Integrating Renewable Energy into the Power Grid
Transcript of Integrating Renewable Energy into the Power Grid
Integrating Renewable Energy into the Power Grid
Rob GramlichSenior Vice President for Public Policy
American Wind Energy Association
Integrating wind is no harder than it was to integrate conventional generation in
previous decades.
As part of a balanced portfolio, wind integration is not a reliability issue, only a
cost issue.
The costs are modest.
Current U.S. Wind Penetration
Source: AWEA data, EIA forms 906 and 920, 2008 data
Current European Wind Energy Penetration
21.22%
11.76%
9.26%
8.42%
7.00%
4.28%
3.89%
3.78%
3.67%
3.40%
3.28%
1.82%
0.00% 5.00% 10.00% 15.00% 20.00% 25.00%
Denmark
Spain
Portugal
Ireland
Germany
EU-15
EU-25
EU-27
Greece
Netherlands
Austria
UK
Source: EWEA 2007 and Eurelectic
2006
Power System Operations
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Supply and demand of electricity must match at all times•
Electricity demand and supply are both variable and uncertain.
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Grid operators hold generation in reserve:•
Regulation reserves
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Load-following reserves •
Contingency reserves
•
Reserves are shared for all sources of variability
Wind generator performance All quotes from NERC Variable Generation Report
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NERC: “It is now possible to design variable generators with the full range of performance capability which is comparable, and in some cases superior, to conventional synchronous generators.” (p. 18)
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NERC: “Unlike a typical thermal power plant whose output ramps downward rather slowly, wind plants can react quickly to a dispatch instruction taking seconds, rather than minutes.” (p. 19)
Variability is not new and need not be significant
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“Power system planners and operators are already familiar with designing a system which can be operated reliably while containing a certain amount of variability and uncertainty, particularly as it relates to system demand and, to a lesser extent, to conventional generation.” (p. 4)
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“The aggregate energy output from wind plants spread over a reasonably large area tends to remain relatively constant on a minute-to-minute time frame, with changes in output tending to occur gradually over an hour or more.” (p. 15)
Wind’s Variability: The Time Element
Study Wind PenetrationOne minute
Five minutes
One hour
Texas 2008[1] 15,000 MW 6.5 MW 30 MW 328 MW
California Energy Comm-ission2007[2]
2,100 MW, + 330 MW solar 0.1 MW 0.3 MW 15 MW
7,500 MW, + 1,900 MW solar 1.6 MW 7 MW 48 MW12,500 MW,
+ 2,600 MW solar 3.3 MW 14.2 MW 129 MW
New York 2005[3] 3,300 MW
- -1.8 MW 52 MW
[1]
http://www.uwig.org/Wind_Generation_Impact_on_Ancillary_Services_-_GE_Study.zip[2]
http://www.uwig.org/CEC-500-2007-081-APB.pdf[3]
http://www.uwig.org/nyserdaphase2appendices.pdf
Wind’s Variability: The Distance Element
Correlation in Wind Plant Output as a Function of Time and Distance
Source: NREL
Wind Integration CostsDate Study Wind
Capacity Penetration (%)
Regulation Cost ($/MWh)
Load Following Cost ($/MWh)
Unit Commit-
ment
Cost ($/MWh)
GasSupplyCost($/MWh)
Total Operating Cost Impact($/MWh)
May ‘03 Xcel-UWIG 3.5 0 0.41 1.44 na 1.85
Sep ‘04 Xcel-MNDOC 15 0.23 na 4.37 na 4.60
June ‘06 CA RPS 4 0.45* trace na na 0.45
Feb ‘07 GE/Pier/CAI
AP
20 0-0.69 trace na*** na 0-0.69***
June ‘03 We Energies 4 1.12 0.09 0.69 na 1.90
June ‘03 We Energies 29 1.02 0.15 1.75 na 2.92
2005 PacifiCorp 20 0 1.6 3.0 na 4.60
April ‘06 Xcel-PSCo 10 0.20 na 2.26 1.26 3.72
April ‘06 Xcel-PSCo 15 0.20 na 3.32 1.45 4.97
Dec ’08 Xcel-PSCo 20 3.95 1.18 5.13-
6.30****
Dec ‘06 MN 20% 31** 4.41**
Jul ‘07 APS 14.8 0.37 2.65 1.06 na 4.08
Source: NREL
NREL’s Flexibility Supply Curve
Source: NREL
Improved Pricing
Demand Response
Gas Generation
Coal Cycling
Existing Hydro
Pumped Hydro
Gas Storage
Increasing RE Penetration
LowCost
HighCost
IceHeat
Heating
Transportation
Demand Side
Flexibility
Supply Side
FlexibilityCSP
Markets
Thermal
Storage
New
Loads
Electricity
Storage
Electricity
Storage
Existing
Storage
RE
Curtailment
Thermal
Storage
Flexible
Generation
There are many ways to reduce wind integration costs
NERC Variable Generation report
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“Transmission expansion, including greater connectivity between balancing areas, and coordination on a broader regional basis, is a tool which can aggregate variable generators leading to the reduction of overall variability. Sufficient transmission capacity serves to blend and smooth the output of individual variable and conventional generation plants across a broader geographical region. Large balancing areas or participation in wider-area balancing management may be needed to enable high levels of variable resources. (p. 43)
Flexibility through markets
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NERC: “Additional sources of system flexibility include the operation of structured markets, shorter scheduling intervals, demand-side management, reservoir hydro systems, gas storage and energy storage.”
