The impact of renewable injections on cycling of conventional power plants

Renewable injections from wind and solar affect the variability in residual electricity demand (demand minus renewable injections) to be covered by the conventional electricity generation system. In order to meet the variable residual demand, conventional power plants are required to cycle, meaning that they have to change their generation output by ramping or switching on/off. As cycling of conventional power plants entails technical and economical issues, it is imperative to know the effect of increasing renewable injections on cycling. This paper quantifies conventional power plant cycling as function of the amount of renewable injections. The results follow from a unit commitment model of a realistic electricity system. The study shows that the change in variability in residual demand due to renewable injections is rather limited. The way conventional power plants meet this variable demand, however, changes considerably as renewable injections force more base load plants to cycle. The take-away of this paper is that required flexibility from the conventional power plant portfolio is not the issue; the way this flexibility is delivered is the issue when it comes to conventional power plant cycling.