Consultation Update Details

Consultation Update #9


Webinar 9: CETA Assumptions, Demand Forecast, Resource Adequacy, Resource Need

Posted 10/20/2020 | Open in new window

The following consultation update is the result of stakeholder suggestions gathered through an online Feedback Form, collected between October 13 and October 27, 2020 and summarized in the November 3 Feedback Report. The report themes have been summarized and along with a response to the suggestions that have been implemented. If a suggestion was not implemented, the reason is provided.

PSE thanks Kare Ware and Sashwat Roy (Renewable Northwest) for follow-up discussions concerning the loss of load probability question on November 6, 2020.

Temperature trends and temperature sensitivity

PSE received feedback from James Adcock, Katie Ware (Renewable Northwest), Kyle Frankiewich (WUTC Staff) and Don Marsh (CENSE) regarding the temperature years used to model PSE’s load forecast and in the resource adequacy model. Stakeholders suggest that more recent temperature data (i.e. most recent 20 years) should be used to inform PSE models to limit the impact of colder weather observed in older records and accentuate warming trends present in more recent records.

PSE has committed to completing a temperature sensitivity for the 2021 IRP which will address the concerns raised by stakeholders. PSE has proposed three options for modeling temperature data for the temperature sensitivity:

  1. Trended normal based on historical observed trends (trended normal analysis completed by Itron Inc.)
  2. Temperature normal based on most recent 15 years of temperature data
  3. Northwest Power and Conservation Council’s climate model temperature assumption

More information on these options is available for review in the October 20 Webinar presentation. A stakeholder survey was conducted between October 19 and October 27 to collect feedback on which temperature option was of greatest interest. The results of the survey indicate the stakeholders suggest using the Northwest Power and Conservation Council (“NPCC” or “the Council”) climate model temperature assumption (option 3). The full results of the survey are presented below.

Don Marsh and a group of stakeholders also prepared and presented an additional temperature sensitivity methodology as part of the feedback process. During this IRP process, many stakeholders provided recommendations in IRP meetings, feedback forms and e-mails to IRP staff requesting that PSE use the most recent 15 or 20-years of temperature data. PSE listened to stakeholders and included the most recent 15 years of temperature data as one of the options for stakeholder consideration. In addition to this stakeholder request, PSE has hired a consulting firm, Itron, to perform a separate temperature analysis and PSE also researched the work done by the Council on climate change modeling. Both of these analyses were included as additional options for temperature sensitivity analysis during the October 20 Webinar and in the sensitivity survey. Over 140 stakeholders responded to the sensitivity survey and 93 stakeholders selected the Council’s climate change model temperature assumptions. PSE will follow the stakeholders’ recommendation to use the Council’s climate change model tempertuare assumptions and will consider the materials presented by Don Marsh et al for future IRP cycles.

The Northwest Power Conservation Council (the “Council”) is using global climate models that are downscaled to forecast temperatures for many locations within the Pacific Northwest. PSE has chosen to look at one of these models. The Council weighs temperatures by population from metropolitan regions throughout the Northwest.  However, PSE received data from the Council that is representative of SeaTac airport.  This data is, therefore, consistent with how PSE plans for its service area and this data is not mixed with temperatures from Idaho, Oregon or Eastern Washington.  The climate model data provided by the Council is hourly data from 2020 through 2049.  This data resembles a weather pattern where the temperatures fluctuate over time, but generally trend upward.  For the load forecast portion of the temperature sensitivity, PSE proposes to smooth out the fluctuations in the temperatures and increase the heating degree days (HDDs) and cooling degree days (CDDs) over time at 0.9 degrees/decade, which is the rate of temperature increase found in the Council’s climate model.

Montana transmission capacity

PSE received feedback from Willard Westre (Union of Concerned Scientists), Kyle Frankiewich (WUTC Staff) and Brian Fadie (Northwest Energy Coalition) concerning the transmission capacity between PSE service territory and the Colstrip region of Montana. In the June 30 Webinar, and again in the October 20 Webinar, PSE presented an upper transmission capacity limit of 565 MW to Montana. At the time these values represented the most-likely transmission capacity available to PSE in the region. Since the presentation of these materials, negotiations for sale of PSE’s portion of Colstrip Unit 4 have ceased. Therefore, PSE will model 750 MW of available transmission capacity to Montana for the 2021 IRP process as the base assumption.

