wind energy - status and current issues · plus network losses + _ wind energy:- current status...

Lecture for the Engineers Australia, Southern Highlands Group23 March 2006Hugh OuthredCentre for Energy and Environmental MarketsThe University of New South Wales

Wind Energy - status and current issues

2Wind energy:- current status & issues March 2006

Outline� Why the interest in wind energy?� Trends in wind farm installations� Wind energy as intermittent generation� Planning issues� Network-related issues � Power variability issues

– Forecasting; spot & derivative markets

� Commercial viability of wind farms in the NEM


CO2 concentration in the atmosphere(Climate Action Group, 2004)


(Nature, 26/1/06)


Expected climate change impacts on Australia (Senate Environment Committee, 2000)

� Australia probably “very negatively affected”:– Large size, long coastline, soil salinity, exposure

to cyclones & El Nino/La Nina cycle, economic dependence on agriculture & tourism

� Likely changes in next 50 years:– Higher temperatures, more frequent extreme

weather events, reduced available water resources, reduced area of arable land, reduced crop & livestock yield & quality, severe damage to coral reefs


Australian electricity industry emissions scenarios to 2030 (Beyond Kyoto, PMSEIC Report, 2002)

Implications of these scenarios:• Essential to improve end-use efficiency• Avoid new coal power stations unless “zero emission”• CCGT only a transition technology unless “zero emission”

“Zero emissions” coal: carbon capture & storage (CCS)won’t be available for widespread use before 2020


Comparing generation options(CO2 Coefficients & Costs: Securing Australia’s Energy Future (most); Energy payback: Wind:www.windpower.dk; PV: www.eere.energy.gov)

<1

<1

<1

2-5

<1(n/a)

<1(n/a)

Egy Payback (yr)

3-11

9-21

6-29

100-280

450-660(80-150)

700-1100 (150-200)

CO2 g/kWh

30-70Hydro

n/a (Aust.)Nuclear

50-80Wind

250-400Solar

35-45(n/a)

Gas CC (CCS)

30-40(n/a)

Coal SC (CCS)

Cost in 2010 ($/MWh)

Type


(World Wind Assoc, 2006)

Global installed wind capacity (MW)


Wind energy characteristics

� Renewable energy fluxes are time-varying:– Solar, wind, hydro (tidal), biomass, geothermal, wave

� Wind & solar are non-storable:– Can be described as intermittent energy resources

� Electricity generation based on wind & solar energy is described as intermittent generation– Electric power systems don’t store electrical energy,

hence intermittency reduces value of wind energy– Prediction can reduce the loss of value


Intermittent generation (NER)� National Electricity Code (NER) definition of

intermittent generation:– “A generating unit whose output is not readily

predictable, including, without limitation, solar generators, wave turbine generators, wind turbine generators and hydro generators without any material storage capability”

� Issues identified by NEMMCO:– Forecasting; Frequency Control Ancillary Services

(FCAS); voltage control; management of network flows


Wind power density

Doubling the wind speed increases the power eight times but doubling the turbine area only doubles the power.

(European Commission, 2005)


Power curve for a Bonus 1.3MW wind turbine(typically 30 minute average data)

Controllableconversion efficiency

Cut-out wind speed

Cut-in wind speed


A modern 2MW wind turbine• Vestas V80 (eg. Canunda, SA)• Rotor Diameter: 80 m• Speed revolution: 16.7 rpm

• Operational: 9 - 19 rpm• Number of blades: 3• Tower Hub height: 60 - 67 - 78 - 100 m

• Operational data • Cut-in wind speed: 4 m/s• Nominal wind speed: 15 m/s• Stop wind speed: 25 m/s

• Generator Type: Asynchronous• Gearbox Type: Planet/parallel axles

• Control Type: Microprocessor; optional remote.Output regulation and optimisation via OptiSpeedT and OptiTip® pitch regulation.


Wind turbine design option: gearbox & induction generator

SwitchInduction

generator stator

Supply frequency AC

Variable speed induction generator (eg Codrington)

IG with wound rotor

Slip frequencyinverter

pf correctioncapacitor

(www.hydro.com.au)


Wind turbine design option: direct-drive variable speed alternator

Inverter SwitchRectifierAlternator

variablefrequency AC

supplyfrequency AC

DC

Variable speed alternator & inverter (eg Albany)

Load bank

(www.enercon.de)


Wind turbine type comparison(Slootweg & Kling, 2003, http://local.iee.org/ireland/Senior/Wind%20Event.htm)


Wind turbine starting transients for Esperance 2 MW wind farm 9 x 225 kW turbines with squirrel cage IGMagnetisation inrush current may cause a voltage dip - starts should be spaced out

(Rosser, 1995)

19Wind energy:- current status & issues March 2006(European Commission, 2005)


Size of wind turbines used by Western Power (www.wpc.com.au)


Australian wind resource(Estimate of background wind (m/s) – AGO)


SEDA NSW Wind atlas(www.seda.nsw.gov.au)


