December 15, 2011 Conference Call/Webinar

1. Technical Advisory Subcommittee (TAS) Modeling Working GroupProposal for Modeling of Operating Reserves December 15, 2011 Conference Call/Webinar

2. Discussion Topics • Proposed Operating Reserve Modifications for TEPPC Dataset • Reserve Modeling Issues • Operating Reserve Definitions • Proposed Reserve Modeling Concept • WECC-Wide Modeling of Operating Reserves • Composite Hourly Reserve Requirement • Modeling Technique For PROMOD • Spinning and Non-Spin Generators • Status and Next Steps

3. Reserve Modeling Issues • The reserve modeling in Promod is not implemented at the same granularity as much of the other data. • Only a “spinning” reserve requirement has been specified in the dataset. • The “fixed” hydro does not contribute to operating reserves in Promod. • Increases in the amount of variable generation, such as wind and solar, are expected to impact the required level of reserves and/or the unit commitment decisions.

4. Operating Reserve Definitions • Operating Reserve (spinning and non-spinning): That capability above firm system demand required to provide for regulation, load forecasting error, equipment forced and scheduled outages and local area protection (NERC). • Regulating Reserve (or Frequency Response Reserve): An amount of reserve responsive to Automatic Generation Control (AGC), which is sufficient to provide normal regulating margin (NERC). • Operating Reserve Margin The amount of unused available capability of an electric power system at peak-load for a utility system as a percentage of total capability (EIA). • “Flexibility Reserves”: additional reserves required to manage the variability and uncertainty associated with variable generation resources like wind and solar (NREL).

5. Proposed Reserve Modeling Overview • A: Base Operating Reserves (Spin and Regulation) requirement of 4% of load will be calculated based on daily peak demand for each sub-region. • Non-spin Reserves not explicitly modeled; simplified assumption is that there is sufficient short-start resources available (e.g. GT’s) • B: Flexibility Reserves as calculation will be derived from the variability of renewable generation (will not include load variability) in each of the TEPPC sub-regions • C: Total Composite Reserve Requirement (A+B): will be sum of Base reserves plus Flexibility reserves, which will be modeled in PROMOD using a transaction methodology.

6. WECC-Wide Modeling of Reserves • New calculation will be based on dataset for the TEPPC 2022 case. • Use current TEPPC topology with reserves defined at the sub-region level. • Sub-region reserves will reflect mid-range of EIM/ dynamic scheduling among BA’s within a sub-region. • Pumping loads do not require any reserves. • Proposal will be implemented, wholly or partially, in either the 2022 PC1 common case or a sensitivity case.

7. Composite Hourly Reserve Requirement • Base Reserve Requirement (4%): derived from daily peaks (previously based on weekly peaks). • Flexibility Reserves Requirement: reflect intra-hour fluctuations in variable generation. and will be defined hourly. • Must be recalculated for each wind and solar scenario • There may be up to four study cases where load, wind, and/or solar will vary.

8. Modeling Technique for PROMOD • Combination of three inputs simulates an hourly reserve requirement • Hourly reserves requirement: can be implemented by inserting a Model purchase that contributes to reserves • Model sale that cancels the purchase as depicted

9. Spinning and Non-Spin Generators Table 1 - Spinning & Non-Spinning Generation Note: fixed scheduled hydro does not contribute to reserve requirements

10. Status and Next Steps • Data Coordination for Flexibility Reserve Calculation (NREL/WECC) • Renewables By CREZ • WECC Topology • Calculation of Flexibility Reserves (Jack King) • Review by HMTF of Hydro Contribution to Reserves • Composite Reserve Modeling (WECC Staff) • Perform PROMOD Run and Validation (Staff and WG’s) • Present Results and Recommendation to TAS regarding using reserve modeling as Sensitivity or Common Case assumptions

11. Questions?