Evaluating Hydro Capacity for Capacity Adequacy Standard: Selection of Hydro Events Eric King/ Mary Johannis PNW Resource Adequacy Technical Committee Mtg November 1, 2007

PNW Resource Adequacy Technical Committee Meeting2

November 1, 2007PNW Resource Adequacy Technical Committee Meeting3 Historical vs. Calculated Calculated Sustained FCRPS Cap Purchases Cap to meet Expected Load Surplus + Cap to meet PRM

November 1, 2007PNW Resource Adequacy Technical Committee Meeting4 1 in 20 Probability Winter & Summer Events Suggested Approach: –Select combination 1 in 20 year probability event, which includes both adverse hydro capacity and adverse temperature-induced load conditions For purposes of reporting Hydro Capacity to WECC and for Resource Adequacy Forum purposes, best to define common winter and summer adverse event for which to evaluate hydro capacity –Utilities could then define temperature-induced adverse load conditions for their own resource planning efforts which approximate 1 in 20 probability

November 1, 2007PNW Resource Adequacy Technical Committee Meeting5 Representative NW Hydro Projects ROSS Round Butte Columbia River Hydro

November 1, 2007PNW Resource Adequacy Technical Committee Meeting6 Suggested Representative Projects FCRPS –FCRPS & Probably all Columbia River Hydro not very sensitive to Selection of Adverse Event Non-Columbia River Projects –PGE’s Round Butte Project on Deschutes River is representative of Williamettes –Seattle’s ROSS on Skagit River is a representative West-side project

November 1, 2007PNW Resource Adequacy Technical Committee Meeting7 Selection of Winter Event

November 1, 2007PNW Resource Adequacy Technical Committee Meeting8 Selecting Adverse Hydro Condition for Winter Event Approach –Look at candidate events, which constitute similar adverse probabilities (except Columbia River) –Investigate events with February flows close to 1 standard deviation (α) lower than mean, except for Columbia River –Pick event closest to 1 α for river systems other than Columbia River Candidate Events – : too adverse (≤ 1 α) for Round Butte – : not sufficiently adverse for Round Butte & ROSS – : too adverse for ROSS – : not sufficiently adverse for Round Butte & ROSS – : ≈ adverse for Round Butte & ROSS= Selected Event

November 1, 2007PNW Resource Adequacy Technical Committee Meeting9

November 1, 2007PNW Resource Adequacy Technical Committee Meeting10

November 1, 2007PNW Resource Adequacy Technical Committee Meeting11

November 1, 2007PNW Resource Adequacy Technical Committee Meeting12

November 1, 2007PNW Resource Adequacy Technical Committee Meeting13

November 1, 2007PNW Resource Adequacy Technical Committee Meeting14 Suggested Winter Hydro Event Use historical modified February 1969 flows for Columbia River, West-side and Williamette hydro projects Evaluate 18 hour Sustained Peaking Capacity for individual hydro PNW hydro projects using Methodology on Slide 2 Compare ∑ individual hydro capacities to 18 Trapezoidal Approximation of Regional Hydro Capacity under February 1969 water condition Decide whether to select February 1969 Event as Winter Event for which to Evaluate PNW Hydro

November 1, 2007PNW Resource Adequacy Technical Committee Meeting15 Selection of Summer Event

November 1, 2007PNW Resource Adequacy Technical Committee Meeting16 Next steps Decide whether to use same approach to select summer event as winter event Form subcommittee to perform hydro evaluations of individual PNW hydro projects for winter event (either Feb 1969 or other events from this meeting) Have subcommittee explore possible summer events