Contribution of storage to adequacy in power systems with a large share of renewable energy resources

The variability of renewable energy sources (RES), threatening the adequacy of power systems, could be dampened using storage. Concretely, RES would be stored during periods of excess and used when needed. However, the impact of the operating strategy on the loss of load expectation (LOLE) remains an open question. Therefore, this paper studies the impact of different storage operating strategies on adequacy indicators. To do so, five strategies are defined: yearly costs minimization with single and depth-dependent value of lost load (VoLL), LOLE minimization, and weekly costs minimization, with and without water values. Using Monte Carlo methods, these are applied to three case studies. The various operating strategies give spread results in terms of LOLE, with up to a factor 10 between the lowest and highest value. Weekly minimization gives poorer adequacy indicators. This paper recommends weekly costs optimization, with a depth-dependent VoLL and with water values, in adequacy studies.