Shining a Light on Advanced Transmission Technologies
- Nov 12, 2020 1:03 am GMT
The Colorado PUC conducted an excellent Commissioner’s Information Meeting (CIM) last week on the subject of “Advanced Transmission Technologies”. I think a lot of people’s eyes glaze over when you start talking about transmission. But once you understand just how pivotal transmission is to decarbonizing the grid in the West, you begin to recognize the importance of getting the most out of the existing transmission grid, and growing it in the best way possible. It turns out that there is a set of little-known, and infrequently utilized technologies that can expand transmission capacity and solve sometimes vexing transmission problems while saving consumers lots of money. This CIM was intended to shine a spotlight on these technologies, provide a high-level introduction to how they work, where they’re best applied, provide some case-studies of real-world applications, and consider the factors that have thus far inhibited their deployment.
The day featured presentations by six subject matter experts. I’ll provide a brief synopsis of the presentations below, but before I do, I want to mention that all of them are available here, and the audio to go with them can be found here.
Transmission’s Role in Decarbonizing the Colorado Grid
The session began with Chaz Teplin of the Rocky Mountain Institute discussing the role of transmission in decarbonizing Colorado’s grid. Chaz described several recent national and Colorado-specific studies that investigate possible cost-effective paths to meeting both emissions reduction goals and the needs of a growing economy. The common thread running through all of the studies is that they all involve tremendous growth in electricity consumption in the next three decades, highlighting the need for rapid transmission improvements. One study estimates that CO will need about 10 GW of added transmission capacity by 2050. Chaz then described the very limited transfer capability between Public Service of Colorado and its neighboring balancing authorities, followed by a fascinating case study of what additional regional transmission could mean for decarbonizing the grid. On September 10th of this year, a snowstorm blanketed everything and dramatically reduced solar output. On the same date, there was very little wind until late in the day. Interestingly, Public Service of New Mexico (PNM) experienced the same conditions the following day, but on September 10th, had substantial wind resource. The point? In a future with large amounts of variable resources, adequate regional transmission can both ease renewables integration and take advantage of resource diversity across large geographic distances. Decarbonizing the grid will be much cheaper if we can share power regionally—i.e. if we build the transmission capacity that enables it. The following picture says it pretty well:
Optimizing Transmission at a Continental Scale
Chaz’s presentation was the perfect set-up for our next speaker: Jay Caspary of Grid Strategies, LLC. Jay has a long career in transmission planning, engineering and management at the Southwest Power Pool, and served as the co-lead of the Technical Review Committee on the infamous NREL Interconnections Seams Study, which was suppressed for about two years by the Trump administration, until being released in late October, 2020 (under pressure from the House Science Committee). Jay provided a fascinating overview of the Seams Study, which investigated a variety of options for the evolution of the transmission grids in the Eastern and Western Interconnections over the next two decades, including options that bridge the East-West electrical divide using high-voltage DC transmission (HVDC) links. This is a seminal, and incredibly important study that demonstrated very significant benefits to building new HVDC transmission across the seam. One scenario keeps the two interconnections largely as they are, but optimizes the existing DC ties along with conventional AC transmission additions. Two other scenarios envision significantly greater levels of cross-seam HVDC capacity, the most ambitious of which adds 126 GW of HVDC and creates a continental scale “Macro Grid”. The short story is that bridging the seam and the huge geographical scales contemplated by the study enables tremendous levels of inter-regional power transfers, aids renewables integration, thereby speeding and reducing the cost of decarbonization, and saves consumers on the order of $40 billion through 2038 compared to conventional transmission expansion planning. The following slide doesn’t do justice to either Jay’s presentation or the Interconnection Seams Study, so I strongly encourage you to download his presentation and read more about the study at the link above.
The SOO Green Line: Shipping Electrons by Rail
OK, that’s a somewhat misleading heading, but it’s not too far off the mark. Following Jay’s presentation on what HVDC could do at the national level, Brian Lammers of the DirectConnect Development Company presented on a very practical example of what HVDC can do at a regional level. Brian described his company’s innovative, first-of-a-kind plan to bury a 2,100 MW, 350 mile-long HVDC line along existing rail corridors between Mason City, IA and Plano, IL. Named for the Canadian Pacific RR line that it follows, the SOO Green HVDC Link will bring plentiful, low cost wind power from all over MISO-land to power-hungry Chicago and points east throughout PJM. By utilizing railroad rights of way, DirectConnect avoids eminent domain and contentious siting and permitting issues, and by putting the line underground in a 3’ by 5’ trench, visual impact is eliminated. Perhaps best of all, the line enables renewable development where the best resources are, and delivers that power to remote loads with low loss (see figure below). In addition to power delivery, the innovative power converters will be able to provide significant ancillary services and corresponding grid benefits at both ends of the line. DirectConnect currently has an open solicitation to allocate transmission rights. The company’s plan is to have the line up (well down…) and operating by the end of 2024.
