Assessment of the economic impact of environmental constraints on short-term hydropower plant operation

Environmental constraints imposed on hydropower plant operation are usually given in the form of minimum environmental flows and, in some cases, in the form of maximum and minimum rates of change of flows, or ramping rates. Environmental constraints reduce the amount of water available to produce electricity and limit the contribution of peak hydropower plants to adapting the power supply to the demand and to providing certain ancillary services to the electrical grid, such as spinning reserve or load-frequency control. The objective of this paper is to assess the economic impact of environmental constraints on short-term hydropower plant operation. For that purpose, a revenue-driven daily optimization model based on mixed integer linear programming is used. The model considers the head variation and its influence on the units' efficiency, as well as the option of starting-up or shutting-down the plant at any hour of the day, should it be advantageous, while releasing the environmental flow through the bottom outlets. In order to illustrate the applicability of the methodology, it is applied in a real hydropower plant under different operating conditions and environmental constraints. - Research Highlights: → Economic impact of environmental constraints on hydropower operation has been evaluated. → The reduction in revenues obtained from selling energy in the day-ahead market has been calculated. → The sensitivity of hydropower revenues to different minimum environmental flows has been explored. → The sensitivity of hydropower revenues to different maximum flow ramping rates has been explored. → The importance of controlling the flow released through the bottom outlets has been highlighted.