PLANS 00001 Published On: 02/24/2021
Question: In the Session I Advisory Group Presentation, DESC explains that it has verified the capability to optimally retire units and replace them with efficient mix of resource additions. How was this verified and how were "optimal" retirement and "efficient mix" defined in this process?
Answer: Optimal and most efficient mix are based solely on lowest NPV of all utility related costs. Reliability is handled outside the model. DESC has not independently verified the “optimal” results produced by PLEXOS, rather it is relying on the credibility of the model in the public domain at this point in time.
PLANS 00002 Published On: 03/05/2021
Question: Could Stakeholders get written follow-up on the ability to use the DSM cost curve? How are you collaborating on the retirement studies?
Answer: The DSM cost curve was not used in the IRP. No collaboration on retirement studies has taken place but this is expected to take place as we move forward with our studies over the next two years.
PLANS 00003 Published On: 04/26/2021
Question: Help me understand how replacement assumptions impacts analysis on the front end? Would it be better to deploy this at this stage?
Answer: Due to required process for evaluating transmission impacts, we have to describe exactly what changes to the system we want the transmission group to study. We have added the request letter to the Stakeholder Website for your review.
PLANS 00004 Published On: 04/26/2021
Question: Why is DESC already laying out the retirement order rather than allow the study to determine the order? Part of doing the analysis is to optimize the order. What criteria are you using to determine Wateree, then Williams, and then Cope? For the replacement cases on Slide 63, wouldn't the use of a capacity expansion model provide a more robust set of replacement options for retired units?
Answer: DESC decided on the retirement order according to plant characteristics. Cope is ordered last since it is the youngest, newest, most reliable, and has dual fuel capability with gas. Wateree has lowest capacity factor and lowest site cost. Finally, due to its location on the transmission system, outages at Williams result in the most operational difficulty meaning it may be more complicated to replace.
PLANS 00005 Published On: 04/26/2021
Question: Why will this retirement study take years? Last year, Dominion completed a retirement study in Virginia in a few months. Can you give a more specific timeline?
Answer: DESC aims to have the Wateree retirement study completed by the end of 2021.
PLANS 00006 Published On: 04/26/2021
Question: The peaking proposal does not appear to be a one-for-one replacement. It proposes an additional 85 MW. Can you explain?
Answer: The turbine replacement is a one for one replacement of like kind vital resources at the end of their useful life. The 85 MW being questioned appears to compare winter and summer ratings inappropriately.
PLANS 00007 Published On: 04/26/2021
Question: Why were certain retirements presented here omitted from the IRP?
Answer: The retirements were not omitted in the IRP. RP3 considered retirement of Wateree, RP4 evaluated retirement of McMeekin and Urquhart, and retirements of both Wateree and Williams were in RP 8. DESC still needs to do a full study of the retirements to understand the full impacts of their retirements.
PLANS 00008 Published On: 04/26/2021
Question: For cost implications, will a securitization option be considered as part of any sensitivity analysis included in these studies?
Answer: Securitization requires legislation from the General Assembly, and we don’t have it in South Carolina. Without legislation, securitization is not an available option at this time. There is no enabling legislation giving the Commission the authority to approve or order securitization of any retired plants.
PLANS 00009 Published On: 04/26/2021
Question: A one-for-one replacement seems to be built-in assumptions across scenarios. Given that DESC already has excess capacity and Wateree 2 is already offline for a significant period, are you considering scenarios that do not include 1 for 1 replacement of coal plants?
Answer: DESC dos not assume a 1-for-1 replacement standard. Rather, resources are added to meet the required reserve margin in MW.
PLANS 00010 Published On: 04/26/2021
Question: About reliability: where does the possibility of planned and unplanned outages fit in?
Answer: DESC does build in planned outages to modeling, and updates forced outage rates while considering generation units. If a unit has a high forced outage rate, this value will count against the generating unit.
PLANS 00011 Published On: 05/11/2021
Question: Why is the timeline for the coal plant retirement studies so unnecessarily and unjustifiably long?
Answer: The timeline for a comprehensive coal retirement study (“Retirement Study”) is neither unnecessarily nor unjustifiably long. A Retirement Study involves the coordinated efforts of multiple Dominion Energy functions. DESC Resource Planning will lead the overall effort and perform resource adequacy, reserve margin calculations, reliability, and system cost/resource optimization studies. To meet the pace of implementation required by SC PSC Order No. 2020-832, DESC Transmission will now perform a transmission impact analysis (“TIA”) for the coincident retirements of both the Wateree Station and the A.M. Williams Station. The TIA will show if the electrical impacts of the retirements are technically achievable and identify transmission cost estimates at the retirement site as well as upgrades at the replacement capacity study sites. DESC Power Generation will plan for the community impact including employee relations and will develop plans and costs for demolition, site restoration and any site re-use, and develop plans and costs for DE-owned replacement projects. The DE Environmental Department will study and report on environmental impact/benefits, areas of continuing compliance, and closure costs with special attention toward ash ponds and ash landfills. Performing the TIA has been identified as the longest lead time item and is required to inform other activities mentioned above for the timely and successful completion of the Retirement Study.
