Wind Workshop

Technical Characterization:

Dependable Capacity & FirmEnergy

10:00-10:30am

January 25 - 26, 2005

Objective of this session:• Understand BC Hydro’s definitions and calculation

methodology of dependable capacity

• Understand other definitions and calculationmethodologies

• Formulate new approach?

January 25 - 26, 2005

Agenda

Dependable CapacityOther jurisdictions (PJM,CallSO, NYISO)BC Hydro definition and methodologyGeographic Smoothing

Firm EnergyOther jurisdictions (CallSO, NYISO)BC Hydro definition and methodologyMonthly energy profile and coincident peak

January 25 - 26, 2005

Capacity Credit – PJM

From PJM News Release April 24, 2003:

-Based on a wind farms actual performance-Calculated as three-year rolling average of a unitsoutput during Peak hours(3 pm and 6 pm) during June,July, August-Class average is 20%

January 25 - 26, 2005

Capacity Credit – California

From Study of Renewables Integration Costs forCalifornia’s RPS (Phase 1)

• Based on California ISO Plant Information for windfarms in Altamont, San Gorgonio and Tehachapi

• Calculated as the Effective Load Carrying Capacity(ELCC) of wind farms

• Wind in the Altamont area contributed ELCC of26%, San Gorgonio 24% and Tehachapi 22%

• The California class average is 24%

January 25 - 26, 2005

Capacity Credit – New York

From NYISO/NYSERDA Wind Study

• Unforced Capacity (UCAP) of wind farms whenload exceeds 90% of peak load was used to estimatethe ELCC

• This modified UCAP ranged between 3% and 23%

• The modified UCAP was low because New Yorkwind farms have low outputs during summerevenings, which are the highest load times in thearea

January 25 - 26, 2005

Capacity Credit – PacificCorp

Effective Load Carrying Capability- amount of load that can be supported by a wind unitwhile holding some risk measure constant

(Energy not served)

- for 100 MW Wind unit, contribution to load ranged from19-24.5%- suggested using 20% contribution to load

(study based on limited data)

January 25 - 26, 2005

Capacity Credit – Colorado

Colorado PUC’s decision regarding Xcel Energy- wind farm provides ~30% equivalent

European Wide study by Giebel- suggests ~19% equivalent

January 25 - 26, 2005

BC Hydro Definition- Dependable Capacity

• A generating plants dependable capacity is themaximum megawatt output it can reliably producewhen required, assuming all units are in service

• Reliably Produce: means availability coincident withsystem peak with high confidence level

January 25 - 26, 2005

BC Hydro Definition- Dependable Capacity

Dependable Capacity is affected by factors external to theplant– I.e. streamflow conditions; fuel supply constraints; wind

• Not affected by:– Forced outages not included - in planning reserves– Planned outages not included - assumed to be scheduled

around winter peak

January 25 - 26, 2005

BC Hydro Definition- Dependable Capacity

• For annual supply-demand balance:“3 hours in peak load period of weekday during thecontinuous two weeks of cold weather ”

• Pragmatic definition for calculation“capacity available during 2 consecutive months of lowflow/fuel supply for the period of concern (i.e. 3 hours)based on 85% confidence level.”

January 25 - 26, 2005

Dependable Capacity - calculation methodology

• Major Generating Plants with upstream storage: - 85% confidence level of assumed 50 years stream flows

• Existing IPP projects: - based on actual performance (85% confidence level )

• Planned IPP projects: - based on their contracted capacity

• Projects in Resource Options Database: - some projects have site specific information available

(Site C, Rev5), others base on “class average” Dependable Capacity Factors

January 25 - 26, 2005

BC Hydro Methodology for Wind

Dependable Capacity Factor= dependable capacity/installed capacity

“class average percent”

Used data (Dec & Jan) from BC Hydro monitoring sites• Moving minimum across 3-hour intervals (using

average hourly data)• Determine wind speed that is exceeded 85% of the

time• Use turbine power curve to determine the power• Fraction of this value compared to nameplate

capacity is DCF

January 25 - 26, 2005

DCF Results for BC Hydro Sites

Average 85 % confidenceMt Hays 0.00Mt Wartenbe 0.00Aasen 0.00Bear Mountain 0.00Sugar Loaf 0.55Ashcroft South 0.00Rumble Ridge 0.05

January 25 - 26, 2005

Capacity Summary

Capacity Equivalentother utilities 0 to 30%

• California 24%• New York 3% to 23%• PacifiCorp 20%• Xcel 30%

Dependable CapacityBC Hydro sites 0 to 55%

• Class Average 0%

January 25 - 26, 2005

Capacity Credit – Vancouver Island

From BC Hydro Rumble Ridge Meteorological Tower and BCHydro Load Profile

• The ELCC of wind farms can be accurately calculated withan Expected Energy not Served (EENS) study

• Otherwise, the ELCC can be estimated using the modified(UCAP) methodology of the NYISO Study

• A Rumble Ridge farm with an annual capacity factor of 30%has a 40% capacity factor at times of peak loads

• The modified UCAP is high because Vancouver Islandwinds are strongest during winter, when BC loads peak

January 25 - 26, 2005

Wind – Hydro Correlation

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B.C. Reservoir Storage Wind Speed at Port Hardy Peak Load on Vancouver Island

January 25 - 26, 2005

BC Hydro Methodology for Wind

Using the BC Hydro methodology for winddependable capacity and Sea Breeze data

• The dependable capacity of a typical wind farm onVancouver Island is 3%

• The dependable capacity of wind farms in a smallregion of Vancouver Island is 14%

• The dependable capacity of wind farms over theentire island would be greater still

• With PJM or NYISO methodology, the capacitycredit would be 40%

January 25 - 26, 2005

Geographic Smoothing

Concept – instead of evaluating Dependable Capacity ofan individual site, consider for a number of sites

Journal of Geophysical Research (May 2003)- power output average over 1, 3, 8 stations- Intermittency of wind energy from multiple windfarms less than from a single farm.

Example using BCH data:Rumble Ridge (VI), Mt Hays (Prince Rupert),andBear Mountain (Peace)

January 25 - 26, 2005

BC Hydro Definition - Energy Capability

• Average energy - expected annual energy– for hydro is based on average water conditions– average energy for dispatchable thermals incorporates

economic dispatch– Small hydro, wind, wave etc.:

• Currently not enough information to discern firm & average inportfolios

• Firm energy - what a project can generate annually onan assured basis– based on historic low water for BC Hydro projects– for thermals - based on installed capacity, fuel supply & unit

availability

January 25 - 26, 2005

Firm Energy – other jurisdictions

-Only an issue for Hydro systems that are energy constrained.Thermal systems are capacity constrained so do not usuallyconsider firm energy.

-BPA : Firm energy based on “critical water years”

-North West Planning Council recently introduced standard to planfor energy based on 85% quantile.

January 25 - 26, 2005

Energy Capability of Wind

• Annual wind farm output has a standarddeviation of about 7%

• 93% of the average annual output is exceededby 85% of years

• Since wind has low annual variation, it canserve as energy insurance for the “criticalwater years” in the BC Hydro system

January 25 - 26, 2005

Monthly Energy Profile and load

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January 25 - 26, 2005

Monthly Energy Profile and load

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January 25 - 26, 2005

Summary of Discussion:• Dependable Capacity

• Firm Energy