Milligan Faq Missouri Aug 2009 Converted

8/9/2019 Milligan Faq Missouri Aug 2009 Converted

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NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC

Michael MilliganNational Renewable Energy Laboratory

Golden, Colorado USA

10 FAQs(Frequently Asked Questions)

About Wind Energy Integration

and Answers

State of the Electric

Industry

Missouri Public Service

Commission

August 24, 2009


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National Renewable Ener Laborator Innovation for Our Ener Future

10 FAQs about Wind

1) How much wind is currently installedin the US?

2) What are the benefits of wind energyto the power system?

3) How can winds variability beincorporated into power systemoperations

4) Does wind plant output start/stopsuddenly?

5) Can wind be predicted?


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10 FAQs about Wind

6) Can the power system be reliablyoperated with wind energy?

7) Does wind need backup or storage?

8) Is there a limit to how much wind canbe accommodated on the grid?

9) Can wind power plants be controlled?

10)Can wind energy make effective useof transmission lines?

11)Bonus Question: How can more windbe accommodated on the grid?


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Where do the Answers Come From?

Extensive analysis

Power system simulations that mimic real-timeoperations

Statistical analysis of wind and load data Experience operating power systems with wind

International Energy Agency Task 25 Report:Design and operation of power systems with largeamounts of wind power State of the art report. http://www.vtt.fi/inf/pdf/workingpapers/2007/W82.pdf

Utility Wind Integration Group www.uwig.org

NREL Systems Integration http://www.nrel.gov/wind/systemsintegration/ http://www.nrel.gov/publications
http://www.vtt.fi/inf/pdf/workingpapers/2007/W82.pdfhttp://www.uwig.org/http://www.nrel.gov/wind/systemsintegration/http://www.nrel.gov/publicationshttp://www.nrel.gov/publicationshttp://www.nrel.gov/wind/systemsintegration/http://www.uwig.org/http://www.vtt.fi/inf/pdf/workingpapers/2007/W82.pdf


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1) How much wind is currently installed in the US?


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1) How much wind is currently installed in the US?

Colorado/Xcel:

Approx 20% windpenetration (wind

capacity/system peak)

Iowa: Approx 18%

wind penetration(wind energy/annual

demand, est. 2009)


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MW Installed End 2006 Installed 2007 End 2007

Total EU-12 419 263 675

Total EU-15 47,651 8,291 55,860

Total EU-27 48,069 8,554 56,535

1b) How much wind is currently installed in Europe?


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Wind energy displaces Fuel Emissions; carbon

Wind provides a hedgeagainst rising fuel prices

(natural gas, coal) Wind is an energy source

with limited capacitycontribution other

generation is also required Wind can be cost-competitive with otherforms of generation andmay reduce electricity cost

2) What are the benefits of wind energy to the

power system?

)


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3) How can winds variability be

incorporated into power system operations?

(Approximately 8 hours)National Renewable Energy Laboratory Innovation fo r Our Energy Future

1.6

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OutputNormalizedtoMe

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15 Turbines Stdev = 1.21, Stdev/Mean = .184

200 Turbines Stdev = 14.89, Stdev/Mean = .126215 Turbines Stdev = 15.63, Stdev/Mean = .125

3) H i d i bilit b i t d i t


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Electric load (without wind) varies considerably

Power system operating practices are built aroundmeeting the variable load with dispatchable generatorsthat can change their output level

Wind adds more variability to the system Existing operating practice can be used/expanded

upon with wind

3) How can winds variability be incorporated into

power system operations?

3) H i d i bilit b i t d i t


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Minnesota 25% wind energy penetration (by energy)causes an increase in variability that must be met bypower system operators and the non-wind generation fleet

5-minute variability does not increase as much as

variability over 10s of minutes to a few hours

14x103

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Load(MW)

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5-Minute Periods for Approximately 9 Months

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5-minutechanges

6,600 Hours of 5-minute Electric Load and Wind

L

3) How can winds variability be incorporated into

power system operations?


