Transcript Risk Assessment of Hydro Projects in the Face of Climate

Climate Change and Seattle City
Light Operations
Wing Cheng and Ron Tressler
Seattle City Light
September 16, 2009
Presentation Outline
• Background on Seattle City Light
• Climatic Effects on Hydrology and
Operations
• Potential Impacts
– Power Generation
– Power Delivery
– Power Management
– Asset Management
• Moving Forward
City of Seattle
Seattle City Light Facts
•
•
•
•
•
Municipal Electric Utility
376,000 customers
About 90% hydro
Skagit River – 711 MW capacity
Boundary (Pend Oreille River) – 1,047
MW capacity
• Carbon Neutral for last 5 years
• Skagit is certified Low Impact Hydro
City of Seattle
Power Resources
Source
Average Megawatts
(2007)
5 SCL-owned Hydroelectric Projects
745
Skagit, Boundary, Newhalem, Cedar Falls, Tolt
Power Purchase Contracts with
Federal Bonneville Power
Administration (BPA)
682
Contract with BC Hydro (Canadian)
- International Treaty
Contracts with other Utilities in
Washington, California and Idaho
38
Wind and Small Biomass Plant
Contracts
TOTAL
44
34
1,543
Canada
United States
Ross Dam
Climate Change in the PNW
• Temperatures: 1.5°F  (1920 and 2003)
• Precipitation: 14%  (1930-1995)
• April 1 SWE: 25%  in Washington Cascades
• Runoff Timing: Shifted 0-20 Days Earlier
• Following Charts Shows Climate Change in the
Skagit Watershed as observed by SCL
•
Source: CIG website
City of Seattle
Diablo Monthly Average Temperature
70.00
65.00
Average (1931-2003)
Average (2000-2008)
60.00
Degree F
55.00
50.00
45.00
40.00
35.00
Note: More than 1 Deg. F increase in January, February and July
30.00
JAN
FEB
MAR
APR
MAY
JUN
Month
City of Seattle
JUL
AUG
SEP
OCT
NOV
DEC
Diablo Monthly Average Precipitation
22.00
Note: An annual decrease of about 1/3 inch
Average (1931-1995)
20.00
Average (2000-2008)
10 Percentile (1931-1995)
18.00
90 Percentile (1931-1995)
16.00
Inches
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
JAN
FEB
MAR
APR
MAY
JUN
Month
City of Seattle
JUL
AUG
SEP
OCT
NOV
DEC
Climate Change Impacts Detected

Reduced spring-summer inflow
PDO Positive
PDO Negative
No official PDO Classification
Average Ross Inflow by Month
(Cubic Feet/Sec)
9,000
Average (1970-1999)
8,000
Average (2000-2008)
7,000
6,000
An 14.5% annual reduction and
an 18.2% May-July reduction.
5,000
4,000
3,000
2,000
1,000
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Month of Water Year
City of Seattle
May
Jun
Jul
Aug
Sep
Ross Runoff Starting and Ending Dates
8/28
8/13
7/29
7/14
6/29
Date
6/14
Note: Trends of runoffs shifting to earlier starts and ends
Start day
End day
Linear (Start day)
Linear (End day)
5/30
5/15
4/30
4/15
3/31
3/16
3/1
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
Year
City of Seattle
1993
1995
1997
1999
2001
2003
2005
2007
2009
Power Generation
• Skagit Project Managed for “Fish First”
– All Pacific salmonid species
– Listed Chinook salmon, steelhead, and bull trout
• Intricate annual flow management planning
with monthly updates
– Protect salmonids during spawning and fry
development
– Meet Corps flood control mandates and
recreation pool elevations in Ross Lake
City of Seattle
Power Generation
• Model Skagit Hydrology based on the following:
– 3Tier’s DHVSM Water Years 86-03
– Temperature +2.7oF by 2020 and +4.1oF by 2040 over 19901999
– Precipitation Unchanged
• Output is Reservoir Inflow
• Optimize Ross Reservoir Outflow based on Inflow Data
City of Seattle
Ross Average Monthly Inflow
8000
Historical
CC 2020
CC 2040
7000
6000
CFS
5000
4000
3000
2000
1000
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Month in Water Year
City of Seattle
Jun
Jul
Aug
Sep
Ross Average Monthly Outflow
6500
Historical
6000
Year 2020
5500
Year 2040
5000
CFS
4500
4000
3500
3000
2500
More power will be generated during winter
and less during spring and summer
2000
1500
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Month in Water Year
City of Seattle
Apr
May
Jun
Jul
Increased
frequency of
extreme events
Skagit River Fisheries
High-flow events
scouring redds and
rearing habitat
Thermal barriers
during low flows
