meOmZ.

>U<_m0m< 

Egajmg 0232 83 

 

SOUTH AUSTRALIAN WIND STUDY REPORT

IMPORTANT NOTICE
Purpose
The purpose of this publication is to provide information about wind generation in South Australia.
AEMO publishes this South Australian Electricity Wind Study Report in accordance with its additional
advisory functions under section 50B of the National Electricity Law. This publication is based on
information available to AEMO as at 26 October 2015.

Disclaimer
AEMO has made every effort to ensure the quality of the information in this publication but cannot
guarantee that information, forecasts and assumptions are accurate, complete or appropriate for your
circumstances. This publication does not include all of the information that an investor, participant or
potential participant in the National Electricity Market might require, and does not amount to a
recommendation of any investment.
Anyone proposing to use the information in this publication (including information and reports provided
by third parties) should independently verify and check its accuracy, completeness and suitability for
that purpose, and obtain independent and specific advice from appropriate experts.
Accordingly, to the maximum extent permitted by law, AEMO and its officers, employees and
consultants involved in the preparation of this publication:
 make no representation or warranty, express or implied, as to the currency, accuracy, reliability
or completeness of the information in this publication; and
 are not liable (whether by reason of negligence or otherwise) for any statements, opinions,
information or other matters contained in or derived from this publication, or any omissions from it,
or in respect of a person’s use of the information in this publication.

© The material in this publication may be used in accordance with the copyright permissions on AEMO’s website.
Australian Energy Market Operator Ltd
NEW SOUTH WALES

ABN 94 072 010 327

QUEENSLAND

SOUTH AUSTRALIA

www.aemo.com.au
VICTORIA

info@aemo.com.au

AUSTRALIAN CAPITAL TERRITORY

TASMANIA

 SOUTH AUSTRALIAN WIND STUDY REPORT

EXECUTIVE SUMMARY
South Australian electricity supply and demand is evolving, with:
 Withdrawal of coal and gas-fired generation.
 Increases in wind generation.
 Increasing rooftop photovoltaics (PV), contributing to declining operational electricity consumption
and minimum demand levels.
Alinta Energy’s recent announcement to withdraw the Northern and Playford coal-fired power stations
by 31 March 2016, means that South Australia will rely heavily on interconnection with Victoria for
reliable and secure power supply in future.
When levels of instantaneous wind penetration are high, frequency control and network support
services need to be sourced from Victoria to maintain power system security. And at times of high
operational demand in South Australia, reliable supply depends on the contribution from wind
generation and imports. Therefore, understanding the performance of wind generation in South
Australia is key to managing operational risks in maintaining system security and reliability.
This report focuses on the performance of wind generation in South Australia over the last five financial
years. Key insights include:
 Instantaneous wind penetration (ratio of wind energy to demand), continues to increase over time.
Wind generation exceeded demand from the grid for around 30 hours in 2014–15, with surplus
wind generation available for export to Victoria. In 2013–14, 100% of demand was met by wind
generation for the first time, and for less than one hour.
 In 2014–15, maximum instantaneous wind penetration occurred in the middle of the day, when
rooftop PV generation was high and operational demand was low. In contrast, in 2013–14
maximum instantaneous wind penetration occurred at around 4.30 am.1
 South Australia has 1,473 MW of registered wind capacity, more than any other region in the
National Electricity Market (NEM). At least 9.9% of installed wind capacity has been available
during summer peak demand periods (85% of the time in the past five years).
 The geographic diversity of wind across the state helps to reduce the aggregate variability of wind.
As more wind farms come online, however, the residual demand (demand less wind generation)
changes in South Australia are becoming more variable.
 The volume-weighted average spot price for wind generation continues to be lower than the
volume-weighted average spot price for thermal generation in the state, with negative prices
typically coinciding with high instantaneous wind penetration levels.

Instantaneous wind penetration
The maximum instantaneous wind penetration in 2014–15 reached 110% on 29 December 2014 at
around 1.20 pm. Wind penetration was over 100% on 12 separate days (about 30 hours) between
August and May.
Wind generation is generally slightly higher overnight than during the day. Because of this, average
wind penetration levels are greatest between 3.00 am and 4.00 am, when average demand is lowest. In
contrast to daily averages, both minimum demand for South Australia (driven by rooftop PV generation)
and maximum instantaneous wind penetration, occurred around midday in 2014–15, although on
different days.
Table 1 summarises the change in maximum instantaneous penetration, along with a number of other
internationally-recognised wind generation indices, from 2013–14 to 2014–15.

1

All times reported are National Electricity Market (NEM) Standard Time, which is equivalent to Australian Eastern Standard Time and is not
altered during daylight saving time.

© AEMO 2015

3

 SOUTH AUSTRALIAN WIND STUDY REPORT

Table 1

South Australian wind generation indices

Description

Value for South Australia
2013–14**

2014–15

Capacity penetration: installed capacity as a percentage of total installed generation*

30%

30%

Energy penetration: ratio of annual wind energy to annual total energy consumption

31%

33%

Maximum instantaneous penetration (excluding exports): maximum observed ratio of
wind energy to demand at any instant in time during the year

100%

110%

Maximum possible instantaneous penetration: the ratio of installed capacity to
minimum demand

127%

191%

<1 hour

30 hours

Periods of 100% (or greater) instantaneous wind penetration

* Capacity penetration analysis for these years excludes the mothballed Playford B power station.
** Values for some indices are different to those published in the 2014 SAWSR due to improved time-alignment between non-scheduled and semischeduled wind farm data. For the maximum possible instantaneous penetration, the approach taken in 2015 better reflects the actual wind capacity
at time of minimum demand.

Figure 1 shows 5-minute wind generation, demand from the grid, and instantaneous wind penetration,
for 29 December 2014, when maximum wind penetration occurred. It also shows a trace of estimated
30-minute rooftop PV generation during this period, which highlights that rooftop PV is influencing the
timing of maximum penetration observed, by lowering demand during the middle of the day. 2
South Australian wind generation, demand and wind penetration for 29 December 2014

11:05 PM

10:05 PM

9:05 PM

0%

8:05 PM

300
7:05 PM

10%
6:05 PM

600

5:05 PM

20%

4:05 PM

900

3:05 PM

30%

2:05 PM

1200

1:05 PM

40%

12:05 PM

1500

11:05 AM

50%

10:05 AM

1800

9:05 AM

60%

8:05 AM

2100

7:05 AM

70%

6:05 AM

2400

5:05 AM

80%

4:05 AM

2700

3:05 AM

90%

2:05 AM

3000

1:05 AM

100%

12:05 AM

3300

Wind penetration (%)

110%

0

SA demand, wind farm generation and rooftop PV (MW)

Figure 1

Time of day
Rooftop PV (estimated)

2

Wind Penetration

Wind Generation

Demand

Rooftop PV generation is seen as a reduction in demand, as it is not metered by AEMO.

