ABSTRACT
Eskom, as is the case with most system operators globally, works within a frequency band of between 49.5 Hz and 50.5 Hz. The variable costs are mostly fuel-related and are incurred only when the plant is producing electricity. Gas-fired plants are predominantly weighted towards variable costs, because they are relatively cheap to build and maintain, but the fuel is expensive. Interestingly, the most capital-intensive power stations of all are solar photovoltaic (PV) installations and wind farms, because they have no variable costs whatsoever. For solar PV and wind, the utilisation is determined by the weather, whereas for all other power generators, utilisation depends on the operator's dispatch decision. The economic viability is breaching tipping points country by country, with those with the highest solar and wind resources and the least area constraints, such as South Africa, being first to be beyond the tipping point.
