Wind Workshop
Technical Characterization:
Dependable Capacity & Firm
Energy
10:00-10:30am
Objective of this session:
•
Understand BC Hydro’s definitions and calculation
methodology of dependable capacity
•
Understand other definitions and calculation
methodologies
•
Formulate new approach?
January 25 - 26, 2005
Agenda
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Dependable Capacity
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Other jurisdictions (PJM,CallSO, NYISO)
BC Hydro definition and methodology
Geographic Smoothing
Firm Energy
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Other jurisdictions (CallSO, NYISO)
BC Hydro definition and methodology
Monthly 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 units
output 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 for
California’s RPS (Phase 1)
• Based on California ISO Plant Information for wind
farms in Altamont, San Gorgonio and Tehachapi
• Calculated as the Effective Load Carrying Capacity
(ELCC) of wind farms
• Wind in the Altamont area contributed ELCC of
26%, 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 when
load exceeds 90% of peak load was used to estimate
the ELCC
• This modified UCAP ranged between 3% and 23%
• The modified UCAP was low because New York
wind farms have low outputs during summer
evenings, which are the highest load times in the
area
January 25 - 26, 2005
Capacity Credit – PacificCorp
Effective Load Carrying Capability
- amount of load that can be supported by a wind unit
while holding some risk measure constant
(Energy not served)
- for 100 MW Wind unit, contribution to load ranged from
19-24.5%
- 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 the
maximum megawatt output it can reliably produce
when required, assuming all units are in service
• Reliably Produce: means availability coincident with
system peak with high confidence level
January 25 - 26, 2005
BC Hydro Definition
- Dependable Capacity
Dependable Capacity is affected by factors external to the
plant
– 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 the
continuous two weeks of cold weather ”
• Pragmatic definition for calculation
“capacity available during 2 consecutive months of low
flow/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
Mt Hays
Mt Wartenbe
Aasen
Bear Mountain
Sugar Loaf
Ashcroft South
Rumble Ridge
January 25 - 26, 2005
85 % confidence
0.00
0.00
0.00
0.00
0.55
0.00
0.05
Capacity Summary
Capacity Equivalent
other utilities 0 to 30%
• California 24%
• New York 3% to 23%
• PacifiCorp 20%
• Xcel 30%
Dependable Capacity
BC Hydro sites 0 to 55%
• Class Average 0%
January 25 - 26, 2005
Capacity Credit – Vancouver Island
From BC Hydro Rumble Ridge Meteorological Tower and BC
Hydro Load Profile
• The ELCC of wind farms can be accurately calculated with
an 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 Island
winds are strongest during winter, when BC loads peak
January 25 - 26, 2005
Wind – Hydro Correlation
100
Percent of Peak
90
80
70
60
50
40
Jun
Jul
Aug
B.C. Reservoir Storage
January 25 - 26, 2005
Sep
Oct
Nov
Dec
Wind Speed at Port Hardy
Jan
Feb
Mar
Apr
May
Peak Load on Vancouver Island
BC Hydro Methodology for Wind
Using the BC Hydro methodology for wind
dependable capacity and Sea Breeze data
• The dependable capacity of a typical wind farm on
Vancouver Island is 3%
• The dependable capacity of wind farms in a small
region of Vancouver Island is 14%
• The dependable capacity of wind farms over the
entire island would be greater still
• With PJM or NYISO methodology, the capacity
credit would be 40%
January 25 - 26, 2005
Geographic Smoothing
Concept – instead of evaluating Dependable Capacity of
an 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 wind
farms less than from a single farm.
Example using BCH data:
Rumble Ridge (VI), Mt Hays (Prince Rupert),and
Bear 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 in
portfolios
• Firm energy - what a project can generate annually on
an 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 usually
consider firm energy.
-BPA : Firm energy based on “critical water years”
-North West Planning Council recently introduced standard to plan
for energy based on 85% quantile.
January 25 - 26, 2005
Energy Capability of Wind
• Annual wind farm output has a standard
deviation of about 7%
• 93% of the average annual output is exceeded
by 85% of years
• Since wind has low annual variation, it can
serve as energy insurance for the “critical
water years” in the BC Hydro system
January 25 - 26, 2005
Monthly Energy Profile and load
% of Annual Energy
12%
10%
8%
Peace
6%
Van Island
Load
4%
2%
January 25 - 26, 2005
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
0%
Monthly Energy Profile and load
% of of max month
120%
100%
80%
Peace
Van Island
60%
Load
40%
20%
January 25 - 26, 2005
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
0%
Summary of Discussion:
•
Dependable Capacity
•
Firm Energy
January 25 - 26, 2005