Lab Notes: Let's Talk Transmission Planning

Electricity demand is rapidly increasing in the United States—so much so that we may need to double or even triple our transmission system by 2050! But how does that work? 

In this special Lab Notes episode, you’ll hear directly from experts at NREL—Jarrad Wright, Christina Simeone, and Faith Smith—about key findings from the National Transmission Planning Study. Providing concrete examples and data from the study, they dive into why exactly the U.S. grid needs an upgrade, where the barriers and opportunities are for improving it, and what these changes look like on a local level. 

Find out how these experts envision the future of the U.S. grid and how collaboration is can achieve a reliable, affordable energy future. 

This episode was hosted by Kerrin Jeromin and Taylor Mankle, written and produced by Allison Montroy and Kaitlyn Stottler, and edited by James Wilcox, Joe DelNero, and Brittany Falch. Graphics are by Brittnee Gayet. Our title music is written and performed by Ted Vaca and episode music by Chuck Kurnik, Jim Riley, and Mark Sanseverino of Drift BC. Transforming Energy: The NREL Podcast is created by the U.S. Department of Energy’s National Renewable Energy Laboratory in Golden, Colorado. We express our gratitude and acknowledge that the land we are on is the traditional and ancestral homelands of the Arapaho, Cheyenne, and Ute peoples. Email us at podcast@nrel.gov. Follow NREL on X, Instagram, LinkedIn, YouTube, Threads, and Facebook.

Transcript

[Intro Music] 

Kerrin: Welcome to Transforming Energy: The NREL Podcast, brought to you by the U.S. Department of Energy’s National Renewable Energy Laboratory. I’m Kerrin Jeromin. 

Taylor: And I’m Taylor Mankle. 

Kerrin: Taylor, you and I talk a lot about energy and awesome new innovations, but I wonder how much you think about the basic idea—how electricity gets to your home. 

Taylor: Yeah! You know, I feel I’m similar to the overall majority here and can say I barely think about it at all—unless my bills are way too high—but I do know from my time at NREL that this process is far from simple and super important! 

Kerrin: Yeah, the power that flows into your home can sometimes be generated hundreds of miles away. And it travels along those large power lines called transmission lines. 

Taylor: Now, transmission lines are the ones we all see out in open spaces, like along highways, maybe when you’re on a road trip. There are already more than half a million miles of transmission lines that bring power to more than 160 million customers. 

Kerrin:  And as we look to the future of our power grid, we could see more of those transmission lines spanning longer distances.  

Taylor: In the future, they may even cross regions to get power to where it needs to be. That’s because most of the most abundant low-cost energy sources in the country like wind and solar are in remote areas like the Plains and desert southwest regions of the United States.  

Kerrin: And NREL has been at the helm of looking into the potential future of transmission in the U.S. over the last three years. You may remember in October, we talked about the National Transmission Planning study and heard from one NRELian who led a team of researchers in the study. 

David Palchak: You know, what we're good at at NREL is looking at high renewable energy futures and understanding where these resources might go around the country and trying to create those futures and understand the role that transmission will play. 

Kerrin: That was NREL grid analyst David Palchak, the principal investigator of the National Transmission Planning Study.  

Taylor: We heard from him shortly after the study’s final report was released. The report outlines the value of doubling or even tripling the U.S. transmission system by 2050!  So today, we wanted to take a deeper dive into the study and see what it could mean for the future of the U.S. power grid. To dive into this topic, we welcome today's guest host, Tim Meehan. Tim is a communications specialist who worked directly with the researchers and the project team who conducted the scientific analysis and authored the study, so he can help us learn more about it! Tim, welcome to the podcast. 

Tim: Thanks, Taylor and Kerrin! Let’s get right into the National Transmission Planning – or NTP – Study. It was led by the U.S. Department of Energy’s Grid Deployment Office along with NREL and the Pacific Northwest National Lab. And it has the potential to inform the next few decades of decisions when it comes to grid planning. So, before we speak with a few special guests, I’d like to share some background on the study. 

Taylor: That would be great—let's set the stage for our listeners here. 

