PNNL

Abstract

Hydropower is expected to play a new role in the US electricity grid as more variable renewable energy sources like wind and solar come online. Wind and solar generation increase fluctuations in electrical supply, increasing the need and value of flexible generation sources that are able to quickly ramp generation up and down. The flexible generation and ancillary services (e.g., frequency and voltage regulation and reserves, black start capability) hydropower can provide for balancing and stabilizing the power grid are predicted to be of increased value in future grid scenarios. Yet, the flexibility of hydropower may come with environmental costs due to up- and down-ramping of hydropower plants (i.e., quickly increasing or decreasing generation flows, respectively) which may strand fish, dewater or scour fish nests, alter habitat, or create unsafe recreational conditions that may be unacceptable to participants in the hydropower regulatory process. These types of environmental impacts are often mitigated through environmental flow requirements that specify minimum or maximum flow releases, or ramp-rates changes allowed at a hydropower facility. While it is not currently known to what degree electrical grid reliability could be affected by environmental flow requirements, gaining a better understanding of these interactions before the grid becomes more deeply decarbonized is needed for policy and decision makers to define what policy, regulation, or infrastructure may be needed to support the clean energy transition. In this perspective, we discuss key opportunities and caveats for aligning hydropower environmental and power system needs for decarbonizing the electric grid.