PLANS 00012 Published On: 05/28/2021
Question: How will your long, two-year schedule for coal retirement studies align with your decision due by October 2021 to select an ELG compliance pathway for each coal plant? How will you avoid committing DESC and its shareholders and ratepayers to unnecessary ELG upgrade costs?
Answer:
With respect to the October 2021 ELG “decision” referenced in the question – this is a deadline for the Company to make a regulatory filing with SC DHEC regarding its compliance plans with the ELG rule, not an actual expenditure.
The Company is actively undertaking the coal retirement studies prior to committing to the substantial ELG compliance project costs while also continuing with engineering and pilot study activities such that it can quickly move into compliance project implementation, if required for continued system reliability.
PLANS 00013 Published On: 07/14/2021
Question: As to the additional near term solar and storage modeling for RP8 that DESC plans to model [described in 7/7 email as a response to Stakeholders], can you provide additional details as to what exactly DESC plans to model? Our reading of the PSC's order requires DESC to model near term solar and storage additions for RP8 that were previously ordered by the PSC and modeled for RP7a and RP7b.
Answer: We are pleased to inform Stakeholders that based on the comments filed in response to the 2020 Modified IRP and feedback received during the Session III IRP Stakeholder Advisory Group, DESC intends to model an additional resource plan in its 2021 IRP Update that introduces nearer term solar and storage resources to its approved Resource Plan 8. DESC appreciates the feedback from its Stakeholders.
In development of the 2021 IRP Update resource plan specifications and in response to feedback from the DESC IRP Stakeholder Advisory Group, DESC will introduce a resource plan that incorporates near term renewables which is the addition of solar and storage in 2023. The new resource plan will be RP8a and will be based on the preferred plan, RP8, but will also include the near-term renewables from RP7b, RP7b2, and RP7b3 which were the better performing plans as compared to the RP7a plans. Like the RP7b plans, RP8a will include PPA Solar and PPA battery energy storage in the amounts of 400 MW and 100 MW respectively starting in 2023. Results will be shown for three levels of solar PPA pricing, $34/MWh, $36/MWh, and $38.94/MWh, as previously specified for the Modified 2020 IRP (RP8a, RP8a2, and RP8a3). The cost of the PPA battery storage will be based on the “4Hr Battery Storage – Advanced” case of the NREL 2020 Annual Technology Baseline (ATB).
PLANS 00014 Published On: 12/21/2021
Question: Whether you are talking about concurrent vs. competing attributes or whether a resource can provide a service vs. whether it does provide that service, those are all problems that can often be solved through contracting, e.g., through requiring new storage to maintain a SOC that allows it to provide AGC. So will DESC be able to articulate why these services are needed?
Answer: DESC is proposing reliability factors that describe what services are needed to maintain reliability at the portfolio level. DESC is working with its Transmission Planning group to define the level(s) of each service that are needed and will communicate this information to interested Stakeholders.
PLANS 00015 Published On: 12/21/2021
Question: Did DESC consider modeling "Fast Start" explicitly in PLEXOS as a Non-Spin reserve, either a function of the largest contingency or wind/solar uncertainty?
Answer: Yes, we will include it in the modeling. Since it is a minimum requirement, DESC may not indicate the total number of fast start resources on the system. Despite this, we will want to understand whether a candidate resource plan negatively impacts the number of and amount of fast start resources.
PLANS 00016 Published On: 12/21/2021
Question: For those factors that you are scoring outside of PLEXOS, will there be any way to answer the question of whether that service is needed for any given factor? I.e., whether you will need additional black start capability? Because if you are scoring each portfolio for each of these factors, I am assuming you intend these as incremental needs to the system?
PLANS 00017 Published On: 12/21/2021
Question: Can DESC clarify how it is treating: 1. inertial response; 2. primary frequency response; 3. secondary frequency response (i.e., frequency regulation, usually provided by units on AGC).
Answer: DESC does not propose to reflect inertial response as a reliability factor in future IRP analyses. Primary frequency response may be provided by frequency controllers, but DESC does not plan to consider this factor explicitly as part of the IRP analysis. AGC and ramping will be addressed in the DESC reliability analysis and future IRPs.
