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Language and Framing Suggestions for MISO re: Resource Adequacy
Environmental Sector April 2023
During the MISO RASC meeting on February 28th, MISO made a presentation titled “Resource Adequacy Framing”. Members of the Environmental Sector took issue with both the language and the framing MISO presented, and MISO followed up to ask what language we would suggest. We urge MISO to be accurate in describing what the grid needs. MISO’s language has been imprecise, and that imprecision can limit opportunities for a broader range of solutions to address the issues MISO and its members are facing. We offer the language and framing suggestions below in response.
In particular, we raised concern about the language on slide 5 which states, “MISO’s resource portfolio is on track for continued decarbonization in the future, necessitating controllable resources to balance weather-dependent resources.” MISO seems to be using the term “controllable resources” to refer to thermal generators only, and “weather-dependent resources” to refer to wind and solar resources only. We take issue with both of these uses, which, as we noted in our verbal comments, we believe are inaccurate and misleading.
We also continue to raise concerns about MISO’s proposed “long-duration high-energy output” attribute as it forecloses the opportunity for many resources to meet grid needs and may be counterproductive to developing an efficient, affordable, reliable grid. We discuss these phrases below.
Weather-Dependent:
The phrase “weather dependent” has two primary uses,
In terms of resources whose availability depends on the weather, gas and coal resources have also shown themselves to have a lower availability or higher forced outage rates during winter storms, heat waves, and droughts. And we acknowledge that wind and solar resource availability is sensitive to temperature and other aspects of weather. For this aspect of “weather-dependent” we suggest that MISO use the terminology “temperature- or weather-sensitive availability.” Given the impacts of drought or ice, which are not solely a function of extreme temperature, “weather sensitive” is more accurate. For generation resources that depend on the weather as fuel, we suggest MISO simply use the terms “wind” and “solar” or “weather-fueled resources” similar to “fossil-fueled resources”.
Controllable:
MISO has been using “controllable” to refer to thermal generators and to energy storage. Yet, wind and solar resources are controllable in that they are very quick to respond when dispatched down and can also be rapidly dispatched up if they are operating below their EcoMax. In this case, we suggest the use of more specific terminology to get at the generation characteristics that MISO is seeking. We see two primary attributes related to “controllability”:
1. “dispatchability” for the ability to adjust the output level of a generator easily and quickly, and
2. “fuel-availability” for whether the generator has fuel available when MISO needs it to generate.
All resource types have varying degrees of dispatchability and fuel-availability. Wind and solar resources are very quick and flexible when it comes to dispatch down, but in order to be able to dispatch them up, they need to both have fuel-availability and be operating below their current peak capacity. Thermal generators have varying degrees of dispatchability, with gas resources being more flexible than coal, which is more flexible than nuclear. That said, all thermal generators are not dispatchable if they are fuel limited due to lack of firm contracts, frozen fuel piles, frozen supply lines, etc. and whether they can be brought on-line or ramped up soon enough to serve load.
MISO should use dispatchability or fuel-availability instead of controllable to accurately reflect the need that are seeking to fill.
Wind Drought:
The term “wind-drought” also needs further clarity as MISO has been consistently mis-applying the phrase. MISO has mostly been applying the term “wind-drought” during periods when wind generators cut out due to low-temperature cutout settings used to protect wind plants machinery. (Natural gas plants also shut down in cold weather without sufficient weatherization packages, but MISO has never referenced a “natural gas drought.”) Less often, MISO has used the term “wind drought” to refer to periods of low wind availability. These two situations are not synonymous, and they have different solutions. It is noteworthy that both of these events are predictable and incorporated into MISO’s wind forecasting software as forecastable events.
A “wind-drought” should refer only to a period of very low wind availability. We strongly recommend that MISO explicitly address and clarify this distinction in the PAC and the RASC (and anywhere else that “wind drought” was applied to mechanical cutouts). Specifically, MISO should address the following:
(a) Distinguish these two separate types of events (lack of wind fuel and low-temperature mechanical cutouts of wind generators)
(b) Define “wind drought” as only those events that involve very low wind availability. We recommend that the definition of “wind drought” be specific and include the following details:
(i) How long a period of low wind availability constitutes a “wind drought”, i.e., when does it become material for MISO’s operations?
(ii) How large a geographic area must have very low wind availability to materially impact MISO’s system and be deemed a “wind drought”? Or rather than geographic area, should MISO instead specify material impacts to a certain MWs of wind capacity?
(iii) How low relative to accredited capacity constitutes a “wind drought”?
To meaningfully discuss solutions, we must clearly identify the actual problem and its causes.
