MODL 00001 Published On: 02/23/2021
Question: What feedback is DESC seeking on the model requirements matrix?
Answer: DESC is primarily seeking feedback on the evaluation criteria and the models to be evaluated, that is the columns and rows of the matrix. DESC also welcomes Stakeholder input on how the models presented rank against the defined criteria. Please see further details under the "Stakeholder Materials" page of the website.
MODL 00002 Published On: 02/23/2021
Question: It sounds like Dominion Virginia does not currently use Partial Chronology in PLEXOS (please confirm), do they currently use Fitted or Sample Chronology and how many blocks per month do they use?
Answer: DESC intends to use PLEXOS in a chronological configuration, if selected, through the Fitted Chronology methodology. DESC and Dominion VA are currently using between 6-12 blocks per day to solve PLEXOS.
MODL 00003 Published On: 02/23/2021
Question: In addition to capacity expansion modeling, will production cost modeling be performed to assess the portfolios identified by the capacity expansion model? If so, which production cost model?
Answer: DESC and many utilities use PLEXOS for both capabilities. The LT module sets the optimal resource portfolio and then the ST module is used to determine the optimized production costs.
MODL 00004 Published On: 02/23/2021
Question: What are Energy Exemplar's licensing terms? Are any restrictions on use of the license, is it the same version of PLEXOS that DESC is using, do you still need a license to view the manual?
Answer: We will need to discuss this question with Energy Exemplar to get a specific description of the licensing restrictions or lack thereof. Our presumption is that they are offering the same model as is being used by DESC.
MODL 00005 Published On: 02/23/2021
Question: When does DESC anticipate deploying PLEXOS or another chosen model, the 2023 IRP?
Answer: We anticipate PLEXOS to be fully implemented by the 2022 IRP Update as directed in the Commission Order. If another model is selected, PLEXOS may have to be used as an interim solution for the 2022 IRP Update in which case the new model would be adopted for 2023 IRP.
MODL 00006 (revised 02/25/2021) Published On: 02/23/2021
Question: Slide 37 of the Session I Advisory Group Presentation states that inputs to PLEXOS can be an equation. Are inputs limited to vectors that change over time or can DSM cost and availability change dynamically based on the model’s selection?
Answer: The DSM inputs can be set as a constant or input as time series of values in a datafile. DESC will work with ICF to evaluate combinations of DSM measures and estimate the cost of those measures needed to achieve various levels of reductions in load. These load reductions will be modeled as load scenarios or DSM resources in PLEXOS as appropriate.
MODL 00007 Published On: 02/23/2021
Question: When modeling DSM as resources, can PLEXOS and does DESC plan to use supply curves based on penetration rates, or does the model have to use a set cost similar to a generation asset?
Answer: PLEXOS can model resources based on characteristics like energy and cost, but not specific types of DSM measures. Adding more than a few DSM resource options is likely to increase solver complexity greatly and reduce the ability to find a solution. Much like a turbine or combined cycle, there will be a limited set of DSM resource options and costs that represent entire suites of measures at different penetration levels. Currently, DESC plans to model DSM portfolios with different cost and reduction potentials such as 1%, 1,25%, 1.5%, etc. The model will have DSM candidate resources with progressive cost and energy reductions.
MODL 00008 Published On: 02/23/2021
Question: Can you review all the models that were considered by DESC for use in the IRP, not just PLEXOS?
Answer: DESC and the Stakeholder Advisory Group will be reviewing a wide range of models for potential use in future IRPs. See Slide 42 of the Stakeholder Advisory Materials from Session I for a full list of the models considered. Stakeholders will also have an opportunity to suggest additional models as part of the Session I homework.
MODL 00009 Published On: 03/01/2021
Question: What are the hardware and software requirements for the version of PLEXOS that intervenors will license?
Answer: Energy Exemplar provides the system requirements for PLEXOS on its website here: https://www.plexosproject.com/articulo-download-plexos
MODL 00010 Published On: 03/02/2021
Question: The Commission's IRP order requires DESC to file contemporaneously with each future IRP, the modeling inputs, outputs, assumptions, and any post-processing spreadsheets, as well as the model manual. How will DESC provide this access to those intervenors who do not want to or cannot devote resources to utilizing a PLEXOS license?
Answer: The data will be made available in the same manner to all Stakeholders. Excel spreadsheets will be provided for all input and output data in addition to any native PLEXOS formats. The PLEXOS manual cannot be provided without a license.
MODL 00011 Published On: 04/26/2021
Question: A few concerns were raised pertaining to the examples provided on how PLEXOS was used in other IRP processes, which are listed below: 1. Exhibit A says that the license may only be used "for the purpose of reviewing or analyzing the electric price or power cost forecasts developed by the Client." That would exclude its use for IRP purposes. 2. Section 8 and the "Base Fees" section of Exhibit A say that no training or support are covered except as specified in Exhibit A. And Exhibit A says a fee of $2500 per day is required. That seems inconsistent with the provision of unlimited support and training that was encompassed in the $8000 option discussed during the IRP workshop. 3. The agreement is written as if someone other than DESC is the licensee and therefore, that someone other than DESC is paying the license fees. 4. The agreement would seem to restrict use of the license to an employee of licensee (Exhibit A), which would be problematic. A consultant to an intervenor would not be able to use it. 5. The agreement also prevents more than one employee from using the license. Consumers is providing two-seat Aurora licenses to intervenors, so EE should do the same here or let more than one person access the license, so that we can work as a team to set up runs. 6. The agreement also states, "License granted by this Agreement shall be for the duration of the Proceeding, but in no event longer than twelve months." The current IRP has gone on for longer than twelve months from the date it was filed, this provision would potentially restrict us from using the license during the duration of the proceeding.