Advanced Transmission: Making the Most of What Ya Got
Next up, Bruce Tsuchida, a Principal with the Brattle Group, spoke about the potential for three categories of new-ish technologies to increase the capacity of the existing AC grid, at far lower cost than conventional capacity upgrades. Bruce began by pointing out that most think of transmission systems as having fixed capacities, like road networks or railways. But just as cell-phone based GPS systems and advanced control systems have enabled roads and railways to get more drivers and passengers safely from point A to point B in a given time, these advanced transmission technologies can allow system operators to safely and reliably increase the power transfer capabilities of their existing systems. These technologies have been supported by advancements in power electronics, communication devices, computational processing power, and optimization algorithms. Representative examples include: 1) Dynamic Line Ratings (DLR), 2) Power Flow Control (PFC) devices and 3) Topology Optimization (TO). Rather than assuming that a given transmission line has a single, static, year-round power rating, DLR incorporates information on ambient (e.g. temperature and wind speed) and line conditions to calculate real-time line capacity that can be as much as 25% higher than the overly-conservative static rating. PFC devices utilize a variety of techniques to dynamically alter the reactance of a transmission line (essentially, how easy or difficult it is to push AC power through a line), thereby providing transmission operators a far greater measure of control over how power flows through their networks—for example redirecting power from an overloaded line to one with lots of spare capacity and expanding the capacity of the whole network. Finally, TO models alternative power flow scenarios in real time and then uses transmission circuit breakers to route power around congested elements in a network to increase the network’s overall throughput.
These technologies are quite inexpensive, provide resilience and reliability benefits, and can yield tremendous savings, which Bruce told the audience can reach into the tens- to hundreds of millions of dollars annually—on par with savings generated by RTO- or ISO-operated regional markets. They do this by reducing congestion and reducing renewables curtailment.
So if these technologies are so great and have been around for a while, why haven’t they been adopted by more utilities or grid operators? More on that in a moment, but first…
Power Flow Control Devices: Traffic Cops for Transmission
Our next speaker was Alberto Del Rosso, a Principal Project Manager with EPRI, who took a deeper dive into PFC devices, which alter power flow by changing a line’s impedance or phase angle, or by injecting voltage in series with the line. Alberto described six different categories of PFCs: phase-shifting transformers, series reactors, fixed and variable series capacitors, unified power flow controllers, distributed series compensators, and back-to-back HVDC converters. After describing each of these at a high level and noting some current applications where they’re solving vexing transmission problems, Alberto turned our attention to why a utility would choose these technologies over traditional solutions. As the following slide summarizes, in some cases, there simply are no traditional solutions to the types of problems PFC devices can solve. But in most cases, utilities are installing them because they are much less costly, can be deployed faster, avoid the challenges of siting new transmission capacity, and some are re-deployable to new locations as transmission needs change.
Alberto concluded by noting that while both mature and emerging PFCs are capable of solving transmission challenges cost-effectively, most have yet to achieve widespread adoption. What’s holding them back? Alberto pointed to five factors:
1. Inadequate understanding of PFCs by transmission operators and planners
2. Lack of models & analysis methods to evaluate PFC solutions
3. Need for standard operational practices and procedures
4. Regulatory cost-recovery mechanisms that make costlier solutions more attractive
5. The need to integrate PFC models into energy management system applications
Addressing these impediments will require the development of new modeling tools, new frameworks for evaluating the reliability and economic benefits of PFCs, and more field demonstrations and pilot commercial installations of the newest members of this class of devices. EPRI is doing its part by conducting a project on Power Flow Control Integration, which offers members the latest information on device options, detailed field performance and a software planning tool called CPLANET that helps determine the location and size of new power flow controllers for mitigating thermal overloads in a power system over a range of operating scenarios.
Breaching the Barriers to Advanced Transmission Technologies
Our final speaker was Rob Gramlich, Founder and President of Grid Strategies, LLC, a consulting firm that helps its clients understand the opportunities and barriers to integrating clean energy into the grid. Rob’s presentation focused on why the technologies we’d been discussing all day aren’t being deployed in greater numbers. Rob picked up on some of the factors Alberto mentioned, namely the fact that few utilities, regulators, or stakeholders are familiar with the technologies, and that even where they are, regulatory incentives usually favor the more capital-intensive, traditional approaches. Rob described two overseas approaches to align utility incentives with ratepayer interests: the UK’s RIIO (Revenue=Incentives + Innovation + Output) model and Australia’s Network Capability Incentive Parameter Action Plan. He then outlined the main points of an incentive proposal he has submitted to FERC on behalf of a group of transmission technology providers known as the WATT Coalition. This proposal would establish a shared savings approach focused on smaller projects with quantifiable congestion reduction benefits, and would provide incentives for both advanced planning for these technologies and for applications where they provide benefits as retrofits designed to alleviate shorter-term constraints.
The WATT Coalition proposal comes in the context of FERC’s rulemaking docket RM20-10-000, which is investigating incentives to promote advanced transmission technologies. Rob noted that the rulemaking, which is expected to close around the end of this year, is unlikely to impact transmission planning in Colorado (unless and until we have a regional ISO…). In response to questions from Commissioner John Gavan and energy policy advocate Larry Miloshevich, Rob said that given the quantities of renewable energy already on the system and the plans for increasing levels of renewable resources in the future, there are probably plenty of opportunities to deploy these technologies in Colorado. He also noted the critical role of state regulators in motivating utilities to integrate these technologies into their planning quivers using both carrots, sticks and what he termed “orange sticks” (policies including both penalties and incentives).
Commissioner Gavan closed the session by wondering aloud how many participants were aware of these technologies before this session, and noting that “awareness is the first step.” Watch this space!