WGG Coal Retirement Case Transmission Repurposed for Renewables

1. WGG Coal Retirement CaseTransmission Repurposed for Renewables

2. 2022 PC6 – WGG Coal Retirement Case (transmission repurposed) Purpose: to attempt to maximize the delivery of renewable energy and minimize the construction of new transmission while also trying to achieve a targeted reduction in carbon emissions.

3. 2022 PC6 – WGG Coal Retirement Case (transmission repurposed) Central Questions 1) How much transmission capacity can be made available by retiring 5400 MW coal resources? 2) What is the amount of new renewable resource capacity that could feasibly utilize this freed up transmission capacity? 3) What is the resulting utilization of the transmission facilities when re-purposed to transport renewables? 4) What is the resulting reduction in WECC-wide carbon emissions produced by this re-purposing?

4. 2022 PC6 – WGG Coal Retirement Case (transmission repurposed) Assumptions Loads – decreased to reflect the assumption that “all cost-effective EE potential” is achieved throughout the West (PC4 assumption) Transmission System – Path rating reductions Generation – • DG resources increased based on ‘interconnection potential’ of distributed PV and ‘technical potential’ of distributed CHP as estimated by E3 (link to E3 report) • RPS resources adjusted for lower loads due to EE and behind-the-meter DG, and for increased PV DG • DSM increased based on LBNL analysis of demand response potential estimated using an updated FERC DR Potential Estimates model • Retired 25% of WECC coal fleet (5400 MW) • Added renewables to repurpose transmission (~4400 MW)

5. Perform EE load adjustments; Add DG resources, adjust RPS Add DR and “tune” Retire coal plants Check for reliability impact due to retirement Run case Quantify new renewable generation that could be accessed/delivered using transmission capacity previously utilized by retired coal Add renewables from (7) Run final study Study ExecutionBuild and run study in steps… PC4 Complete PC6 Complete

6. WGG Coal Retirement Case Loads Generation Transmission PC4 Assumptions: Low load PC4 Assumptions: DG + DR Path rating reductions Retire Coal (5400 MW) Add Renewables (4400 MW)

7. WGG Coal Retirement Case Loads Generation Transmission PC4 Assumptions: Low load PC4 Assumptions: DG + DR Path rating reductions Retire Coal (5400 MW) Add Renewables (4400 MW)

8. Summary of Aggressive EE Load Adjustments

9. WGG Coal Retirement Case Loads Generation Transmission PC4 Assumptions: Low load PC4 Assumptions: DG + DR Path rating reductions Retire Coal (5400 MW) Add Renewables (4400 MW)

10. 2022 Incremental Distributed CHP in PC1 and PC4 – Big Picture WECC total ~ 9,900 MW

11. DR Capacity chart

12. WGG Coal Retirement Case Loads Generation Transmission PC4 Assumptions: Low load PC4 Assumptions: DG + DR Path rating reductions Retire Coal (5400 MW) Add Renewables (4400 MW)

13. Coal Retirements Selected

14. 25% of WECC coal fleet 3250 MW retired prior to 2022 in the Common Case 5370 MW retired based on WGG’s economic analysis Coal Retirements Selected

15. WGG Coal Retirement Case Loads Generation Transmission PC4 Assumptions: Low load PC4 Assumptions: DG + DR Path rating reductions Retire Coal (5400 MW) Add Renewables (4400 MW)

16. Path Rating Impacts of Selected Retirements • Incomplete information provided by the Technical Studies Subcommittee (TSS) • Retirement – Colstrip 1 and 2 • Path 8 Montana-Northwest derated to 1600 MW • Retirement – Nucla 1-4 • TOT 2 derated to 690 MW minus output of Nucla 1-4 (total max cap of 115 MW) • Path rating catalog reviewed to identify additional path rating impacts; no conclusive information found

17. WGG Coal Retirement Case Loads Generation Transmission PC4 Assumptions: Low load PC4 Assumptions: DG + DR Path rating reductions Retire Coal (5400 MW) Add Renewables (4400 MW)

18. Adding Incremental Renewables • Add incremental renewable resources to WREZ zones closest to the retired coal plants, attempting to take advantage of any freed-up transmission capacity • Used capacity values from various resources to recalculate PRM and decide how many new CTs to add