Answer: The DESC team had raised these concerns with Energy Exemplar (EE).
MODL 00012 Published On: 04/26/2021
Question: Provision of the model manual is not a "nice to have." It is required on page 29 of Order No. 2020-832.
Answer: The DESC IRP team agrees that the minimum requirement includes that Stakeholders or other intervenors have access to all the model documentation. With that understanding, the team evaluated access to the manual as part of the Commission scorecard, which was composed of “need-to-have” requirements. The team was not attempting to determine the exact threshold of what qualifies as a manual, whether that would be a collection of files or a standalone document.
MODL 00013 Published On: 04/26/2021
Question: Slides 39-40 provide an overview of how PLEXOS is used in other IRP processes. Do you have similar information for the other four models?
Answer: Our analysis approach focused on assessing the functionality of other options and whether PLEXOS met certain criteria. We did not perform the same review of intervenor use for the other models were assessed.
MODL 00014 Published On: 04/26/2021
Question: Typically, I think of "support" as the ability to ask questions of the vendor if we encounter an issue executing runs, e.g. the model isn't interpreting cost inputs in the way you intend. Is that kind of support available through Energy Exemplar for PLEXOS?
Answer: Yes. PLEXOS has a support email that is used by DESC to address the types of issues that you describe in a timely manner.
MODL 00015 Published On: 12/21/2021
Question: Is DESC proposing that the "requirement levels for each Reliability Factor" would be constraints in the capacity expansion model? If so, does this apply to all the RFs, Including e.g., fast start, AGC, black start?
Answer: Not all factors will be included in the optimization analysis. Some will be evaluated separately. Slide 18 of the Session V Stakeholder slides indicates the reliability elements that will be modeled explicitly in PLEXOS and those that will be considered outside of the PLEXOS model.
MODL 00016 Published On: 12/21/2021
Question: Did DESC consider stochastic ST runs, instead of using PASA, to calculate LOLE? If not, would DESC consider testing both approaches in a portfolio with increased wind, solar, and storage. I ask because PASA does not do sequential Monte Carlo 8760 analysis, and the storage will be scheduled against the average capacity reserves rather than the specific needs in a particular sample (i.e., one weather year and one outage draw).
Answer: In the past, DESC used a peak hour study for calculating the reserve margin requirement and for calculating the contribution of solar resource towards meeting the reserve margin. Based on prior feedback provided by Stakeholders and DESC, the Commission has ordered DESC to use an LOLE-based reserve margin analysis and ELCC-based assessment of resource capacity value. DESC will comply with the Commission’s orders and use LOLE and ELCC methods through the 2023 IRP. To DESC’s knowledge, Energy Exemplar has not directly promoted PLEXOS ST Plan for reliability studies. Energy Exemplar has instead recommended relying upon the purpose-built PASA for performing system reliability studies. However, DESC is interested in better understanding the method recently proposed by Stakeholders at IRP Advisory Group Session V. DESC requests that you send any available reference materials to the DESC-IRP-Group at DESC-IRP-Group@crai.com. Following the review of this material, DESC will schedule a follow up call to discuss the proposed approach as well as any benefits or draw-backs relative to the LOLE method ordered by the Commission.
MODL 00017 Published On: 12/21/2021
Question: Is DESC proposing to use Marginal ELCC of each resource or the Average ELCC? Will portfolio effects of ELCC be considered?
Answer: DESC uses average ELCC when evaluating existing units on the system and marginal ELCC when evaluating incremental units.
MODL 00018 Published On: 12/21/2021
Question: How are PPA costs modeled?
Answer: Unfortunately, PLEXOS does not have the option to input a PPA with price flexibility from one year to the next. Therefore, we represent the annual cost of those resources as the levelized cost of the contract over the life of the PPA. Additionally, when PLEXOS adds new units, the model wants to simulate a utility-owned asset that will be depreciated, rather than a PPA for which these treatments are not needed. As a workaround, we take the levelized cost of the PPA and input it as a build cost. This solution was also faced by the Richmond team, and they use a similar solution which we developed independently of one another.
MODL 00019 Published On: 12/21/2021
Question: We'd love to see the replacement cost assumptions in specifics and the spreadsheets that would be used to translate those into PLEXOS inputs.
Answer: DESC will share the cost and performance assumptions for new utility-scale resources with interested Stakeholders as requested. However, DESC cautions that these initial values may be subject to modification as new information is gathered through the All-Source RFP or when Dominion updates its internal assessment of new resource costs.
MODL 00020 Published On: 06/17/2022
Question: Stakeholders are seeking descriptions of model settings for the PLEXOS LT capacity expansion module. Of particular interest is the model horizon, any splits in the horizon, and how the model is handling chronology and week/day sampling.
Answer: In all models, LT Plan was run in a single 30- year step. Per written recommendation of Energy Exemplar, DESC found that run times improved and the model converged regularly using the global slicing blocks with five time slices per day, as recommended for systems with higher percentages of solar. This creates a mini load duration curve each day, does not maintain chronology within the day, has better results than a fitted solution when high levels of solar are included, and does maintain chronology daily, weekly and monthly.
MODL 00021 Published On: 06/17/2022
Question: For the modelling battery storage operations, charging constraints for solar investment tax credit (ITC) can be included, but DESC should avoid over constraining the model. PLEXOS has the option to make these constraints a “soft constraint,” incurring an economic penalty to violate. We recommend including a PLEXOS parameter for “RHS Penalty” of $500/MWh for any grid charging.
Answer: Expansion candidates are generic units and DESC will continue to evaluate paired resources as being charged by the solar component. DESC will model PPAs in configurations that are presented to the company through the RFP process.