Rooftop solar photo voltaic potential: Rand Water as case study

Abstract

South Africa has an abundance of coal reserves and about 85.7% of energy is generated from coal. However, the requirements of the United Nations Framework Convention on Climate Change, Kyoto Protocol, National Climate Change Response White Paper, Clean Development Mechanism, Integrated Resource Plan and National Electricity Plan emphasise the need for the use of renewable energy sources. The purpose of this research is to study and identify the potential to save energy through the installation of rooftop solar photovoltaic (PV) systems at Rand Water buildings. The rooftop solar PV installation at Rand Wate's head office is used as a case study and the information gathered from the case study is then used to analyse the potential for similar installations in other Rand Water buildings. Solar PV potential is described as physical, geographical, technical, and economic potential. The characteristics of the location provide both physical and geographical potential, the type of equipment and controls selected for the PV system provide technical potential, economic potential provides financial benefits in terms of net present value, internal rate of return, levelised cost of energy and simple payback period. The reduction in greenhouse gas emissions is discussed extensively in literature but it is not included as environmental potential or greenhouse payback time. This research proposes a methodology to analyse potential of a rooftop solar PV system installation with focus on the physical, geographical, technical and economic solar PV potential. The methodology indicates the importance of the geographical and meteorological data of the area identified as a potential location and the important variables to be considered in order to determine a suitable PV system size. Economic factors such as PV system cost, operation and maintenance cost, levelised cost of energy (in R/kWh) and simple payback period are discussed. It is evident that technical potential is the most extensive variable in determining solar PV potential. The proposed methodology was used to determine the potential rooftop solar PV system installation at Rand Water's head office, which resulted in a 338kWp rooftop solar PV system. The actual energy production measurements showed a performance ratio of 80% for the 338 kWp system with an energy cost saving of about R550 000 per year. An additional 18 buildings were identified as potential buildings for a rollout of rooftop solar PV systems. Twelve of the 18 identified buildings showed potential for rooftop solar PV system installation with an estimated energy saving of 2 163 420 kWh/year, an energy cost saving of R1 794 492.64/year and a reduction in carbon emissions of 2 141 tons CO₂/year. The return on investment for these buildings is unattractive but there is potential to achieve a substantial reduction in energy, energy costs and carbon emissions.