12/35National Renewable Ener Laborator Innovation for Our Ener Future

Comparison of Cost-Based Integration Studies

* 3-year average; total is non-market cost

** highest integration cost of 3 years; 30.7% capacity penetration corresponding to 25% energy penetration;

24.7% capacity penetration at 20% energy penetration

*** found $4.37/MWh reduction in UC cost when wind forecasting is used in UC decision



Large wind farmshave many individualwind turbines

The turbines arespread over many

miles and do notexperience the samewind at the sametime

TX event Feb 24,2007: drop of 1,500MW over 2 hours issimilar to behavior ofload

Total WIND

0

500

1000

1500

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2500

2/24/07 9:00 2/24/07 9:28 2/24/07 9:57 2/24/07 10:26 2/24/07 10:55 2/24/07 11:24 2/24/07 11:52 2/24/07 12:21 2/24/07 12:50

Total WIND

2 Hours

www.osei.noaa.gov

4) Can wind power start and stop suddenly?



5) Can wind be predicted?

Wind forecastsare derivedfrom weatherprediction

models Wind forecast

accuracy isimproving

Several windforecastingfirms in U.S.

Courtesy: WindLogics, Inc. St. Paul, MN



Forecasts must be tuned to the needs of the system

operator and integrated in control room Forecasts of potentially large ramp events?

High-wind warning systems?

Aggregate wind forecast error is reduced with large

geographic aggregation Geographic dispersion can reduce forecast errors by

30-50% (WindLogics, UWIG Forecasting Workshop, Feb 2008)

Mean Absolute Error (Percent)

Next day hourly wind power forecast 10-14% of rated capacity

Next day total energy forecast 20% of energy delivered

Next 2-3 hour power schedule 5-7% of rated capacity

Are wind forecasts being used?



UWIG/WindLogics RDF Xcel/CO

http://www.ercot.com/meetings/ros/keydocs/2008/0313/07._ERCOT_OPERATIONS_REPORT_EECP022608_pub

Wind Forecasts in the Control Room

6) C th t b li bl t d ith
http://www.ercot.com/meetings/ros/keydocs/2008/0313/07._ERCOT_OPERATIONS_REPORT_EECP022608_public.dochttp://www.ercot.com/meetings/ros/keydocs/2008/0313/07._ERCOT_OPERATIONS_REPORT_EECP022608_public.doc



Yes additional flexible generation (operating reserves)

may be necessary at higher wind penetrations This additional operating reserve has a modest cost,

typically about 10% of the cost of the wind energy itself

Graph shows this level of operating reserve (blue) is a

relatively small, varying fraction of wind generation Split between spinning and non-spinning reserves

EnerNex: Minnesota 20% Wind study

6) Can the power system be reliably operated with

wind energy?



Increased operating reserves may benecessary, but not dedicated backup

Although new storage has value, it maynot be cost effective

There is typically already storage on thesystem Natural gas in the pipeline or storage

facility

Controllable hydro A recent study by Xcel Energy in

Colorado found existing pumped storage provided

$1.30/MWh offset to wind integrationcost

Enlarging existing gas storage facilitywas economic at large wind penetration

Wind Penetration 10% 15%

$/ MWH Gas Impact No Storage Benefits $2.17 $2.52

$ / MWH Gas Impact With Storage Benefits $1.26 $1.45

EnerNex: Xcel ColoradoWind Integration Study

7) Does wind need backup or storage?

8) Is there a limit to how much wind can be



Current studies in theU.S. have analyzed upto 25% of all electricenergy from wind

Based on work done sofar, the question is notwhetherwind can beaccommodated at high

penetrations, thequestion is howand atwhat cost of integration


accommodated on the grid?





accommodated on the grid?

