Accumulation and Run-Of-The-River Hydropower Plants: A Case Study of The Brazilian Hydroenergetic System

Large Hydroelectric Power Plants (HPP) are of great importance for Brazilian Electric System (SEB), with about 60% of the installed power capacity coming from HPP`s. However, in the last 20 years, environmental restrictions have hampered the construction of plants with accumulation reservoir, which negatively impact the system. The study aims to highlight the importance of HPP`s with accumulation reservoirs for the power service reliability, since these have the capacity to reserve water to be used during periods of drought and to balance the volatility caused by renewable energy sources such as solar and wind. The study is divided into two sections. The first presents the historical evolution SEB`s installed hydropower generation and water accumulation capacity in terms of useful volume. The second contemplates a case study on the Iguaçu river basin using synthetic generation with stochastic model, including simulations of different configurations for the Baixo Iguaçu power plant (regulation vs. run-of-the-river reservoir) and the consequences on energy generation. The historical evolution demonstrates each hydroelectric project contribution to the system and shows how the implementation of run-of-the-river hydroelectric plants significantly impacted the capacity of flow regularization and water accumulation in the hydroelectric generation park over the years. Since the 2000s, it’s observed a stagnation in the accumulation of water capacity, even with 73 HPP’s incorporated into the system. These 73 plants are responsible for generating 37% of SEB`s total installed hydropower capacity, but stores only 8% of the total water accumulation capacity in terms of useful volume. The case study on the Iguaçu river basin uses the Natural Energy Method to simulate the power generation capacity and maximum water storage of the eight Iguaçu river hydropower plants in three different scenarios. The first simulation considers the Baixo Iguaçu plant with its actual run-of-the-river configuration. The second considers a hypothetical accumulation reservoir for this plant, and the third includes the accumulation reservoir and consider a heightened liquid average fall. The Baixo Iguaçu plant is under construction, and has an installed power capacity of 350 MW and is the last plant of the Iguaçu River. The results show that an accumulation reservoir in the Baixo Iguaçu plant would increase the energy accumulation in up to 7,4% and the generation of the system in 5,5% on average, allowing water storage during periods of drought, regulating the generation of energy and requiring less of complementary sources such as thermoelectric, which are more expensive and pollutants.