Robustness and flexibility in strategic energy planning: a case of study on the Spanish carbon budget for the 1.5ºC target

Energy planning deals with the long life of energy investments, which usually last between 20 and 50 years. Such a long period of time gives rise to many uncertainties, which need to be addressed correctly so that the best possible decisions are taken. However, when uncertainty is considered in energy planning, it is usually done on a limited basis. Robust optimisation can deal with deep uncertainties, but its application is not frequent in energy planning. Moreover, it typically only considers a few uncertain parameters and yields too conservative results. This paper rethinks the conceptual framework around robustness and flexibility. These concepts are fundamental in treating uncertainty, but they are often confused in the literature. A robust optimisation methodology is applied in a novel way to an energy planning dynamic model for dealing with uncertainties, the Dynamic Energy MOdel (DEMO). A case of study for the Spanish energy system is presented, analysing the possibility of meeting Spain's carbon budget to reach the 1.5ºC target when different degrees of protection against uncertainties are considered. Merits and limits of this methodology are pointed out, and future steps in its application are discussed.