© AEMO 2015

4

 SOUTH AUSTRALIAN WIND STUDY REPORT

Wind generation and contribution to peak demand
Total installed wind generation capacity remained at 1,473 MW in 2014–15, with no new wind farms
registered in South Australia. Total wind farm generation in South Australia for the year was 4,219
GWh. This was 3% higher than in 2013–14, largely driven by Snowtown Stage 2 Wind Farm’s
availability for the full financial year in 2014–15.
Analysis of the contribution of wind generation to the top 10% of summer peak demand periods in the
past five years shows that more than 9.9% of South Australia’s registered wind capacity was generating
85% of the time. In winter, the 85th percentile wind contribution is 6.8%. These contribution factors are
the highest in the NEM for summer peak demand, and equal highest (alongside Victoria) for winter peak
demand.

Wind generation variation
Due to the intermittent nature of wind, there is potential for sudden variations in generation from wind
farms. Analysis of output in 2014-15 shows that for 90% of the time, South Australian total wind
generation varies by no more than 24 MW (1.6% of registered capacity) across five-minute periods, and
by no more than 38 MW (2.6% of registered capacity) across 10-minute periods. This variability in wind
generation means the residual demand must be met by more responsive non-wind generators, or by
changes in power flow on the Heywood Interconnector. As more wind farms come online, larger
residual demand changes in South Australia are observed more often.
Of the three South Australian geographical areas, the mid-north shows lower variation than the
south-east and coastal peninsula areas. The aggregated South Australian variation is lower than any
single area, reflecting the smoothing effect of multiple generating units in different areas across the
state.

Wind generation and electricity price
In 2014–15, there was a continuing link between times of high wind generation and low spot prices for
the region. Very high spot prices tended to occur when wind generation was low, while low spot prices
occurred when wind generation was high.
Negative spot prices were observed in 154 price intervals in 2014–15, the second highest level in five
years. Negative spot prices typically coincided with high wind energy penetration during the trading
interval.

© AEMO 2015

5

 SOUTH AUSTRALIAN WIND STUDY REPORT

CONTENTS
EXECUTIVE SUMMARY

3

1.
1.1
1.2

INTRODUCTION
Generating systems maps
Recent generation and network developments

9
9
12

2.
2.1
2.2
2.3
2.4
2.5
2.6
2.7

SOUTH AUSTRALIAN WIND GENERATION PERFORMANCE
Summary
Data and methodology
Registered capacity and maximum wind generation
Wind contribution during maximum demand
Total wind generation
Wind penetration
Short-term wind generation and demand variations

14
14
14
14
15
17
21
25

3.
3.1
3.2
3.3
3.4
3.5

WIND GENERATION AND THE NATIONAL ELECTRICITY MARKET
Data and methodology
Wind generation and market prices
Positive spot price trading intervals
Negative spot price trading intervals
Wind forecast performance

30
30
30
33
34
39

APPENDIX A. WIND FARM STATISTICS
A.1 Wind farm capacities
A.2 Wind farm capacity factors
A.3 Wind generation variation

41
41
42
43

MEASURES AND ABBREVIATIONS
Units of measure
Abbreviations

44
44
44

GLOSSARY

45

© AEMO 2015

6

 SOUTH AUSTRALIAN WIND STUDY REPORT

TABLES
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table 8
Table 9
Table 10
Table 11
Table 12
Table 13
Table 14
Table 15

South Australian wind generation indices
South Australian registered capacity by fuel type
Publicly announced generation withdrawals
Registered wind generation capacity and maximum five-minute wind generation
85th percentile wind contribution (% of registered capacity) of top 10% seasonal
peak demand
Expected wind contribution at peak demand (% of registered wind capacity)
Total South Australian wind generation
South Australian wind penetration indices
Total registered capacity and historical maximum variation outputs (MW) by area
Frequency of occurrence of spot prices for South Australia
Volume-weighted average spot prices for wind generation (real Q4 2014–15 dollars)
Registered capacities of South Australian wind farms
Capacity factors of South Australian wind farms
Key statistical characteristics and five- and 10-minute wind generation variation for
2014–15
Key statistical characteristics and five- and 10-minute wind generation variation for
2013–14

4
9
12
15
15
16
18
21
29
31
32
41
42
43
43

FIGURES
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16
Figure 17
Figure 18

© AEMO 2015

South Australian wind generation, demand and wind penetration for 29 December
2014
Location and capacity of South Australian generating systems
Location and capacity of proposed South Australian generation projects
Summer peak demand wind generation duration curve (% of registered wind
capacity)
Winter peak demand wind generation duration curve (% of registered wind capacity)
South Australian total monthly wind energy output and average monthly contribution
South Australian wind generation capacity factors
Annual South Australian wind generation duration curves
Daily demand, wind generation and penetration profile
South Australian wind generation, demand and wind penetration for 29 December
2014
Instantaneous wind penetration duration curves
South Australian wind generation, demand, and residual demand (variation
distribution)
South Australian residual demand (variation distribution)
Five- and 10-minute absolute wind generation variation for 2014–15
Absolute wind variation as percentage of registered capacity
South Australian average wind generation and spot prices (30-minute data for
2010–11 to 2014–15)
South Australian 30-minute spot prices and average wind generation (positive
market prices)
South Australian 30-minute spot prices and average wind generation (negative
market prices)

4
10
11
16
17
18
19
20
22
23
24
25
26
27
28
31
33
34

7

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 19
Figure 20
Figure 21
Figure 22
Figure 23

© AEMO 2015

Negative South Australian spot price and average wind generation by time of day
(2014-15)
Count of negative price trading intervals per year
South Australian spot price duration curves, negative values only
Supply summary at selected times of negative South Australian spot price during
2014–15
Normalised mean absolute error of AWEFS forecasts for South Australia 2014-15

35
36
37
38
40

8

 SOUTH AUSTRALIAN WIND STUDY REPORT

1.

