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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