The increasing share of energy produced by non-programmable renewable energy sources (NDRS) is causing various issues for the safe operation of electrical grids. NDRS require greater availability of flexibility resources within the power system due to their variability, volatility, and forecast uncertainty.

Pumped storage plants represent a valuable flexibility resource within this new energy paradigm. Considering that the new National Integrated Energy and Climate Plan (PNIEC) foresees progressive increases in NDRS production, there is a need to study new configurations of even more flexible plants than traditional hydroelectric pumped storage. This includes integrating pumped storage with flywheels (FESS Flywheel Energy Storage Systems), batteries, and floating photovoltaic systems to address the growing need for reserve resources. This work addresses this issue, starting with an analysis of the state-of-the-art of technological solutions and plant configurations involving the integrated presence of pumped storage hydropower plants with batteries, flywheels, and floating photovoltaics.

Based on simulations carried out in previous years of the System Research program to evaluate the feasibility of a marine pumped storage plant at Foxi Murdegu in Sardinia (190 MW for pumping, 140 MW for generation), and considering parameters derived from the literature regarding the short-interval functionalities of the machines, a simplified model was developed to simulate the response over 1-second intervals. A Virtual Power Plant (VPP) was then simulated, consisting of the integration of the marine pumped storage plant with batteries to study the potential flexibility gains offered by the VPP solution compared to the standalone pumped storage plant during startup, allowing for increasingly advanced grid services. The results were elaborated into tables that show the performance valuation of the Foxi Murdegu marine pumped storage plant, both as a standalone system and as a hybrid VPP with different battery sizes.