Brazil has abundant water resources and depends on them for hydroelectric power generation. In 2011, 81.9% of the electricity in the country was produced by hydropower. A significant change in the Brazilian hydrological cycle reduced this percentage to 64% in 2015. The scarcity of rain decreased the volumes in the reservoirs of the hydroelectric power plants located mainly in the Southeast, Center-West and Northeast regions. In this scenario, the National Operator System authorized the use in full load of thermoelectric plants powered by natural gas, biomass and coal. As a result, thermoelectric generation grew 329%, increasing carbon dioxide (CO2) emissions. The intensification in the use of thermoelectric energy leads to a vicious energy–environment cycle, as it increases the CO2 emissions. Brazilian government is aware of the necessity of electricity generation, and future uncertainties generated by the instabilities of hydrological cycles may jeopardize the country’s energy security. The country has proposed programs to encourage energy generation by other renewable sources (wind and solar) and avoid the use of thermoelectric plants, which increase the generation costs and environmental impacts. This could compromise the goals of reducing carbon emissions signed by Brazil at Paris Conference (COP21).
This case study reports the expansion of thermoelectric plants use by Brazil due to the reduction in the hydroelectric generation, which was caused by an abrupt change in the hydrological cycle in the period from 2011 to 2015. As result, a reduction in the environmental sustainability of the Brazilian electricity matrix can be detected.
Hydropower and thermal generation yield 98% of the world’s electricity. However, in countries where hydroelectricity predominates, greater vulnerability occurs because the hydrological cycle is being altered by global climate change [1, 2]. Thermal generation is an important source of pollutant gases, such as CO, NO2, SO2, O3, CO2, N2O and CH4, and particulate matter, which are harmful to human health [1–5] and are aggressive to the environment, generating acid rainfall, photochemical smog and global climate change [3–7]. The use of thermal plants for electricity production is the subject of intense studies in several countries, especially in regard to the emission of greenhouse gases (GHG) [8–14]. To ensure Brazilian energy security, in the 2000s, the government policy directed investments to thermal plants. This action has hampered the perception of advances in other renewable energy sources and currently hinders GHG reduction programs in the electricity sector.
What is reported in this case study is the fact that Brazil, in spite of its immense water resources, has been reducing this type of generation in its energy matrix. In recent years, the country has faced a severe water crisis [15–17], which reduced the participation of water generation from 81.9% in 2011 to 64% in 2015 (Figures 1 and 2) [18, 19]. This situation was aggravated by the increase of 1.101 GWh/year in electricity consumption in the same period. Thus, the Brazilian government saw the National Operator System (NOS), the agency responsible for managing and operating the electricity generation which authorizes the operation of all thermal plants, mainly driven by natural gas, biomass and coal, therefore guaranteeing the country’s energy security, despite the well-known socioenvironmental impacts produced by this source [20–22]. Figure 3 illustrates the evolution of emissions in millions of tons of GHG from the Brazilian electricity sector between 2011 and 2015 . It is observed that there was an increase of approximately 460% in CO2 equivalent emissions between the years 2011 and 2014 and there was a reduction of around 10% between 2014 and 2015, this decrease is related to a strong economic recession the country experienced in this period. The Brazilian electricity generation system is characterized by a combination of hydro and thermal sources with predominance of hydro generation. By opting to increase the use of thermal power plants in order to compensate for the reduction in water generation, the country entered a vicious energy–environmental cycle whose main characteristic is the increase of GHG emissions, which in turn can intensify climate change.
This water crisis served as a warning. The country has always used its abundant water resources for electricity generation, but in face of the new climatic conjuncture, Brazil should not rely only on these resources. In order to break this vicious energy–environment cycle, the government invested on new legislation and incentives to favor companies and individuals who employ other renewable sources, such as wind and solar, in accordance with policies adopted in several countries [24–32].
