minus 10°, Latitude, and Latitude plus 10° serve as the basis of this study. These
optimum tilt angles are utilised based on the recommendations by Heywood and Chinnery.
A key recommendation is that PV modules should be mounted at Latitude minus 10° for
the summertime period in the Highveld region of South Africa.
KEYWORDS
PV module, LabVIEW, Latitude, Tilt angles.
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1. INTRODUCTION
Solar photovoltaic (PV) systems are classied as a clean and renewable energy source
and therefore, they have been drawing more and more attention, especially in the eld of
electricity generation due to the shortage and pollution eects of fossil fuels. Solar energy
is one of the primary sources of clean, abundant and inexhaustible energy, that not only
provides alternative energy resources, but also improves environmental pollution. The use
of renewable energy resources to produce electricity is a rising trend in various countries
worldwide. This is because these energies do not produce the greenhouse gases; therefore,
do not become a destructive factor on the ozone layer and the environment. The eects that
fossil fuels have on the environment have led to scientists trying to nd more environmentally
friendly fuels and cleaner sources of energy (Yao et al., 2014; Lawless & Kärrfelt, 2018).
In order to maximise energy production from PV modules, the latter requires the use of
optimum tilt and orientation angle for the location of interest. Optimizing the output power
of any PV array or module requires a number of factors to be considered, including the tilt
angle, orientation angle and environmental conditions (Yadav & Chandel, 2013; Moghadam
et al., 2011). Before the introduction of solar tracking methods, xed PV modules were
positioned with a reasonable tilted angle based on the latitude of the location. A number
of studies have been carried out to nd the optimum tilt angles of PV modules in various
environments (Ferdaus et al., 2014; Moghadam & Deymeh, 2015).
Sunlight incidence angle varies throughout the year due to the rotation of the earth around
its own axis and its elliptical orbit. While sunlight falls to the earth with steep (high) angles
in summer in the Northern Hemisphere, it falls with shallow (low) angles in winter. Many
xed PV modules are not installed at the suggested tilt angle, for example, true North in
South Africa, thereby indicating a non- alignment to the maximum solar radiation available
for a given day (Karal et al., 2015; Swart & Hertzog, 2015). Furthermore, as the sun is
not a stationery object it is essential to install the xed PV modules at optimum tilt and
orientation angle for the location of interest. Climate change has also resulted in the rise of
atmospheric temperature and a modied pattern of precipitation and evapotranspiration,
which has directly led to alteration of regional hydrological cycles. Repetitive testing of key
variables associated with renewable energy systems under ever-changing environmental
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conditions must be maintained, to either strengthen or reconstruct previously published
literature in this eld. Repeated testing of any construct in research is just as necessary as it
reinforces knowledge, promotes validity and enables its successful use in other applications
(Hertzog & Swart, 2018a, 2018b).
The purpose of this paper is to empirically validate the optimum tilt for PV modules in the
Highveld of South Africa. The motive behind validating these angles is mainly to establish
if the recommendations by Heywood and Chinnery still holds truth in the Highveld of
South Africa under ever-changing environmental conditions that are related to climate
change. The paper will rstly provide a brief description of tilt angles, and then outline
the context of the research site. The experimental setup will then be explained, followed by
the research methodology. Quantitative data is then presented in a number of tables and
gures along with discussions.
2. LITERATURE STUDY
Ecient operation of PV modules depends on many factors, among which are the installation
angles. The optimum installation angles involve placing a xed PV module at an orientation
angle of 0˚ and changing the angle of tilt to Latitude minus 10˚, Latitude and Latitude
+10˚ respectively. These angles are derived from the Heywood and Chinnery equations of
Latitude for calculating tilt angles of PV modules in South Africa. The orientation angle is
dened as the angle between true South (or true North) and the projection of the normal of
the PV module to the horizontal plane. The tilt angle is dened as the angle between the PV
module surface and the horizontal plane (Swart & Hertzog, 2015). Figure 1 illustrates both
the orientation and tilt angle of PV modules. The PV modules should face “true north”
in the northern Hemisphere and “true south” in the southern Hemisphere (Kaldellis &
Zarakis, 2012; Chin, Babu, & McBride, 2011).
