The increasing penetration of variable Renewable Energy Sources (RES) has intensified short-term price volatility in electricity markets. This trend reinforces the need for flexible assets that can adapt to uncertain operating conditions. In this context, Pumped Storage Power Plants (PSPs), especially when integrated with Photovoltaic (PV) systems and Battery Energy Storage Systems (BESS), offer a promising solution for coordinated participation across multiple markets.

This work proposes a two-stage optimization framework for a hybrid PSP-PV-BESS system participating in day-ahead (DA) and intraday (ID) electricity markets. The methodology uses Mixed-Integer Linear Programming (MILP). First, an initial DA schedule is computed using forecasted time series. This schedule is then refined through a rolling horizon ID optimization. The intraday stage incorporates updated forecasts and penalizes deviations from DA commitments. The formulation accounts for hydraulic behaviour, unit commitment, ramping constraints, and multi-energy interactions among system components.

The study is developed in the context of a research project and uses the Alqueva dam as a case study. Historical market price data from OMIE is used for both DA and ID markets, while renewable generation and inflow time series are forecasted. This setup enables the evaluation of operational strategies under realistic market conditions and forecast uncertainty.

The impact of the two-stage optimization model is evaluated through operational and economic indicators. To assess the viability of the hybrid system, such indicators are computed under three scenarios, where the first scenario consists of the sole PSP, the second scenario includes both PSP and PV, and the third scenario consists of the full equipment (PSP-PV-BESS).

Results show that participation in the intraday market enhances profitability by enabling adjustments closer to real time. The optimization prioritizes higher-value transactions in the day-ahead market, while the intraday market is primarily used for corrective actions under forecast uncertainty. The PSP acts as the main long-duration storage asset, performing bulk energy shifting between low and high-price periods. In contrast, the BESS provides short-term operational flexibility through fast charge/discharge adjustments that support intraday rescheduling and reduce deviations from day-ahead commitments. While hydraulic limitations constrain PSP operation, the integration of PV and BESS improves system responsiveness. However, the economic contribution of the BESS remains limited due to its comparatively small capacity.

The daily market revenue from both ID and DA participation is on average 371240 €. The results reveal that the DA generates the highest share of revenue, while the ID market generates the lowest share. As expected, this is primarily due to the marginal liquidity that characterizes the ID compared to the DA. Furthermore, the curtailment ratio is on average 0.02, which reflects the promising viability of the fully equipped asset.

The findings of this work open several directions for further development of energy management models for market participation. The results highlight the economic value of ID market participation for large-scale storage systems and underline the complementary, yet secondary, role of smaller distributed assets in enhancing operational flexibility.