INTRODUCTION

The South Australian Wind Study Report (SAWSR) analyses the state’s historical wind farm
performance, including electricity market pricing insights, over the five years 2010–11 to 2014–15.
 Chapter 1 − Introduction provides an overview of the report, generation sites and an update on
recent relevant developments.
 Chapter 2 − South Australian wind generation performance provides capacity, maximum
instantaneous generation, contribution to demand, total generation and share, penetration, and
short-term generation variation.
 Chapter 3 − Wind generation and the National Electricity Market provides analyses of
historical generation, the relationship between wind generation and price in South Australia, and a
brief discussion on performance of wind forecasting.
 Appendix A − Wind farm statistics provides the name, geographic area, scheduling type, and
registered capacity of the wind farms considered in this report, as well as their capacity factors and
generation variation metrics.
South Australian demand refers to the operational demand met by local scheduled, semi-scheduled
and selected non-scheduled generating systems plus interconnector imports from Victoria, and
excludes demand supplied by rooftop photovoltaic (PV) generation.
Operational demand refers to electricity used at a specific point in time (typically at a 5 or 30 minute
interval, measured in megawatts (MW)), while operational consumption is the electricity used over a
period of time (typically over one year, measured in gigawatt-hours (GWh)). 3
South Australian generating systems included in operational reporting are shown in Figure 2. For this
report, however, demand or consumption analysed is always operational demand or consumption, less
output from Angaston, Port Stanvac 1 and Port Stanvac 2 generating systems.
All time references in this report are to National Electricity Market (NEM) Standard Time.4

1.1

Generating systems maps

Figure 2 shows the location and nameplate capacity of the South Australian scheduled, semi-scheduled
and significant non-scheduled generating systems, and Figure 3 shows the location and capacity of
publicly announced generation projects as at October 2015.5
Table 2 summarises the capacity mix of fuel types for all registered generation in South Australia as at
October 2015.
Table 2

South Australian registered capacity by fuel type

Fuel Type

Registered Capacity (MW)

Wind

1,473

Coal*

770

Gas

2,668

Diesel

270

Other

28

* Coal capacity includes Playford B power station, but the power station has been mothballed since 2012.

3

4
5

Operational reporting includes the electrical energy used by all residential, commercial, and large industrial consumption, and transmission losses
(as supplied by scheduled, semi-scheduled and significant non-scheduled generating units). Significant non-scheduled generating units in South
Australia are Angaston, Port Stanvac 1, Port Stanvac 2 and all non-scheduled wind farms. It does not include the output of small non-scheduled
generating systems, typically less than 30 MW capacity.
NEM Standard Time is equivalent to Australian Eastern Standard Time and is not altered during daylight saving time.
AEMO Generation Information for South Australia. 2015, October 26. Available at: http://www.aemo.com.au/Electricity/Planning/RelatedInformation/Generation-Information. Viewed: 26 October 2015.

© AEMO 2015

9

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 2

© AEMO 2015

Location and capacity of South Australian generating systems

10

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 3

© AEMO 2015

Location and capacity of proposed South Australian generation projects

11

 SOUTH AUSTRALIAN WIND STUDY REPORT

1.2

Recent generation and network developments

The South Australian generation mix is changing. Current and announced withdrawals of synchronous
coal and gas-fired generation within the state is leading to greater reliance on wind generation, rooftop
PV and interconnector imports to meet South Australia’s electricity consumption. This section outlines
the recent generation and network developments in the state.
Since 2014, AEMO and ElectraNet have been undertaking power system security studies to understand
the operational impacts of high levels of renewable generation (from wind farms and rooftop PV) and
low levels of online synchronous generation in South Australia.
The key conclusion to date is that the South Australian power system can operate securely and reliably
with a high percentage of wind and rooftop PV generation as long as the Heywood Interconnector is
operational. Further information can be found in the 2015 South Australian Electricity Report (SAER) 6,
and a new report updating the challenges is due to be published December 2015.

1.2.1

New wind farm generating systems

Operation of the Snowtown Stage 2 Wind Farm (270 MW) commenced in 2013–14, with commissioning
completed in November 2014. The site consists of two separately metered wind farms: Snowtown 2
Stage 2 North (144 MW) and Snowtown 2 Stage 2 South (126 MW). Generation totals in this report
include all output from Snowtown Stage 2 Wind Farm, unless otherwise indicated. For the SAWSR
analysis, South Australia’s wind farm capacity total is considered to have increased by 270 MW in June
2014, when Snowtown Stage 2 Wind Farm generation first reached 90% of registered capacity.
The first 102.4 MW of the Hornsdale wind farm project progressed to committed status on
21 August 2015 and is expected to be operating by November 2016.

1.2.2

Generating system withdrawals

A summary of existing and announced South Australian generation withdrawals is listed in Table 3.
Table 3

Publicly announced generation withdrawals

Station Name

Fuel Type

Capacity Change
(MW)**

Change details

Northern

Coal

-546

Full retirement in March 2016

Playford B

Coal

-240

Full retirement in March 2016*

Torrens Island A

Gas

-480

Out of service from 2017

Pelican Point

Gas

-239

Operating at half capacity

Total

-1,505

* Playford B power station is currently mothballed.
** Capacity reported is nameplate capacity.

6

AEMO. 2015 South Australian Electricity Report (SAER), Section 4.1.1. Available at: http://www.aemo.com.au/Electricity/Planning/SouthAustralian-Advisory-Functions/South-Australian-Electricity-Report. Viewed: 20 October 2015.

© AEMO 2015

12

 SOUTH AUSTRALIAN WIND STUDY REPORT

Northern and Playford B power stations
In 2014−15, Northern Power Station returned to normal service (from October 2014) and Playford B
remained mothballed with a recall time of around 90 days. 7
Alinta Energy has announced that both power stations will cease generation around 31 March 2016.8
These are the last two operational coal-fired power stations in South Australia.

Torrens Island A power station
Torrens Island Power Station A is to be taken out of service indefinitely from winter 2017, subject to
review if market conditions change materially.9

Pelican Point power station
Pelican Point Power Station has been available at half capacity from 1 April 2015, and shows 0 MW
availability in the medium term projected assessment of system adequacy (MT PASA) for winter 2016,
given the current dynamics and outlook in the electricity and gas markets.10

1.2.3

Heywood Interconnector upgrade

Completion of the Heywood Interconnector upgrade is scheduled for July 2016. The project increases
the power transfer capacity of the interconnector from 460 MW to a nominal 650 MW. The staged
delivery of sub-components of the upgrade is expected to deliver portions of the capacity increase
before this date. More information on the Heywood Interconnector upgrade is available on AEMO’s
website.11

7

Alinta Energy advised: Northern Power Station returned back to normal service in October 2014 (following periods of withdrawal from April to
September in 2013 and 2014), and Playford B Power Station will be available with a recall time of around 90 days.
Source: AEMO Generation Information for South Australia. 2015, October 26. Available at: http://www.aemo.com.au/Electricity/Planning/RelatedInformation/Generation-Information. Viewed: 26 October 2015.
8
AEMO Generation Information for South Australia. 2015, October 26. Available at: http://www.aemo.com.au/Electricity/Planning/RelatedInformation/Generation-Information. Viewed: 26 October 2015.
9
Refer to Note 8.
10
Refer to Note 8.
11
AEMO. Heywood Interconnector Update. Available: http://www.aemo.com.au/Electricity/Planning/South-Australian-Advisory-Functions/HeywoodInterconnector-Update. Viewed: 1 October 2015.

