Study Request: Opportunity/Variable Cost Dispatch for Solar, Wind, Geothermal and Nuclear Requestor

1. 
   Requested Study Year? 2026
   

2. 
   What is the key question you would like the study to answer?
   

3. 
   Summary of the study’s key load, resource, transmission, and/or policy assumptions. Note: If the 10-year study request links to the 20 year, please identify basis for the linkage between the expected 10 year study results and inputs into the 20 year study case.
   

• 
  2026 Common Case:
  
  • 
    Report the following outputs for this case (the “reference case”) on a WECC-wide basis:
    
    • 
      Average on-peak and off-peak LMPs within each of the WECC Balancing Authorities, on a monthly basis
      
    • 
      Annual production costs (exclude opportunity costs)
      
    • 
      Annual tons of CO₂ produced
      
    • 
      Theoretical renewable resource production that had to be curtailed to obtain model solution, by technology and location
      

• 
  Create an “opportunity/variable cost dispatch case” by modifying the reference case:
  
  • 
    Remove the must-run flag for geothermal units.
    
  • 
    Double the variable O&M cost for geothermal units.
    
  • 
    Change the minimum output level for nuclear plants to 50% of the maximum output level.
    
  • 
    Reduce the MW/minute ramp rates for nuclear by 50%.¹
    
  • 
    Double the variable O&M cost for nuclear plants.
    
  • 
    Change the “hourly” modeling for all wind resources to allow the wind resources to be dispatchable:
    
    • 
      Set the maximum capacity in each hour of the year equal to the hourly profile quantity for each corresponding hour.
      
    • 
      Input a variable O&M cost equal to the sum of (i) variable O&M ($8.94/MWh, 2015$) and (ii) an opportunity cost based on lost Production Tax Credit (-$23/MWh 2015$ in year 2026).
      
    • 
      Input a fuel cost of $0/MWh.
      

• 
  Change the “hourly” modeling for all solar resources to allow the solar resources to be dispatchable:
  
  • 
    Set the maximum capacity in each hour of the year equal to the hourly profile quantity for each corresponding hour.
    
  • 
    Input a variable O&M cost of $0.00/MWh.
    
  • 
    Input a fuel cost of $0/MWh.
    

• 
  Report the following outputs for the “opportunity/variable cost dispatch case” on a WECC-wide basis:
  
  • 
    Average on-peak and off-peak LMPs within each of the WECC Balancing Authorities, on a monthly basis
    
  • 
    Annual production costs (exclude opportunity costs)
    
  • 
    Annual tons of CO₂ produced
    
  • 
    Theoretical renewable resource production that had to be curtailed to obtain model solution, by technology and location
    

4. 
   How will this study provide information of broad value to stakeholders in the Western Interconnection, e.g. customers, regulators, Transmission Providers?
   

With large increases in the amount of intermittent generation, it is likely that LMPs will be negative in some hours of the years. To date, TEPPC’s GridView analysis has not attempted to estimate the degree to which LMPs will become negative in hours when renewable resources must be curtailed in order to achieve a market solution. TEPPC’s analysis has, so far, not used opportunity costs for solar and wind resources when determining the expected output of these resources; variable costs are assumed to be $0/MWh. It would be useful to get a sense of how negative LMPs may be in various hours of the year—this information could be important in assessing the value of potential demand response programs and storage additions in grid planning. Additionally, this information will provide insights into the incentives that consumers will have to change their current consumption practices.

5. 
   Can you offer expertise or information to WECC to assist in the development of this study case? Describe the information or support you will be able to provide, if any.
   

Yes. SDG&E has experience in economic grid simulation modeling using GridView.

6. 
   Do you know of other stakeholders interested in the issues on which this request is based? If so, please provide their contact information.
   

SDG&E believes stakeholders focused on minimizing consumer costs, and stakeholders concerned with over-generation and the possibility that renewable resources will be curtailed, will be interested in the study results.

7. 
   Is the requested study necessary to meet a member Transmission Provider's compliance with its Open Access Transmission Tariff (OATT), Attachment K?
   

No.

8. 
   Requested Study Year? 2026
   

9. 
   What is the key question you would like the study to answer?
   

10. 
    Summary of the study’s key load, resource, transmission, and/or policy assumptions. Note: If the 10-year study request links to the 20 year, please identify basis for the linkage between the expected 10 year study results and inputs into the 20 year study case.
    

