Nexo energia-água: estudo de caso para a Matriz Elétrica do Ceará 2050

Abstract

The energy-water nexus is a challenge that can affect the electricity production of Ceará (CE), especially in long periods of drought. This dependence is more evident due to the fact that the state's current matrix has four thermoelectric plants (Porto do Pecém I and II, Termofortaleza, Termoceará), which demand a high amount of water, and the concurrent use of limited water resources. Based on this motivation, this dissertation presents energy scenarios and quantifies the withdrawal of water from generation technologies, with the objective of assisting state planning and optimizing electrical production, pointing out vulnerabilities and solutions. The adopted methodology gathers technical coefficients of the main electric generation technologies, totaling 31 configurations between source or fuel and cooling systems. Then, the generating structures for the construction of the scenarios that allow the estimation of consumption flows for the state are characterized. The estimated flow of the electric matrix of the CE in 2020, the reference scenario operating at full load, is 0.86 m³/s. The scenario of the International Energy Agency, which foresees installing carbon capture and storage in coal and natural gas plants, would increase water withdrawal in the CE by 90% (increasing to 1.66 m³/s), without increasing power. Finally, the estimated scenario for the electrical matrix of the CE in 2050, predicted by the autoregressive integrated moving average (ARIMA) model, results in an annual generation for the CE of 86 GWh, with an estimated withdrawal of 3.35 m³/s. In view of the withdrawal values, the feasibility of the scenarios with the Q90 permanence curve for the largest reservoir in the state (Castanhão) is analyzed, following the guidelines of Decree Nº 23.067/94, used in the granting process, confirming difficulties in managing the concurrent use of electrical generation and human supply. As a proposal for a solution, the use of dry (air) or hybrid cooling systems is indicated as a priority in the installation of new thermoelectric plants in the CE, in addition to indicating that the existing coal plants must start using sea water (demineralized), having in view of the proximity to the sea and the limited fresh water supply of the state.