© AEMO 2015

13

 SOUTH AUSTRALIAN WIND STUDY REPORT

2.

SOUTH AUSTRALIAN WIND GENERATION
PERFORMANCE

2.1

Summary

This chapter presents an historical analysis of South Australian wind generation performance, including
information highlighting the relationship between wind generation and consumption (as aggregated
across a financial year), and wind generation and maximum demand (as measured at five-minute
intervals). Key observations include:
 Overall, the maximum five-minute generation from South Australian wind farms increased by 2.4%,
from 1,332 MW in 2013–14 to 1,364 MW in 2014–15. This increase was likely due to seasonal
variations in wind.
 Total energy from wind generation increased by 3%, from 4,087 GWh in 2013–14 to 4,219 GWh in
2014–15, largely driven by Snowtown Stage 2 Wind Farm’s availability for the full financial year in
2014–15.
 With reduced consumption and higher wind generation, 2014–15 saw higher or equal wind
penetration indices. Maximum instantaneous penetration reached 110% in 2014–15, with wind
supplying 33% of the state’s consumption from the grid, up from 31% in 2013–14.
 Average wind penetration was highest between 3.00 am and 4.00 am, but maximum instantaneous
penetration and minimum demand occurred in the middle of the day.

2.2

Data and methodology

AEMO used the following methodology with regard to data throughout this chapter:
 Cleared supply values (unless otherwise indicated) for all semi-scheduled wind generation totals,
based on a five-minute dispatch interval. Non-scheduled wind generation is not dispatched so
corresponding five-minute generation output is used instead.
 Wind generation (unless otherwise indicated) during commissioning periods is included.

2.3

Registered capacity and maximum wind generation

South Australia has the highest registered wind generation capacity of any state in Australia. Table 4
shows the total capacity for all South Australian semi-scheduled and non-scheduled wind farms
registered by AEMO, together with the maximum five-minute generation output over the past five
financial years from 2010–11 to 2014–15.
Changes in registered wind farm capacity do not always match changes in maximum five-minute
generation, because small variations in maximum five-minute generation are attributed to seasonal
variations in wind speed across the geographically diverse locations of the state’s wind farms.

© AEMO 2015

14

 SOUTH AUSTRALIAN WIND STUDY REPORT

Table 4

Registered wind generation capacity and maximum five-minute wind generation

Financial year

Registered
capacity (MW)*

Reason for increase in capacity

Maximum five-minute generation
(MW)*

2010–11

1,151

N/A

1,061

2011–12

1,203

Hallett 5 (The Bluff) Wind Farm (52 MW)

1,082

2012–13

1,203

N/A

1,069

2013–14

1,473

Snowtown Stage 2 Wind Farm (270 MW)

1,332

2014–15

1,473

N/A

1,364

* Data is captured from when each wind farm was entered into AEMO systems, and includes the commissioning period. Values for some years are
different to those published in the 2014 SAWSR due to improved time-alignment between non-scheduled and semi-scheduled wind farm data.

2.4

Wind contribution during maximum demand

Wind generation during peak demand depends on both wind speed and the operational limitations of
wind turbines across the state. Wind is intermittent by nature, with periods of low wind (and in some
cases very high wind12) resulting in low generation output.
When these situations arise in South Australia, excess demand must be met by other types of
generation within the state or by imports from Victoria. Currently, non-renewable generation such as
gas, coal, or diesel meets any shortfall. However, with the recent announcement that Northern Power
Station will close by 31 March 2016, at times of high operational demand and low wind output, there will
be greater reliance on imports from Victoria to maintain reliability.
To meet its medium-term projected assessment of system adequacy (MT PASA) reliability obligations,
AEMO forecasts a minimum level of expected wind generation over the next two years, with a 90%
probability of exceedance (POE). This conservatively assesses supply adequacy to cover anticipated
consumption, especially during times of high or peak demand. Wind generation forecasts for MT PASA
are taken from the Australian Wind Energy Forecasting System (AWEFS).
A review of wind generation performance for the top 10% of five-minute demand dispatch intervals, over
a five year period, highlights that the contribution from wind generation is variable between seasons and
across years. Table 5 provides the 85th percentile level of expected wind generation across summer
and winter peak periods over the past five years.13 The wind contribution is generally higher in summer
than in winter.
Table 5

85th percentile wind contribution (% of registered capacity) of top 10% seasonal peak demand

Summer peak period

% of registered capacity

Winter peak period

% of registered capacity

2010–11

9.0%

2010

3.9%

2011–12

9.2%

2011

8.8%

2012–13

9.9%

2012

9.4%

2013–14

9.7%

2013

6.2%

2014–15

11.7%

2014

6.0%

5-year winter average*

6.8%

5-year summer average

9.9%

* Seasonal averages are calculated from non-rounded seasonal data for 2010 to 2014, which explains why the winter average does not exactly
match the average of the rounded winter values for 2010 to 2014 which are shown in this table.

South Australia has the highest expected contribution factor to summer peak demand in the NEM (9.9%
of registered capacity) and equal highest factor alongside Victoria for winter peak demand (6.8% of
registered capacity). Table 6 compares the minimum expected contribution of wind generation to peak
demand across different NEM regions.14

12

13
14

The occurrence of high winds, potentially in combination with high temperatures, can often result in mechanical and thermal design limitations
being reached. In extreme cases this may result in individual units shutting down to prevent physical damage.
Analysis for wind contribution factors excludes wind generation from the period before a new wind farm first reached 90% of registered capacity.
Queensland region is not included in the analysis as there is insufficient historical data compared to other NEM regions.

© AEMO 2015

15

 SOUTH AUSTRALIAN WIND STUDY REPORT

Table 6

Expected wind contribution at peak demand (% of registered wind capacity)

Minimum expected wind
contribution to peak demand*

South Australia

Victoria

Tasmania

New South Wales

5-year summer average

9.9%

7.0%

7.8%

1.2%

5-year winter average

6.8%

6.8%

3.5%

3.4%

* Expressed as a percentage of registered capacity, with peak demand defined as the top 10% of demand periods.

