COREGS: An optimization framework to analyze water and power systems together under a changing climate

Abstract:

Seasonal climate variability can result in distinct seasonal differences in electricity demand and streamflow potential. Electricity generation systems rely on the availability of water to generate hydropower and to cool thermal power plants. Understanding the interactions between reservoir networks and power generation networks under varying climate conditions requires an integrated analysis of both system. Given the complexity and spatial differences in their domain of operation (reservoirs considering river basins and power systems considering the distribution grid), both systems are typically run separately with reservoirs providing the available hydropower to develop seasonal power generation scenarios. We propose Co-Optimization of Reservoir and Electricity Generation Systems (COREGS), a modeling framework that co-optimizes both systems with respect to power generation costs using the Generalized Reservoir Analyses using Probabilistic Streamflow (GRAPS) multi-reservoir model and the Tools for Energy Model Optimization and Analysis (Temoa) model. COREGS is a heuristic-based optimization framework that constrains hydropower allocation in Temoa using simulated hydropower from GRAPS. Release for hydropower is increased proportionally to the dual variables on hydropower constraints in Temoa; ensuring water is allocated where it is most beneficial. COREGS is evaluated for Tennessee Valley Authority’s (TVA’s) water and power systems at the seasonal timescale and compared with results from optimization with the Feasible Sequential Quadratic Programming (FSQP) algorithm. COREGS consistently provides solutions that meet power demand at a lower cost and release less total water than FSQP by reducing spill during wet years and in meeting the target storage in dry years. Simultaneous allocation of water and power through COREGS provides support for developing climate-water-energy nexus strategies such as fuel stockpiling, ensuring target storage, and scheduled maintenance of power plants. Potential for extending COREGS beyond TVA to the national scale as well as for long-term (e.g., 5-10 years) analyses will also be discussed.