PLANS 00018 Published On: 12/21/2021
Question: How will DESC characterize renewables for the 2022 IRP Update?
Answer: Typically for an IRP, DESC takes the load profile of a year with substantial solar potential and builds the profiles using those data. We do this this for 30 years. As part of the LOLE study, DESC sees that the difficulty lies in syncing the load profile to 20 years of weather data. DESC is looking back at the weather data to assess periods when there was little to no solar resource. Unfortunately, we do not have actual solar data going back 20 years.
PLANS 00019 Published On: 12/21/2021
Question: There are reasons to limit service and IRPs are not used to determine energy adequacy, but if there are non-firm off system transactions being transacted in the IRP simulation, then why wouldn’t it be part of the resource adequacy study?
Answer: DESC does not count on neighbors for reliability, since we believe that reliability of the system is our responsibility. Further, there have been events, for example in January 2014, where DESC has called for reserves from neighboring regions and these resources were not available.
PLANS 00020 Published On: 12/21/2021
Question: To clarify, is 2028 likely to be the earliest date that Williams or Wateree could retire, or were you merely giving that as an example?
Answer: It is DESC’s viewpoint that 2028 is likely the first possible retirement date for Williams. This view is informed by previous experiences with replacing a similar MW amount and knowing the Williams plant is critical for voltage support. The Wateree plant may have more latitude, but additional research is necessary to confirm this inclination. This evaluation will be informed by the TIA and the selection of the first feasible retirement date will be substantiated with that study.
PLANS 00021 Published On: 12/21/2021
Question: I think it's important to derive scenario assumptions based on an internally consistent methodology and not match up a Low Gas price and a High CO2 price just because they are available. Put another way, can we confirm what market conditions would result in a Low Gas and High CO2 price and what else would that implicate about what you model?
Answer: Thank you for this feedback. DESC will evaluate the proposed scenarios and determine whether any changes are warranted in light of this comment prior to proceeding with the Retirement Study analysis.
PLANS 00022 Published On: 12/21/2021
Question: Is there a reason there's no option listed for utility-owned solar plus storage?
Answer: Historically, DESC has credited third-party developers with lower cost renewable resources. We are re-evaluating the cost of ownership and are considering the inclusion of utility-owned solar and storage in the Retirement Study and IRP.
PLANS 00023 Published On: 12/21/2021
Question: How does DESC propose using the outputs of the Retirement Study? What decisions will be made based on those outputs and how do these decisions feed into the IRP?
Answer: The goal is to recommend the retirement of one or both of the Wateree or Williams sites and better understand the expected impact of these retirements on system operation and the cost to serve customers.
PLANS 00024 Published On: 12/21/2021
Question: If you are going to do the work of issuing an all-source RFP is there a reason to limit it to CT replacements? Can DESC instead also use it to inform how you characterize all resource costs in the IRP?
Answer: DESC is reviewing Docket 2021-93-E and waiting for final decisions to see if there are alternative resources that could compete on our system. Depending on the bids that are received, the responses may impact the resource cost assumptions used in future analyses.
PLANS 00025 Published On: 12/21/2021
Question: When do you expect to issue the RFP, and can we offer comments on the RFP after the briefing session and review of the documents?
Answer: DESC intends to issue the All-Source Peaker Replacement RFP in mid-November. We reserve the right to amend this following the briefing session on November 1 and based on the feedback that arises out of Session V.
PLANS 00026 Published On: 12/21/2021
Question: How will maintenance capex of Williams and Wateree be treated based on retirement date, i.e., will it vary based on costs that can be avoided by retirement? Will the ELG costs in the retirement analysis as well?
Answer: The model will be populated with a schedule of costs that can be avoided if the unit retires. These “avoidable” costs will include ongoing operational costs and any capital projects, including ELG projects, that are needed to keep the plant operating reliably. DESC will also consider how the ongoing maintenance capital schedule would be affected in instances where DESC knows that the plants are going to retire in a specific year. In other words, if you’re going to retire the plant early, you might operate and maintain it differently than if you plan to keep operating it through the end of its useful life. DESC may also reach one step further and run with the lower capex first before considering other options when comparing the results to determine the ideal retirement date.
PLANS 00027 Published On: 03/18/2022
Question: Is there a general range of early retirement dates selected?
Answer: The model can select a variety of different retirement dates depending on the market conditions. For Wateree 1 and 2, retirements can be selected after 12/31/2028. For the Williams unit retirement can be selected after 12/31/2031.