Figures 4 and 5 illustrate the wind generation duration curves over the top 10% summer and winter
demand periods for South Australia, with the 85th percentile point indicated. The duration curves provide
additional insight into wind generation during peak demand periods.
Figures 4 and 5 illustrate that:
 For 10% of summer peak demand periods, wind generation contributes about 49%–61% of its
registered capacity, and for 50% of summer peak demand periods, it contributes about 20%–27%
of its registered capacity.
 For 10% of winter peak demand periods, wind generation contributes about 77%–82% of its
registered capacity, and for 50% of winter peak demand periods, it contributes about 23%–41% of
its registered capacity.
Figure 4

Summer peak demand wind generation duration curve (% of registered wind capacity)

Wind generation (percentage of registered capacity)

100%
90%
80%
70%
60%

50%
40%
30%
20%
10%
0%
0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cumulative percentage of time (top 10% demand periods)
2010-11

© AEMO 2015

2011-12

2012-13

2013-14

2014-15

85th percentile

16

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 5

Winter peak demand wind generation duration curve (% of registered wind capacity)

Wind generation (percentage of registered capacity)

100%
90%
80%
70%
60%

50%
40%
30%
20%
10%
0%
0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cumulative percentage of time (top 10% demand periods)
2010

2.5

2011

2012

2013

2014

85th percentile

Total wind generation

Annual energy from wind generation
Table 7 summarises annual wind generation and its annual change since 2010–11.
Key observations are:
 Annual wind generation in South Australia has increased in line with installed capacity increases
since 2010–11. In 2012–13, when there was no new registered wind capacity and lower wind
resources, a 2% reduction in annual output was observed.
 In 2013–14, Snowtown Stage 2 Wind Farm was brought online, and first reached 90% of its
registered capacity in June 2014. Growth in wind generation in 2014–15 was largely driven by
Snowtown Stage 2 Wind Farm’s availability for the full financial year.

© AEMO 2015

17

 SOUTH AUSTRALIAN WIND STUDY REPORT

Table 7

Total South Australian wind generation

Financial year

Annual South Australian wind generation
(GWh)*

Annual change
in wind
generation

2010–11

3,039

2011–12

3,563

2012–13
2013–14
2014–15

Annual capacity
factor**
38%

17%

34%

3,474

-2%

35%

4,087

18%

36%

4,219

3%

35%

* Wind generation is calculated using 5-minute Supervisory Control and Data Acquisition (SCADA) readings for all wind farms, and differs from the
use of cleared dispatch values used elsewhere for semi-scheduled wind farms.
** Capacity factor is simply the ratio of annual generation in this table to the annual capacity reported in Section 2.3, Table 4.

Monthly wind generation variability
Figure 6 shows the monthly South Australian wind generation in GWh over the last five financial years
from 2010–11 to 2014–15. Also shown is the average monthly contribution to financial year totals.
Monthly totals show significant variation and some underlying seasonal deviations, with average
contribution peaking in late winter and early spring, and some reduction of output in autumn.
Snowtown Stage 2 Wind Farm commenced generation in October 2013 and reached 90% of registered
capacity in June 2014. Waterloo Wind Farm reached 90% of registered capacity in August 2010 and
Hallet 5 (The Bluff) Wind Farm reached 90% of registered capacity in July 2011.

550

11%

500

10%

450

9%

400

8%

350

7%

300

6%

250

5%

200

4%

150

3%

100

2%

50

1%

0
2010-11
2011-12
2012-13
2013-14
2014-15
Avg %

© AEMO 2015

Jul
Aug Sep
Oct
Nov Dec
Jan
Feb Mar
Apr May Jun
177
323
214
251
215
283
227
266
302
235
226
330
335
274
358
267
263
282
390
262
294
221
270
354
276
390
348
289
279
306
283
239
305
222
322
227
366
454
368
381
307
312
356
303
260
263
311
421
521
260
378
344
340
330
399
332
298
325
400
299
8.9% 9.3% 9.0% 8.3% 7.6% 8.3% 8.9% 7.6% 8.1% 6.9% 8.3% 8.9%

Average monthly contribution (%)

South Australian total monthly wind energy output and average monthly contribution

Total wind farm monthly energy output (GWh)

Figure 6

0%

18

 SOUTH AUSTRALIAN WIND STUDY REPORT

Seasonal capacity factors - conclusions
Figure 7 shows the capacity factors for South Australian wind generation, based on the total registered
capacity for each month, over the last five financial years from 2010–11 to 2014–15.
Key observations are:
 Average winter capacity factors are usually higher than average summer ones.
 Capacity factors are usually highest in the winter months and lowest in the autumn months.
 There is variation across the years for any given month or season, which is attributable to seasonal
changes in wind speeds across the state’s wind farm sites.
 Capacity factors for 2014–15 are lower than for 2013–14, and this is also seen when examining
individual wind farm capacity factors (refer to Appendix A.2). Less wind was measured at the wind
farm locations in 2014–15.15
Figure 7

South Australian wind generation capacity factors

55%

South Australian wind capacity factors

50%
45%
40%
35%
30%
25%
20%
15%
10%
5%

Apr-2015

Jan-2015

Oct-2014

Jul-2014

Apr-2014

Jan-2014

Oct-2013

Jul-2013

Apr-2013

Jan-2013

Oct-2012

Jul-2012

Apr-2012

Jan-2012

Oct-2011

Jul-2011

Apr-2011

Jan-2011

Oct-2010

Jul-2010

0%

Year and month
Summer capacity factor (average)

15

Winter capacity factor (average)

Monthly capacity factor

Based on AEMO’s analysis of average wind speed telemetry from wind farm sites across South Australia.

© AEMO 2015

19

 SOUTH AUSTRALIAN WIND STUDY REPORT

Wind generation duration curves
Figure 8 shows the wind generation duration curves for 2010–11 to 2014–15, indicating the percentage
of time wind generation was at or above a given level for each financial year. Calculations are based on
five-minute dispatch intervals and show:
 Increasing wind generation since 2010–11 (except in 2012–13 when no new capacity was
registered).
 Increased wind generation for 2013–14 and 2014–15 following commencement of Snowtown
Stage 2 Wind Farm.
Figure 8

Annual South Australian wind generation duration curves

1,400
1,300

5-minute wind generation (MW)

1,200
1,100
1,000
900
800
700
600
500
400
300
200
100
0
0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cumulative percentage of time
2010-11

© AEMO 2015

2011-12

2012-13

2013-14

2014-15

20

 SOUTH AUSTRALIAN WIND STUDY REPORT

2.6

Wind penetration

Wind penetration indices
Internationally, a number of indices are used to measure wind penetration. Table 8 sets out the
calculations for South Australian wind penetration using four common indices. In line with increases in
installed wind generation capacity, all other indices have tended to increase over time, with 2014–15
values the highest to date. The increasing trends in energy and instantaneous penetration are also
partly attributable to the state’s decreasing operational consumption and increasing rooftop PV
generation.
Table 8

South Australian wind penetration indices

Description

South Australian value
2010–11

2011–12

2012–13

2013–14

2014–15

Capacity penetration: installed capacity as a percentage
of total installed generation*

24%

24%

26%

30%

30%

Energy penetration: ratio of annual wind energy to annual
total energy consumption

21%

25%

25%

31%

33%

Maximum instantaneous penetration (excluding exports):
maximum observed ratio of wind energy to demand at any
instant in time during the year

76%

83%

88%

100%

110%

Maximum possible instantaneous penetration: the ratio of
installed capacity to minimum demand**

107%

115%

116%

127%

191%

* Calculations are based on AEMO registered capacity for all South Australian generating systems for any time during the financial year, but exclude
generating units that are effectively mothballed for at least the last six months of the financial year. Wind farms can also qualify for inclusion when
their output reaches 90% of registered capacity.
** Values for some years are different to those published in the 2014 SAWSR due to improved time-alignment between non-scheduled and semischeduled wind farm data. For the maximum possible instantaneous penetration, the approach taken in 2015 better reflects the actual capacity at
time of minimum demand.

