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Alan F. Hamlet, Nathalie Voisin,
Dennis P. Lettenmaier, David W. Pierce, Tim Barnett
Center for Science in the Earth System Climate Impacts Group
and Department of Civil and Environmental EngineeringUniversity of Washington
Scripps Institute of OceanographyCalifornia Energy Commission
April, 2005
The Role of Climate Forecasts in Western U.S. Power Planning
Background
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Effects of the PDO and ENSO on Columbia River Summer Streamflows
Cool CoolWarm Warm
PDO
Red=warm ENSO Green=ENSO neutral Blue=cool ENSO
Value of Long-Range Streamflow Forecasts for PNW Hydro Marketing
~ $150 million/yr
This value is created in part by marketing additional energy in late summer (when energy is more valuable) in expected wet years.
Hamlet, A.F., Huppert, D., Lettenmaier, D.P., 2002, Economic Value of Long-Lead Streamflow Forecasts for Columbia River Hydropower, ASCE J. of Water Res. Planning and Mgmt, 128 (2), pp 91-101
http://www.abb.com/global/abbzh/abbzh251.nsf!OpenDatabase&db=/global/gad/gad02181.nsf&v=17EA&e=us&m=100A&c=C1256D71001E0037C1256B8000371E41
~8000 MW IntertieCapacity
In normal or above normal water years in the PNW, net transfers are typically from PNW to CA
In below normal water years in the PNW, transfers from CA to PNW can occur in winter and transfers from PNW to CA in spring and summer may be
reduced or suspended.
Research Questions:
How do hydropower resources in the PNW and CA vary with climate and how predictable are these variations?
How does electrical demand vary with climate in the PNW and CA and how predictable are these variations? Are extreme loads predictable?
How do supply and demand co-vary in time? How predictable are energy surpluses and deficits in each region?
How can we best use this information to maximize the benefits of the PNW - CA electrical intertie?
Tools and Methods
Snow Model
Schematic of VIC Hydrologic Model and Energy Balance Snow Model
PNW
CACRB
GB
Evaluation of VIC Streamflow Simulations
Schematic Overview of CVMod and ColSim Reservoir Models
CVMod
ColSim
IrrigationDominates
Flood ControlWinter HydroDominate
Evaluation of Daily Time Step Energy Demand Model
Demand vs Tmax
Model Validation
Daily Peak Demand Models
PNW(Nov-March)
CA(May-Sept)
Met Data1915-2003
VIC
Overview of Simulation and Analysis
CVMod
ColSim PNW Hydro
SacramentoSan Joaquin Hydro
StatisticalDemand Models
PNW Demand
CA Demand
Population Weighted
TemperatureTime Series
Urban PopulationData
Observed DemandData
Results
Relationship Between Annual Discharge at The Dalles and Annual Hydropower Production in the PNW
-3.000
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191719221927193219371942194719521957196219671972197719821987199219972002
PNW*
CA*
Covariation of Normalized PNW and CA Hydropower Production
California hydropower is less than 10% of total CA demand, but may play a significant role in energy trading on short time scales. Transferable energy from the PNW is also about 10%.
R2 =0.541
Predictability of Seasonal Demand in the PNW and CA
•Winter demand in the PNW is predictable with long lead times via ENSO forecasts:
Warm ENSO = lower winter electrical demandCool ENSO = higher winter electrical load
•Load is in phase with water availability.
•Summer demand in CA has been recently demonstrated to be predictable with several months lead time using the NPO (PDO) index in spring (Alfaro et al. 2005). •
B.Normal NPO (MAM) = B. Normal CDD in S. CA. (JJA)A.Normal NPO (MAM) = A. Normal CDD in S. CA. (JJA)
•Load is out of phase with PNW water availability.
