Midwest Transmission Operator Planning for a High-Renewables Future

June 27, 2018 | 9:56 am
Sam Gomberg
Senior Analyst

Driven by clean energy policies, customer demand, and simple economics, renewable energy technologies are becoming the dominant part of our energy future. Studies consistently show that wind and solar technologies could produce far more electricity than we currently demand, but questions loom about the transmission system’s ability to enable this transition to clean energy and maximize its potential benefits.

A new study undertaken by the regional transmission operator serving much of the central United States is seeking answers to some of these questions. But navigating the complexity and uncertainty inherent in planning our electricity future is a daunting task.

The Mid-Continent Independent System Operator (MISO) is a federally authorized regional transmission organization charged with maintaining reliability and operating wholesale energy markets across much of central North America. MISO has initiated a study and stakeholder process—named the Renewables Integration Impact Assessment (RIIA)—to evaluate how the current transmission system responds to increasing levels of renewable energy. MISO’s approach searches for those “inflection points” at which operating the system reliably becomes significantly more complex. If these inflection points can be identified, they can help inform MISO of both when and what investments or operational changes may be necessary to maintain reliability while enabling increasing levels of renewable energy.

A unique approach to answering a common question

MISO’s RIIA study takes a different approach to exploring our clean energy future. It does not explore several issues we typically see from renewable energy studies, such as what the “optimal” mix of resources is, what the costs and benefits are of the clean energy transition, or what kind of new policies or regulations should be enacted to achieve high levels of renewable energy faster or more equitably. Many renewable energy studies also look 20 or more years into the future premised on assumptions about policies that may be enacted or how the cost and performance of various technologies may change over time. Given the uncertainty inherent in predicting the future, MISO’s study design excludes many of these typical approaches.

MISO’s RIIA study is specifically designed to minimize the uncertainty (and stakeholder disagreements) over what the future holds. The study makes no assumptions about future policy or regulatory changes. Nor will it evaluate the costs or benefits of this transition. MISO can’t eliminate all the uncertainty from this study (more on that below), but this approach helps maintain focus on identifying when investments in the transmission system (or changes to how we operate that system) may be necessary as renewable energy grows.

The figure below provides a synopsis of MISO’s proposed methodology.

MISO’s methodology layers increasing levels of renewable energy onto the current transmission system to find “inflection points” where maintaining reliability becomes increasingly complex. At those points, MISO will explore solutions that allow increasing levels of renewable energy. Source: MISO

As the figure above shows, MISO will be seeking out “inflection points” when the complexity of maintaining reliability across the system increases due to the level of renewable energy connected to the grid.

An example of an inflection point is when the system experiences significant congestion that makes it difficult to get energy from where it is sourced (for example, the wind-rich areas of Iowa or the solar-rich areas of Louisiana), to where it is needed. Another may be when there is enough solar on the system to require increased flexibility during evening hours as solar systems go offline and other resources need to ramp up. These are worthwhile questions to be asking (and seeking solutions to) now rather than waiting for issues to arise.

Seeking insight in a time of rapid change

MISO’s RIIA study responds to growing recognition that the current pace of renewable energy development will drive rapid and unprecedented change across the electric system. The figure below shows how wind and solar resources have come to dominate MISO’s interconnection queue—the backlog of electricity generation projects waiting to be approved to connect to the grid.

Across the MISO system more than 86 percent of new resources looking to connect – nearly 80,000 megawatts of new capacity (bottom right) – are wind and solar resources. Understanding how this will affect the flow of energy across the system and how to maintain reliability under these dynamics, are the central questions being explored in MISO’s Renewable Integration Impacts Assessment study. Source: MISO

Not all projects in MISO’s interconnection queue will get built, but it serves as a strong indicator of looming changes to the system that MISO must prepare for. The RIIA study will inform how MISO maintains reliability in the face of this rapidly changing portfolio of energy resources.

Can the RIIA study overcome uncertainty to be useful to near-term planning?

MISO has already made some decisions—such as not trying to project the future cost of resources or future policy and regulatory conditions—to help minimize the RIIA study’s uncertainty and focus on impacts to the current system. This will help clarify the results and identify near-term next steps. However, some critical educated guesswork about the future is still needed and MISO must be responsive to real-world changes that occur during the study process.

For example, when MISO began this process just over a year ago, the mix of wind and solar resources being developed was significantly different than where we are today, as solar continues to improve in both availability and cost-effectiveness across MISO’s system.

The mix of resources being developed across the MISO system is changing rapidly. Just four years ago, solar was relatively non-existent. Today it makes up more than half of all resources moving into the interconnection process. Being responsive to ongoing changes is critical to the RIIA study’s usefulness. Source: MISO

The figure above shows how the mix of resources being developed across the MISO system is changing, and highlights the need to be responsive to these changes. While more than half of all new resources entering the queue in 2018 are solar resources, MISO’s current assumption about the ratio of wind to solar in its RIIA study is 75 percent wind and 25 percent solar, based on data from just one year ago. This latest data raises the question of whether MISO should update its assumptions regarding the ratio of wind and solar in the renewable energy portfolios that its examining.

Another big uncertainty is where these renewable resources will ultimately be developed. While this can also be informed by the project in the queue, keeping an eye out for significant shifts in expectations—and adjusting the study process accordingly—will be important.

Departures between study assumptions and the reality we’re experiencing today threaten to undermine the relevance of the RIIA study. Conversely, continuously reacting to the myriad changes that can occur across the system threatens the ability to complete the study in a timely manner, if at all. It’s a difficult balance to achieve. Being diligent and collaborating closely with stakeholders (including renewable energy developers) is crucial for ensuring robust analytics and a clear understanding of what the results can tell us.

In all, MISO’s efforts to plan for expected system changes in collaboration with stakeholders is a good thing. Our clean energy future depends on the ability to accommodate increasing levels of renewable energy without threatening reliability or incurring excessive cost. The RIIA study is a step in that direction—one that will help all of us keep pace with the energy evolution going on around us.