Recent International Energy Agency Report:

Design and operation of power systems withlarge amounts of wind power

http://www.uwig.org/IEA_Annex25-State_of_the_Art_Report.pdf

International Energy Agency Report: Wind Integration Studies

010

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Lennart Sder,KTH, Sweden, presented at UWIG,Oct 23-25, 2006

Denmark has access to large export markets



9) Can wind power plants be controlled?

New low-voltage ride-through (LVRT) grid codes in the U.S. willhelp wind turbines contribute to grid reliability

Wind turbines can be controlled but not to the extent thatconventional generation can be controlled Ramp rate limits Up-regulation (operate below potential so that wind output can be

increased if needed) [Kirby and Milligan, forthcoming] Curtailment, if necessary and economic, at low-load/high-wind

conditions

10) Can wind energy make effective use of



10) Can wind energy make effective use of

transmission lines?

Conditional-firmtransmission tariff (recentFERC ruling)

Wind does not need

transmission all of thetime

Most transmission pathshave some open capacity

most of the time Adding wind can result in

more efficient usage ofexisting transmission

11) Bonus: How can more wind be accommodated




on the grid?

-1000

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Ramp(MW/hr)

53045298529252865280

Hour of Year (one day)

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0200

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ExcessRampingandRampPenalty(MW

/hr)

Operating separate balancing areas causesextra ramping compared to combined operations.Blue: up-rampGreen: down-rampYellow: combined ramp

Ramping that could be eliminated by combining operations

Some areas are ramping up nearly 1000 MW/hrwhile other areas are ramping down nearly 500 MW/hr

Utility balancing areas

can combine orcooperate largeelectricity markets

Example: Ramping, orchanging output of

generators that can beeliminated with largerbalancing areas

Milligan & Kirby 2007, Impact of Balancing AreasSize, Obligation Sharing, and Ramping Capabilityon Wind Integration .http://www.nrel.gov/docs/fy07osti/41809.pdf

http://www.nrel.gov/docs/fy07osti/41809.pdfhttp://www.nrel.gov/docs/fy07osti/41809.pdf




on the grid?

Power system operations

practices and wind farmcontrol/curtailment

Integration of windforecasting and real timemeasurements into controlroom operations ongoingwork at ERCOT, AESO

Coordination between BAs Bi-lateral agreement

Fast scheduling Pseudo-tie or dynamic

schedule

Virtual BA (ACE DiversityInterchange, Joint Initiative)

Responsive load

Hydro dispatch, pumpedhydro

Longer term: other storageand markets (plug-hybridelectric vehicles, hydrogen)



Large-Scale Studies in Process

Western Wind & Solar Integration Study 30% wind + % solar in footprint, 20% in WECC

Eastern Wind Integration and Transmission Study,20-30% in study footprint

LEGEND

WestConnect LinesCalifornia Lines

LADWP LinesDC Lines

Control areas:

APS

El Paso

Nevada Power

PNM

Sierra Pacific

SRP

Tristate

Tucson

Xcel

WAPA



IEEE Transactions on PowerSystems (2007)IEEE Power Engineering SocietyMagazine, November/December2005Updated in 2007 and upcoming

Nov-Dec issue in 2009Wind Power CoordinatingCommittee Wind Super-Session,Summer 2008Utility Wind Integration Group(UWIG): Operating Impacts and

Integration Studies User Group www.uwig.org

Increasing Attention in North America
http://www.uwig.org/http://www.uwig.org/


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Discussion (if time/interest)

Impact of 25% Wind Energy Penetration:



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-10005-minutechanges

6,600 Hours of 5-minute Electric Load

Ramp requirements increase with 25% wind energypenetration. The upper panel also shows theimportance of being able to achieve lower minimumloads by the conventional generation fleet.