Many authors presented models to predict solar radiation received on inclined surfaces from
the typically measured global horizontal irradiance and diuse horizontal irradiance. While
the direct beam radiation on a tilted surface can be calculated using geometric relations,
the conversion for the diuse radiation is more complex and has been approached using
dierent models. Studies have been done in South Africa to determine the optimum angles
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of xed solar collectors, but these studies do have some limitations. Like other locations in
the world, results were based on mathematical models of solar resource, measured solar
data or both. Various other studies on the optimisation of tilt angles have considered the
eects of cloudiness, wind speed cooling, maximising radiation on at plate collectors,
Latitude, clearness index, day number and dierent geographical locations. In line with
many theoretical and experimental investigations on optimizing the output power of a PV
module by varying its tilt angle, it is essential to empirically validate the results.
Figure 1. The tilt and orientation angles of a PV module. Source: (Asowata, Swart, & Pienaar, 2012).
In 2013, a research study was conducted at the Vaal University of Technology (VUT)
(subsequently called the VUT study) to determine the xed PV module tilt angle for
optimum power yield throughout the year. A Latitude plus 10º angle was suggested. The
research was conducted in an area that was declared an ‘airshed priority area’ due to the
concern of elevated pollutant concentrations within the area, being specically particulates
(Kaddoura, Ramli, & Al-Turki, 2016; Khoo et al., 2013; Hertzog & Swart, 2016). Another
study conducted at the Central University of Technology (CUT) (subsequently called the
CUT study) was done to validate three dierent tilt angles for PV modules in a semi-arid
region. Results suggest that PV modules need to be installed at a tilt angle of Latitude
plus 10º for semi-arid regions during the summer season. Contrary to the VUT and CUT
study, the current location of interest is a residential area aected mainly by domestic fuel
burning, vehicles emission and it is also known for its thunderstorms.
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3. RESEARCH SITE
South Africa is zoned into six regions namely; arid, semi-arid, dry sub-humid, humid and
very humid (Gauché, 2016). Arid are regions where a combination of high temperatures
and low rainfall causes evaporation that exceeds precipitation (Barakat, 2009). Humidity
is a measure of how much moisture is present compared to how much moisture the
air could hold at a specic temperature. Figure 2 illustrates the South African map of
climate indicators aridity. The current location of interest is the University of South Africa
(UNISA), Science campus, Florida with the given coordinates of 26.1586° S and 27.9033°
E (classied under the Highveld region of South Africa). From Figure 2, it can be noted that
the current study (also called the UNISA study) is in the dry sub-humid region while the
CUT study is located in the semi-arid region. Even though the VUT study is also located in
the sub-humid region, it was in the area that was declared airshed priority area because of
high level of pollution as compared to the UNISA study. With ever-changing environmental
conditions, it is important to continue investigating the optimum installation angles for PV
modules around the globe. The results of this UNISA study will help in establishing if the
VUT and CUT studies recommendations’ still hold truth.
Figure 2. The climate indicators aridity. Source: (Gauché, 2016).
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4. PRACTICAL SETUP
Three PV modules with the same load prole were used (4 by 0.82 Ω resistors in series with
a 1 Ω resistor (100 W)). All the PV modules were set to an orientation angle of 0°. Their tilt
angles varied between 16°, 26° and 36°. The angles were derived using Latitude minus 10°
(26° - 10°), Latitude (26°) and Latitude plus 10° (26° + 10°) (see Table 1 for mathematical
calculations). A reference tilt angle of 26° was used in this study, corresponding to the
Latitude value of the installation site at the UNISA, Florida campus, which is lying on the
elevated plateau of the interior of South Africa (Highveld).
Table 1. Calculation of tilt angles.
