The share of renewable energy sources has increased worldwide, especially those considered unconventional (i.e. without considering hydropower). Besides proved as economically competitive, these sources cause less environmental impacts when compared to other sources of traditional power generation such as coal and oil. However, solar and wind power plants are intermittent, i.e., the generation varies according to the availability of the respective natural resources and therefore are considered non-dispatchable by the System Operator (SO). Because of that, the electrical systems must be able to somehow compensate the variability from the non-dispatchable energy sources to meet the supply-demand equilibrium. Storage technologies such as electrochemical (e.g. batteries) and electromechanical (e.g. flywheel) could be used in that sense. Recent developments of these technologies opened space for several ancillary services and products to be offered by the storage systems to the electrical system. In addition to that, the sustained reduction in operation and maintenance (O&M) costs summed to the payments for providing ancillary services could make some of these technologies economically attractive, under certain conditions. Given this new scenario, the representation of these storage systems in the expansion planning and power systems mathematical models becomes necessary. In this study, we simulated the Brazilian electrical system at 2035, considering batteries (corresponding to 7% of the installed capacity) and a 30% share of unconventional renewable energy in the system generation capacity.

The problem of poor carbon source is a common factor limiting the nutrients removal in bioretention cells (BRCs). This study aimed to investigate the feasibility of using modified biomass in BRCs filled with a mixture of fly ash ceramsite and pumice fillers to enhance nitrogen removal. Different pretreatment methods (hydrothermal-treated, acid-treated and alkali-treated) were attempted, and hydrothermal pretreatment showed a best performance in carbon release ability. The scanning electron microscopy showed that the lignin in hydrothermal pretreated pine barks (H-PBs) was destroyed, and the fiber structure became thinner with more irregular folds, which improved the accessibility of cellulose and attachment of microorganisms. The addition of H-PBs significantly enhanced the nutrients removal in BRCs, and the removal rates of TN and NO3−-N increased by 23.25% and 38.22% compared with those in BRC-A (without external carbon source), but the removal rate of NH4+-N was inferior to BRC-A. Besides, the large carbon release amount of H-PBs did not deteriorate the effluent quality, with COD removal rate of 87.98% in the 48 d. These results indicate that the BRCs by adding H-PBs could intensify the denitrification process.