Tim: Great! So right now, electricity demand is growing in the United States. More and more electric devices and vehicles are being incorporated on the grid, and the amount of new renewable energy sources, like wind and solar, are growing too. But the buildout of new transmission lines to connect customers with clean energy resources has slowed dramatically in the last decade. Couple that with recent extreme weather events that shined a spotlight on the importance of a resilient grid, and the need for new transmission is now a focal point for the future of our power grid. Simply put: Transmission is what keeps the energy flowing from its source to your home, and it’s a key piece to the puzzle of a clean and reliable energy future. 

Taylor: Great insight to lay the foundation for this episode, Tim. And you spoke with a few NREL researchers to dig into the topic even further! 

[Interstitial Music]  

Tim: I’d like to welcome NREL’s Jarrad Wright, Christina Simeone, and Faith Smith, who were each at the heart of different facets of the study. Jarrad was a task lead, Christina was the lead author for one of the chapters of the study, and Faith led stakeholder engagement. Welcome to the show, everyone! 

Jarrad, Christina, and Faith: Hi! Thanks! 

Tim: Alright, thank you for joining us. Let’s start by taking a closer look at some of the key findings in the NTP Study. They show expanded transmission could lead to several wins. It could both help maintain reliability amid increasing extreme weather events and lower overall electric system costs. Those cost savings are to the tune of up to 490 billion dollars through the year 2050! So Jarrad, let’s take a look at those two factors briefly. What is driving those cost savings? And how could new transmission help maintain grid reliability? 

Jarrad: Well, in the first aspects with respect to reliability, the first step to better understanding potential future resource mixes, all of the technologies that supply electricity across the U.S. as well as the transmission networks that can enable the movement of power from where it's supplied to where it's needed, we use what's called a capacity expansion model. At NREL, that implementation is called ReEDS, and specifically more on that, the way that we did this was to explore various scenarios that primarily focus on transmission expansion topologies, followed by the expectations for future demand, expectations for future cost of resources, as well as the availability of these resources.  

And the capacity expansion brings all of this together and optimizes existing resources and the transmission with the expansion of the generation storage as well as transmission with an implicit consideration of one aspect of reliability—ensuring an acceptable level of resource adequacy at a relatively coarse level of spatial detail. And what I mean by this, specifically, is at a zonal level. On that is 134 zones that are represented at a contiguous U.S. level. And in addition, we applied further downstream tools to allow us to then further explore at a higher spatial resolution a nodal level where each bus and branch in the bulk United States electric power system are represented and where we gain insights into this, another aspect of reliability is here: and that is system security. This is implemented in a combination of tools that ensure the balancing of supply and demand at an hourly resolution as well as then the representation of these expanded transmission networks to ensure a reasonable level of system security at a national scale, and thus covering the second aspect of reliability. 

On the second aspect that you mentioned though on cost, these were primarily explored in the capacity expansion scenarios that I previously was describing, where the complete study arising is represented all the way up to 2050. And the relative cost differences between these scenarios and all of the sensitivities that went with that were established. And this is where the savings of up to $490 billion come from: it's the difference between a limited transmission expansion paradigm where transmission expansion only happens within existing planning areas and is constrained based on historical levels and a set of expanded transmission topologies that apply various transmission technologies and arrangements. 

Tim: That sounds like it was really complex. To piggyback off this, the study also focused on the potential of interregional transmission. So, in simple terms, Jarrad, what is interregional transmission and what is its current state? And how could it be a pathway to greater reliability and cost savings? 

Jarrad: That's a lot of questions, but we defined interregional transmission as the transmission capacity or effectively the amount of power that can flow securely between planning regions in the U.S. These regions have been established by the Federal Energy Regulatory Commission—or FERC—through what is called FERC Order 1000, which was established in 2011. There's ten of these regions, plus ERCOT in Texas, that we focused on, which covers the contiguous U.S., and the interregional transmission between these regions can be thought of as the large corridors of transmission lines that enables the movement of power between each of them.  

The current state of interregional transmission is expressed as the level of power that can move between these, as I was just describing, securely. And we have some great summary graphics of these that show these in the published reports from the NTP study. But for those not as familiar, there's almost no interregional transmission capacity between the East, the West, as well as Texas at the moment. These are what are also known as the seams, where only very small capacity exists through a very specific set of technologies: High voltage DC, but more on that later. However, there is a relatively large amount of transmission capacity within each of these interconnects. In the East, the West, as well as in Texas, more commonly known as the Interconnect, and these provide the exchanges of power between each of these planning regions. 