Source Site Latitude Equation Calculation Tilt angle
Heywood and
Chinnery (1971)
26ᵒ Latitude - 10ᵒ 26ᵒ-10ᵒ 16ᵒ
26ᵒ Latitude 26ᵒ 26ᵒ
26ᵒ Latitude + 10ᵒ 26ᵒ+10ᵒ 36ᵒ
The system block diagram is illustrated in Figure 3 while the practical setup is illustrated
in Figure 4. The practical setup has three identical PV modules (a 310 W YL310P-35b
polycrystalline PV module with a rated voltage = 36.3 V, open circuit voltage = 45.6 V,
rated current = 8.53 A and short circuit current = 8.99 A). The data logging interface
circuit provides signal conditioning between the PV module and the data acquisition (DAQ)
equipment. Figure 5 illustrates the National Instruments (NI) data acquisition (DAQ)
hardware installed inside the control boxes. The DAQ incorporates other PV modules which
are not part of this research study. Voltage and current measured from the PV modules are
relayed to LabVIEW where the optimum power is calculated. The LabVIEW user interface
was used to visualize the measured data. The main function of a signal conditioning circuit
(also used as a load) is to scale down signal voltage and add oset voltages (Juhana & Irawan,
2015). It is oriented towards limiting the input voltage to the DAQ system to less than 10 V
as the DAQ system can only handle a maximum input of 10 V.
Calibration
Start
Measured
weight to high
Measured
weight to low
Zero scale with current
tare weight
Yes
Ask user to place
calibration weight on scale
Measure calibration
weight
Yes
Decrease calibration
factor
Increase calibration
factor
Calibration completed
PV module Logging interface Load LabVIEW
Figure 3. Block diagram of the system.
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Figure 4. The three PV modules xed at different tilt angles.
Figure 5. The DAQ system hardware box.
Figure 6 illustrates the load resistance circuit diagram that provides signal conditioning and
that is also used as the system load (Figure 7), featuring high power resistors that are chosen
to satisfy the voltage divider rule. An economic viable load for considering output power
results from identical PV module can include the following:
• Batteries with a solar charger;
• Batteries with a maximum power point tracker (MPPTs);
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• Regulated and non-regulated light emitting diode (LED) lamps; and
• Fixed load resistors (Swart & Hertzog, 2016a).
Figure 6. The circuit diagram of the load resistance.
Using xed load resistance instead of a solar charger or maximum power point tracker
(MPPT) was discovered to be an eective and easy method to start loading PV modules
located outdoors for measurement purposes and could be a more viable option for
monitoring long-term PV module performance. Fixed resistive loads can greatly reduce
the test system costs and complexity, however, the disadvantage is that there is no way
to implement maximum power tracking (MPT). Fixed load resistors in this study form a
typical voltage divider circuit, where ve resistors are connected in series across a source
voltage. As the source voltage is dropped in successive steps through the series resistors,
any desired portion of the source voltage may be “tapped o” to supply individual voltage
requirements. The voltage divider circuit provides signal conditioning, as the optimum
voltage of the PV module is 36.3 V which is much higher than the allowed input voltage
to the NI DAQ unit which is limited to 10 V (eq. 1). Using three 0.82 Ω and 1 Ω resistors
(100 W) in series enables the input voltage to the NI DAQ to be less than 10 V. This
DAQ is connected directly to a personal computer running the LABVIEW software where
measurements are recorded (Swart & Hertzog, 2016b; Tien & Shin, 2016).
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(1)
Where: V
out
= Voltage divider output to the DAQ system
V
in
= PV module output voltage
R
1
= System 1 Ω resistor where the voltmeter is connected across
R
T
= Total resistance of the circuit in series (R
1
+ R
2
+ R
3
+ R
4
+ R
5
= 4.28 Ω)
Figure 7. The system loads.
