Increasing the grid flexibility with unconventional operations in one of the largest Pumped Storage Units in EU: The tests of XFLEX Hydro in Frades II

Pumped Storage Hydro (PSH) serves as a significant contributor to the transition toward net zero emissions, primarily due to its capacity to store large amounts of energy with very high round trip efficiency (RTE). This is especially important given the volatility and unpredictability associated with the current energy mix, largely influenced by sources like wind and solar. Managing these fluctuations poses operational challenges for pumped storage schemes. Within the EU's XFLEX Hydro project, various developments and operational strategies have been tested in one of the largest Pumped Storage Units globally, aiming to enhance actual Pumped Storage flexibility services. This paper provides an overview of the effects of some of the most demanding operations, such as fast ramps, variations in power as pumps, and hydraulic short-circuit operations in the hydraulic and mechanical components of the Pumped Storage Plant.