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Impact of 25% Wind Energy Penetration:

5-minute data

T d i i d



Lower Turn-down is required

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Load OnlyLoad and Wind


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3200

3000

2800

2600

2400

4:00 AM 6:00 AM 8:00 AM 10:00 AM 12:00 PM 2:00 PM 4:00 PM 6:00 PM

Base Load - $10/MWh

Peaking -$90/MWh

Energy Price $10/MWhEnergy Price $10/MWh

Energy Price Increasesto $90/MWh becausebase unit can't rampfast enough

Can the non-wind fleet ramp quickly enough?

B tt f i ti fl ibilit


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Better use of existing flexibility

Tap into maneuverable

generation that may bebehind the wall1

Provide a mechanism(market, contract, other)that benefits systemoperator and generator

Fast energy markets helpprovide needed flexibility2

and can often supply load

following flexibility at nocost31Kirby & Milligan, 2005 Methodology for Examining Control Area Ramping Capabilities with Implications for Windhttp://www.nrel.gov/docs/fy05osti/38153.pdf2Kirby & Milligan, 2008 Facilitating Wind Development: The Importance of Electric Industry Structure.http://www.nrel.gov/docs/fy08osti/43251.pdf3Milligan & Kirby 2007, Impact of Balancing Areas Size, Obligation Sharing, and Ramping Capability on Wind Integration .http://www.nrel.gov/docs/fy07osti/41809.pdf

0%

1000%

2000%

3000%

4000%

5000%

0 2000 4000 6000 8000

Hours/Year

PJM

CA ISO

CA ISO PJM WAPA

42,400 55,600 3,087 MW Peak Load Generation21,900 47,000 2,911 Fossil (measured)13,100 2,500 700 Hydro4,600 13,500 0 Nuclear3,700 600 11 Other

2002 Hourly Data and Generation Capacity

WAPA

A i dditi l fl ibilit BA
http://www.nrel.gov/docs/fy05osti/38153.pdfhttp://www.nrel.gov/docs/fy08osti/43251.pdfhttp://www.nrel.gov/docs/fy07osti/41809.pdfhttp://www.nrel.gov/docs/fy07osti/41809.pdfhttp://www.nrel.gov/docs/fy08osti/43251.pdfhttp://www.nrel.gov/docs/fy05osti/38153.pdf


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Reduce the need for ramping by combined BAs (real or virtual) Ramping capabilityadds linearly

Ramping needadds less than linearly

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1000

Ramp(M

W/hr)

53045298529252865280

Hour of Year (one day)

-400

-200

0

200

400

ExcessRamping(MW/hr)

Operating separate balancing areas causesextra ramping compared to combined operations.Blue: up-rampGreen: down-rampYellow: combined ramp

Ramping that could be eliminated by combining operations

Some areas are ramping up nearly 1000 MW/hrwhile other areas are ramping down nearly 500 MW/hr

Milligan & Kirby 2007, Impact of Balancing Areas Size, Obligation Sharing, and Ramping

Capability on Wind Integration . http://www.nrel.gov/docs/fy07osti/41809.pdf

Acquire additional flexibility across BAs
http://www.nrel.gov/docs/fy07osti/41809.pdfhttp://www.nrel.gov/docs/fy07osti/41809.pdf


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BA Consolidation Reduces Ramp Requirements

-400

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ExcessRamp(MW/hr)

80006000400020000

Hour of Year

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Combined ramp requirements, Load+Wind

Excess ramping required by separate operations

Excess ramp durationHourly data

ns

Large infrequent 5


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-600

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ExcessRampComparison:Separatevs.

CombinedOperation

1086420

5-Minute Periods

Load and WindLoad Only

This graph shows the difference in excess rampingrequirements between wind and no-wind cases.

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ExcessRampComparison:Separate

vs.CombinedOperations

100080060040020 00

5-Minute Periods

Load and WindLoad Only

Milligan & Kirby 2008, An Analysis of Sub-Hourly Ramping Impacts

of Wind Energy and Balancing Area Size

Large, infrequent 5-

Minute Ramps can be

significantly reduced

Milligan Faq Missouri Aug 2009 Converted

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