As the share of variable renewables in the power system generation mix increases, meeting capacity requirements becomes challenging. In this context, hydropower reservoirs can play a vital role in integrating renewable energy due to their storage potential, contributing to meeting power supply criteria. However, given that reservoirs serve multiple purposes, various constraints can limit their capacity potential. This article introduces an analytical methodology that is designed to evaluate the maximum available power of hydro plants in critical scenarios. By applying concepts related to hydropower production calculations for the peak power demand and metrics evaluating the compliance with supply criteria, this study distinguishes itself from region-specific investigations. It conducts a generalized analysis of power availability across all regions of Brazil, with a focus on identifying the reasons for the most significant power losses and their specific locations. The results of this analysis demonstrate the feasibility of enhancing the available power of reservoirs, effectively addressing demand fluctuations, and sustainably improving energy security. This is particularly crucial in countries that are heavily reliant on renewables, including hydropower, for a huge portion of their electricity. The findings underscore the feasibility of increasing the penetration of variable renewable generation by optimizing the operation of existing hydropower plants. This optimization not only enhances energy security but also contributes to a more resilient and sustainable future, benefiting policy makers, energy planners, and stakeholders in the field of hydropower with reservoirs.

The global power sector is undergoing a profound transformation driven by the rapid expansion of variable renewable energy sources, supported by climate commitments and increasingly competitive technologies. This shift heightens the need for operational flexibility. Hydropower plants with storage play a central role in enabling renewable integration and ensuring that the system can balance the supply; however, their flexibility is often limited by environmental constraints and competing water uses. This study assesses strategies to enhance renewable integration through improved operational flexibility in hydropower plants. The analysis combines Stochastic Dual Dynamic Programming (SDDP) with hourly operational simulations to represent system operation under uncertain inflows and variable renewable energy (VRE) in Brazil’s Northeast region—an area marked by a high share of hydropower and VRE. The methodology incorporates critical hydrological conditions and evaluates how relaxing selected operational constraints, commonly imposed for environmental purposes, influences energy and capacity supply. Results show that hydropower can provide substantial generation modulation to offset renewable variability. Enhanced coordination between hydropower and renewables also reduces thermal dispatch, lowering associated emissions and costs. The findings reinforce that hydropower remains essential in low-carbon power systems and suggest that adapting operational rules and regulatory frameworks is necessary to unlock its full flexibility potential while meeting power-system requirements.

Electricity expansion planning is inherently subject to uncertainty, shaped by climatic, regulatory, and economic risks. In Brazil, this challenge is compounded by recurrent crises that have repeatedly reduced electricity demand. This study proposes a complementary decision-support approach to make planning more resilient to such crises. Using Brazil’s official optimization models (NEWAVE), we introduce two analytical elements: (i) a regret-minimization screen for choosing between conservative and optimistic demand trajectories and (ii) a flexibility stress test that evaluates the cost impact of compulsory-dispatch shares in generation portfolios. Key findings show that conservative demand projections systematically minimize consumer-cost regret when crises occur, while portfolios with lower compulsory-dispatch shares reduce total system cost and improve adaptability across 2000 hydro inflow scenarios. These results highlight that crisis-robust planning requires combining cautious demand assumptions with flexible supply portfolios. Although grounded in the Brazilian context, the methodological contributions are generalizable and provide practical guidance for other electricity markets facing deep and recurrent uncertainty.