N.A.Renewable Integration Study Highlights Opportunities for a Coordinated, Continental Low-Carbon Grid

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Multiyear Analysis Shows Increasing Electricity Trade Between Countries and Expanding Interregional Transmission Can Support a Reliable Future Power System

The North American electric power system is undergoing significant change, with renewable resources now contributing more generation than ever before—a transformation that is poised to continue given decreasing technology costs and ambitious decarbonization goals at the federal, state, local, corporate, and consumer levels.

With a series of reports released today by the National Renewable Energy Laboratory (NREL), the North American Renewable Integration Study (NARIS) aims to inform grid planners, utilities, industry, policymakers, and other stakeholders about challenges and opportunities for continental system integration of large amounts of wind, solar, and hydropower to support a low-carbon future grid. The NARIS project began in 2016.

“We used a suite of models to study a range of future scenarios and gain insights—including potential impacts on costs, emissions, resource adequacy, and the specific technologies that help enable the transition,” said Greg Brinkman, NREL energy analysis engineer and principal investigator for NARIS. “Our analysis focused in particular on the potential role of cooperation across North America and between regions within each country, and how transmission can support sharing of supply and demand diversity across the continent.”

NREL has released a report on the U.S. perspective in coordination with the U.S. Department of Energy (DOE), and a companion report describing a Canadian perspective in coordination with Natural Resources Canada.

Results show that a future low-carbon North American grid can be achieved through multiple pathways that can balance supply and demand using a variety of flexible resources. The study also shows that increasing electricity trade and expanding transmission could have significant benefits, highlighting opportunities for a coordinated, low-carbon continental grid.

First-of-a-Kind Power System Modeling for the Entire Continent

With input from the NARIS Technical Review Committee, NREL developed and evaluated a set of four scenarios to understand the impacts of future renewable technology costs, emission constraints, and growth in electricity demand on key study outcomes. The scenarios were informed by the goals set in 2016 for the Paris Agreement in each country, with up to 80% carbon reductions continent-wide by mid-century.

Leveraging NREL’s high-performance computing capabilities, NREL evaluated the scenarios using a variety of models, including NREL’s Regional Energy Deployment System (ReEDS), Distributed Generation Market Demand (dGen™) model, and Probabilistic Resource Adequacy Suite (PRAS), as well as Energy Exemplar’s PLEXOS tool. All modeling was sourced by consistent data sets through the NREL Renewable Energy Potential (reV) model, National Solar Radiation Database (NSRDB), and WIND Toolkit.

“NARIS builds on decades of previous work studying power systems with high levels of renewable generation, including the Western Wind and Solar Integration Study, Eastern Renewable Generation Integration Study, Interconnections Seam Study, and Pan Canadian Wind Integration Study,” Brinkman said. “Here, we analyzed the entire continent in detail while studying higher renewable generation than these previous studies.”

Four key findings emerged from the analysis.

Finding 1: Multiple Pathways Can Lead to 80% Power-Sector Carbon Reduction Continent-Wide by 2050

Steeper cost reduction of wind and solar technologies can lead to a faster and less costly transition, and carbon targets can still be achieved with conservative wind and solar cost assumptions. When it comes to total system costs of achieving 80% power-sector emissions reductions, wind and solar cost trajectories have a more significant impact than carbon policy assumptions.

Line graphs of CO2 emissions in metric tons for the United States and Canada through 2050 in four scenarios: 1) business as usual, 2) low cost vg, 3) CO2 constrained, and 4) electrification. Emissions decreases significantly by 2030 with low VG and then evens out for both the U.S. and Canada. Emissions continue to decline from 2030 through 2050 with electrification for both the U.S. and Canada.
Projected U.S. (left) and Canadian (right) power sector annual CO₂ emissions trajectories through 2050 in the four core NARIS scenarios.

Finding 2: The Future Low-Carbon Power System Can Balance Supply and Demand in a Wide Range of Future Conditions

For each core NARIS scenario, NREL estimated the number of hours in a year where supply would not be expected to meet demand in a region, as well as shortages that may occur due to generator or transmission outages. For both the United States and Canada, these metrics compare favorably with the North American Energy Reliability Corporation’s projections for the contemporary grid, meaning the scenarios analyzed in NARIS would not fundamentally impact the power system’s ability to balance supply and demand.

