Implications of renewable energy intermittency for power system supply planning

Integrated resource plans have changed. While, in the past, nearly all generation technologies could be dispatched on demand, modern planners must incorporate intermittent renewable energy into their scenarios of the future energy mix. Based on forecasts of power and energy requirements and the costs of various technologies, selected scenarios test the trajectories of future prices and adequacy. The draft Integrated Resource Plan for South Africa published by the government in 2016, together with the diverse reactions to it, provide extensive material for analysis. Lessons include the need for careful identification of technical constraints, not simply basing a plan on the cost models; that forecasting the effects of the intermittency of solar and wind energy in South Africa is possible with available measured outputs; and that storage or curtailment of high renewable energy output when penetration levels increase are important. The analysis indicates the effects of intermittency on the cost models, and the significance of electricity supply industry structure and tariffs in supply planning. It appears bias in the planning group may affect the outcomes of integrated resource plans. The practical constraints in the plans advocating greater renewables penetration could reduce system reliability, which means that decisions about the trajectory need to be taken now. The South African situation appears to be relevant for other developing and emerging economies.