Skip navigation to main content.
NREL - National Renewable Energy Laboratory
About NRELEnergy AnalysisScience and TechnologyTechnology TransferTechnology DeploymentEnergy Systems Integration

Eastern Renewable Generation Integration Study

The Eastern Renewable Generation Integration Study (ERGIS) is a multi-year U.S. Department of Energy-funded research project designed to simulate operations of the largest power system in the world with high penetrations of wind and solar generation. The study will inform critical questions on how system operations could be impacted by various wind and solar deployment strategies and operational paradigms. It is the first study to simulate the entire Eastern Interconnection and Hydro-Québec with hourly day-ahead unit commitment, 5-minute real-time dispatch, and a nodal DC-power flow. NREL staff developed new modeling capabilities to study the system at this resolution and fidelity and applied advanced computational techniques to the problem.

Map of power lines in the eastern part of the United States.

Map of the Eastern Interconnection as simulated in 2026.

ERGIS is a follow-on study to the Eastern Wind Integration and Transmission Study, the Western Wind and Solar Integration Study Phase 1, and other analyses. These studies showed that the variability and uncertainty of wind and solar power at high penetration levels require new ways of planning and operating electric power systems. However, new questions are being posed about future regulatory, market, and environmental policies; the siting and timing of new nonrenewable generation and transmission; and even load profiles with embedded and distributed generation. ERGIS will address these follow-up questions and place additional emphasis on the question of how to plan and operate the Eastern Interconnection in the face of generation and transmission uncertainty.

One way to bound this uncertainty in the analytical environment is to evaluate more than one possible future scenario. Another way is to test system robustness with a sensitivity analysis to key input parameters. This study will do both. ERGIS developed four study scenarios with the assistance of a technical review committee. This panel of industry experts is composed of individuals from every Regional Transmission Organization, several utilities, trade associations, and government agencies. The Current Variable Generation (VG) and State Renewable Portfolio Standard (RPS) scenarios provide insights into low penetrations of renewables. The Current VG case includes all wind and solar generation physically connected to the Eastern Interconnection in the year 2012. The State RPS scenario builds out wind and solar generation to existing State RPS requirements and interconnection queues as of 2012. This scenario has a penetration of about 12% on an energy basis. The two 30% scenarios book-end two approaches to reaching 30% penetration, on an energy basis. The Regional 30% scenario features 10% solar and 20% wind penetration. In the National 30% scenario, the solar penetration is 5% and the wind is 25%. The Regional 30% scenario is a logical extension of existing State RPS strategies and forces wind and solar generation to be built within each of the ERGIS regions. The National 30% scenario chooses the best resources in the interconnection to meet the 30% target and would be akin to an RPS implemented over the entire U.S. portion of the Eastern Interconnection.

Four graphs showing various scenarios for electricity generation.

Four ERGIS study scenarios.

ERGIS will evaluate the impact of various operating practices on production costs, curtailment, unit starts and stops, and emissions. In specific, ERGIS will evaluate the impacts of greater inter-regional cooperation, new reserve products, and intra-day unit commitment to provide operational flexibility.

Both statistical analysis and grid operation simulations with an Eastern Interconnection transmission system model will be performed to inform these questions. Final results are expected in the winter of 2015.

For more information, view this presentation.

Text Version

Eastern Wind Integration and Transmission Study

NREL researchers initiated the Eastern Wind Integration and Transmission Study to examine the operational impact of 20%–30% wind energy penetration on the power system of the Eastern Interconnect of the United States. This study was a response to questions about wind energy and transmission development posed by utilities, regional transmission operators, and planning organizations.

The Eastern Wind Integration and Transmission Study addressed these questions:

  • How do local wind resources compare with higher capacity-factor wind power that requires more transmission?
  • How does geographic diversity of wind reduce wind integration costs?
  • How do offshore and onshore wind power compare?
  • What transmission is needed to facilitate higher penetrations of wind power?
  • What is the role and value of wind forecasting?
  • How are wind integration costs spread over large market footprints and regions?
  • What additional operating reserves are needed for large wind power deployments?

A key task of the Eastern Wind Integration and Transmission Study was the development of a dataset of three years of modeled time series of wind speed and power output that was used to model the impacts of wind energy.

A technical review committee composed of regional and national experts on wind generation and power systems analysis guided and reviewed the study by providing feedback on key assumptions, methodology, and preliminary results.

The Eastern Wind Integration and Transmission Study was completed in 2010.

For More Information

For more information about the Eastern Renewable Generation Integration Study and the Eastern Wind Integration and Transmission Study, see the following resources. Additional publications can be found in the NREL Publications Database.


Aaron Bloom