Increasing wind and solar penetration into the electric power system in the Western United States leads to increased demand for flexible resources to balance net load (load minus wind and solar). Hydropower generation is one option for a resource that already exists throughout much of the Western Interconnection and is physically capable of providing flexibility. However, multipurpose reservoirs must meet an ever-growing, complex mix of power and nonpower objectives and constraints including ESA and other environmental objectives, navigation, flood control, water supply, and recreation among others. Generally, these objectives and constraints prevail over the generation of electricity and prevent utilizing the full amount of the physical flexibility that hydropower can provide.
Studies such as NREL’s Western Wind and Solar Integration Study (WWSIS) to understand the costs and operating impacts of variable and uncertain renewals on the grid typically simplify assumptions about the availability and flexibility of hydropower. Conversely, studies that focus on hydropower system optimization typically omit detailed representation of the power system, thus cannot accurately value the hydropower objectives in the multi-objective solution. The mutual and dynamic feedback between these two complex systems is not captured, thus both system analyses are incomplete. The result is less than optimal operations of hydro systems and less than complete understanding of the true impacts of variable and uncertain renewables on the grid. This project utilized the detailed hydro modeling system RiverWare, developed at CU-Boulder, to optimize the operation of hydropower facilities taking into account all the objectives and constraints mentioned above, while maximizing their participation in the production of electricity and ancillary services as modeled by NREL into the power system production model PLEXOS.
The study examined the value of bridging the gap between power system models and detailed hydropower models with a demonstration case. The United States Western Interconnection was modeled with PLEXOS, and ten large reservoirs on the Columbia River were modeled with RiverWare. The results show the effect of detailed hydropower modeling on the power system and its benefits to the power system, such as the decrease in overall production cost and the reduction of variable generation curtailment.
This study was conducted in 2012-13. The results of the study are published here:
Ibanez, E., T. Magee, M. Clement, G. Brinkman, M. Milligan, and E. Zagona (2014). Enhancing Hydropower Modeling in Variable Generation Integration Studies. Energy, 74 (2014), 518–528.