1. Study Results Drought Scenario Study
This slide deck contains results from the 2011 TEPPC Study Program. This study shows the impact in the interconection of increased thermal plant forced outages and decreased hydro caused by drought conditions.

2. 2022 PC7 WGA Drought Study Change to starting input assumptions:
Central Question: What impact do changes in thermal plant operation and hydro generation availability have on transmission utilization, production cost, and the ability of the Western Interconnection to continue serving its load obligation?
Change to starting input assumptions:
Loads – Peak demand increased to reflect higher temperatures in drought year (inputs provided by NREL)
Transmission System – None
Generation – Low hydro (2001) data used; increased thermal plant forced outages modeled (inputs provided by Argonne National Laboratory)
Results follow…

3. Drought Condition Selected for Study
1977 western drought
Selected due to severity and coincidence within multiple basins
Defined by USGS HUC-2 Basin flows
Presented by Chris Harto (ANL) on Nov 15 DWG call

4. Modeling of Hydro Generation
Hydroelectric Generation :
Same as TEPPC low flow hydro case (2001)
Differences:
Slight overestimation of impact to Pacific NW and CA
Slight underestimation for Great Basin and Lower CO
Presented by Chris Harto on Nov 15 DWG call

5. Impact of Drought on Thermal Plants
“At-risk” thermal plants identified based on their dependence upon surface water for cooling
Impacted plants identified in sub-basins where flow under drought was less than 50% of normal flow
List of impacted plants in WECC will not be reported since no plant-specific analysis of drought mitigation plans was conducted
Impact to “at-risk” plants modeled as increased forced outage rates

6. Determining Increased Forced Outage Rates (Down Days)
Based on estimate of lost generation
Calculated using EIA data for impacted plants
Lost generation proportional to the loss of flow relative to the minimum of the average basin flow or 2010 water demand
Lost generation was allocated monthly based on deviation from normal flow in that month relative to other months

7. Overview of Lost Thermoelectric Generation
Basin
Lower Colorado
California
Lost Generation (MWh)
6,470,000
4,670,000
at risk capacity under 50% historical flow (MW)
1,908
1,791
at risk with WECC equivalent found (MW)
1,837
1460*
Fraction of at risk capacity found in WECC database
0.96
0.82
average down days
147
133
day/month
12.2
11.1
*Includes 407 MW of CA geothermal at risk

8. Monthly Variability in Lost Generation
Lower Colorado
California
Flow Ratio
Lost Generation MWh
Down Days
JAN
0.3649
1,097,515
24.9
0.2632
652,592
18.6
FEB
0.2935
1,220,901
27.7
0.2538
660,918
18.9
MAR
0.5556
767,967
17.4
0.2783
639,218
18.2
APR
0.6923
531,736
12.1
0.292
627,083
17.9
MAY
0.6667
575,975
13.1
0.3013
618,846
17.7
JUN
0.8182
314,168
7.1
0.4333
501,932
14.3
JUL
1.125
0.0
0.6183
338,076
9.6
AUG
0.931
119,239
2.7
0.6788
284,490
8.1
SEP
0.8571
246,945
5.6
0.6592
301,850
8.6
OCT
0.878
210,828
4.8
0.6438
315,490
9.0
NOV
0.4737
909,498
20.6
1.2627
DEC
0.6
691,239
15.7
1.0427

9. Modifying Forced Outage Rates
Forced outage rates modified to reflect increased “down days” for all impacted plants within a basin
All impacted plants assumed to be down the same number of days in a given month
Overlap allowed with scheduled maintenance

10. Impact of Drought on Demand
Developed by NREL
Basis for demand changes: ‘99 California Energy Commission Study titled High Temperatures & Electricity Demand: An Assessment of Supply Adequacy in California, Trends & Outlook
Study provided an estimate for the change in peak demand for 17 areas in the WSCC for two high temperature scenarios (1-in-5 and 1-in-40 probability)

11. Peak Load Adjustment Method
Match 17 WSCC areas to 2022 TEPPC load bubbles
Identify hottest month for each load area in 1977 (Drought year)
Increase peak demand for this month only by the 1-in-40 % change value reported for the WSCC area in the CEC study
Monthly energy was increased by ½ of the peak demand change to preserve the demand shape

12. Peak Load Adjustments Summary
2022 PC1 WECC-Wide Coincident Peak Demand: 172,082 MW
2022 PC7 Adjusted Coincident Peak Demand: 176,080 MW (2.3% inc.)

13. 2022 WGA Drought – Changes in Total Annual Generation vs. Common Case
Only an increase in areas with emergency in the Common Case (CFE, AESO)
GWh
Low Hydro Results

14. 2022 WGA Drought – Changes in Total Annual Generation vs. Low Hydro
GWh

15. 2022 WGA Drought – Changes in Generation by State vs. Common Case
Low Hydro Results

16. 2022 WGA Drought – Changes in Generation by State vs. Low Hydro
Result of increased forced outages applied to plants in the California water basin
Result of increased forced outages applied to plants in the Lower Colorado water basin

17. 2022 WGA Drought – Changes in Region to Region Transfers

18. 2022 WGA Drought – Changes in Transmission Utilization
Most Heavily Utilized Paths
Increases in U90 Relative to Common >5% Case Indicated in Red
P01 Alberta-British Columbia
P03 Northwest-British Columbia
P08 Montana to Northwest
P11 West of Crossover
P10 West of Colstrip
Similar to Low Hydro results
P29 Intermountain-Gonder
P27 IPP DC Line
P60 Inyo-Control
P26 Northern-Southern California
P47 – Southern New Mexico
P45 SDG&E-CFE

19. Questions or thoughts on this study?