Less water forces hydroelectric plants in Brazil to invest in more efficient systems

RIO DE JANEIRO, BRAZIL – Large hydroelectric power generators are investing billions of reais in replacing turbines to face a trend of reduction in water supply, caused by environmental issues or by the dispute for the use of the natural asset with other segments of the economy such as irrigation and industry. The objective is to try to maintain the same energy generation using less water.

Research conducted by the Energy Studies Group of the Federal University of Paraná (UFPR) proved that, between 2010 and 2020, the volume of water that reached the reservoirs of the main Hydroelectric Power Plants (HPPs) in Brazil fell by 10.3% compared to the complete average from 1931 to 2020.

The coordinator of the study, Daniel Detzel, says that the changes in the flows of large hydroelectric plants are due to an interaction between climate change, natural variability, and human action.

The data are from the historical series of the National Electric System Operator (ONS) and the historical cutout of the last decade shows a reduction in the volume of water that arrives in most of the 161 reservoirs of Brazil’s hydroelectric plants with more than 30 megawatts (MW) of installed capacity.

As some of these plants date back to the 1950s, they still face the process of silting up of the reservoirs, which reduces their capacity to accumulate water.

After 37 years of operation, Itaipu Binacional started the technological modernization and foresaw another 12 years for the updating of the generating units, with investments that exceed US$650 million.

The plants in the Northeast were the most affected by the reduction in the volume of water reaching the reservoirs. According to Detzel’s calculations, the region’s subsystem suffered a 43.4% reduction in volume, while in the South, the tendency to increase the flow remains positive but has lost strength.

The Companhia Hidrelétrica do São Francisco (Chesf) announced investments of R$1.5 billion (US$280 million) for the modernization of the generation facilities to be executed in the period 2021-2030, which include the hydroelectric plants of Sobradinho, Paulo Afonso IV, Luiz Gonzaga and Xingó for the substitution of analog equipment for digital resources.

In the first year, the investments reached R$100 million.

“By 2021, all our plants exceeded their availability targets and had approved results in the system reestablishment simulations,” said Operations Director João Henrique Franklin.

Voith modernized Tucuruí and is responsible for the contract for the modernization of Paulo Afonso IV. With the repowering, the plant will increase 2.5 GW of installed power. The project can increase the plant’s capacity by offering energy capable of supplying a city of 170,000 people.

Ricardo Lee, Modernization Sales Director for Voith Hydro Latin America, says that the biggest crisis in the sector is due to the reduction of rainfall rates, which is accentuated in the Northeast.

“With the application of hybrid technologies, we can make hydroelectric plants operate in different ranges of reservoir levels, which may be one of the ways out of this water crisis,” says the executive.

Today Brazil is dependent on hydroelectric plants for energy generation. Data from the National Electric Energy Agency (Aneel) show that these plants are responsible for 56.59% of the installed capacity in Brazil.

Lee evaluates that modernization and repowering have conditions to make the plants generate again with the same efficiency and increase the asset’s reliability. “When we modernize the large plants in Brazil, with the same amount of water, we will be able to make these plants more efficient,” he says.

Voith recently signed a new contract to refurbish the Paulo Afonso II hydroelectric plant, in operation since the 1960s.

Detzel says that the most critical period of the historical series was from 1949 to 1956. The energy generated at this time is what today defines the physical guarantee of the plants, which is how much they can sell.

“It is important to understand why this critical period is changing because, in the 2010s, they generated less energy than they sold. So they will be in danger of frequent deficits. It is bad for the system, which will receive less energy, and for the entrepreneurs, who will be in debt having to resort to another market mechanism to buy energy at a higher price,” he analyzes.

Detzel adds that the increase in water use for other purposes, such as irrigation, fish farming, navigability for transportation, among others, contributes to the reservoirs emptying more quickly.

According to the National Water Agency (ANA), in 2020, the largest consumer of water was the irrigation segment (34%), followed by urban supply (17%) and industry (7%).

Detzel evaluates that the construction of new reservoirs would be an alternative to guarantee storable energy. However, the Ten Year Energy Plan (PDE) doesn’t contemplate new storage plants and foresees that hydroelectric plants will be responsible for less than half of the Brazilian electricity supply by 2031.

“In the medium and long term, I believe that the diversification of energy sources is an alternative.

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