RASC: Draft 2021 Wind & Solar Capacity Credit Report

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Feedback

Solar generation has the largest number of interconnection requests in the current queue.  With relatively low capital costs compared to other generation types, solar development and penetration should continue to grow faster than load.  This increased generation should change the risk profiles for loss of load expectation.  Solar generation should be evaluated in the same manner as wind to determine its effective load carrying capacity.  

Similarly, storage technologies are becoming more prevalent in both stand-alone and hybrid configurations with renewable generation.  MISO should include studies on the ELCC of these classes of generation as well.

MGE and MPPA support WPPI Energy's feedback.

I would add that the term "deliverability" and its derivatives has (at least) 2 different meanings in MISO rules related to capacity accreditation for wind, solar, and other resources.  MISO should avoid using 2 definitions for the same formal term, especially in official rules (e.g., BPM-011). 

Thanks,

David 

Consumers Energy appreciates the opportunity to provide feedback on the DRAFT Planning Year 2021/2022 Wind & Solar Capacity Credit Report.  A few items for MISO's consideration:

(1) Regarding paragraph One of the Executive Summary on Page 4 of 22 of the Report, MISO states that it uses a two-step process to calculate the wind capacity credit, namely (i) “a probabilistic approach to calculate the MISO system-wide ELCC value for all wind resources in the MISO footprint” and (ii) a deterministic approach using historical output of wind resources.  The last sentence of the paragraph makes it sound like only the first of the two steps is used: “The MISO system-wide ELCC value is then allocated across all operational wind Commercial Pricing Nodes (CPNodes)…”.  It might make sense to include a sentence regarding the second step for the sake of completeness.

(2) In paragraph 2 of the Executive Summary on Page 4 of 22, unforced wind capacity is alternately cited as 3,598 MW and 3,405 MW.  Based on the data provided, namely 22,040 MW of wind @ 16.3% capacity, the correct number appears to be the former.

(3) While recognizing that the solar capacity credit methodology is detailed in BPM-011, this report could benefit by providing some information and analysis for the current year (e.g. how much capacity received credit via historical performance vs. class average, capacity by LRZ, etc.) for solar resources.

Thank you once again for the opportunity to provide feedback.

MidAmerican Energy Company appreciates this opportunity to submit comments on the annual Wind and Solar Capacity Credit report. 

General comments

As we’ve noted in prior years, the forecast of future ELCCs in Figure 2-4 shows a general trend downward as wind penetration increases in the future; yet the actual values of historic ELCCs in the same figure has shown a general trend upward as wind penetration has increased. While there are several reasons that this might occur, MISO should assure itself that this is reasonable. Intuitively, one wouldn’t expect future estimates to be so out of line with historic results.

Specific comments

Page 4, Section 1 (Executive Summary), second paragraph, incorrectly retains a number from last year’s report:

As of June 30, 2020, the MISO system had 22,040 MW (228 CPNodes) of in-service installed wind capacity. This means 3,598 MW (22,040 MW x 16.3%) of unforced wind capacity potentially qualifies under Module E-1 of MISO’s tariff. To the extent that the 3,405 3,598 MW of unforced wind capacity is deliverable at ....

Page 4, Section 1 (Executive Summary), second paragraph under “Solar:” The following sentence seems odd compared to last year:

As of December 2020, there are 1,048 MW installed capacity (ICAP) of registered solar resources (including behind-the-meter) with 727 MW ICAP being in-service solar with a CPNode (front-of-meter).

Last year, the equivalent sentence read:

As of December 2019, there are 464 MW installed capacity (ICAP) of in front of the meter solar and 575 MW ICAP of registered behind-the-meter solar in the MISO system.

There’s been hardly any change in solar capacity since last year (1048 MW this year, 464+575 = 1039 MW last year), but there’s been an increase of several hundred MW of front-of-meter solar (727 MW this year, 464 MW last year) – which implies a decrease in behind-the-meter solar. Is that right?

Table 3-1:

Beginning approximately with 2016, the “Wind Output at Daily Peak Load (MW)” column in this year’s data doesn’t always match the equivalent data in last year’s table. It appears that some of the data in the “Wind Output at Daily Peak Load” column has been increased over last year by the “Estimated Curtailment MW.” If that was intentional, it’s not clear why the change has only been applied to recent years.

Beginning approximately with 2019, some of the data for Daily Peak Loads in this year’s report doesn’t match the equivalent data from last year’s report. It would seem like this data wouldn’t change from one year to the next.

Section 4.1, second paragraph, should read:

Market Participants can use this to curve ….

MISO needs to update the solar capacity credit from the current 50% level.  As more solar gets added on the distribution level, the MISO load shape changes, pushing the peak to later in the day.  This decreases the amount of solar capacity available at the peak.

Below are the editorial items WPPI found while reviewing the Draft Report.  We did not have any substantive comments.

1. At p. 4/22 the posted draft refers to the extent that “unforced wind capacity is deliverable.” We suggest that a more accurate description would be the extent that this capacity “has demonstrated deliverability.” Please consider also replacing “deliverability” with “demonstrated deliverability at p. 14/22.
2. In the Solar section at p. 4/22, the posted draft refers to section 4.2.3.5.1 of BPM-011. This section no longer exists in the current version (v24) of this BPM.
3. At p. 4/22 the posted draft refers to “solar resources with less than 30 consecutive days of metered summer output” receiving “the class average solar capacity credit of 50%.” We suggest that the 50% figure is not actually any kind of class average—unlike the class-average XEFORd rates that are applied to certain small groups of conventional generators—and that the better terminology here would be “the default solar capacity credit of 50%.”
4. At p. 6 the posted draft refers to LOLE analysis that considers “the probabilistic nature of generation shortfalls and random forced outages.” We would suggest that this is duplicative as “the probabilistic nature of generation shortfalls” and random “forced outages” are essentially the same thing in this context. Consider substituting something along the lines of “time-varying electric demand” (which is the other key input to LOLE analysis) for one of these terms.
5. The first sentence of Section 3.1 at p. 12/22 merits review. Based on last year’s report, it appears the intent is to say that deterministic assignment of capacity credit to individual CPNodes is used because of the number of such CPNodes. Adding discussion of two separate allocation techniques to this sentence makes it unreasonably long and confusing. This point could be left for the 3rd paragraph, where it is discussed in some detail (and where “their Total UCAP” should be replaced with “its Total UCAP). Also, consider replacing, in the first paragraph of 3.1, “where the wind resources are approximately more effective” with something like: “where the wind resources tend to provide more capacity value.”
6. The description of deliverability-adjusted capacity factor and its application, at pp. 13-14/22, is out of place. Logically, it appears this should follow Table 3.1 rather than precede it. Please consider making this a new Section 3.2, and changing the existing designations of Sections 3.2 & 3.3 accordingly (or, alternatively, move these sections to Section 4—Appendix—as these appear to be descriptions most appropriate to an appendix.