Power Management
SCL Average Monthly Generation and Load, 2001-2007
1300
SCL Generation
1200
SCL System Load
1100
aMW
1000
Peak Load in winter (California Summer)
Surplus Power in Summer (California Winter)
900
800
700
600
500
SCL Owned Generation Only – BPA and
Other Power Contracts not Included, e.g. in
2007, SCL Generated 48.3% and Purchased
42.3% from BPA
400
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Month of Year
Power Exchange with California
City of Seattle
Nov
Dec
Power Management…..continued
• California Load-Resource Change
Currently Lacking for Understanding
• SCL Load-Resource Change
Slight Load Decrease in Winter and Increase in Summer
• SCL Adaptation Strategies
Explore Exchange with Other Regions
Expand Sales and Purchases in Spot Market
Develop Prudent Hedging Strategies
Improve System Load Forecast
City of Seattle
Cooling Load on 07/29/09 Heat Wave
Hourly SCL System load on Wednesday
1600
Daily Averae = 85.5 deg and Maximum = 104.8 deg
1500
1400
Previous Summer
Peak Load Record
MWHr
1300
Daily Average = 69.8 deg and Maximum 82.5 deg
1200
1100
Daily Average = 64.9 deg and Maximum 75.9 deg
1000
7/22/2009
7/29/2009
8/5/2009
7/24/2006 (Monday)
900
800
700
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour of Day
City of Seattle
Uncertainty in System Load Modeling
Average Monthly SCL System Load, aMW
(based on 2.7 and 4.1 degrees adjustment)
1300
2020 Hourly Peak Load = 1765.5 MW
1250
Daily Average MW
Ave 01_07
Ave 2020
Ave 2040
1200
1150
1100
1050
1000
950
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month of Year
Monthly Average SCL System Load, aMW
(based on MM5 6-Hour Simulation)
1400
Yr 1990
Yr 2020
Yr 2050
2020 6-Hours Peak Load = 2175 MW
1350
Yr 2090
1300
aMW
1250
1200
1150
1100
1050
1000
Jan
Feb
Mar
Apr
May
Jun
Jul
Month of Year
City of Seattle
Aug
Sep
Oct
Nov
Dec
Power Delivery
• Transmission/Distribution Line Rating
+ 5o F on 1000’ span = 2’’ more Sag
Not Significant Now; but Could be at + 10o F
• Transformer Thermal Rating
Aging Acceleration Factor = 1 with Hottest Spot at 110o F
Insulation Deterioration Rate Doubles every 7o F Increase
Water Spray Now Required During Very Hot Days
De-rate or Replace with Increasing Hot Days?
City of Seattle
Healey Fire Protection – Outdoor Transformer Protection with Water Spray System
City of Seattle
Asset Management
Normal Period for Plant Maintenance
Ross Third Quartile Monthly Outflow
8000
7500
7000
Historical
6500
Year 2020
6000
Year 2040
CFS
5500
5000
4500
4000
3500
Heavy
Glacial
Runoff
Downstream
3000
2500
Period
Maintenance Works
Normally Scheduled
2000
Possible Loss of a Month
1500
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Month of Water Year
City of Seattle
Slide 13
Asset Management…..continued
• Decision on Capital Investments
Example of Gorge Second Tunnel
Three 30-MW Units Completed in 1929
A 4th 67-MW Unit Added in 1951
One 20.5’ Diameter, 11000 Feet Long Tunnel
Tunnel Loss at Full Capacity about 60 Feet or 34 MW
City of Seattle
New 18 Feet Diameter Tunnel to Supply Water to the Large Unit Only
Recover Slightly More Than Half of Tunnel Loss at Full Capacity
Annual Reduction in Tunnel Loss Enough to Power over 7000 Households
City of Seattle
Gorge Companion Tunnel Total Energy Gain by Month
16000
Historical (Total = 64,437)
CC 2020 (Total = 78,057)
CC 2040 (Total = 81,711)
14000
12000
MWHrs
10000
8000
6000
4000
2000
0
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Month of Water Year
Climate Change May Favor this Project but What About Others?
City of Seattle
Moving Forward
• Expand Conservation
Program (12 aMW in 2009)
• Purchase power to meet I937 renewable energy
portfolio requirement
• Adapt hydroelectric project
operations to changing
conditions (cannot solely use
historical data)
City of Seattle
Research and Next Steps
• Improve River Flow Forecasting
• Track Frequency and Timing of Floods
• Need Improved Downscaling of Global
Climate Models – Dynamic and Statistical
Methods
• Gain Additional Understanding of Glacier
Melting Patterns
• Continue to Monitor Impacts on Fisheries
City of Seattle