Multiobjective optimization of hybrid wind-photovoltaic plants with battery energy storage system: Current situation and possible regulatory changes

The challenges presented by increased electricity generation from intermittent renewable energy sources can be minimized by incorporating energy storage systems (ESS). Despite the benefits, this is still an emerging technology with limited use in Brazil. The aim of the present study is to use a multiobjective optimization process to support the planning of hybrid wind-photovoltaic projects with utility-scale Li-ion battery ESS. Levelised cost of energy (LCOE), diversified energy production density, and net present value are considered as the objectives. The multiobjective optimization is conducted in view of the possible impact of regulatory adjustments necessary for the integration of ESS in the Brazilian context. The optimization problem has been formulated using the mixture arrangement technique and the Normal Boundary Intersection approach is adopted for search in the design space. It is shown that in the current scenario, the possibility of integrating storage reaches only 17.7% of the project capacity. In addition, the investment cost in ESS impacts the viability of the project more than the payout for the service provided. Thus, regulatory adjustments must (i) allow the generation of multiple revenues and avoid double taxation; (ii) predict whether there will be a defined minimum payment for services rendered and/ or whether there will be a subsidized credit line; and (iii) develop the production chain that involves storage or create tax incentives for importing equipment to reduce costs. Finally, it is important to highlight that the ESS imposes an increase in the load for the system as a whole and this characteristic needs to be considered for longterm planning.