  The inherent intermittency of wind and solar generation presents a
significant challenge as we seek to increase the penetration of renewable
generation in the power grid. Increasingly, energy storage is being deployed
alongside renewable generation to counter this intermittency. However, a formal
characterization of the reliability of renewable generators bundled with
storage is lacking in the literature. The present paper seeks to fill this gap.
We use a Markov modulated fluid queue to model the loss of load probability
(LOLP) associated with a renewable generator bundled with a battery, serving an
uncertain demand process. Further, we characterize the asymptotic behavior of
the LOLP as the battery size scales to infinity. Our results shed light on the
fundamental limits of reliability achievable, and also guide the sizing of the
storage required in order to meet a given reliability target. Finally, we
present a case study using real-world wind power data to demonstrate the
applicability of our results in practice.