PLANS 00028 Published On: 03/18/2022
Question: Could DESC by itself meeting a 55% reduction by 2035 without retirements?
Answer: No. Without early coal retirements, the 2021 IRP Update modeling projects that DESC will only reduce CO2 by approximately 32% by 2035, with the exact amount depending on the market conditions that are studied.
PLANS 00029 Published On: 03/18/2022
Question: Why were there changes from the 2020 IRP to the 2021 IRP? When you consider the high case inputs, there was a change in both costs and shape of savings?
Answer: We were required in the 2020 modified IRP update to incorporate marginal line losses in calculations. So, there was a per MWh change and energy change, but cost didn’t change.
PLANS 00030 Published On: 03/18/2022
Question: Are you quite certain that the EE inputs have been discussed in the EE Advisory Group? For example, they changed somewhat from the Modified 2020 IRP to the 2021 IRP Update but I don't believe the EE Advisory Group discussed them. Our primary concern relates back to the Modified 2020 IRP order which states, "DESC is required to use "cost effective, reasonable and achievable" as the standard going forward for evaluating the potential for higher savings portfolios in future IRPs and updates beginning with the 2021 IRP Update.
Answer: The 2019 Potential Study and the 2020 High Case Rapid Assessment form the basis for inputs to the 2020 and 2021 IRPs. This will also be the case for the 2022 IRP. The rapid assessment determined that the DSM portfolio could achieve the 1% high case and met the standard of cost effective, reasonable, and achievable. The potential study underway will allow stakeholders to engaged in deeper discussions about how the standard of cost effective, reasonable, and achievable will be applied for inputs to the 2023 IRP.
PLANS 00031 Published On: 04/20/2022
Question: RE: Retirement Option 2 Does "DESC optimized" relate only to the forced earliest possible date retirements for Wateree and Williams? Also, were these runs only conducted in LT or was ST used as well?
Answer: The retirement dates were selected by DESC in Retirement Options 2-4. Then PLEXOS was allowed to optimized replacements in each of the five Market Scenarios around these assumed retirement dates. The ST model was used to estimate portfolio operational costs.
PLANS 00032 Published On: 04/20/2022
Question: Additional general question for the retirement options. Was NPV calculated from the LT (or ST if run) outputs and was the Revenue Requirements model from the IRP used?
Answer: The output of the both the LT and ST Plan was used to inform a revenue requirement calculation. Fixed costs were loaded from the output of the LT build plan and the variable costs were loaded from the ST Plan. The revenue requirement spreadsheet used is similar to the one used in the IRP.
PLANS 00033 Published On: 04/20/2022
Question: What was the rationale for end of 2028 (Wateree) and end of 2031 (Williams) as the earliest retirement dates?
Answer: The transmission project lead times in the TIA were a factor. The earliest retirement dates were also informed by the expected timeline for developing new gas pipelines in the service territory as well as time needed for regulatory review and approvals. After additional analysis, DESC has determined that a 12/31/2030 date for Williams will be modeled and will adjust the Retirement Study inputs accordingly.
PLANS 00034 Published On: 04/20/2022
Question: While we understand the hesitation in sharing actual values during preliminary results, can DESC provide an indicative summary of what types of replacement resources were selected by the PLEXOS LT simulations?
Answer: DESC wants to emphasize that the point of the retirement study is to evaluate the impact of different retirement dates, not to indicate a preferred path forward for replacements. However, DESC will share the build plan results once the study has been finalized.
PLANS 00035 Published On: 06/17/2022
Question: It remains unclear why DESC is assuming Williams cannot retire by 12/31/2028 and avoid the ELG upgrade requirements. We request that in a future stakeholder session DESC clearly discuss the ELG compliance options available to both Williams and Wateree, and discuss any determinations the company has made regarding those options.
Answer: DESC will provide a schedule detailing the critical path and required duration of the replacement project. DESC will also provide the commitments, constraints and determinations for ELGs as presented in the Retirement Study.
PLANS 00036 Published On: 06/17/2022
Question: To our knowledge Canadys was the site of a 490 MW coal generator, but most replacement resources evaluated at this location were larger than the previous coal plant (1057 MW in Case 3 and 534 MW in Case 4). It is unclear from the results how much of the network upgrade costs are attributed to the increased capacity sited at the location. An alternative scenario should evaluate a like-for-like capacity replacement of the 490 MW plant to avoid additional network upgrades.