Maximum instantaneous wind penetration reached 100% for the first time in June 2013–14. This was a
significant milestone, where South Australian demand (excluding exports) equalled total wind
generation for a five-minute dispatch interval.
In 2014–15, the maximum instantaneous wind penetration reached 110% on 29 December 2014 at
around 1.20 pm. Wind penetration was over 100% on 12 separate days between August and May, with
instances occurring between about 2.00 am and 4.00 pm. On these occasions, South Australia could
have supplied its local demand entirely from wind generation, with surplus wind generation available to
export to Victoria. Periods of 100% (or greater) instantaneous wind penetration occurred for around 30
hours in 2014–15, compared to less than 1 hour in 2013–14.
When high levels of wind penetration occur, close assessment of network performance is required to
ensure network security and reliability obligations are met. Refer to Section 1.2 for more information on
renewable energy integration studies being undertaken by AEMO and ElectraNet.

Daily demand, wind generation, and penetration profile
Wind generation and demand vary both seasonally and throughout the day. When high wind generation
coincides with low operational demand, instantaneous wind penetration tends to be maximised.
Figure 9 illustrates the average South Australian demand, wind generation, and wind penetration values
throughout the day for 2013–14 and 2014–15. It indicates that:
 The average daily demand profile decreased in 2014–15, especially between 8.00 am and 6.00 pm
(coinciding with periods of increasing rooftop PV generation during the middle of the day).
 While total wind generation increased in 2014–15, it maintained a similar daily profile, peaking
overnight from around 10.00 pm through to 6.00 am the next day.
 Average wind penetration is highest around 3.00 am to 4.00 am, when average demand is lowest.

© AEMO 2015

21

 SOUTH AUSTRALIAN WIND STUDY REPORT

11:00 PM

10:00 PM

9:00 PM

8:00 PM

0

7:00 PM

0%

6:00 PM

200
5:00 PM

5%
4:00 PM

400

3:00 PM

10%

2:00 PM

600

1:00 PM

15%

12:00 PM

800

11:00 AM

20%

10:00 AM

1,000

9:00 AM

25%

8:00 AM

1,200

7:00 AM

30%

6:00 AM

1,400

5:00 AM

35%

4:00 AM

1,600

3:00 AM

40%

2:00 AM

1,800

1:00 AM

45%

SA demand and wind farm generation (MW)

Daily demand, wind generation and penetration profile

12:00 AM

Wind penetration (%)

Figure 9

Time of day

© AEMO 2015

2013-14 Wind Penetration

2014-15 Wind Penetration

2013-14 Wind Generation

2014-15 Wind Generation

2013-14 Demand

2014-15 Demand

22

 SOUTH AUSTRALIAN WIND STUDY REPORT

While average wind penetration is highest at 3:00 am – 4:00 am, the maximum penetration occurred in
the middle of the day. Figure 10 shows the South Australian demand, wind generation and wind
penetration for 29 December 2014 (the day when maximum instantaneous wind penetration occurred).
Also shown in this figure is an estimation of South Australian rooftop PV generation output at half hourly
intervals16, which indicates a correlation between low demand periods and high rooftop PV generation
in South Australia. Figure 10 illustrates that maximum penetration is occurring around the middle of the
day when rooftop PV generation is typically highest and hence demand lowest. 17

11:05 PM

10:05 PM

9:05 PM

0%

8:05 PM

300
7:05 PM

10%
6:05 PM

600

5:05 PM

20%

4:05 PM

900

3:05 PM

30%

2:05 PM

1200

1:05 PM

40%

12:05 PM

1500

11:05 AM

50%

10:05 AM

1800

9:05 AM

60%

8:05 AM

2100

7:05 AM

70%

6:05 AM

2400

5:05 AM

80%

4:05 AM

2700

3:05 AM

90%

2:05 AM

3000

1:05 AM

100%

12:05 AM

3300

Wind penetration (%)

110%

0

SA demand, wind farm generation and rooftop PV (MW)

Figure 10 South Australian wind generation, demand and wind penetration for 29 December 2014

Time of day
Rooftop PV (estimated)

16

17

Wind Penetration

Wind Generation

Demand

The estimated rooftop PV generation output is sourced from AEMO’s in-development Australian Solar Energy Forecasting System Phase 2
(ASEFS2) which will be used to forecast rooftop PV generation in the NEM.
Rooftop PV generation is seen as a reduction in demand, as it is not metered by AEMO.

© AEMO 2015

23

 SOUTH AUSTRALIAN WIND STUDY REPORT

Wind penetration duration curves
Figure 11 provides wind penetration duration curves for the past five financial years, indicating that high
penetration levels have increased over time. This is due to a combination of increasing wind generation
with declining operational consumption and minimum demand.18
Overall, extremely high penetration levels occur for a small percentage of time, as indicated by the
steep gradient at the left-hand side of the curves. In 2014–15, penetration values below 80% were
observed for 95% of the time.
Figure 11

Instantaneous wind penetration duration curves

120%
110%

Instantaneous wind penetration level

100%
90%
80%
70%

60%
50%

40%
30%
20%
10%
0%
0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 95% 100%

Percentage of time
2010-11

18

2011-12

2012-13

2013-14

2014-15

Details of operational consumption and minimum demand trends can be found in the 2015 SAER. Available at:
http://www.aemo.com.au/Electricity/Planning/South-Australian-Advisory-Functions/South-Australian-Electricity-Report. Viewed: 13 October 2015.

