Article evaluates the insertion of floating photovoltaic energy to reduce the use of water by hydroelectric plants

São José dos Campos, June 20, 2021

Researchers from the Laboratory of Modeling and Studies on Renewable Energy Resources - LABREN of the National Institute for Space Research - INPE, a unit linked to the Ministry of Science, Technology and Innovations - MCTI, published the article "Hybrid power generation for increasing water and energy securities during drought: Exploring local and regional effects in a semi-arid basin" in the Journal of Environmental Management. The study had the collaboration of researchers from UNIFESP and Wageningen University, and was conducted in the context of the National Institute of Science and Technology for Climate Change (INCT - MC) Phase 2 and the Nexus Project - Transition to sustainability and the water-agriculture-energy nexus: exploring an integrative approach with case studies in the Cerrado and Caatinga biomes.

Led by Researcher Érica Ferraz de Campos - PhD student in the Graduate Program in Earth System Science - the article aimed to evaluate the insertion of the solar source to generate electricity by floating photovoltaic technology to replace the use of water. This is a critical issue, since in drier periods the priority of energy demand aggravates the conditions of scarcity of water resources for multiple uses. The theme gains importance on the agenda of scientific discussions because of the emergency water alert recently issued by the National Meteorology System of the Federal Government, with the climate outlook for 2021/2022.

The reservoirs of hydroelectric power plants (UHEs in portuguese) can be key elements for water, energy and food security in semi-arid regions. To reduce the dependence on water for energy purposes, one possible measure is the adoption of the solar source, abundant in semi-arid regions. The study evaluated the influence of adding floating photovoltaic plants to the reservoir of the Sobradinho Hydroelectric Plant, located on the São Francisco River, between the years 2009 and 2018. During this period, the São Francisco River experienced a severe drought, with ecological, social, and economic impacts that affected the population and activities dependent on its waters. The simulated scenarios varied in PV power intensity, with the adoption of installed capacity between 50 and 1000 MW, and for each scenario, the water allocation was modified based on hydro-solar equivalence, which restricted the historical flow of Sobradinho to maintain water in the reservoir. In addition, a different operating rule for the cascade reservoirs of the São Francisco River was adopted to avoid the most severe ecological impacts of the low flow practiced.

The results show that a PV system starting at 250 MW would have been sufficient to increase water security during severe drought. With this configuration, the capacity factor of the Sobradinho UHE would be optimized from 29% to 34-47%, improving the use of existing transmission lines. However, since the UHEs on the São Francisco operate as a system, the restricted river flow has reduced total hydroelectricity in the period by up to 4.4%. The study indicates that floating PV has significantly influenced the water security and ecological conditions of the São Francisco River, providing information to support decisions by operators of water and energy supply systems, and public policies aimed at integrated resource management in semi-arid regions.

The article can be accessed at this link: https://doi.org/10.1016/j.jenvman.2021.112989