5. RESEARCH METHODOLOGY
This section describes the research methodology that was engaged in for the empirical
experimental design portion of the study. The outcome was to establish the tilt angle that
yields optimal output power from three identical PV modules set at three dierent tilt angles
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in the Highveld region of South Africa during the summer season. This was done by setting
the PV modules with the same load prole at Latitude minus 10° (16°), Latitude (26°) and
Latitude plus 10° (36°) respectively. For calibration purposes, the three PV modules were set
at xed angles of 0° (orientation) and 26° (tilt) (see Figure 8). The intention of calibrating
the system was to eliminate any bias between the systems. Calibration of equipment is of
vital importance before measurements can be taken to ensure accuracy and to validate any
future measurements as being reliable (Swart & Hertzog, 2019). To check validity of the
system, the three PV modules were set to the same tilt angle of 26° for few hours on the
3
rd
of February 2019. The measurements were taken using a Rish Multi 16S True RMS
digital multimeter. The readings on the digital multimeter correlated with the ones on the
LabVIEW user interface software resulting with no need for any adjustment. Subsequently,
the PV modules were set to their respective tilt angles again.
Figure 8. The three PV modules xed at 0° orientation angle and 26° tilt angle.
The LabVIEW user interface was used to visualize the measured data. It was designed
and developed for this research pertaining to the operating parameters of PV modules
and linear actuators. The sample interval (measurements taken every 4 seconds from the
LabVIEW user interface) and cycle duration of 12 hours (6 am – 6 pm) may be adjusted
after each complete cycle, as LabVIEW rst needs to close an opened text le on the hard
drive of the computer. This text le contains the measurements displayed on the user
interface, which are only saved at the end of the complete cycle. The system was let to run
for a period of three months being December 2018 to February 2019 which is the summer
season in South Africa.
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6. THE LABVIEW USER INTERFACE
Figure 9 shows the LabVIEW user interface that was used to display voltage and current
readings from the PV modules. The measure voltage and current were used to calculate
the output power (P=VI). The LabVIEW user interface provides the following information:
• Analog instantaneous value of voltage for each PV module (point A);
• Digital instantaneous value of voltage for each PV module (point B);
• Analog instantaneous value of current for each PV module (point C);
• Digital instantaneous value of voltage for each PV module (point D);
• Instantaneous value of voltage for each PV module in graph form (point I);
• Instantaneous value of current for each PV module in graph form (point J);
• Date-time string function to start and stop the data recording process at predened
moments of time e.g sunrise time and sunset time (E and F);
• Numeric indicator indicating direction to which the PV modules are taking e.g
vertical or horizontal (H-I); and
• The stop button function to control the while loop execution.
Figure 9. The LabVIEW front panel.
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7. RESULTS
This section provides results regarding calibration and the dierent output powers of the
three PV modules set at dierent tilt angles. The calibration readings highlighted on Figure
10 show the physically measured voltage of 34.9 V and current of 8.29 A on the digital
multimeters.
Figure 10. The Rish Multi 16S True RMS multimeter.
Table 2. Calibration results.
Name
Angle
LabVIEW
Current (A)
Module
Current
(A)
Current Error
percentage
(%)
LabVIEW
Voltage (V)
Module
Voltage (V)
Voltage Error
percentage
(%)
16ᵒ 8.27 8.29 0.24 34.7 34.9 0.57
26ᵒ 8.27 8.29 0.24 34.4 34.5 0.29
36ᵒ 8.27 8.29 0.24 34.7 34.8 0.29
These values correlated well with those shown on the LabVIEW user interface as shown
in Table 2. The calibration readings were compared to the available readings in the
LabVIEW user interface, so that the instantaneous voltage and current values displayed
on the interface equalled the values displayed on the digital multimeter. The system was
calibrated between 12:30 noon and 1 pm when the sun was perpendicular to all the PV
modules. The measurements were rst done on the latitude minus 10° (16°) PV module.
Current of 8.29 A from the PV module was measured (physically) while the LabVIEW
interface displayed 8.27 A. The readings (currents and voltages) measured physically on
the other modules and displayed by the LabVIEW interface within the 30 minutes time are
displayed in Table 2. Table 2 further presents the percentage dierence between the digital
multimeter and LabVIEW readings. The highest error percentage for voltage occurred
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for the 16° PV module (being 0,57 %). Results indicate that three identical PV systems
can be calibrated to produce the same results, with variability of less than 1 % (Swart &
Hertzog, 2019). A consistent percentage (0,24 %) between the multimeter and LabVIEW
user interface was established for the current values. The voltage measured for one day was
utilised to plot a graph as illustrated in Figure 11 where the three PV modules were xed at
the same tilt and orientation angles (0° and 26°) for calibration purposes.
