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

•

Supply and demand of electricity must match at all times•

Electricity demand and supply are both variable and uncertain.

•

Grid operators hold generation in reserve:•

Regulation reserves

•

Load-following reserves •

Contingency reserves

•

Reserves are shared for all sources of variability

Wind generator performance All quotes from NERC Variable Generation Report

●

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)

●

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

●

“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)

●

“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

●

“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

●

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)

•

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

•

Allow excess power in one region to be shared with neighboring regions

•

Enable diverse wind resources spread over a larger area to be connected to the same grid, canceling out their variability

•

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

•

Savings are large even on power systems without wind energy

•

Consolidation can be done physically or virtually

•

NERC: “More frequent and shorter scheduling intervals for energy transactions may assist in the large-scale integration of variable generation.”

(p. 61)

•

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.

•

Studies show significant savings from 5-

or 10-minute intervals instead of hourly:

•

Bonneville Power: 80% reduction in wind integration costs

•

Avista: 40-60% reduction in wind integration costs

Shorten Power Plant Dispatch Intervals

•

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)

•

Largest opportunities for improvement:•

Better integrating forecasts into power system operations

•

Providing grid operators with useful information

Improve Use of Wind Forecasting

•

Transmission capacity is often physically available when wind output is highest, but contractual and operating rules prevent use of this capacity

•

Conditional firm allows available transmission capacity to be used by others outside of a few peak hours

•

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

•

THE driver of bringing wind manufacturing to the US.•

Drives deployment from 2010-2015 when cap and trade will not.

•

Perfect (cap and trade or tax) is the friend of many supporters of the status quo.

•

All 5 EIA studies show electricity rate reductions (through reduction of gas demand).

•

Fuel diversity has always been the subject of public policy, this is nothing new.

•

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.