Long-Duration High-Energy Output:
We urge MISO and stakeholders to shift from talking about specific resource types directed or indirectly to talking about the attributes needed by the system and to clearly identify what attributes are necessary. MISO consistently lists “long-duration high-energy output” as an attribute that is required. This phrase implies that the solution set must come from a single resource (“an output”) that provides high energy over a long duration. By misnaming the attribute/s, MISO is foreclosing consideration of many complementary solutions working together to address the need. Instead, MISO should identify what specific attribute or attributes it is seeking under such an “output.”
The “long duration” component is apparently in response to the unavailability of generators during Winter Storm Uri that lasted several days. As noted above, the problem was due mostly to mechanical failures or cutouts due to weatherization limitations in extreme cold. Shouldn’t the attribute then be tied to solving the problem of functionality during extreme weather? The need for energy over a period of time could be met by multiple solutions.
The “high energy” component is particularly puzzling. Why does MISO need a single “output” with high energy? Wouldn’t multiple outputs with lower energy also meet the need? Isn’t the attribute (or really the need) the ability to deliver energy that matches demand in every hour of the day every year (minus the one-day-in-ten-years)? And how is this attribute different from the goal of resource adequacy overall? In short, we question whether the “high energy” component is a useful attribute.
Conclusion:
The key question is whether MISO has, in sum, the resources necessary to meet demand in all hours over a range of reasonably foreseeable operating conditions. The answer to this question depends on fuel availability, weather sensitivity, maintenance needs, mechanical settings, and other variables that will vary across resource types under different conditions. Wind and solar are dispatchable, and thermal generators are weather sensitive, and no generating resource is available or controllable when it does not have fuel. Focusing more on the interaction between resource characteristics and system needs rather than static resource classes (renewable vs. thermal) would be more helpful and inclusive of the various solutions that MISO and stakeholders must consider. MISO’s terminology is particularly important because the way the issue is framed ultimately sets the boundaries for the solutions that will be considered. Clarity in terminology will also help other decision makers who may not be as deeply involved in the discussions that MISO and its stakeholders are currently undertaking. For these reasons, we request MISO revisit its terminology to be more specific about the issues we are seeking to resolve and the resource attributes we must consider when seeking those solutions.
Respectfully submitted on behalf of the Environmental Sector,
Natalie McIntire
Senior Advocate
Sustainable FERC Project
Natural Resources Defense Council
WPPI Comments on MISO’s Preliminary LRTP Tranche 2 Maps and Questions
In its November 29 PAC presentation, MISO shared a discussion map of potential Tranche 2 projects along with the following “Conversations / Questions”:
WPPI offers its initial thoughts in response below.
1. MISO asks whether 765 kV should be considered for Tranche 2 and beyond. New 765 kV facilities may be difficult to permit and site but may be worth pursuing under certain circumstances. These include where a suitable corridor can be identified, where a state appears amenable to approval of 765 kV facilities, and where gaps in the existing 765 kV system can be filled to allow for fuller use of these existing facilities. A single new 765 kV extension into a particular area risks creating a new largest single contingency, so 765 kV extension may only make sense where it is paralleled by either another 765 kV circuit or a similarly strong path. Ideally these parallel paths would be arranged with strong connections between them in a few locations to better withstand outage of individual portions of the lines. Extending the existing 765 kV network west across Illinois appears the most logical focus for 765 kV.
a. MISO’s preliminary Tranche 2 maps appear to indicate a new 765 kV line connecting Quad Cities (IL) to Reynolds and Dumont (IN), via a new path that circles south of the Commonwealth Edison service territory. This may not be the most cost-effective way to create a new strong connection between these areas. A better approach may be to connect Quad Cities with the existing northwesternmost terminal on the existing 765 kV system at the PJM (ComEd) Plano (IL) Substation. This would be a much shorter segment than proposed by MISO and has the added advantage of providing an opportunity for cost-sharing with PJM. A more southerly route could then provide a second, parallel, path to provide resilient benefit even for single contingencies.
b. MISO's preliminary Tranche 2 maps include a southern 765 kV route that appears to connect Lutesville (MO) to Joppa (IL) via a Mississippi River crossing, before continuing northeast to (perhaps) Petersburg, IN. While this 765 kV route might make sense for improving transfer capability to MISO South, it appears rather roundabout for the purpose of better interconnecting the North-Central subregion, particularly if the Grain Belt Express HVDC line is completed to the Sullivan Substation, bringing substantial wind energy to southern Indiana. Other opportunities for additional EHV system reinforcements connecting MO, IL and IN exist and should be exploited first. These are described further below.
