Abstract
On our path to a cleaner and ultimately carbon-free power system, energy storage technologies are bound to play an indispensable role. In this work, we assess the importance of storage in both market-based services (e.g. energy arbitrage, or reserves) and system-stability services (such as the provision of virtual inertia) in an expansion planning framework that considers an AC power flow, unit commitment, and RoCoF inertia constraints.