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Nino3.4 Anomaly (C)
Ave
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MW
)Nino3.4 Anomaly vs Avg NDJF Peak Electrical Demand
MAM-PDO IndexExplains about 20% of the Variance in monthly average TMAX in CA.
y = 189.49x + 36876
R2 = 0.0014
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MAM avg PDO
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Relationship Between MAM avg PDO and CA Daily Peak LoadApproximate Threshold of Capacity Problems
May-June-July Hydropower available for Transfer
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Available Energy
Surplus Energy in Spring the PNW is Predictable with Long Lead Times
Above normal surplus hydro from the PNW is more likely in cool PDO and cool ENSO years, less likely in warm PDO and warm ENSO years.
Probability of Exceedance for Spring Surplus Energy Resources in the PNW
Simple Monthly Energy Transfer Model
April May June July August
CA Natural Gas electricity $/MWh 59.52 59.52 59.52 59.52 59.52
PNW hydropower sale (HHL + load variance)
$/MWh 19.15 19.08 23.63 30.71 44.94
(PNW transmission) $/MWh 3.39 3.39 3.39 3.39 3.39
(PNW high load hour sale (HHL), PNW benefit)
$/MWh 18.05 17.98 22.53 29.61 43.84
If surplus energy is available (i.e. system-wide supply > PNW load) then energy can be shipped from the PNW to CA subject to the following constraints.
•Transferred energy does not exceed the intertie capacity during daylight hours ( instant intertie cap*10 hr*days per month)
•Transferred energy does not exceed the hydro production at John Day and The Dalles hydro plants
•Transfer is economically feasible (less cost than gas turbine generation in CA)
April Benefits:
CA = $36.98/ MW-hr
PNW = $18.05/ MW-hr
Apr-July Surplus System Wide Energy Available for Transfer(value is constrained by intertie capacity and the capacity of John Day and The Dalles hydro plants)
Extra Benefits and Costs over April-May-June-July in millions $
CA BENEFIT
PNW BENEFIT
WARM
ENSO 132 77
PDO 135 78
ENSO/PDO 120 69
COLD ENSO 172 102
PDO 186 111
ENSO/PDO 189 112
AVG 159 95
Estimate of Economic Benefits of Current Energy Transfers
Why is transferable energy so much higher in the most recent decades?
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Effects of the PDO and ENSO on Columbia River Summer Streamflows
Cool CoolWarm Warm
PDO
Red=warm ENSO Green=ENSO neutral Blue=cool ENSO
y = 632.52x + 196974
R2 = 0.0598y = 1257.6x + 379657
R2 = 0.0842y = 2077.8x + 389645
R2 = 0.1032y = 780.89x + 244524
R2 = 0.0478
0
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Linear (April)
Linear (May)
Linear (June)
Linear (July)
Reservoir Storage “Resets”
Sys. Storage 80%
Sys. Storage 90%
Reservoir system storage in the most recent decades has been relatively high, which increases efficiency.
A Forecast Timeline
Jun Aug Jun
On ~June 1 we have:
•CurrentReservoirContents (PNW and CA)
•Current SummerStreamflow Forecast (PNW and CA)
•ENSO forecast•PDO forecast
CA Demand
Surplus PNWEnergy forComing Spring
PNW Winter Demand
Jan
Forecasts:
Two Primary Energy Planning Applications:
1) Predicting Natural Gas Consumption in CA
CA hydro and transferable surplus hydro in spring from the PNW to CA represents gas that will not be burned in CA to produce peaking energy in spring and summer. The probability distribution of this number is known with about 12-months lead time. Because CA and PNW hydro are typically in phase the effect is typically amplified.
2) Changes in Water Management in the PNW
Releases of water in late summer are at a premium in the PNW. Using streamflow forecasts, an available energy pool can be estimated that will not jeopardize reservoir refill in spring. Power from this pool could then be sold to spot market customers in CA depending on their needs. This effective transfer of energy from the coming spring to the current summer would benefit the PNW in terms of achieving more reliable fish flows in late summer and higher power revenues on average.
•Such actions would not reduce drought risks to fish (no energy to ship to CA).
•CA would almost always produce a marginal economic benefit by buying power from the PNW, but since the net $ benefit to CA is higher in spring than summer, CA would not necessarily want to trade spring energy for summer energy.