Comparing AusWEA forecast (www.auswea.com.au) & readily acceptable (RA) wind capacity for Australia(Outhred, 2004)

8900500500500220031002100RA MW

193010028012003008013Total MW

132067220800207620App MW

6102967400921713Inst MW

AusWATasSAVicNSWQld


Australian wind farm planning

� AusWEA best practice guidelines:– www.auswea.com.au

� State handbooks & planning protocols:– NSW (SEDA); Victoria (SEAV):� Project-based, some variations between states

� Stages in the process (AusWEA):– Site selection; feasibility; detailed assessment,

development application; construction; operation; decommissioning


Australian wind farm planning experience to date� Limited experience to date:

– Some strong support, some strong opposition

� Mixed federal, state & local government approvals process lacks coherence:– Project based - may not manage cumulative issues &

interactions well

� Other industries have a comprehensive planning framework, eg:– Strong, state-based planning framework for the

minerals industry


Network issues for wind farms #1

� Networks are shared, centrally planned resources:– Must limit network disturbances caused by wind farms– Wind farms must survive disturbances from the network

� Renewable resources are often distributed differently from fossil fuel resources:– Weak network conditions likely to be more common in

Australia & New Zealand than Europe or North America

� Network must be built to carry peak flows:– Want good estimates of aggregation & seasonal effects

� Benefits of staged development of wind resources:– Network savings; reduced voltage & frequency impacts


Network issues for wind farms #2� Wind turbine starting & stopping transients:

– Severity can be alleviated by soft-start & high wind-speed power-management

� Some wind turbine designs:– May cause voltage distortions:� Harmonics &/or transients

– May have poor power factor, eg:� Uncompensated induction generator

– May not ride-through system disturbances� Temporary voltage or frequency excursions


Network connection issues & examples� Approximate ability of a transmission line to

accept a wind farm:– 66kV ≤ 20MVA– 132kV ≤ 100MVA– 330kV ≤ 200MVA– Constraints may be determined by several factors:� Thermal, voltage, fault clearance, quality of supply� Thermal ratings depend on line temperature & wind speed

� Relevant wind farm rating is its maximum output, not the sum of turbine rated powers:– Coincident output of the connected wind turbines


Connection costs to 330kV(Transgrid, 2002)

15028.32004

18017.71002

65012.9201

2,50012.751

Conn.cost$/kW

Conn. cost $MTotal wind MW

Wind farm number

Important to capture economies of scale of grid connection


Wind resource & network issues in South Australia

Map: ESIPC, 2002

Good wind resources along entire coastline including:

• Eyre Peninsula• Yorke Peninsula• Fleurieu Peninsula• Kangaroo Island• South-East

Sites available for up to 2000MW


SA regions with existing Tx infrastructure

� Opportunities to interconnect large wind farms but potential impacts on existing generation and interconnection capability


SA regions with very limited Tx infrastructure


Eyre Peninsula Backbone network upgrade to support 500MW wind

(Meritec, 2002)

Estimated cost of 275kV backbone upgrade: $140M or $280/MW assuming equally shared by 500MW of wind.

Wind may not have to pay full cost of backbone upgrade.


NEMMCO concerns about wind energy (NEMMCO, 2003)

� Frequency control in normal operation:– Frequency regulating service costs ~5 $/MWH

� Security control - largest single contingency– Will wind farms ride-through disturbances?

� Interconnection flow fluctuations:– Exceeding flow limit may cause high spot price

� Forecast errors due to wind resource uncertainty:– Five minute dispatch forecast (spot price)– Pre-dispatch & longer term (PASA & SOO) forecasts


Western Power’s proposed wind penalty charge (c/kWh) (Western Power, 2002)


Managing supply-demand balance in the electricity industry

� Frequency is a measure of supply-demand balance:– always varying due to fluctuations in the power flows

associated with particular devices– Wind energy is only one of many fluctuating power flows

Thermalpower stations

Wind farms

Hydrogenerators

Industrial

Commercial

Residential

Generator input power Load electrical powerplus network losses

+ _


Simulated dispatch with 500MW wind in SA(Oakeshott, 2005)

