Sustainability and power generation: a comprehensive analysis of the Brazilian power sector's energy and exergy aspects

Given the increasing use of electricity and the current environmental challenges, ensuring efficiency and sustainability in power generation must be a major concern for society. In this context, energy and exergy analysis are useful to assess the efficiency and sustainability of different economic sectors. Hence, an exergy-based sustainability analysis of the Brazilian power generation sector was performed based on operational data from 2000 to 2020. The overall exergy efficiency of this sector varied from 63.3% to 75.0%. Thermal power generation was identified with the largest improvement potential. Several sustainability indicators were used to address the sector's sustainability. It was found that the depletion number varied between 0.25 and 0.37, while the sustainability index ranged from 2.73 to 4.00. The behavior of the indicators, such as relative irreversibility, lack of productivity, waste exergy ratio, and environmental effect factor, revealed that the exergetic cost of natural gas generation is already equivalent to that of hydropower generation, while electricity generated from natural gas represents only about 14% of the hydropower generation in the country. Over the evaluated period, cumulative exergy loss increased to more than twice the exergy provided by the system. In addition, a hypothetical scenario with no natural gas power generation was evaluated and compared; results showed a huge potential for exergy savings. This study is expected to contribute to enhancing energy policy formulation for sustainable development in Brazil.