January 29, 2010 Resource Adequacy Steering Committee

1

Sustained Peaking Capacity Analysis

Initiated by the Adequacy Forum

Input Information from Utilities

Assembled by Don Long

January 29, 2010 Resource Adequacy Steering Committee

2

PNW Sustained Hydro Peaking Capacity Analysis

• Study Goal:– Perform a “bottom-up” assessment of the sustained peaking

capacity of the Pacific Northwest Hydro System over the highest 18 hours in a 3-day cold snap or heat wave under critical, adverse and average water conditions.

• Study Purposes:– Inform Hydro utilities’ resource planning efforts– Assure consistent assumptions are used for individual sustained

hydro peaking studies, such as assumed flows on common tributaries

– Provide a check of the GENESYS-based Regional Sustained Hydro Peaking Capability result

– Help assure consistent reporting of hydro capacity to the Western Electricity Coordinating Council’s Loads and Resources Subcommittee (WECC LRS) and the Pacific Northwest Utilities Conference Committee (PNUCC).

January 29, 2010 Resource Adequacy Steering Committee

3

Inputs• Council provides regional load shape• Some utilities chose to model their own hydro

generation, submit hourly info for 3-day events:– Generation – Flow– Purchase assumptions

• Other utilities asked consultant to model for them (utility provides modeling data and purchase assumptions)

• Consultant also responsible for consistency of assumptions (e.g. upstream discharge is in-line with downstream inflow)

January 29, 2010 Resource Adequacy Steering Committee

4

Regional load shape supplied by NWPCC for highest “normal” 3 day (72 hour) period in July and January. Hourly load shapes are expressed as a percentage of the load during the highest hour of the 72 hours.

First trial load = Regional load shape applied to utility’s normal weather energy load forecast for January or July.

Utility specified limits on reservoir operation. Expressed in feet or acre-feet of draft, or percent flow can exceed monthly average, adverse or critical flows.

Utility specified non-hydro resources and purchases.

Residual hydro = Utility load – non-hydro resources and purchases.

Can residual hydro be allocated among utility’s hydro projects so that no project constraints are violated?

Utility specified project operational and limiting parameters for hydro projects.

Increment trial load by a constant factor each hour*

Yes

No Decrement trial load by a constant factor each hour*

Is further tuning possible?

*Note: Tuning will actually be slightly more complicated than indicated in the flowchart. Based on successes and failures to allocate the load to the hydro resources during the iterative process, the hourly adjustment factor will be reduced until no further successful allocations are possible.

Yes

No

Report utility sustained peaking capability as the sum of the hydro generation during the highest 6 hours each day over the 3 day period, divided by 18.

Report utility one-hour hydro peaking capability as the highest one hour hydro generation over the 3 days.

Hydro Sustained Peaking Capability Modeling Flowchart

Study will be by utility system. Each utility will be modeled assuming January and July average weather conditions and average, adverse and critical water conditions, for a total of 6 model runs per utility.

An alternative first trial load shape could be to apply the regional load shape to the utility’s average hydro generation in the applicable seasonal regulation plus non-hydro resources plus purchases. This would result in the first trial residual hydro load being equal to the hydro generation in the regulation.

Initial reservoir content from seasonal regulation. Reservoir inflows from upstream project or seasonal regulation

12/31/2008 DEL

January 29, 2010 Resource Adequacy Steering Committee

5

Output• “Bottom-up” assessment of hydro sustained

peak capability for January Cold Spells and July Heat Waves, for 3 water conditions

• Details of utility study to remain confidential between consultant and utility, other than reporting 1-hour and 18-hour peak capacities.

• Aggregate purchase assumptions for all utilities will be compared with assumptions used in the PNW Resource Adequacy Standard.

• Documentation of methodology to allow the analysis to be repeated (at least every 3 years)

January 29, 2010 Resource Adequacy Steering Committee

6

Status• Completed:

– By utilities: Avista (Clark Fork), EWEB, Federal System (except Elwha River), Idaho Power, PGE, Tacoma

– By consultant: Avista (Spokane River), Bonners Ferry, City of Centralia, Chelan PUD, Douglas PUD, Energy Northwest, Fall River REA, Grant PUD, Lewis County PUD, Pend Oreille PUD, PPL Montana

• In progress:– By consultant: City of Idaho Falls, City of Portland,

Snohomish, Twin Falls Hydro, Warm Springs Tribe

• Data or studies needed:– Utility studies: two missing

– Data for consultant studies: one still to come