Answer: Case 4 of the original TIA already examined the installation of a similarly sized unit (534 MW) at the former Canadys site. The system has changed significantly over the last 10 years. While Canadys had 230 and 115 kV interconnection capability the conductors must be uprated and/or additional lines must be built to accommodate new generation at the site. There are no longer existing interconnection rights at the site. DESC is considering options to take advantage of the existing equipment to the maximum extent reasonably possible.
PLANS 00037 Published On: 06/17/2022
Question: A scenario should explicitly evaluate the proposed Winyah coal retirement in neighboring Santee Cooper region. There may be either increased transmission costs or potential cost savings associated with interregional transmission planning.
Answer: Thank you for that insight. That is one of the reasons a joint study with Santee was undertaken. Together, the two companies make up the South Carolina Regional Transmission Planning regional planning entity. For this reason, and the highly integrated nature of the two systems, joint planning must continue to occur. The Winyah retirement was assumed to occur in the first five TIA cases that was performed by DESC.
PLANS 00038 Published On: 06/17/2022
Question: The preliminary results of the retirement study presented to stakeholders do not comply with the Commission’s order on the Company’s 2020 IRP. The Company has decided that it is simply not feasible to avoid ELG costs at Williams, despite having requested a December 31, 2025 ELG compliance date to Williams. We have some serious concerns about the quality and validity of the TIA, including its ability to speak to the transmission upgrades that are universally necessary to facilitate retirement of this unit.
Answer: The Company has serious concerns about maintaining reliability in the greater Charleston area without the Williams plant. DESC has seen the importance of the unit in the day-to-day operation of the system, not just planning models. DESC must ensure that reliability of the grid in all instances including peak loads with loss of multiple transmission elements. The TIA and future studies are evaluating the upgrades needed to meet the Company’s responsibilities under all conditions.
PLANS 00039 Published On: 06/17/2022
Question: The absence of a baseline study for the TIA analysis raises the question of how many system reinforcements would be necessary or prudent independent of coal retirement.
Answer: The DESC system is assessed annually for the 10 year planning horizon. All reinforcements that were identified as part of that assessment by year-end 2020 were included as part of the of the base TIA cases.
PLANS 00040 Published On: 06/17/2022
Question: Given current macroeconomic conditions, inflationary pressure and supply chain constraints are likely across the industry in the short term. DESC should avoid applying any additional costs solely to renewable or storage resources. While these challenges have been a topic of concern across the industry, these disruptions will be true for conventional thermal technologies and transmission investment as well - including for replacement parts and plant upgrades.
Answer: DESC has a basis for the costs applied to all candidate resources, regardless of technology.
PLANS 00041 Published On: 06/17/2022
Question: Similar to the proposed TIA scenario, we propose DESC evaluate a scenario that assumes an early retirement (12/31/2028 at the latest) for both Williams and Wateree. This is consistent with the 2021 IRP Update preferred portfolio RP8. In addition, this scenario should not include transmission upgrades for the Williams retirement, on the assumption that replacement resources are located at or near the Williams site.
Answer: DESC does not believe that the replacement generation needed to maintain system reliability can be brought online by 12/31/2028. This finding is supported by the Retirement Study.
PLANS 00042 Published On: 06/17/2022
Question: While the DESC proposed scenario matrix includes base and high load forecasts, a low load forecast scenario is not evaluated. As a result, we recommend a scenario that assumes lower load growth.
Answer: The market scenarios included in the Retirement Study were developed in consultation with Stakeholders. A low load scenario is not expected to materially change the within 10 years, and DESC’s intent was to focus on the most impactful scenarios.
PLANS 00043 Published On: 06/17/2022
Question: We propose scenarios (both PLEXOS LT and ST) that assume coal retirements and no new gas resources are available. This will properly bookend the analysis to show the costs, benefits, emissions, and operations with a clean energy replacement portfolio.
Answer: DESC is open to exploring such a scenario in the 2022 IRP Update. The Company also intends to include new carbon-free options, such as nuclear SMRs, in future IRP studies.
PLANS 00044 Published On: 06/17/2022
Question: Stakeholders continue to recommend that DESC use NRELs SAM tool and NSRDB dataset for estimate contribution of solar units as part of the reliability evaluation. Stakeholders suggest that DESC could further validate the NRSDB solar radiation data by comparing estimates of solar unit output using NRELs SAM tool and NSRDB dataset at 10 or more solar sites over a significant period of measurement with the actual outputs at existing units on the DESC system.
Answer: DESC continues to be open to using NSRDB data if it can be validated as consistent with observed values. DESC will validate hourly outputs provided by Stakeholders using the proposed data and methods against actual outputs at solar sites operating on the DESC system. DESC requests that Stakeholders provide a description the approach taken and supporting assumptions used to estimate unit outputs.