11
These values correlated well with those shown on the LabVIEW user interface as shown in Table
2. The calibration readings were compared to the available readings in the LabVIEW user
interface, so that the instantaneous voltage and current values displayed on the interface
equalled the values displayed on the digital multimeter. The system was calibrated between
12:30 noon and 1 pm when the sun was perpendicular to all the PV modules. The measurements
were first done on the latitude minus 10° (16°) PV module. Current of 8.29 A from the PV module
was measured (physically) while the LabVIEW interface displayed 8.27 A. The readings (currents
and voltages) measured physically on the other modules and displayed by the LabVIEW interface
within the 30 minutes time are displayed in Table 2. Table 2 further presents the percentage
difference between the digital multimeter and LabVIEW readings. The highest error percentage
for voltage occurred for the 16° PV module (being 0,57 %). Results indicate that three identical
PV systems can be calibrated to produce the same results, with variability of less than 1 % (Swart
& Hertzog, 2019). A consistent percentage (0,24 %) between the multimeter and LabVIEW user
interface was established for the current values. The voltage measured for one day was utilised
to plot a graph as illustrated in Figure 11 where the three PV modules were fixed at the same tilt
and orientation angles (0° and 26°) for calibration purposes.
Figure 11. The three PV modules fixed at 0° orientation and 26° tilt angles.
The PV modules continued to behave similarly throughout the day. From 10 am to 15:00 pm the
PV modules were aligned to the larger portion of the solar radiation which is normally maximum
at 12 noon. The PV modules were producing constant output voltage which was nearly the
maximum rated voltage. The purpose of the calibration was to produce the same results from all
three PV modules that were orientated similarly. This was achieved, resulting in a valid setup
where subsequent measurements or results will be reliable.
Table 3 shows the results of the instantaneous average power for a period of three months,
0,0
5,0
10,0
15,0
20,0
25,0
30,0
35,0
40,0
06:00:00 AM
06:30:01 AM
07:00:04 AM
07:30:04 AM
08:00:00 AM
08:30:08 AM
09:00:01 AM
09:30:01 AM
10:00:03 AM
10:30:02 AM
11:00:09 AM
11:30:05 AM
12:00:02 PM
12:30:04 PM
01:00:01 PM
01:30:26 PM
02:00:32 PM
02:30:11 PM
03:00:31 PM
03:30:38 PM
04:00:35 PM
04:30:09 PM
05:00:08 PM
05:30:29 PM
05:59:55 PM
Voltage (V)
Time of the day (hours)
Voltage 16ᵒ Voltage 26ᵒ Voltage 36ᵒ
Figure 11. The three PV modules xed at 0° orientation and 26° tilt angles.
The PV modules continued to behave similarly throughout the day. From 10 am to 15:00 pm
the PV modules were aligned to the larger portion of the solar radiation which is normally
maximum at 12 noon. The PV modules were producing constant output voltage which
was nearly the maximum rated voltage. The purpose of the calibration was to produce the
same results from all three PV modules that were orientated similarly. This was achieved,
resulting in a valid setup where subsequent measurements or results will be reliable.
Table 3 shows the results of the instantaneous average power for a period of three months,
being December 2018, January and February 2019. The results on Table 3 were used to
plot a chart as illustrated in Figure 12 and a graph in Figure 13 for further analysis.
Table 3. The three months instantaneous power readings and the total Wh.
