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In order to effectively utilize hydro production flexibility, a sufficient amount of transmission capacity has to be available between the hydro-dominated part of the system and the part that requires operational flexibility. This chapter starts with a rough categorization of “base” hydropower flexibility, investigating the types of hydropower plants installed in power systems today. The “effective” hydropower flexibility available to support the integration of variable generation is a far more complex and case-specific aspect. It is discussed through national experiences. The chapter presents potential developments that would increase the participation of hydropower and discuss the ensuing challenges. Modeling a flow-based hydro system is a complex exercise, as is modeling the power system. Especially important is the correct assessment of hydropower flexibility to support power systems with a large share of variable generation (VG) and its value for storage. With increasing uncertainty and variability, a stochastic scheduling approach should yield lower costs., QC 20240314Part of ISBN 9781119508311Part of ISBN 9781119508281

This chapter describes some of the recent research into the capacity value of wind power. It builds on previous reviews from IEEE and International Energy Agency (IEA) Wind Task 25, and examines recent work that evaluates the impact of multiple-year data sets and the impact of interconnected systems on resource adequacy. The chapter provides examples that explore the use of alternative reliability metrics for wind capacity value calculations. It shows how multiple-year data sets significantly increase the robustness of results compared to single-year assessments. The preferred method for assessing the capacity value of wind and solar generation is a probabilistic approach grounded in the well-known loss of load probability (LOLP) and related reliability metrics. While reliability-based methods are widely accepted and provide accurate measures of wind and solar capacity values, they require detailed system data and can be computationally expensive to evaluate., QC 20240711

Greater penetrations of variable renewable generation on some electric grids have resulted in increased levels of curtailment in recent years. Studies of renewable energy grid integration have found that curtailment levels may grow as the penetration of wind and solar energy generation increases. This paper reviews international experience with curtailment of wind and solar energy on bulk power systems in recent years, with a focus on eleven countries in Europe, North America, and Asia. It examines levels of curtailment, the causes of curtailment, curtailment methods and use of market based dispatch, as well as operational, institutional, and other changes that are being made to reduce renewable energy curtailment., QC 20161014