2. MISO asks whether dispatchable HVDC should be considered for Tranche 2 and beyond. WPPI’s view is that HVDC likely has a major role to play in Tranche 2. MISO’s RIAA analysis found that HVDC was a key tool for allowing reliable interconnection of very high levels of intermittent generation (a description that applies to the Tranche 2A models under development). HVDC provides multiple potential advantages relative to AC expansion, including better use of right-of-way and materials, flow control that allows for more-efficient dispatch and the ability to effectively move large amounts of power injection out of weak areas of the system. MISO has previously discussed the notion of building AC circuits with consideration to later conversion to HVDC operation (notably, at the February 16, 2021 workshop). This may be reasonable, but we would also suggest that consideration of new HVDC lines for initial operation as direct-current facilities is appropriate for Tranche 2 study. WPPI envisions that, in order to maximize their benefit, HVDC lines in Tranche 2 would be dispatchable by MISO (or by MISO in coordination with other involved RTOs). This would enable MISO to use the capability to control the flow on such lines to stretch the capability of the surrounding AC system (e.g., by improving stability limits or reducing post-contingent flows on limiting facilities).
3. Finally, MISO asks about neighboring RTOs. As already described above, close coordination with PJM appears important for cost-effective expansion of MISO’s grid. We provide additional examples below involving coordination with both PJM and SPP. WPPI believes that coordination with these RTOs about best uses of existing facilities and rights-of-way will be a key component of an appropriate Tranche 2 plan and early discussion with these parties should be a critical early priority for MISO.
4. One project idea involving both HVDC and coordination with neighboring RTOs that we recommend considering would be modifying the SPP Antelope Valley (ND)-Broadland (SD) line, which was built to 500 kV standards but operated at 345 kV, and currently carries only a fraction of the power that its large bundled conductors are capable of. MISO should evaluate, in conjunction with SPP, both conversion to 500 kV operation and convertion to +/- ~400 kV HVDC operation. This converted line would be most effective if extended east from Broadland to the Brookings area—or better yet to the Sioux Falls area—from which additional outlet-enhancement options are available (as described further below). We suspect the HVDC approach may be the most cost-beneficial, but look forward to an appropriate analysis. Of course, the existing line is an SPP facility and they would have to be involved in any conversion or extension, along with the facility owners. Cost-sharing with these parties may also be possible. Finally, we note that Antelope Valley could be made an even stronger source with addition of a ~10-mile 345 kV circuit connecting to MDU’s Coyote Switchyard.
5. Broadly speaking, we would suggest the following principles to guide development of additional Tranche 2 preliminary projects:
a. Consider rebuilding existing lower-voltage rights-of-way to higher voltage and much-higher capacity with a focus on rebuilding to double-circuit where feasible;
b. Make use of open or underutilized circuit positions on double-circuit lines, both Extra High Voltage (EHV) and lower voltage;
c. Given the particular difficulty of obtaining approvals for new Mississippi River crossings, work to make best use of existing crossings;
d. Consider balance of parallel paths of different voltages to avoid situations where sparse lower-voltage lines are overstressed for outage of new EHV facilities;
e. Consider filling in existing gaps that may become more significant with Tranche 1 projects and expected future resource-mix changes;
f. Beyond HVDC, consider strategically located AC flow-control technologies to allow MISO to better manage congestion and more fully use renewable generation.
6. A logical extension of an HVDC line from Antelope Valley to Sioux Falls (discussed above) would involve rebuilding the Sioux Falls-Sioux City and Sioux City-Denison 230 kV lines, and the 161 kV line extending southeast from Denison to near Orient, to 345 kV (preferably double-circuit). These are SPP facilities, introducing complication, but they appear to be high-quality rights-of-way that may be under-utilized today. A new 161 kV connection between Denison and the 161 kV line to the north (e.g. at the Crawford Substation) could support Denison during reconstruction, and also support outlet from the high-quality Crawford Co. wind resource area thereafter.