Time 16ᵒ 26ᵒ 36ᵒ
Dec ‘18 Week 1 125,9 121,2 114,1
Dec ‘18 Week 2 133,0 128,2 120,7
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Time 16ᵒ 26ᵒ 36ᵒ
Dec ‘18 Week 3 153,6 147,9 139,3
Dec ‘18 Week 4 107,6 103,7 97,6
Jan ‘19 Week 1 154,6 148,9 140,2
Jan ‘19 Week 2 139,4 134,2 126,4
Jan ‘19 Week 3 119,8 115,4 108,6
Jan ‘19 Week 4 42,0 40,6 38,4
Feb ‘19 Week 1 123,9 119,4 112,4
Feb ‘19 Week 2 166,2 160,1 150,7
Feb ‘19 Week 3 166,6 160,5 151,1
Feb ‘19 Week 4 157,9 152,1 143,2
Total ave. Wh 266108,8 258424,2 212786,1
Percentage
difference 16° > 26° = 5,3 % 26° > 36°= 8,8 % 16° > 36°=14,2 %
From both gures, it is evident that the Latitude minus 10° (16°) PV module outperformed
the Latitude (26°) and Latitude plus 10° (36°) PV modules in power harvesting throughout
the summer season. Similar research has shown that a PV module with a tilt angle of
Latitude minus 10° yields the highest output power for summer months in a semi-arid
region of South Africa (Hertzog & Swart, 2018a). The percentage dierence between
the total Wh produced for the summer season between 16° and 26° PV modules was 5,3
%. The percentage dierence between 16° and 36° PV modules was 14,2 %, while the
percentage dierence between 26° and 36° PV modules was 8,8 %.
12
being December 2018, January and February 2019. The results on Table 3 were used to plot a
chart as illustrated in Figure 12 and a graph in Figure 13 for further analysis.
Table 3. The three months instantaneous power readings and the total Wh.
Time
16ᵒ
26ᵒ
36ᵒ
Dec '18 Week 1
125,9
121,2
114,1
Dec '18 Week 2
133,0
128,2
120,7
Dec '18 Week 3
153,6
147,9
139,3
Dec '18 Week 4
107,6
103,7
97,6
Jan '19 Week 1
154,6
148,9
140,2
Jan '19 Week 2
139,4
134,2
126,4
Jan '19 Week 3
119,8
115,4
108,6
Jan '19 Week 4
42,0
40,6
38,4
Feb '19 Week 1
123,9
119,4
112,4
Feb '19 Week 2
166,2
160,1
150,7
Feb '19 Week 3
166,6
160,5
151,1
Feb '19 Week 4
157,9
152,1
143,2
Total ave. Wh
266108,8
258424,2
212786,1
Percentage difference
16° > 26° = 5,3 %
26° > 36°= 8,8 %
16° > 36°=14,2 %
From both figures, it is evident that the Latitude minus 10° (16°) PV module outperformed the
Latitude (26°) and Latitude plus 10° (36°) PV modules in power harvesting throughout the
summer season. Similar research has shown that a PV module with a tilt angle of Latitude minus
10° yields the highest output power for summer months in a semi-arid region of South Africa
(Hertzog & Swart, 2018a). The percentage difference between the total Wh produced for the
summer season between 16° and 26° PV modules was 5,3 %. The percentage difference between
16° and 36° PV modules was 14,2 %, while the percentage difference between 26° and 36° PV
modules was 8,8 %.
Figure 12. Number of samples for the three-month period.
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
160,0
180,0
Dec '18 Week 1
Dec '18 Week 2
Dec '18 Week 3
Dec '18 Week 4
Jan '19 Week 1
Jan '19 Week 2
Jan '19 Week 3
Jan '19 Week 4
Feb '19 Week 1
Feb '19 Week 2
Feb '19 Week 3
Feb '19 Week 4
Power (W)
Time of the year (3-months)
16ᵒ 26ᵒ 36ᵒ
Figure 12. Number of samples for the three-month period.
152
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13
Figure 13. The three PV modules fixed at 0° orientation and different tilt angles for three
months.