© AEMO 2015

24

 SOUTH AUSTRALIAN WIND STUDY REPORT

2.7

Short-term wind generation and demand variations

This section provides statistical information on aggregate wind generation output variations occurring in
response to changing wind conditions. Variation is calculated as the difference in generation between
each five-minute dispatch interval.
The intermittency of wind generation, leading to sudden changes in the supply and demand balance,
makes managing the power system more challenging.
In terms of power system operation, aggregate wind farm generation variation is considered rather than
individual wind farm variation. Aggregation across a number of wind farms allows for smoothing, where
variation in individual wind farms is partially offset by other nearby wind farms. Three geographical
areas are used across South Australia to facilitate analysis: mid-north, south-east, and coastal
peninsula. The areas are described in Appendix Section A.1, noting that the term “all South Australian
wind farms” in this report refers to all semi-scheduled and non-scheduled wind farms in the state.

Wind and demand variation
Figure 12 shows the frequency-of-occurrence distributions for five-minute variations in South Australian
wind generation, demand, and their combined effect (residual demand) from 2010–11 to 2014–15.
Operationally this combined variation must be managed by AEMO and network service providers to
ensure power system reliability.
Figure 12

South Australian wind generation, demand, and residual demand (variation distribution)

30,000

Frequency of occurrence

25,000

20,000

15,000

10,000

5,000

0
-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

Change in 5-minute output (MW)
SA wind generation

© AEMO 2015

SA Demand

Residual Demand (demand less wind generation)

25

 SOUTH AUSTRALIAN WIND STUDY REPORT

Wider and flatter distributions indicate a higher frequency of larger changes in output between
five-minute intervals, while steeper and taller distributions indicate a higher frequency of smaller
changes in output. While the wind generation is less variable than South Australian demand, its
combined effect on the residual demand is more noteworthy. This residual demand is met by generation
other than wind, with wider distributions requiring more responsive units, able to manage large
variations. Residual demand change can also be met by changes in power flow on the Heywood
Interconnector.
Analysis of the residual demand each year from 2010–11 to 2014–15 in Figure 13 indicates that the
distribution has flattened over this period, with fewer changes in the plus or minus 10 MW range and
more changes occurring across larger ranges. This means that, as more wind farms come online, the
residual demand changes in South Australia are becoming more variable.
Figure 13

South Australian residual demand (variation distribution)

2,250

2,000

Frequency of occurrence

1,750

1,500

1,250

1,000

750

500

250

0

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

Change in 5-minute output (MW)
2010-11

© AEMO 2015

2011-12

2012-13

2013-14

2014-15

26

 SOUTH AUSTRALIAN WIND STUDY REPORT

Wind variation across geographical areas
Figure 14 presents key statistical information about five-minute and 10-minute wind generation variation
for the mid-north, south-east, and coastal peninsula areas in South Australia, and all South Australian
wind farms in aggregate, for 2014–15. Appendix Section A.3 shows tables of the statistics for 2013–14
and 2014–15. In 2014–15, the mean 5-minute variation for all South Australian wind farms in aggregate
was 10.7 MW and the maximum variation was 240 MW.
Key observations from Figure 14 are:
 Wind generation variation differs by area. For 90% of the time, the variation across a 10-minute
period for south-east and coastal peninsula areas is no more than 5.7% and 5.4% of registered
capacity respectively, whereas, total South Australian absolute wind generation variation is no
more than 2.6%.
 The mean is higher than the median for all areas and all South Australian wind farms, indicating
that while occurrences are skewed toward the lower values, larger fluctuations (though less
frequent) do exist.

Absolute variation as percentage of registered capacity

Figure 14

Five- and 10-minute absolute wind generation variation for 2014–15

6.0%

5.0%

4.0%

3.0%

2.0%

1.0%

0.0%
5-minute

10-minute

Mid-North
Area

5-minute

10-minute

South-East
Area
10th to 90th Percentile

© AEMO 2015

5-minute

10-minute

Coastal Peninsula
Area
Mean

5-minute

10-minute

Total
South Australia

Median

27

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 15 shows the full distribution of the five-minute absolute wind generation variation for the
mid-north, south-east, and coastal peninsula areas, and all South Australian wind farms, for 2014–15.
Key observations are:
 South Australian wind farms in aggregate have lower absolute wind variation than the individual
areas, indicating that greater wind generation geographical diversity leads to lower absolute
wind variation.
 The coastal peninsula has the highest absolute wind variation of the three areas for around 80% of
the time. The south-east has the highest absolute wind variation around 7% of the time.
 In the south-east area, a maximum wind farm variation of 42% was observed from one five-minute
period to another.
Figure 15

Absolute wind variation as percentage of registered capacity
45%

5-minute absolute wind variation by area (percentage of registered capacity)

50%

40%

35%

45%

30%
40%
25%

35%

20%

15%
30%
10%
25%

5%

0%

20%

0%

1%

2%

3%

4%

5%

15%

10%

5%

0%
0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Percent of time
Mid-North Area

© AEMO 2015

South-East Area

Coastal Peninsula Area

Total South Australia

28

 SOUTH AUSTRALIAN WIND STUDY REPORT

Maximum generation increase and decrease
Table 9 shows variations in wind generation for three operational timeframes (five-minutes, 30-minutes,
and 60-minutes) for the three geographical areas and all South Australian wind farms in aggregate,
from 2010–11 to 2014–15.19
Variations at the 30-minute and 60-minute timeframe are larger than within the five-minute timeframe.
South Australian wind farm variations from 2010–11 to 2014–15 show differences year on year. For the
mid-north area and all South Australia, where capacity increased over the five year period, there is a
general upward trend, particularly in the 30-minute and 60-minute variations.
Table 9

Total registered capacity and historical maximum variation outputs (MW) by area
Financial Year

2011–12

2012–13

2013–14

2014–15

Registered capacity

565

618

618

888

888

Max. 5-minute increase

171

174

155

155

180

Max. 5-minute decrease

173

257

206

179

289

Max. 30-minute increase

257

372

279

367

371

Max. 30-minute decrease

231

370

295

382

380

Max. 60-minute increase

339

460

433

444

550

Max. 60-minute decrease

273

437

293

479

442

Registered capacity

325

325

325

325

325

Max. 5-minute increase

103

84

125

131

137

Max. 5-minute decrease

118

132

128

180

126

Max. 30-minute increase

238

244

243

264

296

Max. 30-minute decrease

223

249

266

247

257

Max. 60-minute increase

282

284

268

273

299

Max. 60-minute decrease

252

263

281

262

276

Registered capacity

191

191

191

191

191

Max. 5-minute increase

57

62

63

63

61

Max. 5-minute decrease

81

70

83

86

73

Max. 30-minute increase

89

86

92

118

96

Max. 30-minute decrease

106

93

136

105

89

Max. 60-minute increase

122

113

106

125

116

Max. 60-minute decrease

108

91

136

131

92

1,151

1,203

1,203

1,473

1,473

Max. 5-minute increase

145

230

154

194

180

Max. 5-minute decrease

170

286

211

185

240

Max. 30-minute increase

300

371

446

418

418

Max. 30-minute decrease

336

435

360

415

393

Max. 60-minute increase

375

478

479

556

589

Max. 60-minute decrease

352

524

415

487

466

Registered capacity

19

2010–11

Area

Mid-north
area

South-east
area

Coastal
peninsula
area

All South
Australia

Values for some years are different to those published in earlier SAWSRs due to improved time-alignment between non-scheduled and semischeduled wind farm data.