7. Beyond the Alma (MN-WI) and Marblehead (MO-IL) crossings that are to receive 2nd circuits in Tranche 1 projects, three additional 345 kV double-circuit Mississippi River crossings have only a single 345 kV circuit installed. Installation of second circuits in these locations, along with ancillary upgrades to take full advantage of these new crossings, appear to merit consideration for Tranche 2:
a. Rock Creek (IA)-Quad Cities (IL) — There is an open position on the existing 5-mile double-circuit 345 kV tower line between these two substations. Best use of this new circuit crossing might be facilitated by constructing 345 kV back west to the Tranche 1 Beverly-Sub 92 345 kV line.
b. Sioux (MO)-Roxford (IL)-Stallings (IL) — The Mississippi River crossing, along with the half-mile to Roxford and 2.5 miles back towards Sioux, consists of a set of 345 kV structures with two 138 kV circuits installed. An existing open 345 kV position extends from Roxford to Stallings. The Sioux-Roxford branch has appeared occasionally as a critical contingency in MISO’s SCED and in planning studies. Installation of a 2nd 345 kV circuit from Sioux to Roxford or Stallings shows significant potential to address a weak point in the Tranche 2 study system at modest cost. We anticipate that alternate routing of any needed 138 kV lines would be relatively easy to site.
c. Rush Island (MO)-Illinois — A second set of conductors is already installed at the river crossing east of Rush Island. Connection to the Rush Island Substation and extension of this circuit to the east shows potential to significantly increase transfer capability across the Mississippi River. One possibility would be to extend new 345 kV east from Rush Island to Baldwin, Prairie State or Coulterville, in conjunction with the planned conversion of the existing Cahokia-Joppa 230 kV line to 345 kV operation. In addition, it may make sense to construct a new connection between the two 345 kV paths south of West Frankfort, where they are less than 2 miles apart in places, so as to shorten the ~100 mile 345 distance (and the associated impedance and outage exposure) between these points via Joppa & Shawnee.
8. Additional existing lower-voltage Mississippi River crossings could potentially be modified to provide significant incremental transfer capability at 161 kV or 138 kV.
a. Two lines constructed to 161 kV standards cross the Mississippi River from 8th Street (in Dubuque, IA) to the northwestern corner of Illinois. One of these operates at 69 kV. This voltage fails to take full advantage of this key river crossing. MISO should consider converting the 69 kV crossing to 161 kV and should consider installing higher-capacity conductors. This second 161 kV circuit could be extended to the Galena (IL) area, and then further east to either Lena (IL) (where a double-circuit ComEd 138 kV line terminates) or to the EcoGrove wind project slightly to the northwest, where a single 138 kV circuit extends.
b. Four sets of 69 kV conductors cross the Mississippi River just downstream of Dam 19 at Keokuk, IA. 69 kV circuits are an arguably poor use of existing Mississippi River crossings. MISO should consider rebuilding to create two 161 kV river crossings to connect the >100 kV facilities on both sides of the river. Two 161 kV lines enter Keokuk from the north-south 161 kV line to the west, less than 4 miles from the existing 345 kV line, where a new substation could be installed. The Hamilton-E. Quincy double-circuit 138 kV line extends from the east side of the Keokuk river crossing south to Quincy (IL). This is an older double-circuit line operated as a single circuit, and appears to be a good candidate for reconstruction as a high-capacity 161 kV double-circuit line. Ideally this could tie to the 161 kV system at Marblehead N, and include a second 161-138 kV transformer to relieve the existing often-limiting transformer. Alternatively, transformation could be provided at Hamilton, and an additional outlet extending ~25 miles east from Hamilton to the Macomb-Monument 138 kV line could also be installed, which might make even better use of this crossing.
c. Located immediately north of the Maywood-Herleman 345 kV Mississippi River double-circuit crossing (the second circuit of which MISO proposes to use in Tranche 1), is a double-circuit 161 kV crossing that currently carries only one 161 kV circuit. Use of this existing second 161 kV crossing as part of a ~8.5-mile second 161 kV circuit between Palmyra and Marblehead N could make fuller use of existing facilities to increase transfer capability across the river. Better yet, this second circuit might be built as 138 kV and extend to Herleman, with a new 345/138 kV transformer at Palmyra, providing relief for the existing Marblehead N transformer. Additional outlet for this new 138 kV source could be provided with a new 138 kV circuit extended to Meppen (IL) on the existing double-circuit structures that carry only one circuit (alternatively, given that the existing structures are of older design and construction, and may not support adequate shielding for two circuits, this line could be rebuilt to better support two high-capacity circuits). A new circuit between Meppen (where a 6-position capable ring bus is planned under MTEP 15489) and NW Jerseyville (a distance of 15 miles) would strengthen this underlying network and make best use of existing rights of way. Upgrade of the single 138 kV circuit between Meppen and Sioux (MO) to support expected flows (the Mississippi River crossing has already, recently, been upgraded).
d. In southwestern IL, a single Mississippi River crossing leads from Missouri to the 138 kV switching station at the now-retired Grand Tower Power Plant, with three 138 kV outlets to the east. Extending a new 161 kV circuit from the Trail of Tears (MO) station 12 miles to the south, which is a relatively strong source fed from the nearby Heritage 345 kV transformer, would make better use of this crossing. Existing wide, straight 69 kV right-of-way extends most of that distance. If a second crossing cannot be permitted at Grand Tower, the 161/138 kV transformer could be located on the Missouri side, and the short 138 kV crossing could be upgraded to an appropriately higher capacity.
