|New data shows photovoltaics (PV) in South Africa initially performing significantly better than assumed
The term “load factor” (sometimes referred to as “capacity factor” though definitions may differ) is defined as an installation’s average load divided by its peak load. For intermittent renewables, like PV and wind, which cannot always be dispatched according to the installed capacity, the load factor shows how much electricity is produced for a given installed peak capacity. Load factor accuracy is important when assessing the feasibility of intermittent renewables.
The Electric Power Research Institute (EPRI) provides a consolidated set of technology parameters in the report "Power Generation Technology Data for Integrated Resource Plan of South Africa", including load factors. For PV, EPRI provides average load factors for Cape Town (Western Cape) and Johannesburg (Gauteng) by technology.
REDIS currently provides a complete set of PV load factors by technology for Northern Cape.
Click here to interact with the data dashboard for hourly production and annual load factors by technology.
Load factors cannot be compared directly across provinces due to the difference in solar irradiation. However, in August 2016, the South African Weather Service published a paper comparing average solar irradiation by province. For example, the paper finds that average solar irradiation is 5.8% percent higher in Northern Cape than in Gauteng. Under the reasonable assumption that this difference results in an equally higher production, REDIS load factors for PV by technology in Northern Cape can be compared with EPRI load factor assumptions for Gauteng geographically adjusted for Northern Cape.
The result, illustrated in the chart above, shows that Northern Cape load factors for crystalline-silicon fixed and thin film are similar at around 25%, while the geographically adjusted EPRI load factors are about 21% and 20% respectively. The load factor for crystalline-silicon with single-axis tracking is almost 30%, while the geographically adjusted EPRI load factor is 25.5% In summary, the result shows that actual PV production is initially 17%-23% higher relative to EPRI’s geographically adjusted load factor assumptions.
It must be considered that PV load factors will be higher in the first years of operation due to degradation. For example, a 2012-paper from the National Renewable Energy Laboratories (NREL) under the US Department of Energy finds that PV module efficiency degradation is 0.8%-1.5% per year, lowest for crystalline-silicon, highest for thin film technology. A more recent 2016-paper from the European Commission Joint Research Centre, which is based on actual long-term field performance, finds that efficiency degradation of crystalline-silicon modules is only about 0.2% per year.
It must however also be considered that the degradation of existing installations may be compensated by an increase in PV module efficiency of future installations, resulting in average load factors being maintained at current or even higher levels.