PSE has also proposed modeling of several transmission constrained sensitivities for the 2021 IRP process. These sensitivities are structured around transmission tiers, which represent uncertainty of availability of transmission capacity. The change in Montana transmission capacity will influence BPA transmission redirect assumptions for the Eastern Washington region. These changes are summarized in the table below.

Resource Group Region

Added Transmission (MW)

Tier 0

Tier 1

Tier 2

Tier 3

PSE territory (a)





Eastern Washington




1,515  1,330

Central Washington





Western Washington





Southern Washington/Gorge






565     750



565     750

Idaho / Wyoming






generally unconstrained




(a) Not including the PSE IP Line (cross Cascades) or Kittitas area transmission which is fully subscribed

Sensitivity survey and selection

PSE received questions from Virginia Lohr (Vashon Climate Action Group), Kyle Frankiewich (WUTC Staff) and Nate Sandvig (Rye Development) concerning how the sensitivity prioritization survey would be used. PSE considers the sensitivity survey a tool to help collect stakeholder sentiment on each of the many sensitivities purposed over the course of the 2021 IRP process. PSE intends to use the results as a guideline for prioritizing which sensitivities to run as part of the IRP modeling process. Other factors such as difficulty, length of time and value to the entire IRP process will also be considered as sensitivities are processed.

The full results of the survey are provided below.

ELCC values

PSE received feedback from Willard Westre (Union of Concerned Scientists), Katie Ware (Renewable Northwest), Kyle Frankiewich (WUTC Staff) and Nate Sandvig (Rye Development) concerning the ELCC values presented in the October 20 Webinar. As PSE indicated during the webinar, the ELCC values presented are draft and subject to change over the course of the IRP modeling process. Furthermore, more refined values, including saturation curves, will be provided at a later date.

Specific concerns on the relative value of battery energy storage systems to pumped hydroelectric storage will be addressed with publication of ELCC values for both resources at a nameplate of 100 MW at a later date.

Summer loss of load events

PSE received feedback from Katie Ware (Renewable Northwest), Kyle Frankiewich (WUTC Staff) and Don Marsh (CENSE) concerning summer loss of load events. PSE would like to clarify that the demand forecast for the 2021 IRP process has not changed since its presentation during the September 1 Webinar. However, an inconsistency with the demand forecast dataset used for Resource Adequacy modeling was identified and aligned. PSE regrets that our comments in the meeting, which only related to the Resource Adequacy dataset, gave the appearance that the demand forecast was changed.

The summer-time loss of load events discussed during the meeting represent a very small fraction of the total loss of load events encountered over the course of a full year as shown in the tables below for the two test case years 2027 and 2031. A loss of load event can be caused by many factors which include temperature, demand, hydro conditions, plant forced outages, and variation in wind and solar generation. All of the factors are modeled as stochastic inputs simulated for 7,040 iterations. As mentioned previously, the data shared at the October 20 webinar are draft. PSE has been reviewing the data used for the resource adequacy model and found an inconsistency with the correlations for wind and solar data. PSE has fixed the correlations and is working on updating the peak capacity need and effective load carrying capability (ELCC) values. The table below has been updated since the November 3 feedback report to include the updates to the wind and solar correlations.

Notes: Tables represent the results of 7,040 simulations where each simulation is composed of 8760 operating hours. Tables do not describe the magnitude of any loss of load event, just that the event occurred.

Katie Ware (Renewable Northwest) had also requested a 12x24 of the loss of load probability as part of this feedback cycle. Given the methodology of the Resource Adequacy Model, PSE is not able to produce hour by hour probabilities, so instead these plots represent a relative heat map of the number hours of lost load binned by month and hour of day.



Sensitivity prioritization survey results

Thank you for your active engagement in the IRP process, PSE collected results from over 140 individual respondents with this survey.

Sensitivity Selection Results


Sensitivity #25 Alternative fuel #1, fuel selection

Sensitivity #31 Temperature sensitivity, temperature methodology

Summary of all updates

PSE appreciates the feedback provided by stakeholders. In summary, the following changes will be implemented:

  • The temperature sensitivity will be modeled using the Council’s methodology.
  • The Montana transmission capacity will be set to 750 MW.
  • Sensitivity prioritization has been informed by the stakeholder survey results, as shown above.
  • Hydrogen will be included as an alternate fuel choice in the Alternative Fuel #1 sensitivity (sensitivity #25, must-run).