19. Added Renewables

20. Coal Retirements vs. New Renewables & CTs - Wyoming/Montana Area Coal Plant Retirement WREZ Hub centroid, approximate location of incremental renewables Incremental wind resource 906 MW Incremental CTs WECC Path Cut Plane 370 MW 1,012 MW 450 MW 380 MW 415 MW

21. Wyoming/Montana Area Summary • Wyoming: • Coal retired – 1,297 MW • Incremental wind added – 1,427 MW • Incremental CTs added – 1,200 MW • Montana: • Coal retired – 824 MW • Incremental wind added – 906 MW • Incremental CTs added – 0 MW

22. Coal Retirements vs. New Renewables & CTs – Colorado/New Mexico Area Coal Plant Retirement WREZ Hub centroid, approximate location of incremental renewables Incremental wind resource 330 MW Incremental solar resource Incremental CTs 200 MW WECC Path Cut Plane 684 MW 770 MW

23. Colorado/New Mexico Area Summary • Colorado: • Coal retired – 416 MW • Incremental wind added – 330 MW • Incremental CTs added – 0 MW • New Mexico: • Coal retired – 1,277 MW • Incremental wind added – 684 MW • Incremental solar added – 770 MW • Incremental CTs added – 200 MW

24. Coal Retirements vs. New Renewables & CTs – Nevada/Utah/Arizona Area 265 MW 300 MW Coal Plant Retirement WREZ Hub centroid, approximate location of incremental renewables Incremental wind resource 450 MW Incremental geothermal resource Incremental solar resource Incremental CTs WECC Path Cut Plane 414 MW 115 MW 350 MW

25. Nevada/Utah/Arizona Area Summary • Nevada: • Coal retired – 265 MW • Incremental geothermal added – 265 MW • Incremental CTs added – 0 MW • Utah: • Coal retired – 450 MW • Incremental solar added – 450 MW • Incremental CTs added – 300 MW • Arizona: • Coal retired – 841 MW • Incremental wind added – 414 MW • Incremental solar added – 465 MW • Incremental CTs added – 0 MW

26. Study Caveats to be Noted • Coal retirements selected for this study are based solely on an economic analysis performed by the Synapse modeling tool created for WGG. Tool’s input was public information available at the time of the tool’s creation. • No capital cost analysis was completed as part of this case primarily due to the unavailability of information needed to assess costs associated with plant retirements.

27. Caveats, cont. • A full assessment of the reliability impacts of the modeled coal retirements cannot be completed as part of this study (at this time). • Many possible combinations of renewable resources could be analyzed as part of this study, but only a single selection of incremental renewable resources was selected for this case.

28. What Will This Case Tell Us? • The net transmission impact, production cost impact, generation dispatch impact, and carbon impact of retiring approximately 5400 MW of coal and replacing it with ~5400 MW of renewable resources (plus CTs needed for load/gen balance)

29. What Will This Case Not Tell Us? • The maximum capacity of renewable resources that could replace the retired coal without impacting the transmission system • The reliability impact of retiring 5400 MW of coal around the Western Interconnection • The cost of retiring 5400 MW of coal and replacing it with an equivalent capacity of renewables

30. WGG Coal Retirement CaseGeneration Impact

31. ? Load is 10% less! and change in multiple resource assumptions ?

32. Too many variables!

33. Retire Coal (5400 MW) Same load…isolated variables Add Renewables (4400 MW)

34. Energy Add Renewables (4400 MW) Retire Coal (5400 MW)

35. WGG Coal Retirement CaseProduction Cost and CO2 Impact

36. Production Cost Summary

37. Production Cost Summary

38. Summary of Production Cost and CO2 Production Cost: Savings of 20% from the Common Case is due to the PC4 assumptions, not the Coal Retirement Assumptions CO2: About half of the 20% reduction in CO2 emissions from the Common Case is due to the coal retirements and added renewables. The other half can be credited to PC4 assumptions.

39. WGG Coal Retirement CaseTransmission Impact

40. De-rated De-rated

43. 2022 Common Case Results Most Heavily Utilized Paths P3 P1 Passed 3 P8 P11/10 Passed 2 Passed 1 P29 P60 P27 P26 P47 P45

44. Summary Transmission impact → relatively small? Production cost impact → small Generation dispatch impact → significant Carbon impact → significant