Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Hybrid hydro-solar power generation for increasing water and energy securities in the São Francisco River : exploring local and regional effects during a severe drought

Auteur : Campos, Érica Ferraz de

Université de soutenance : Instituto Nacional de Pesquisas Espaciais – INPE

Grade : Doctorate Thesis of the Graduate Course in Earth System Science 2021

Résumé
Reservoirs of hydropower plants can amend water, energy, and food securities in semi-arid regions. However, during severe droughts, the priority of energy demand leads to critical conditions on the water storage and risk of availability for multiple uses. To reduce water use for energy, one possible measure is the adoption of solar power, an abundant energy source in semi-arid regions. This study assessed the influence of adding a floating photovoltaic powerplant in the large-scale reservoir of the Sobradinho hydropower plant, located in the São Francisco River, in the semi-arid region of Brazil, from 2009-2018. The simulated scenarios varied the installed solar power capacity from 50 to 1000 MW. For each scenario, water allocation was modified based on the solar-hydro equivalence that restrained the historical outflow of Sobradinho to maintain water in the reservoir. Additionally, a diverse set of rules for the operation of the reservoirs in cascade installed at the São Francisco River was adopted to avoid ecological impacts of low streamflow. The scenarios were assessed in water security, solar hydro electricity output, capacity factor of the powerplant, and water and energy losses by evaporation and spilled water. Results show that a photovoltaic system starting from 250 MW was necessary to improve water security during the severe drought, reserving 0.7-2.3 years of water demand. Due to the water scarcity, the scenarios PV-750 and PV-1000 presented the same water storage level in the reservoirs after 2014, which restricted the influence of adding solar power. On the energy side, the capacity factor of the Sobradinho hybrid power plant was optimized from 29% to 34-47%. However, the water allocation of the simulated scenarios maintained the total electricity generation from the system in cascade for the solar power plant of 250 MW but reduced by 4.4% for the 750 MW. Although the reduction in total generation, all scenarios achieved an increment of the electricity output in the most critical years of the severe drought. We concluded that the solar source implied improvements for water and energy securities in the range of 250-750 MW. Additionally, we discussed opportunities and limitations in social, environmental, and economical aspects. This information can support decisions on the operation of water and energy supply systems and subsidize the proposal of public policies and guidelines for governance focused on integrated resources management in semi-arid regions.

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