In the United States, between 1,200 and 2,000 gigawatts of renewable energy can be deployed to produce 70%–80% of U.S. electricity by 2050 while meeting planning reserve requirements. Thermal generation (nuclear, gas, and coal) contributes significantly to the future power system’s ability to balance supply and demand in all scenarios, even when most of the energy generation comes from wind and solar. Storage can also help provide capacity to the system.

In Canada, hydropower, gas, and wind technologies contribute most to the future system’s ability to balance supply and demand. Thermal generation provides 5%–10% of energy in all scenarios in 2050, but still contributes more than a quarter of winter planning reserves in most scenarios. However, existing market structures may not support these generators operating in this manner. Some of this contribution from thermal generation could be replaced by new hydropower or storage. Hydropower continues to provide approximately half of Canadian planning reserve needs by 2050—and hydropower expansion could potentially contribute more, especially in a future with higher electricity demand.

Finding 3: Interregional and International Cooperation Can Provide Significant Net System Benefits Through 2050

Allowing international transmission expansion provides $10 billion to $30 billion (2018 $US) of net value to the continental system between 2020 and 2050 in all but the business-as-usual case—the most conservative of the core scenarios. This demonstrates some of the potential benefits of international collaboration.

Expanding transmission between regions of a country provides $60 billion to $180 billion in net system benefits. Although these values are a small percentage (less than 4%) of the total $5 trillion to $8 trillion total system costs (which include all capital and operating generation and transmission system costs), transmission plays an important role in minimizing costs.

Bar graphs of the system net value of transmission in billions of dollars for international expansion, inter-regional expansion and coordination, and inter-regional expansion and coordination with macrogrid for four scenarios: 1) business as usual, 2) low cost vg, 3) CO2 constrained, and 4) electrification. The system values are estimated by comparing the total system cost in each scenario with and without allowing transmission expansion. The value increases the most with electrification for inter-regional and coordination and inter-regional expansion and coordination with macrogrid. It increases the most with CO2 constrained for the international expansion.
NARIS shows significant value in expanding transmission across North America to support sharing of supply and demand diversity. These values are estimated by comparing the total system cost in each core scenario in model runs with and without allowing additional transmission expansion (either interregional or international). Note the difference in the y-axis for the first chart compared to the second and third charts.

“Transmission expansion benefits are higher with more electrification and more wind and solar, which is a trend that could continue in lower-carbon scenarios or longer-term futures,” said Josh Novacheck, NREL electricity system research engineer and coauthor of the study. “Transmission can also provide reliability benefits and enable exchanging load and renewable generation diversity between regions—during normal conditions as well as in extreme events.”

Finding 4: Operational Flexibility Comes From Transmission, Storage, and Flexible Operation of All Generator Types

The results show the future low-carbon power system will benefit from many different forms of operational flexibility. In the United States, this includes flexible operation of natural gas and hydropower, curtailment (i.e., purposeful reduction) of wind and solar generation, and storage (mostly pumped storage hydropower). International imports, enabled by transmission buildouts, also help to balance the grid.

In Canada, hydropower, wind, solar, and thermal generation are key sources of flexibility. On days when Canada has high energy demand but lower wind energy output, Canada imports electricity from the United States. For days with higher Canadian wind output, the Canadian grid exports electricity to the United States—even when electricity demand peaks in both countries in the evening.

Hydropower provides a zero-carbon source of energy, capacity, and flexibility to the grid. In comparing similar scenarios with and without the ability to adjust power output from U.S. and Canadian hydropower generators, annual system costs are $2.3 billion higher without this flexibility.

Forging a Path for Future Research

“In addition to highlighting several opportunities for a coordinated, continental low-carbon grid, NARIS created open-sourced data and methods for future studies to build on,” Novacheck said. “We also identified several priorities for future research to expand on our findings.”

Follow-on work could focus on studying the stability aspect of power system reliability, analyzing new scenarios that reflect today’s emissions reduction goals as well as technology costs, understanding the impact of different market structures on building new transmission and generation, and refining how we model electricity demand patterns and sources of flexibility under future widespread electrification.

Learn More

For the full NARIS findings, read the U.S. and Canadian reports and executive summaries.

The NARIS webpage also includes links to additional information, including an interactive data viewer.

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