0

500

1,000

1,500

2,000

2,500

3,000

19/1

2/20

02 1

9:30

20/1

2/20

02 0

1:30

20/1

2/20

02 0

7:30

20/1

2/20

02 1

3:30

20/1

2/20

02 1

9:30

21/1

2/20

02 0

1:30

21/1

2/20

02 0

7:30

21/1

2/20

02 1

3:30

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2/20

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9:30

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2/20

02 0

1:30

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2/20

02 0

7:30

22/1

2/20

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3:30

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2/20

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9:30

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2/20

02 0

1:30

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2/20

02 0

7:30

23/1

2/20

02 1

3:30

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2/20

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9:30

24/1

2/20

02 0

1:30

24/1

2/20

02 0

7:30

24/1

2/20

02 1

3:30

24/1

2/20

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9:30

25/1

2/20

02 0

1:30

25/1

2/20

02 0

7:30

25/1

2/20

02 1

3:30

25/1

2/20

02 1

9:30

26/1

2/20

02 0

1:30

26/1

2/20

02 0

7:30

26/1

2/20

02 1

3:30

26/1

2/20

02 1

9:30

27/1

2/20

02 0

1:30

27/1

2/20

02 0

7:30

27/1

2/20

02 1

3:30

27/1

2/20

02 1

9:30

28/1

2/20

02 0

1:30

28/1

2/20

02 0

7:30

28/1

2/20

02 1

3:30

28/1

2/20

02 1

9:30

29/1

2/20

02 0

1:30

29/1

2/20

02 0

7:30

29/1

2/20

02 1

3:30

29/1

2/20

02 1

9:30

Ladbroke OSB-AG Northern PLAYB-AG PPCCGT Torrens B Torrens A Quarantine Total Wind Load Total Wind


1000 MW wind, SA: 1% likelihood variation (ESIPC, 2005)

1 per day

1 per week

1 per month


Spectral analysis of Danish long-term wind data (17 years of data)

Spectral gap between weatherand local turbulence phenomena

(Sorensen, 2001, Fig 2.110, p194)


Forecasting the output of wind farms� 30 minute horizon (FCAS & spot market):

– Turbulence spectrum - likely to be uncorrelated for turbines spaced > 20 km:� Then % power fluctuations ~ N-0.5

– eg for 100 identical wind farms spaced >20 km apart, %fluctuation in total power ~ 0.1x%fluctuation for 1 farm

� 30 minutes to ~3 hours:– ARMA model best predictor of future output

� > 3 hours - NWP model best predictor:– Key issue: predicting large changes in output of

appropriate groups of wind farms


2-hour prediction for Lake Benton wind farm, USA138 turbines, 103.5MW, hourly data (Hirst, 2001)

Two-hour ahead prediction of wind power:MWPred(T+2) = 2.7 +0.9xMW(T) + [MW(T) - MW(T-1)]

potentiallycurtailable

spike

“contingency”


Combined output of 2 wind farms 80 km apart (Gardner et al, 2003)


Cross-correlation function between the output powers of 2 wind farms 80 km apart (Gardner et al, 2003)


Cross-correlations between measured power outputs of German wind farms

(Giebel (2000) Riso National Lab, Denmark)


Wind power scenario forecasting(Jende, 2005)

Actual: ----

Aust Govt is spending $15m ona wind power forecasting system to facilitate high levels of wind power penetration


CSIRO WindscapeTM model (www.clw.csiro.au/products/windenergy)

Windscape derives location-specific wind forecasts from a Numerical Weather Prediction model

(Steggle et al, CSIRO, March 2002)


• Windscape predictions of annual mean wind speed at 65 m, showing nested model results

• More rapid changes in colour probably imply higher local turbulence

(Steggle et al, CSIRO, March 2002)


Hampton Wind Farm, NSW (2x660 kW Vestas, connected to different 11 kV feeders)

3 Second data being collected

Turbulence probably fairly high at this site

Induction generatorsmay not ride throughvoltage dips well.


S1: Infra-red satellite map (BoM Aust,1125 UTC 24/4/05)


S1: Gradient level (~1km) wind map,produced twice daily (BoM Aust, 12 UTC 24/4/05)

7.5 m/s

7.5 m/s


Issues for NEM spot market� Wind farms will operate as “price takers”:

– Generate whenever wind is blowing

� NEM spot market prices are volatile with a “rectangular” price distribution:– Prices are usually low, sometimes high– Timing of high prices not easily predicted

� Value of wind energy in the spot market:– Will depend on how regularly wind farms are

producing when spot prices are high


Price-demand plots for NEMregionsNSW (top) & SA (bottom)Jan-Mar 2004

($/MWH vs MW)(NECA, 04Q1 Stats, 2004)


Smoothed NEM Regional Ref Prices (RRPs) since market inception (NECA, 04Q4 Stats, 2005)


Annual average RRP flat contract prices (NECA, 04Q4 Stats, 2005)


Forward prices for wind energy

� Wind farms may have to accept a lower price than “flat contract” due to uncertainty in production: – Daily– Seasonal, – Annual

(Giebel (2000) Riso National Lab, Denmark)


Renewable Energy Certificate Prices (A$/MWH) (Offer, 2003)

20

25

30

35

40

45

50

55

60

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020


Wind farms marginal at $70/MWH(PWC, 2002)


Conclusions� Intermittent generation:

– Brings new challenges for electricity industry restructuring (technical, market design, regulation)

� Wind energy:– The first significant form of “intermittent generation”– Network connection issues:� often distributed differently to traditional resources

– Planning issues - visual & bird impacts:� Regional, rather than project specific

– Forecasting & system security issues– Usually not cost-competitive on electricity price alone

wind energy - status and current issues · plus network losses + _ wind energy:- current status...

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