However, the expansion of transmission between these regions in each of the interconnects has not really been a big focus in the past, with some exceptions, and hence it’s one of the key drivers behind the NTP study: to explore this gap further. And what we found in NTP is that large scale interregional transmission expansion can support reduced overall costs in a few areas in operations as well as then in expansion in the long term. So, in operations, we'd be saving on fuel as well as operations and maintenance costs at the generation plants, as well as reducing capital expenditures or building less generation capacity as resources can be shared across larger geographical regions.  

And one of the final, key takeaways from this topic is a well-known quip about when large amounts of variable renewable energy like wind and solar exist in a power system. And that is well, “the wind doesn't always blow, and the sun isn't always shining. The sun only shines during the day. So, what do you do then?” And as I was previously mentioning, the resource mixes that result from the capacity expansion ensure resource adequacy by using the existing resources as well as expanding others when needed to fill these gaps. But more importantly is that with large scale transmission able to move power across these large geographical areas, there will almost always be wind somewhere or resources to support during those times of extreme need. 

Tim: Yeah, it sounds like interregional transmission could be very helpful when it comes to moving that power to where it’s needed the most. So, the NTP Study modeled nearly 100 different grid scenarios and dug really deep into several of them. Many involved high-voltage direct current, or HVDC, transmission lines. So, what did you learn from those scenarios specifically, and how could HVDC transmission be a game changer for the grid? 

Jarrad: When exploring HVDC technologies, we showed substantial benefits relative to a limited expansion of transmission, as well as even expansion only using higher voltage AC technologies, which is a dominant way in which power systems are operated today. And this is primarily driven by the economics of high voltage DC relative to high voltage AC, and more specifically on that, HVDC is very suitable for long distance and large power transfers for various reasons, but I'll skip that today for brevity. But, we actually explored two main paradigms on high voltage DC and that's point to point as well as multiterminal. And you can think of the point to point as classical high voltage DC that exists in a lot of countries today, including in the U.S., where power is moved from a single source of supply to a demand center.  

And now, with multiterminal high voltage DC using more modern technologies like voltage source converters, these explore an overlay of high voltage DC on top of the existing high voltage AC transmission grid to move power in a more controlled manner whenever it's needed through the combination of these HVDC overhead lines or underground cables as well as through the high voltage AC to high voltage DC converters. Now, when translating these findings into the detailed nodal models I was previously describing, we found that although high voltage DC supports with moving these large amounts of power across long distances, there's still a very distinct need for high voltage AC networks to support with reliability and specific contingency conditions.  

Now what's contingency? This is an outage of a piece of equipment, it's normally a transmission line, of which, if a large high voltage DC line trips, there's still a need to transfer power interregionally, and this is where the supporting high voltage AC expansions are very helpful and work in combination with the high voltage DC expansions that I was just describing. 

Tim: Thanks, Jarrad. Now let’s turn it to you, Christina. You and your team looked a lot at what it could take to start using existing and new interregional transmission more efficiently. So, what are some of the potential barriers operators currently face? And what are the steps they could take to overcome those barriers? 

Christina: Achieving the cost savings that the NTPS report¾the main report¾found depends a lot on how efficiently and effectively the different transmission systems talk to one another and interact with one another. Amy Rose and I looked at how existing transmission systems interact with each other and where opportunities exist to improve those operational efficiencies. A major opportunity exists to automate the way these different interfaces or interchanges interact with one another through intertie optimization. But there are also discrete opportunities such as developing frameworks for resource adequacy or sharing capacity generation, capacity resources across areas, doing joint studies to identify how large power transfers between systems when needed—an emergency event may affect operations and developing procedures to mitigate any issues. There are different opportunities in market areas and non-market areas.  

