Heat wave affects solar power generation in Brazil

A heat wave drove Brazil’s power demand up to a record high of 102 GW last week. However, it also affected solar power generation and pushed PV module operating temperatures to up to 60 C.

Image: Tempo Ok

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From pv magazine Brazil

A heat wave that passed through Brazil earlier this month pushed energy consumption in the country to record levels. It also raised questions about the impacts of high temperatures on a system with a growing share of solar energy.

At some points, considering the heating effect of photovoltaic systems, the loss of efficiency may have reached 15% in this last heat wave, estimates the strategic leader of marketing and communication solutions at Brazilian meteo data provider Tempo OK, Caetano Mancini.

“The ideal temperature on solar panels is around 25 C,” Mancini told pv magazine. “At least, this is the industry standard for testing and evaluation. On average, PV systems suffer a reduction in efficiency of the order of 0.4% for each [degree Celsius] when the panel temperature exceeds 25 C.”

Mancini said that in the regions of São Paulo and Minas Gerais, air temperatures could eventually increase by 5 C above the average, which would be between 35 C and 40 C. This means panel temperature can reach up to 60 C.

“This would give a drop in efficiency of around 10%, 15%, more or less,” he explained.

Despite the loss of efficiency due to high temperatures, the participation of solar generation in meeting load demand continues to grow, as PV generation coincides with peak demand times associated with high heat.

“The photovoltaic solar source has been increasingly fundamental in supporting the National Interconnected System (SIN) in times of rising temperatures, a challenge that could become even more frequent with ongoing global warming,” said Rodrigo Sauaia, the president of ABSOLAR, the Brazilian Solar Photovoltaic Energy Association. “In addition to protecting the consumer's finances, solar energy avoids greenhouse gas emissions in the country's electricity generation, as it is a source that does not emit any gas, liquid or solid, during its operation.”

Sauaia said that solar reduces pressure on the national electrical system, thereby cutting systemic costs for consumers.

In November 2023, solar covered 10% of Brazil's average monthly demand, according to the network operator. In the northeast, participation in meeting the monthly load reached 19.4% in January 2024.

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Solar, accounting for nearly 28 GW of distributed-generation systems, now accounts for 40 GW, or 17.4%, of Brazil's installed electrical capacity, surpassing wind at 14.8% in centralized generation.

A recent report by Brazilian energy agency Empresa de Pesquisa Energetica (EPE) and German government agency GIZ has shown that it is possible to ramp up the share of these variable renewable sources to more than 40% by 2026, which ensure system reliability, safety and stability.

At the same time, the growing participation of PV in the energy mix requires more energy storage capacity and quickly deployable assets to meet the demand that was met by the solar source during the day. This year, the load ramp could vary between 25 GW and 30 GW.

“We had an El Niño with some temperature records, in September, November, and January, with a huge impact. This contributed to us having some temperature records in a large part here in the southeast of Brazil, with some persistent heat wave events and in November we had episodes with 10 Cabove average,” said Mancini. “What happens, in a very practical way, is the increase in evaporation in the largest region of the globe, which begins to affect the way winds move across the entire planet. This generates a natural impact on what we call the general circulation of the atmosphere and on rainfall patterns.”

During El Niño-influenced years like 2023, Brazil experiences increased rainfall in the southern region and drier conditions in the north and northeast.

“The southeast is a transition region. Between these two environments, it is rainier in the south and drier in the north/northeast,” Mancini said. “So the region is in a kind of ‘limbo', where predictability is lower and it is necessary to understand more factors, among which El Niño ends up being another part.”

La Niña brings a reversal in trends, favoring heavy rains in the north and northeast while causing drier conditions in the south, with other factors influencing behavior in the southeast.

The expert says that El Niño has already been weakening and the transition to La Niña should begin in July and August. Although the fall-winter period normally has a lower amount of solar generation, Tempo OK sees a more favorable pattern for solar generation at this time of year.

Tempo OK has been providing meteorological intelligence services for the electricity sector since 2014, with more than 500 wind and solar farms served, including centralized and distributed generation. It offers generation plants, among other meteorological services, including its own O&M software, including forecasting changes in patterns, months in advance.

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