Integrated System of the Brazilian Electric Energy Generation
The Brazilian electricity matrix relies mostly on hydropower for electricity generation; these water resources are distributed in 16 hydrographic basins located in different regions of the country. However, thermal power plants, used intensively, and an increasing number of wind energy sources also integrate the system, thus forming a hydro-thermal-wind power system with multiple owners for electric power generation. The electricity generation in the country is organized in two groups: National Interconnected System (NIS) and Isolated System (IS). The NIS is the focus of this study. It came into operation in 1999 aiming at interconnecting the generation plants distributed at different regions of the country and, thus, allowing energy transfer between the regions, optimizing costs and energy resources, increasing reliability and homogenizing markets. It is currently responsible for approximately 98% of the country’s energy supply. Figure 3 shows the main hydrographic basins, load centers and interconnections of the Brazilian regions by transmission lines .
The operation and coordination of the NIS are carried by the NOS, and each region of the country has a Regional Operation Center placed in the cities of Brasilia, Recife, Rio de Janeiro and Florianopolis. Thus, NIS is divided in the electric subsystems North (N), Northeast (NE), Southeast (SE)/Midwest (MW), South (S) and Itaipu.
BRAZILIAN WATER CRISIS AND ITS ENVIRONMENTAL CONSEQUENCES
Figure 4 shows the energy average storage potential (GWh) in the period 2011 to 2015 in the hydroelectric reservoirs of the NIS subsystems. The reductions in water volumes in the reservoirs were higher in the SE/MW and NE regions, mainly from 2012 onward, when there was an intensification of the water crisis in these regions (Figures 5 and 6). This is confirmed in Figure 7, which shows the hydroelectricity generation of Itaipu power plant in this period, the largest Brazilian power plant. Itaipu, a subsystem of the NIS, is located in the southern region of Brazil, where a marked variation in electricity generation was not observed in this period, since the water crisis was less pronounced in this region.
Figure 8 shows the Brazilian electricity generation by type of source, between 2011 and 2015, and the increase in generation by thermal sources is evident. This is in accordance with data from Figure 9, which shows the growth in CO2 emissions (MtCO2e) in the same period. The 10% reduction in emissions observed between 2014 and 2015 is due to a strong economic recession in the country. In 2015 at the Paris Conference (COP21), Brazil has committed to reduce its CO2 emissions [38–40]. To reach this goal, the country must break this vicious energy–environment cycle, that is, increase the use of energy solutions that do not depend directly on future climatic oscillations.
The solution involves public policies of government incentives of low carbon renewable sources such as wind and solar energy, which are extremely abundant in the country. In the case of wind energy, a generation of 25.68 GWh in 2016 has already been achieved, and so wind power currently accounts for 6.95% of the Brazilian electricity grid (Figure 10) [42, 43]. In addition, Brazil has great potential solar energy generation, as it is a tropical country and has large territorial dimensions. This trend of increased solar energy use in Brazil is shown in Figure 11. An exponential growth of solar photovoltaic energy generation can be observed, which reached 47,944 kW of accumulated power in 2016 .
The increase of wind and solar sources in the last three years (2014–2016) took place as a result of the public policies implemented by the Brazilian government in order to maintain energy security at times of abrupt climatic variations without increasing CO2 emissions. The Incentive Program for Alternative Energy Sources, Specific Energy Auctions for Renewable Sources and Regulatory Resolutions # 482/2012 and # 687/2015 of the National Electric Energy Agency (NEEA) are part of these policies to reduce reliance on hydro resources [44–46].
Variations of the hydrological cycle led to a significant increase in the use of thermal power plants in Brazil, generating a considerable environmental impact. The commitments of reducing CO2 emissions assumed at the Paris Conference and the increased generation costs led the government to encourage programs destined to the use of new renewable energy sources, which should protect Brazilian society from future hydrological changes, as well as ensure the sustainability of its electricity matrix. If Brazil chooses to continue using thermoelectric power plants, it may compromise its capacity to meet the GHG reduction targets agreed in Paris Conference (COP21).
CASE STUDY QUESTIONS
Has the change in the hydrological cycle produced an environmental impact in Brazil?
What can be learned by the Brazilian society in face of this water crisis?
Will the solution being implemented by Brazil suffice to interrupt the vicious energy–environment cycle of electricity generation?
Both authors collected all the data and wrote the entire article.
This research was supported by the Brazilian agencies CNPq, FAPERJ and CAPES.
The author has declared that no competing interests exist.