So, in non-market areas where there aren't system operators, for example, regional system operators or independent system operators, they could implement more coordinated scheduling and operations platforms or consolidate, again, to make some of the transactions a little bit more transparent and efficient, update processes to prioritize scheduling and wheeling transactions. In market areas, some improvements could include eliminating the fees that are charged for transactions between systems, improving some of the price forecasting for the coordinated transaction scheduling systems, or again, you move towards intertie optimization, which would again automate those transactions for optimal outcomes. Also, integrating the operational control of merchant HVDC lines within regional operators so that any excess capacity could be optimized for the benefit of the system. And those are just some of the opportunities that exist. And I think, you know, one of the large implications is that, again, to achieve these benefits of the assets that are already in place, before you even think of what new assets could be brought to the table is you want to operate as efficiently as possible. And there's a lot of opportunities to move us forward in that regard. 

Tim: Aso, I guess along with that, what lessons did we learn in the NTP study that could help inform planners and decisionmakers as we look towards the future of transmission in the United States? 

Christina: I think the biggest thing is the opportunity to take a national approach or a top-down nationwide approach to thinking about how we expand the transmission system. 

Currently, the way the transmission system planning happens is it starts at the local level and that's where most of the investments are occurring now. And that's a very bottom-up process. And then some areas of the country have relatively stronger or weaker approaches to regional transmission expansion planning.  

Right now, in the United States, there's actually no requirement to plan for interregional transmission lines or lines that can connect these larger regional transmission systems so we can move power over larger distances and share resources that are available for reliability purposes, for resiliency purposes, for decarbonization purposes, etc. So, I think this study really highlights the benefits of taking that approach and also the gap that exists with our current kind of balkanized or parochial view of transmission planning, and it pushes the boundaries of the existing institutions and the institutional approach to planning and opens up the imagination to what could occur if we did things a little differently. 

Tim: OK, let’s turn our attention now to what this study could mean for the future of transmission. Faith, one of the big things the team looked at was the concept of “high opportunity transmission,” or “HOT,” interfaces. Can you explain what those are and how planners could use them to accelerate progress? 

Faith: Yeah, of course! The HOT interfaces represent some of the more common solutions identified in the study. These are those that keep showing up in the scenarios for interregional transmission in particular. Given the persistence of these solutions across a wide range of potential future conditions, we think that these are a great place for decision makers or other grid stakeholders to start as they consider options for interregional transmission. Defining these interfaces was really driven by one of the core mandates of the study, which was really focused on making an approachable resource for industry to pick up and use. 

Tim: So. in the vein of being approachable, another key priority of the NTP Study was community outreach. Why was there such a large emphasis on that specifically in this analysis, Faith? 

Faith: As Jarrad mentioned, the breadth of this study and the focus on identifying transmission opportunities providing broad scale benefits to electric customers to inform and regional and interregional transmission planning processes and in identifying interregional and national strategies as we look to accelerate decarbonization, all while maintaining system reliability, the public really is crucial in this exercise, both from a data reception and sharing, as well as a feedback perspective. 

Tim: It does sound like they’re a pretty key piece to this. So, to follow up, what was the scope of the outreach of this study? How many and what kinds of stakeholders took part in it? 

Faith: That’s a great question. So, there were four main coordinated efforts as part of this. The first was a national level, very public and very forward facing. These are all publicly posted and available on the website that we have. The second was really focused on existing national and regional organizations as we sought to receive technical information, share key findings, really work with them to have an integrated scientific integrity as part of this effort. The third was tribal specific outreach—that was only with interested tribes in the process. We had a back-end process for tribes to be considered as part of that, and then the last was a more structured stakeholder process which included our Technical Review Committee, our TRC, that had subcommittees included in that with side working groups. The TRC was broken down into three different subcommittees with over 80 individuals from different organizations. That included our modelling subcommittee, our government subcommittee, and our environmental exclusion and land use subcommittee. Each of these included subject matter experts and had a range of use cases and meetings that we held with them. 

To simplify it, we had a government subcommittee that helped the modeling team with relevant state and federal policies, and how those should be represented in the power system modeling. That included representatives from PUCs, associations of governing bodies, and state and federal level agencies. The modeling subcommittee provided kind of the key pieces of the study in terms of confirming data, assumptions and methodologies, and the technical modeling aspects.

