Abstract:
Fundamental mathematical principles were applied to calculate the return on investment
(ROI) of a multiple inclination, rooftop-mounted, photovoltaic (PV) system that is connected to a
structured tariff network. Recent history has seen a disproportionate increase in electricity tariffs
within South Africa, enabling an increase in the deployment rates of PV technologies. Given the
inherent uncertainty associated with simulating the electricity yield of a PV system, it can become
difficult to estimate the ROI in advance. This study contributes to existing knowledge by presenting
a process for calculating the ROI of a case study rooftop-mounted PV system using mathematical first
principles where structured tariffs apply. The PV modules were mounted to a curved roof structure,
ranging from 9 towards a southerly direction to 10 towards a northerly direction. The research
results indicate that since the PV system is located within the southern hemisphere, the ROI will
increase when PV modules are orientated towards the northerly direction to attain a maximum of
R0.0059/Wp/Day at 10 , and a minimum of R0.0025/Wp/Day at 9 towards the southerly direction
in the winter season. Summer maximum ROI yielded an average of between R0.0050/Wp/Day
and R0.0052/Wp/Day, irrespective of the angle of inclination of the PV modules. It was concluded
that PV systems must be designed to favour winter electricity production for increased ROI where
structured tariffs apply within a South African context.
