1. Modeling Tres-Amigas Modeling Work Group Meeting August 27, 2009 WECC Staff

2. Overview

3. Tres Amigas The Tres Amigas project connects the ERCOT and SPP systems to the WECC system. In the 2019 dataset both the ERCOT and SPP markets are modeled as a price responsive markets. The models for the ERCOT and SPP markets each use an incremental cost curve and a price signal. The price signal describes the price of power in the WECC. The cost curve describes how the SPP or ERCOT market will respond to the price signal (price of power in the WECC). 3

4. If the price signal to the SPP market is $20/MW, SPP will import 1322 MW from WECC. If the price signal to the SPP market is $60/MW, SPP will export 1979 MW to WECC. Cost Curve - SPP

5. Tres Amigas The price signals that the ERCOT and SPP markets use come from a hub created for the Tres Amigas project. Hub Definition 50% from Midway 25% from Westwing 25% from Palo Verde 5

6. Tres Amigas Would SPP or ERCOT respond to a $40 price signal at 3 a.m. and at 5 pm in the summer in the same way? The way market responds to a given price signal will vary depending on time day, and time of year. To account for this, all hours of the year are divided into six time periods where each time period has its own cost curve. The six time periods are: Summer weekday peak Summer weekday off-peak Summer weekend Non-Summer weekday peak Non-Summer weekday off-peak Non-Summer weekend 6

7. Tres Amigas Z Global provided Staff information to model the Tres Amigas project in Promod. Modeling Parameters: Six incremental heat rate curves for both SPP and ERCOT Seasonal fuel prices for both SPP and ERCOT to be used in conjunction with the incremental heat rate curves. 7

8. Modeling in Promod

9. Tres Amigas Each cost curve is modeled in Promod using three thermal generators and a static load. Each generator models a segment of the cost curve. 9 G G G SPP Import from WECC Export to WECC

10. Tres Amigas 10 Gen 1 Gen 2 Gen 3

11. Tres Amigas 11 The generation parameters for the thermal units: Units are must run Minimum Capacity = 1 MW Minimum up/down time = 1 hour Ramp up/down rates = 9999 MW Forced Outage Rate = 0%

12. Tres Amigas When the static load is netted against the generation, imports and exports can both be modeled: If the generation is greater than the static load, power is exported to WECC. If the generation is less than the static load, power is imported from the WECC. 12 G G G SPP Import from WECC Export to WECC

13. Tres Amigas 13 Gen 1 Gen 2 Gen 3 -3100 -2100 -1100 -100 900 1900 2900

14. Preliminary Results

15. 15

21. Questions ???