Sustainable planning of the operation of reservoirs for hydropower generation

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Rangarajan, Srinivasan
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Consideration of the uncertainties in future reservoir inflows and energy demands is essential for planning the operation of predominantly hydroelectric generation systems. In addition, hydropower generation and flood control are often the conflicting objectives in planning and managing the predominantly hydro systems. A quantification of the impact of the uncertainty in inputs and the tradeoffs involved in the reservoir system allows a planner to compare the economic losses due to this impact with the benefits accrued from the system, thus, leading to planning the sustainable operation of the system. A reliability programming model is developed which considers the uncertainty in inflows and energy demands in planning the operation of a single as well as a system of multipurpose reservoirs, and also evaluates the hydrologic risk as a measure of the system not being able to satisfy the storage requirements for hydropower generation and flood control. The model determines the optimal levels of risk, by trading off the total benefits accrued from the operation of reservoirs with the economic losses which may be incurred as a consequence of these risk levels. The economic losses are explicitly specified in the model through risk-loss functions which quantify the costs of deviations from the goal, and a new four-step algorithm is proposed in this research to derive the risk-loss function for the purpose of hydropower generation. The nonlinear energy production function is linearized, and a three-level algorithm which combines the Complex Box search procedure with a Linear Programming routine is developed to evaluate the optimal risk levels. The direct implementation of the reliability model in its basic form is limited by the assumption of independence between monthly reservoir inflows, which leads to conservative planning of the operation of reservoirs. Three new approaches are proposed in thris research to alleviate the problem of conservative planning, thus, making the reliability model a robust tool for the complex task of planning. The application and the practical implementation of the reliability model are demonstrated for the case study of Manitoba Hydro, a predominantly hydro based electrical utility company for the province of Manitoba, canada