A method to analyze the costs and emissions tradeoffs of connecting ERCOT to WECC

Grid reliability in Texas is an increasingly highlighted concern due to recent winter storms and heat waves threatening the reliability of the power sector. In this analysis, we compare two improvements on power grid reliability: building more firm generation capacity and connecting the Texas electricity grid to other regions, like WECC. To do so, we created a novel analytical framework that is comprised of the following four elements: (1) integration of open-source modeling tools, such as PowerGenome, pyGRETA, and GenX; (2) synthesis of multiple datasets containing information on historic weather, existing power fleet, energy technology performance factors, future projections of economics, etc.; (3) development of unique zonal profiles for load projections and weather dependent renewable resource performance; and (4) a newly consolidated network of 20 model regions representing the Electric Reliability Council of Texas (ERCOT), the grid that serves most of Texas, and the Western Electricity Coordinating Council (WECC), the grid that serves the western half of the contiguous US. Our flexible modeling approach can be applied globally to other grid modeling regions, though the method is demonstrated in this work with unique zonal profiles and a 20-region network, specific to our use case of connecting ERCOT to WECC. These 20 regions were used to simulate different developmental pathways of capacity expansion and operational dispatch across the combined regions while simultaneously optimizing cost and avoiding outage events by planning for winter storm. The primary focus of our work is to analyze the trade-offs of connecting two independently functioning grids and how their future development might be impacted. This analysis considered eight primary forward-looking grid modeling scenarios in ERCOT and WECC. We also completed two sensitivity analyses on some of the critical parameters needed to define the eight primary scenarios. All analyses found that building power plants and transmission connecting ERCOT and WECC lowers total system cost and avoids future CO 2 emissions across both regions when compared to solely expanding ERCOT’s power plant capacity. Further, the analyses found that plant hardening and weatherization is important, and can be done in parallel with transmission development for maximum benefit. • Computational grid modeling to optimize future power sector development. • Novel modeling techniques to construct a zonal model of 20 consolidated regions. • Simulated development with and without interregional transmission construction. • Pathways analyzed with normal and winter storm weather conditions. • Cumulative costs and emissions reduced in scenarios with interregional transmission.