Science & Technology

Multi-model analysis explores the benefits and costs of integrating eastern and western grids

Integrating the eastern and western power grids could provide significant value in strengthening the capacity of power systems to share power resources and flexibility between regions, he said. National Institute of Renewable EnergyInterconnect seam study. The results of a multi-year analysis were recently published in the journal IEEE Transactions on Power Systems.

“Since variable renewable resources such as wind and solar are expanding our share of power supply, the ability to transfer these resources between regions is a time of stress on the power system, such as extreme weather. It’s very valuable, whether it’s a normal day or not, if you want to take advantage of the best resources available, “said Josh Novacheck, senior research engineer and research lead at NREL. “The Interconnections Seam Study quantified the overall value to support utilities, developers, regulators, and policy makers in their efforts to prepare the grid for the future.”

Researchers have developed and studied four transmission grid designs, investigating potential costs and implications, using a new multi-model approach that cost-optimizes both power and transmission resources across the United States. The results show that increasing transmission capacity between the eastern and western interconnects will enable more economically efficient and flexible power exchange across the country. In the scenario, there is a benefit of up to $ 2.50 for every $ 1 cost.

The study was conducted by NREL researchers Novacheck, Greg Brinkman, and Jessica Lau, led by former NREL researcher Aaron Bloom, and another US Department of Energy (DOE) National Laboratory, Iowa State University. And worked with industry partners. A technical review committee consisting of more than 20 utilities, power system operators, and industry organization representatives assisted in guiding the study by reviewing its assumptions, scenarios, methods, and findings. ..

Funding for this study was provided by the DOE and Power Departments of the Energy Efficiency and Renewable Energy Wind Energy Technology Department to support the Grid Modernization Initiative.

Today, the three major parts of the US power system, the Western Interconnection, the Eastern Interconnection, and the Texas Electric Reliability Council, operate virtually independently of each other. However, along the “seam” between the western and eastern interconnects, seven consecutive high-voltage direct current (HVDC) facilities allow a small amount of current to flow between these two grids.

“The transfer function between interconnects is just a round-off error compared to the size of the network to which it connects,” said Greg Brinkman, senior research engineer and co-author of the study at NREL. “But as these facilities are rapidly aging, their potential replacement and expansion provides a timely opportunity to modernize the US power grid.”

The idea of ​​a nationwide power system is not new. In 1923, the Chicago Tribune announced a proposal for a continental power system that combines fluctuating (but flexible) hydropower resources with inflexible (but reliable) coal power generation.

Fast-forwarding for nearly 100 years, so far various challenges have hampered the development of national HVDC transmission designs. At the same time, wind and solar are emerging as key players in the power mix, and modern times require new approaches to planning future grids.

The research team conducted a large-scale and high-scale analysis of transmission plans for western and eastern interconnections up to 2038 with three classes of power system models (long-term capacity expansion, annual production costs, and power flow). It was carried out using a new combination of methods. Details, all consistent data entry.

They have developed four transmission designs: (1) maintaining existing seam capacity, (2) expanding back-to-back converter stations, and (3) adding three new HVDC transmission segments. , (4) A simulation of a nationwide HVDC network or “macro grid”. (Note: This study does not investigate connectivity with the Texas Electrical Reliability Council.)

The team modeled each design in eight different scenarios, using different assumptions about transmission costs, gas prices, wind and solar costs, power plant decommissioning, and renewable energy. In particular, the study modeled renewable energy generation levels, which will reach 40% in 2038, reflecting what the team called the “current policy.”

“This basic research and modeling framework can be extended to the higher levels of renewable energy generation and active demand-side participation envisioned by current national decarbonization goals,” NREL said. Said Jessica Lau, grid system group manager and co-author of the study. “In these futures, increasing flexibility in shifting renewable resources where and when they are needed across the country will support people and their basic electricity rights by utilizing all resources. It’s important for. “

As modeled in the study, power systems not only utilize geographically diverse demand and power generation, but also balance power generation and demand in each scenario, thanks to increased operational flexibility. We were able to reduce the total installed capacity of.

In all the scenarios investigated, the results show robust cost-benefit ratios ranging from 1.2 to 2.5 under different HVDC designs and different conditions, which is significant for increasing transmission capacity and sharing power generation resources between interconnects. Shows that it is worth it. New transmission lines can be used frequently during difficult operating periods throughout the year, such as heat waves and extreme weather events.

“In particular, the cost-benefit ratio we have found is additional, such as improved resiliency of electrical systems to keep supplying low-cost energy in the event of a major disaster such as a large hurricane or a widespread wildfire. It does not reflect potential benefits, “Brinkman adds. “These types of extreme events have not been studied in detail in this study, but are subject to ongoing work.”

Thanks to the series of animations available on the NREL Learning YouTube channel, you can actually see the importance of being able to shift power to where you need it most. Created by NREL data visualization experts, these videos show a modeled hourly system-wide generation and transmission flow under a variety of scenarios and system conditions.

“Looking at the power flow across the macrogrid design on peak load days in August, we can see how power transmission can help the system get out of tricky load distribution situations,” said a director of the Energy Systems Integration Group. Aaron Bloom, who is also the lead, said. Author of the study. “This future power system can use additional sunlight generated in the southwest to meet peak electricity demand in the east. Then, as the sun sets in the west, the Midwest and the Great Plains Strong wind resources can be sent in the opposite direction. “

Insights from the Interconnect Seam Study provide new tools to help decision makers evaluate strategies for strengthening the evolving grid. Future work that builds on analysis can further investigate the technical and economic benefits of alternative grid designs and assess system reliability, security, and restoring force.

Details of interconnect seam research and NREL energy analysis and grid research here..

Multi-model analysis explores the benefits and costs of integrating eastern and western grids Multi-model analysis explores the benefits and costs of integrating eastern and western grids

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