(p. 48)
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Large RTOs
with fast (e.g. 5 minute) energy and ancillary service markets are most reliable, efficient and accommodating of renewables
Consolidate Balancing Areas
Larger Balancing Areas
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Allow excess power in one region to be shared with neighboring regions
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Enable diverse wind resources spread over a larger area to be connected to the same grid, canceling out their variability
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Create cost savings•
Midwest ISO estimates savings from consolidating its 26 balancing areas into one are 3.7 to 6.7 times greater than the costs
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Savings are large even on power systems without wind energy
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Consolidation can be done physically or virtually
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NERC: “More frequent and shorter scheduling intervals for energy transactions may assist in the large-scale integration of variable generation.”
(p. 61)
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In much of the U.S., power plants are scheduled to operate for hourly intervals, and expensive reserves are used to accommodate intra-hour variability.
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Studies show significant savings from 5-
or 10-minute intervals instead of hourly:
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Bonneville Power: 80% reduction in wind integration costs
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Avista: 40-60% reduction in wind integration costs
Shorten Power Plant Dispatch Intervals
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NERC: “Forecasting is one of the key tools needed to increase the operator’s awareness of wind plant output uncertainty and assist the operator in managing this uncertainty.”
(p. 55)
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Largest opportunities for improvement:•
Better integrating forecasts into power system operations
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Providing grid operators with useful information
Improve Use of Wind Forecasting
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Transmission capacity is often physically available when wind output is highest, but contractual and operating rules prevent use of this capacity
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Conditional firm allows available transmission capacity to be used by others outside of a few peak hours
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Dynamic line rating determines real-time capacity of a line, instead of relying on rules of thumb that greatly underestimate available capacity
Use Dynamic Line Ratings and Conditional Firm
American Electric Power Company, Big Lake - McCamey LineDynamic Rating vs. Static Rating, May 2006
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 100.0%
Percent Probability
Rat
ing
(MVA
)
Dynamic rating Static rating Alternate static rating
147.0
168.7
Dynamic Line Rating
Source: The Valley Group
American Electric Power Company, Big Lake – Mc Carney Line
Dynamic Rating vs. Static Rating
Quick comment on Renewable Electricity Standards
Renewable Electricity Standards
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THE driver of bringing wind manufacturing to the US.•
Drives deployment from 2010-2015 when cap and trade will not.
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Perfect (cap and trade or tax) is the friend of many supporters of the status quo.
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All 5 EIA studies show electricity rate reductions (through reduction of gas demand).
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Fuel diversity has always been the subject of public policy, this is nothing new.
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The playing field is already tilted due to other subsidies and policies.
Quick comment on transmission infrastructure policy
Increasing support for grid vision
Interest 2007 support
2009 Future?
Enviros - +/- ++/neutral
Consumer adv. ? ? ++
Utilities - +/- +/-
Economists - +/- +
States - - +/-
National interest ? + ++
Green jobs + ++ +++
Conclusions:
There are no technical barriers to high (~20% national) wind penetration
To reduce costs we should build renewables in optimal resource areas and transmission
to population centers. Need to change planning, permitting, paying (3 P’s).
For reliability, efficiency, and renewable energy integration we should move towards large regional balancing areas with energy
and ancillary services markets.