What is the impact of rain on the Brazilian electrical system?

“We have a real dependence on the energy matrix in relation to rainwater”, this is the analysis of Pedro Regoto, climate specialist at Climatempo.

During the webinar Impact of rain on the Brazilian electrical system, promoted by Canal Solar this Tuesday (25), he discussed the complementarity of renewable sources and how climatology influences the sector.

“Today, more than 60% of our energy generated is produced via hydroelectric power. When we have longer periods of drought, periods that are not so humid, electricity generation ends up suffering more,” he said.

“As of 2011, we are experiencing a negative trend in energy storage in the main reservoirs, mainly in the Southeast and South submarkets of Brazil. So, since then we have not been able to recover the level of the reservoirs to levels so close to that year and higher levels”, explained Regoto.

“We have only been falling over time. We went through some crises, some terrible summers, like 2014 and 2015, where we had major droughts, especially in January. And we know that an adversely affected wet period is no mystery, there is not much that can be done, precisely because our matrix is, above all, hydroelectric, it depends exclusively on water. If the water doesn’t fall in the right place or period, our matrix is ​​really impacted,” she highlighted.

Still in this context of crisis, the expert commented that in 2021 the country went through a summer that was not very positive for the sector. “The level has increased, but not satisfactorily. And then we came with negative anomalies, below-average rainfall for most of the first half of the year for the Center-South in general”.

“In other words, we had an energy imbalance in the Southeast during the humid period, and also an imbalance in the reservoir increase in the South of Brazil from July onwards. This provided us with this crisis scenario that we are still going through,” he added.

Read more: What happens when a reservoir operates at dead volume?

Renewable sources

When we talk about the complementarity of renewable sources, this is fundamental in the Brazilian scenario, because, according to Regoto, Brazil is very fortunate to have climates from North to South, similar in some ways, different in others, which end up complementing each other, such as hydro , wind and solar.

“In the summer months we have a greater increase in rainfall and, consequently, greater energy generation via hydroelectric plants. Thus, most of the river basins belonging to the North, Central-West and Southeast receive this more voluminous and constant rain”, he pointed out.

“Solar irradiance also ends up acting significantly in the summer months, as the sun is more positioned in the Southern Hemisphere, favoring the arrival of this energy in a very beneficial way”, he explained.

Regarding wind, in his view, the winds are not very interesting in the summer months. The Southeast is 'poor' in wind, the Northeast receives interesting intensity, but in a very punctual way, and the South also in a punctual way.

As the country moves into autumn and winter, precipitation decreases in most river basins, “so we lose this generation power through hydroelectric plants”.

“Solar irradiance, as we move towards winter in the middle of the year, also drops considerably, except in the very equatorial range, especially much of the Central-West and Northeast, where we know there is low variability in this irradiance. The winds begin to strengthen precisely during this period,” he explained.

“When we talk about the middle of the year in winter, we lose this power to generate energy through hydroelectric plants and we also lose it through solar irradiance. Therefore, photovoltaic plants end up generating a little less as the sun is already there in the Northern Hemisphere,” he commented.

However, according to the Climatempo expert, the country wins on the wind side. “This is the period we call good wind harvests. Northeast, Southeast and South, especially the continental part of the Northeast, receives a very interesting amount of wind. Bahia, Ceará and Piauí, for example, receive these good winds that favor the generation of energy through wind farms. Precisely because our system is nationally interconnected, we are able to have this complementarity of renewable sources”, he highlighted.

For Pedro Regoto, it is important to emphasize that the analyzes must be carried out based on the climatic factors that end up impacting the wind and rain regime, mainly. We have several factors, perhaps the best known are El Niño and La Niña, the cooling of the waters of the equatorial Pacific.

“These are phenomena that are not occurring above us, they do not occur locally, we call patterns 'teleconnections', patterns that remotely influence the globe. Each event like this can have an impact on increasing and decreasing rain and winds in certain regions of Brazil,” he said.

Extreme rainfall

Throughout the webinar, the impacts of extreme rainfall were also discussed. “The standard is being modified over time. When we talk about extreme, it can be a lot or little rain. Then some think: a lot of rain is good because we will generate a lot of energy through this excess rain. However, everything that is extreme is most of the time not positive.”

“I will cite a case that is tragic, but educational, such as the rain that occurred in December in the north of Minas Gerais and the south of Bahia. Some companies had difficulty servicing the electrical distribution network, as trees fell on the roads, preventing the passage of these professionals and, therefore, many power outages occurred. The teams had to be called, but because the roads were compromised, it ended up getting complicated”, he explained.

“In addition to this case, a company had a serious problem in its management of a PCH (Small Hydroelectric Plant). It had to take drainage measures to restore operation, precisely because it was going through a flood level. Furthermore, we are not just talking about extreme events such as rain, but also about winds and atmospheric discharges, which are linked to the fall of transmission towers. This affects not only the lives of companies but everyone”, he highlighted.

Rain forecast for the coming months

Regarding the forecast for the next 3 months, Climatempo indicated that for February the expectation is to still have an interesting precipitation condition with rains close to and slightly above average in much of the Brazilian Center-South.

“I'm talking about the heart of the Southeast, the Paranapanema basin, a large part of the Paraná basin and the basins included in the South subsystem. The Northeast, especially the São Francisco basin, should not receive high volumes of precipitation as it did in December. The North will be marked by a drier event”, he pointed out.

Referring to March, he emphasized that the idea is that these rains will start to rise more towards the Center-North, leaving the South and Southeast. “It is a March with a similar characteristic to December 2021, where we expect rain to be below average in much of the Center-South and close to above average in much of the Northeast, in the São Francisco basin, and in the basins from Northern Brazil. But in the North, the idea is that not all basins that belong to this subsystem should receive high volumes”.

“Finally, speaking of April, the rain continues to move to the Center-North. When April arrives, there is a shift in a band of more intense precipitation, reaching more of the Northeast. So, the forecast is that the North submarket will receive above-average volumes. And when we talk about the Brazilian Center-South, our expectation is that they will receive less rain than expected”, he concluded.