Abstract
Reservoirs of hydropower plants (HPP) can amend water, energy, and food security in semi-arid regions. However, during severe droughts, the priority of energy demand leads to critical conditions of water availability. 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 floating photovoltaic power (PV) in the large-scale reservoir of Sobradinho HPP, located in the São Francisco River (SFR), in Brazil, from 2009 to 2018. The simulated scenarios varied the installed PV 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. Besides, a diverse operation rule for the reservoirs in cascade of SFR 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, water and energy losses by evaporation and spilled water. Results show that a PV system starting from 250 MW was necessary to improve water security during the severe drought, reserving 0.7–2.3 of the annual water demand. In addition, the capacity factor was optimized from 29% to 34–47%. However, as the HPPs installed at SFR work as one system, the constrain of the river flow reduced the hydroelectricity by 4.4% for 750 MW. We concluded that PV significantly influenced water security and ecological conditions of SFR, with benefits in the range of 250–750 MW. The research provides assessment on substituting hydro for solar power on the operation of reservoirs in cascade and identifies the correlated benefits in social and ecological aspects. This information can support decisions of water and energy supply system operators and public policies focused on integrated resources management in semi-arid regions.
Highlights
Reservoirs can provide water security to water-stressed regions (Pereira et al, 2019; Scott et al, 2020)
The simulated scenarios were analyzed in terms of water allocation and energy output under the solar power adding and operative rules set to the reservoirs in cascade
Solar power generation can be an alternative to saving water in the reservoirs and reducing water use to produce energy
Summary
Reservoirs can provide water security to water-stressed regions (Pereira et al, 2019; Scott et al, 2020). The in clusion of a second power source to the existing HPP, turning it into a hybrid powerplant, can help to save water in the reservoirs, making it available for other purposes and providing a solution for developing integrated resources management and rising governance (Hunt et al, 2018; Maues, 2019). Resource availabilities are driven by environmental characteristics of the site (Link et al, 2016) and the dynamic process of positive and negative feedbacks involving anthropogenic interventions (Van Oel et al, 2014; Van Loon et al, 2016; Garcia et al, 2020) and ecosystem regeneration (Srinivasan et al, 2013). Biggs et al (2015) defend se curity as complementarily driven by: availability of resources in nature, capability to access, dynamics of social power, strength of institutions, and operating governance. The capacity to manage the resources plays an important role to concomitantly protect ecosystems, distribute the resources equitably, and apply them efficiently, making use of advances in research and new technologies
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