This included folks from system operators to load serving entities, academic experts, industry representatives, clean grid representatives and professionals, and then our last subcommittee really focused on general information in terms of siding for both transmission and generation assets as we looked at land constraints or potential issues that could hinder some of the modeling if you will. That really included folks from historical and cultural preservation organizations, local planners and siting offices, state level organizations looking at land management or wildlife entities. And then there was also federal organizations involved with energy siding expertise, in addition to legal scholars with expertise in federal rights of way. 

Tim: Wow! That sounds like a lot of voices were involved. So, I guess my final question is for all of you. How do you envision the U.S. grid looking in 2050, and what will it take to achieve the reliable, and affordable energy future that this study sets out to support? Let's start with you, Christina.  

Christina: So, I would see a more interconnected grid system¾more interconnection between systems, more automation of operation, greater cooperation between system operators, and again, a vast improvement in the planning and operations of the existing system in the expansion of that system. 

Tim: Okay, what do you think about it, Faith? 

Faith: Think about things both from how do we realize the technical potential of these modeling exercises, if you will, and finding pathways forward. So, thinking about potential regulatory changes and frameworks that could happen in the next few years, how to take some of these more low hanging fruit opportunities or HOT opportunities that we've mentioned before. But really, it starts at the local level. Like Christina said, we really have to think through how do we engage the right people and bring the right people to the table to make things happen to prevent any sort of snags and project developments, or to ensure that everyone's cooperating and working together. So, it is really a full technical effort, a full regulatory effort, and a full engagement effort that, I think, could really play the role moving forward, but there's a lot of a lot of small things that can happen outside of these large technical areas. And I think starting at small changes, engagement efforts and practices at the planning level would be useful. 

Tim: Jarrad, the floor is all yours! 

Jarrad: It does seem like the movement towards more deployment of clean energy will continue the economics of these technologies are dictating this, mostly being driven at the moment, at least by renewable energy resources, particularly variable renewable energy resources like wind and solar. But this is complemented by a range of other renewable energy technologies like hydro and geothermal in specific regions, as well as the continued use of existing nuclear technologies, the potential, but so far difficult to solve, long-duration energy storage challenge and then hopefully some technologies that are emissions free that are dispatchable as well in the future. The further sort of scaling of this towards 2050 will definitely require a bulk power system with sufficient transmission and operational plus planning coordination, as Christina was mentioning, that doesn't necessarily constrain these developments, but then also enables them at a pace that meets the needs of potentially growing demand and supply in areas where they haven't necessarily existed before. From a researcher’s perspective, luckily, NREL has more than 3,000 researchers working in this space on various challenging research questions and hopefully innovating to solve them with academia, with industry partners, international counterparts, as well as the USDOE. 

Tim: Wow! This has been a great conversation! Thank you all for the interesting insight into a study that could help inform a path to adding more energy sources to the grid while saving money and ensuring the lights stay on more often for millions of Americans. Jarrad, Christina, and Faith, thank you so much for joining and breaking down the National Transmission Planning Study for us!   

Jarrad, Christina, Faith: Thank you! Thank you so much! 

[Interstitial Music] 

Kerrin: And thanks, Tim Meehan, for guiding all of us through that enlightening discussion! And for our listeners, if you want to read the full study and learn more, head over to nrel.gov.  

Taylor: It sounds like there is a lot to be hopeful for when it comes to the potential for transmission in 2025 and beyond.  

Kerrin: That will do it for another episode of Transforming Energy: the NREL Podcast. Listeners, let us know what other topics you’d like to hear about! You can email us at podcast@nrel.gov, and of course, rate us five stars on your favorite podcast platform. 

Taylor: Have a safe and happy New Year, everyone! 

[Outro Music, fades] 

Taylor: A very special thanks to our guests today. This episode was written by Tim Meehan. Our theme music is written and performed Chuck Kurnik, Jim Riley, and Mark Sanseverino, of Drift B-C and episode music by Ted Vaca. This podcast is produced by NREL’s Communications Office and recorded at the National Renewable Energy Laboratory in Colorado. We express our gratitude and acknowledge that the land we are on is the traditional and ancestral homelands of the Arapaho, Cheyenne, and Ute peoples. We recognize and pay respect to the Indigenous peoples from our past, present, and future, and are grateful to those who have been and continue to be stewards of this land.