We propose a method to analyze the risk of blackouts with high penetration of variable
renewable energy sources (VRESs). We consider a model for the long-term evolution of the power grid
including propagation of cascading failures, day-to-day fluctuations of renewable generation and moderate
use of storage. We analyze grid resilience and stress as VRESs are progressively incorporated. We also
evaluate the VRES performance as the average fraction of daily demand covered by renewables. We find that
in general, VRES intrinsic variability increases the grid stress and the blackout risk. However, if VRESs are
implemented in a distributed way, the spatial spreading of the generation may have a positive effect on grid
resilience. As a case study, we analyze the replacement of conventional power plants by solar photovoltaic
generation combined with storage in the power grid of the Balearic Islands. We also consider the use of
source redundancy and briefly discuss the potential of wind energy.
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