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Öğe Hybrid linear and nonlinear programming model for hydropower reservoir optimization(ASCE, 2021) Doğan, Mustafa S.; Lund, Jay R; Medellin-Azuara, JosueLinear and nonlinear optimization models are common in hydropower reservoir modeling to aid system operators and planners. Different modeling techniques have their advantages and shortcomings. Linear optimization models are faster but less accurate, and nonlinear models are slower with better system representation. A hybrid linear and nonlinear hydropower energy reservoir optimization (HERO) model is introduced, where a hybrid optimization model sequentially solves the overall nonlinear hydropower optimization problem first with a faster-running linear programming (LP) approximation to improve an initial solution for a nonlinear programming (NLP) solution to significantly reduce NLP iterations and run time. The hybrid model is applied to six hydropower plants of California, with capacities of 13.5 to 714 MW. LP and NLP decisions are compared, and run time benchmarks of the LP, NLP, and hybrid LP-NLP models with different numbers of decision variables are presented. The hybrid model reduces the NLP run time by 79% to 88%, depending on model size, but still requires much more run time than the LP solution. For short-term operations with good inflow and energy price forecasts, where accuracy matters more and uncertainties are modest, the hybrid LP-NLP model has advantages. For long-term hydropower planning and management with many more decision variables and greater inflow uncertainty, the LP model, with its greater speed and sensitivity analysis, or stochastic models, representing some uncertainties, will often be preferred.Öğe Hydroeconomic optimization and eroperation of folsom reservoir for flood-managed aquifer recharge implementation(ASCE: American Society of Civil Engineers, 2024) Erfani, Mahdi; Maskey, Mahesh L.; Doğan, Mustafa S.; Medellin-Azuara, Josue; Goharian, ErfanThe increasing occurrence of prolonged droughts and extreme wet events in California poses significant challenges to the management of the region's water resources. To address these challenges, the utilization of Flood-Managed Aquifer Recharge (Flood-MAR) has emerged as a potential solution. This study developed a multiobjective hydroeconomic model to assess the economic impact of implementing Flood-MAR and reoperation of Folsom reservoir within the American River Basin. The simulation module consists of a hydrological model and a linear programming groundwater recharge model. The economic impact evaluation considers three main components: the value of groundwater recharge, surface storage, and hydropower generation. The findings demonstrate that the adoption of Flood-MAR and reoperation of Folsom reservoir offer considerable economic benefits, with minimal adverse effects on the downstream system. Two different model solutions were analyzed: one that aimed to maximize recharge and storage benefits, and one that prioritized hydropower generation. The former exhibited an increase in reservoir storage compared with historical operation, along with increased water allocation for groundwater recharge during wet and normal years. The latter showed substantial gains in hydropower generation but occasional drops in reservoir storage below historical levels. Despite these differences, the solution emphasizing recharge and storage benefits was deemed to be more realistic, considering the risk of future droughts and uncertainties in climate and hydrological forecasts. Overall, this research provides a foundation for assessing the economic impact of Flood-MAR implementation in the Folsom reservoir system.Öğe Hydropower Reservoir Optimization with Solar Generation-Changed Energy Prices in California(Springer Science and Business Media B.V., 2024) Doğan, Mustafa Şahin; Medellin-Azuara, Josue; Lund, Jay R.Growing solar photovoltaic supply has significantly reshaped energy prices, lowering them during solar generating hours. Large-scale hydropower reservoir operations need to adapt to changes in energy prices to maximize hydropower revenue. This paper evaluates effects of solar generation-changed energy prices on hydropower generation for five multipurpose reservoirs in California using a hydroeconomic optimization model. In California, major solar generation began in 2013, so years 2010–2012 are a pre-solar period, and years 2013–2018 are post-solar. Reservoir operations, hydropower generation and revenue between these periods are compared. Operations in the wet season (January to June), and the dry season (July to December) are evaluated. Results show that releases are more profitable when hydropower is generated twice a day during on-peak hours in the morning and evening in the wet season. When water is scarce, energy is generated only during the higher-price evening peak. Hydropower generation is mostly curtailed between 10am and 6pm due to large solar supplies, and increase during morning and evening peaks when solar generation is unavailable. However, by optimizing hydropower scheduling hours, the new energy price pattern can be more profitable. With increased energy price variability and adaptation, overall daily revenue can increase by about 14% in the wet season and 30% in the dry season.Öğe Managing aquifer recharge to overcome overdraft in the lower American river, California, USA(MDPI, 2022) Maskey, Mahesh L.; Doğan, Mustafa S.; Fernandez-Bou, Angel Santiago; Li, Liying; Guzman, Alexander; Arnold, Wyatt; Goharian, Erfan; Lund, Jay R.; Medellin-Azuara, JosueFrequent and prolonged droughts challenge groundwater sustainability in California but managing aquifer recharge can help to partially offset groundwater overdraft. Here, we use managed aquifer recharge (MAR) to examine potential benefits of adding an artificial recharge facility downstream from California’s Lower American River Basin, in part to prepare for drought. We use a statewide hydroeconomic model, CALVIN, which integrates hydrology, the economics of water scarcity cost and operations, environmental flow requirements, and other operational constraints, and allocates water monthly to minimize total scarcity and operating costs. This study considers a recharge facility with unconstrained and constrained flows. The results show that adding a recharge facility increases groundwater storage, reduces groundwater overdraft, and increases hydropower without substantially impacting environmental flows. Further, artificial recharge adds economic benefits by (1) reducing the combined costs of water shortage and surface water storage and (2) by increasing hydropower revenue. This study provides a benchmark tool to evaluate the economic feasibility and water supply reliability impacts of artificial recharge in California.
