Resumo:
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.