9. Some additional gaps in the existing lower-voltage system show potential for significant transfer-capability improvements at modest cost:
a. In northwestern IL, there is relatively poor connectivity between the 161 kV system near the Mississippi River and the 138 kV system farther east. A new 161 kV line between Sub 31 (IL) and the nearest point on the ComEd 138 kV double-circuit Normandy-Kewanee (IL) line would help fill this gap and alleviate contingency flows on other weak elements in the area.
b. In southeastern IL, the Paris South (IL) and Wabash River (IN) 138 kV stations (both west of the Wabash River) are separated by 15 miles, roughly half of which includes railroad or 345 kV right-of way. Closing this gap shows potential to strengthen the system at modest cost and effort.
c. One additional 138 kV gap in the area shows potential to be closed with modest effort. Less than two miles separate the Mt. Carmel (IL) and Gibson (IN) 138 kV systems. This is a Wabash River crossing, but this appears to be a relatively simple way to improve transfer capability, as well as to bolster both 138 kV systems, with retirement of the Gibson units planned over the next several years.
10. With the Tranche 1 projects in service, two 345 kV paths will connect to McCredie (MO) from the north and west, but only one networked circuit leads to the east, leaving a possibly critical weak point in the network. A second networked connection to the southeast could be created via a new 345 kV circuit connecting Kingdom City (MO) and Callaway (MO), a straight-line distance of approximately 15 miles. Existing straight lower-voltage right-of-way extends over most of this distance.
11. MISO's preliminary Tranche 2 maps appear to indicate a new 765 kV line between Sorenson (IN) and Lulu (MI). (While the maps appear to show an intermediate substation, there is no obvious suitable candidate for this location.) This project appears significantly longer, more expensive and more difficult to permit and build than an alternative that might achieve roughly comparable transfer-capability improvements. This alternative would create a new double-circuit 345 kV path between Collingwood (IN) and Lulu (MI) making use of existing circuits at both ends, and would construct a new 345 kV double circuit line between Varner (adjacent to S. Butler) in Indiana and North Star Steel (OH) (a distance of about 48 miles). Very strong connections between Sorenson and the Collingwood location already exist. A new six-position switching station at Lulu (something that would also likely be required to accommodate the 765 kV proposal) would provide strong connections in SE MI. This project would involve improvements to both PJM and MISO facilities, making coordination with PJM critical, and increasing the likelihood of PJM financial contribution.
12. With the upgrade described above to complement Tranche 1 projects, further cost-effective and permittable increases in IN-MI transfer capability appear possible by connecting the MISO MI and adjacent 138 kV systems, filling what is a significant gap today. Promising candidates include lines between PJM Moore Park (MI) and Simpson or Parkville (MI), Lagrange (IN) and Barton Lake (MI), and PJM East Fayette (OH) and Dowling (MI). Three new 138 kV connections could provide transfer capability of the same order of magnitude as a single 345 kV circuit. The distances are approximately 10, 20 and 14 miles, respectively, with two existing 69 kV paths along the longest of these. Upgrades to the existing systems would likely be required to realistically accommodate these new connections, but construction of multiple new 138 kV paths would tend to reduce the loading problems associated with any single path. New 345-138 kV transformers at Brody (MI) and Stryker (OH), both of which are PJM stations with adjacent 345 kV, would strengthen the Moore Park and East Fayette sources, respectively. Coordination with PJM would provide potential for cost-sharing. Several of the endpoints discussed above are radial 138 kV points, so the new lines discussed above would also convert these to 138 kV networked buses.
13. MISO's preliminary Tranche 2 maps appear to include (on the most inclusive map) a new 345 kV circuit between St. John and Schahfer (IN). That could take advantage of an open second 345 kV position for much of the distance between St. John and Schahfer (which extends further east towards Burr Oak). Rather than terminating at St. John, however, this line might be more effective if it connected to a new switching station on the ComEd (PJM) Davis Cr.-Bloom double-circuit 345 kV line. Routing east from that point, parallel to the existing 765 line, would eliminate the need for completely new right-of-way. Extension east in the open position east of Schahfer to the junction with the Reynolds-Burr Oak circuit could further increase transfer capability at relatively modest cost.
14. WPPI would be happy to prepare detailed .idv files for any of these projects that MISO is prepared to consider in its LRTP planning.