• 
  2026 Common Case with following adjustments:
  
  • 
    Diablo Canyon nuclear plant not operating.
    
  • 
    The following planned transmission additions not in service:
    
    • 
      Energy Gateway Project segments:
      
      • 
        500 kV Walla Walla-McNary
        
      • 
        500 kV Boardman-Hemingway
        
      • 
        500 kV Windstar-Populus
        
      • 
        500 kV Populus–Hemingway
        
      • 
        500 kV Aeolus-Mona
        

• 
  New Mexico wind scenario
  
  • 
    Step 1:
    
    • 
      Add 333 MW of installed wind capacity at 345 kV Guadalupe substation (bus #10116) using the E_WT_NM_EA hourly wind profile.
      
    • 
      Add 167 MW of installed wind capacity at 345 kV Amrad substation (bus #11010) using E_WT_NM_SO hourly wind profile
      
  • 
    Step 2:
    
    • 
      Add 667 MW of installed wind capacity at 345 kV Guadalupe substation (bus #10116) using the E_WT_NM_EA hourly wind profile.
      
    • 
      Add 333 MW of installed wind capacity at 345 kV Amrad substation (bus #11010) using the E_WT_NM_SO hourly wind profile.
      
  • 
    Step 3:
    
    • 
      Add 1000 MW of installed wind capacity at 345 kV Guadalupe substation (bus #10116) using the E_WT_NM_EA hourly wind profile. Add 500 MW of installed wind capacity at 345 kV Amrad substation (bus #11010 ) using the E_WT_NM_SO hourly wind profile.
      

• 
  Wyoming wind scenario
  
  • 
    Step 1:
    

• 
  Add 250 MW of installed wind capacity at230 kV Latham substation (bus #67499) using the E_WT_WY_CE hourly wind profile. Add 250 MW of installed wind capacity at 345 kV Laramie River Station substation (bus #73108) using the E_WT_WY_CE hourly wind profile.
  
• 
  Step 2:
  
  • 
    Add 500 MW of installed wind capacity at 230 kV Latham substation (bus #67499) using the E_WT_WY_CE hourly wind profile. Add 500 MW of installed wind capacity at 345 kV Laramie River Station substation (bus #73108) using the E_WT_WY_CE hourly wind profile.
    
• 
  Step 3:
  
  • 
    Add 750 MW of installed wind capacity at 230 kV Latham substation (bus #67499) using the E_WT_WY_CE hourly wind profile.
    
  • 
    Add 750 MW of installed wind capacity at 345 kV Laramie River Station substation (bus #73108) using the E_WT_WY_CE hourly wind profile.
    

• 
  Monitor the following transmission facilities and paths for hourly loading and report U75, U90 and U99 metrics:
  

• 
  Report annual WECC-wide:
  
  • 
    Production costs
    
  • 
    Tons of CO₂ produced
    
  • 
    Theoretical renewable resource production that had to be curtailed to obtain model solution, by location
    

11. 
    How will this study provide information of broad value to stakeholders in the Western Interconnection, e.g. customers, regulators, Transmission Providers?
    

The study results will provide foundational information that can be used to identify (i) the amount of potential “low hanging wind fruit” that can be harvested without major transmission expansion, and (ii) the specific areas of the WECC grid where an expansion of transfer capability should be considered.

12. 
    Can you offer expertise or information to WECC to assist in the development of this study case? Describe the information or support you will be able to provide, if any.
    

Yes. SDG&E has experience in studying the economics of wind resource additions, with economic grid simulation modeling using GridView, and with AC power flow analysis using PSLF.

13. 
    Do you know of other stakeholders interested in the issues on which this request is based? If so, please provide their contact information.
    

SDG&E believes nearly all stakeholders will be interested in study results which provide an analytic basis for identifying (i) the amount of wind resource additions in high-quality wind regimes that can be pursued without the need for major new transmission, (ii) regions of the grid where expansion of the CAISO Balancing Authority would allow new wind resources to avoid contract-path based wheeling charges without risk of significant congestion-related costs, and (iii) grid locations at which new transmission may make sense to pursue.

14. 
    Is the requested study necessary to meet a member Transmission Provider's compliance with its Open Access Transmission Tariff (OATT), Attachment K?
    

No.