Análise da utilização conjunta do gás natural e das energias renováveis para a geração de eletricidade

Abstract

The use of renewables in electricity generation, especially wind and solar, has grown worldwide, taking advantage of reductions in equipment costs and policies to encourage substitution of fossil fuels. However, one of the main characteristics of wind and solar generation is intermittency, which requires increasingly flexible electricity generation systems. In Brazil, renewables have also shown significant growth with an increase in wind and solar generation. Some of the new hydroelectric projects, which have come into operation in recent years, feature run-of-river operation. With smaller reservoirs, the production of electricity in these plants, in periods of drought, drops substantially, making it necessary to complement this production. This work analyzes the use of natural gas, in order to present it as a viable fuel within the scenario of changing the electricity generation matrix, either with the use of renewable energies, around the world, or with the expansion of run-of-river hydroelectric plants in Brazil. The analysis presents several strengths and opportunities for natural gas, such as, for example, technologies that allow electricity generation with efficiencies greater than 60%, in combined cycle plants, and reduction of CO2 emissions in the order of 60%, compared to USC plants operating with two types of coal widely used in Brazil. Furthermore, the combustion of natural gas is practically free from SO2 emissions. The analysis also points out that the investment cost of a natural gas thermoelectric plant is about 50% lower, while the O&M cost is 40% lower compared to a USC plant. However, some factors are negative, there are weaknesses and threats that can make it difficult to use natural gas to generate electricity. Even natural gas has better environmental characteristics, compared to other fossil fuels, policies to encourage the use of renewable energy and replacement of fossil fuels can limit the use of natural gas. Furthermore, the development of energy storage technologies can mitigate the impacts of renewable energies intermittence. From all the factors presented by the analysis, it is possible to affirm that natural gas, despite being a fossil fuel, has, and will continue to play for the next years, a fundamental role in guaranteeing the stability of the electricity supply in the scenario expansion of wind and solar energy. Specifically in the Brazilian case, the complementary operation, during the dry season, with run-of-river hydroelectric plants is essential to guarantee the electricity supply to the country.