8. Conclusions
The purpose of this paper was to empirically validate the optimum tilt angle for PV modules in
the Highveld of South Africa in the summer season. Three fixed PV modules were set at the same
orientation angle of 0°, but at different tilt angles of Latitude minus 10° (16°), Latitude (26°) and
Latitude plus 10° (36°). This was done based on a recommendation by Chinnery and Heywood
for calculating tilt angles for PV module installations in the Southern Hemisphere. The PV
modules were installed at the UNISA Science campus, which lies in the Highveld of South Africa.
Reliability and validity of any results was firstly established by having all three modules set to the
same tilt angle. A variability of less than 1 % was established indicating a higher level of similarity
between the performances of all three PV modules. The main results then showed that the PV
module installed at Latitude minus 10° outperformed the PV module installed at Latitude by 3.48
%. It also outperformed Latitude plus 10° by 10.69 %. This correlates well with literature and
previous results obtained in the CUT and VUT studies which recommended that PV modules be
placed at a tilt angle of Latitude minus 10º during the summer season in South Africa.
It is important to state that possible limitations of this study include the fact that only one
research installation site was used, and that data has not yet been collected for the other seasons
of the year (autumn, winter and spring). It is vital to obtain results for the other seasons of the
year to establish any variability in the optimum tilt angle values.
It is recommended to set a fixed-type PV module to an optimum tilt angle value that allows it to
harvest the maximum power from the sun. Based on the results in this study, it is recommended
to place fixed-type PV modules at a tilt angle of Latitude minus 10º with a 0° orientation angle
during the summer season in the Highveld region of South Africa.
Acknowledgment
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
160,0
180,0
Dec '18
Week 1
Dec '18
Week 2
Dec '18
Week 3
Dec '18
Week 4
Jan '19
Week 1
Jan '19
Week 2
Jan '19
Week 3
Jan '19
Week 4
Feb '19
Week 1
Feb '19
Week 2
Feb '19
Week 3
Feb '19
Week 4
Power (W)
Time of the year (3-months)
16ᵒ 26ᵒ 36ᵒ
Figure 13. The three PV modules xed at 0° orientation and different tilt angles for three months.
8. CONCLUSIONS
The purpose of this paper was to empirically validate the optimum tilt angle for PV modules
in the Highveld of South Africa in the summer season. Three xed PV modules were set
at the same orientation angle of 0°, but at dierent tilt angles of Latitude minus 10° (16°),
Latitude (26°) and Latitude plus 10° (36°). This was done based on a recommendation
by Chinnery and Heywood for calculating tilt angles for PV module installations in the
Southern Hemisphere. The PV modules were installed at the UNISA Science campus,
which lies in the Highveld of South Africa.
Reliability and validity of any results was rstly established by having all three modules
set to the same tilt angle. A variability of less than 1 % was established indicating a higher
level of similarity between the performances of all three PV modules. The main results
then showed that the PV module installed at Latitude minus 10° outperformed the PV
module installed at Latitude by 3.48 %. It also outperformed Latitude plus 10° by 10.69
%. This correlates well with literature and previous results obtained in the CUT and VUT
studies which recommended that PV modules be placed at a tilt angle of Latitude minus
10º during the summer season in South Africa.
It is important to state that possible limitations of this study include the fact that only one
research installation site was used, and that data has not yet been collected for the other
153
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3C Tecnología. Glosas de innovación aplicadas a la pyme. ISSN: 2254 – 4143 Edición Especial Special Issue Abril 2020
seasons of the year (autumn, winter and spring). It is vital to obtain results for the other
seasons of the year to establish any variability in the optimum tilt angle values.
It is recommended to set a xed-type PV module to an optimum tilt angle value that allows
it to harvest the maximum power from the sun. Based on the results in this study, it is
recommended to place xed-type PV modules at a tilt angle of Latitude minus 10º with
a 0° orientation angle during the summer season in the Highveld region of South Africa.
ACKNOWLEDGMENT
The authors wish to acknowledge Prof. Swart and Prof. Hertzog from the Central University
of Technology for their guidance. He also wishes to acknowledge both the Central University
of Technology and the University of South Africa for nancial support.
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