1. Study Results April 16, 2015 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

2. PC17 Wind Forecasting Error Objective – Investigate the impacts of wind forecasting error on: Model Dispatch Production Cost Transmission Path Utilization and Congestion Implementation – The test case would use slightly different wind curves for commitment and dispatch, reflecting limitations of forecasting tools. 2 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

3. ±4% of TEPPC Wind Profiles 3 W ESTERN E LECTRICITY C OORDINATING C OUNCIL To model a forecasting error the TEPPC wind profiles in the Common Case Dataset were randomly adjusted +4% -4% Or remained the same This was done by a random number generator to make the results unbiased run for each profile

4. Generation Change 4 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

5. Generation Change By State 5 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

6. Production Cost and CO2 6 Category2024 PC1 15-01-19 2024 PC17 Wind Forecasting Error Difference Conventional Hydro238,660,400238,660,41110 Energy Storage3,684,9293,673,936(10,993) Steam - Coal231,197,415231,143,097(54,318) Steam - Other3,014,0113,025,72711,716 Nuclear56,167,02356,167,748725 Combined Cycle274,985,932274,992,8226,891 Combustion Turbine55,245,01155,209,120(35,891) IC803,017802,186(830) Biomass RPS19,528,18719,528,060(127) Geothermal31,944,68031,943,183(1,497) Small Hydro RPS4,360,0254,360,10884 Solar35,866,28335,915,73249,449 Wind73,705,85273,714,0788,226 == Total ==1,050,366,7061,050,340,141(26,565) Cost (M$)22,399 0 CO2 Cost (M$)1,0501,0511 CO2 Amount (MMetrTn)368 (0) Dump Energy (MWh)433,485481,02447,539 Pumping (PL+PS) (MWh)15,528,45715,513,815(14,641)

7. Path Flows 7 W ESTERN E LECTRICITY C OORDINATING C OUNCIL 1)Resource assumption overview 2)Portfolio Case generation results 3)Path flow results - Reviewed duration plots for key WECC paths. Will show some that are interesting in this presentation.

8. Path Flows 8 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

9. Path Flows 9 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

10. Path Flows 10 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

11. Path Flows 11 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

12. Observations 12 W ESTERN E LECTRICITY C OORDINATING C OUNCIL +/- 4% wind forecasting error has insignificant impact on; Generation dispatch Production cost Transmission path utilization and congestion.

13. Questions 13 W ESTERN E LECTRICITY C OORDINATING C OUNCIL