© AEMO 2015

29

 SOUTH AUSTRALIAN WIND STUDY REPORT

3.

WIND GENERATION AND THE NATIONAL
ELECTRICITY MARKET

This chapter provides information on wind generation and market prices in South Australia. Generation
analysis in this chapter is restricted to the state’s registered wind farms only.
Additional market pricing information is available in the 2015 South Australian Electricity Market
Economic Trends Report (SAEMETR)20, which demonstrates that wind generation receives a lower
volume-weighted average price than thermal generation.21
Market prices are not typically set by wind generators, except during low demand periods, due to:
 Low marginal cost, and revenue from participation in the renewable energy target scheme, which
results in most wind generation being bid near or below $0/MWh, and seldom being the marginal
(price setting) generator.
 Average wind generation being higher overnight when demand is low, corresponding to periods
when low bids are typically received for thermal generation to remain scheduled on.
 Wind generators depending on wind availability, which precludes them from increasing generation
in response to high market prices.
AEMO has not undertaken a detailed investigation to further explore the relationship between wind
generation and market prices. This would require consideration of demand, generator bidding
strategies, network constraints, and interconnector capacity and spot prices in adjoining regions.
However, of note is the frequency and magnitude of negative pricing intervals, which had both generally
been declining since 2010–11, until 2014–15, when more negative prices were observed than in the
previous three years. This may be the result of a number of factors including increases in wind and
rooftop PV generation, reducing demand, and the return to full-time service of Northern Power Station22,
all placing downward pressure on spot prices at these times.

3.1

Data and methodology

AEMO has used the following data inputs for the analysis in this chapter:
 Spot prices for South Australia for each 30-minute trading interval.
 Wind generation from cleared supply values measured in megawatts at the end of each 30-minute
trading interval, based on a simple average of five-minute values.
 Historical data to 30 June 2015.

3.2

Wind generation and market prices

Figure 16 plots South Australian average wind generation against spot prices for all periods over the
past five financial years. All prices are in nominal dollars unless otherwise indicated, with the market
price cap increasing over the five-year period.
More information on positive and negative prices is provided in sections 3.3 and 3.4.

20

21

22

AEMO. Available at: http://www.aemo.com.au/Electricity/Planning/South-Australian-Advisory-Functions/South-Australian-Electricity-MarketEconomic-Trends-Report. Viewed: 12 October 2015.
Volume-weighted average prices are calculated as earnings ($) divided by amount of generation (MWh) for a given trading period. The
SAEMETR publishes both financial year and summer season volume-weighted average prices.
Alinta Energy advised that Northern Power Station returned to normal service in October 2014. This followed periods of withdrawal from April to
September in 2013 and 2014. Source: AEMO Generation Information for South Australia. 2015, October 26. Available at:
http://www.aemo.com.au/Electricity/Planning/Related-Information/Generation-Information. Viewed: 26 October 2015.

© AEMO 2015

30

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 16

South Australian average wind generation and spot prices (30-minute data for 2010–11
to 2014–15)

South Australian spot prices
Table 10 shows the relative occurrence of spot price bands for the South Australian region, ranging
from negative prices (below $0/MWh) to prices above $300/MWh.
Key observations are:
 The occurrence of negative prices in 2014–15 is 0.9%, the second highest level in five years.
 The impact of carbon pricing is evident, with very little pricing below $25/MWh occurring in
2012–13 and 2013–14, and a greater proportion of pricing in the $50/MWh to $75/MWh
price band.
 The occurrence of high prices above $300/MWh in 2014–15 is 0.3%, slightly below levels seen
during carbon pricing years, but above 2010–11 and 2011–12 levels.
Table 10 Frequency of occurrence of spot prices for South Australia
Price band
Below $0

2010–11

2011–12

2012–13

2013–14

2014–15

1.0%

0.7%

0.2%

0.1%

0.9%

$0–$25

45.5%

29.6%

0.3%

0.5%

25.1%

$25–$50

51.6%

67.1%

36.2%

42.6%

63.1%

$50–$75

1.3%

2.0%

47.4%

46.9%

9.0%

$75–$100

0.3%

0.3%

9.9%

6.8%

0.7%

$100–$300

0.3%

0.2%

5.5%

2.7%

0.9%

Above $300

0.1%

0.1%

0.5%

0.4%

0.3%

© AEMO 2015

31

 SOUTH AUSTRALIAN WIND STUDY REPORT

Wind generation volume-weighted average prices
Table 11 shows volume-weighted average spot prices for South Australian wind generation each
quarter over the past five years from 2010–11 to 2014–15. The values in Table 10 are based on
30-minute averaged dispatched volumes23 and the corresponding spot price (in real fourth quarter (Q4)
2014–15 dollars).
Table 11

Volume-weighted average spot prices for wind generation (real Q4 2014–15 dollars)

Price ($/MWh)

2010–11

2011–12

2012–13

2013–14

2014–15

Q1 (Jul–Sep)

25.30

31.74

58.21

61.99

35.01

Q2 (Oct–Dec)

15.95

29.19

56.87

54.92

26.18

Q3 (Jan–Mar)

34.05

25.38

53.48

56.58

29.77

Q4 (Apr–Jun)

29.10

27.24

74.04

46.34

34.78

Annual (volume-weighted)

26.27

28.41

60.25

55.26

31.56

The impact of carbon pricing is evident in 2012–13 and 2013–14, with annual volume-weighted prices
which are around $25 to $30 higher than the adjacent years. Ignoring these two years, the annual
volume-weighted average spot prices for wind generation have been increasing over time (in real
dollars), since 2010–11.

23

Dispatched volumes refers to cleared supply data for semi-scheduled wind generation plus SCADA readings for non-scheduled wind
generation. The latter does not participate in dispatch but is still considered in the analysis of South Australian wind generation volume-weighted
average prices.

© AEMO 2015

32

 SOUTH AUSTRALIAN WIND STUDY REPORT

3.3

Positive spot price trading intervals

Figure 17 shows spot prices for the South Australian region and the corresponding average wind
generation levels for each 30-minute dispatch interval from 2010–11 to 2014–15. Spot prices are
plotted on a logarithmic axis to better represent the variance.
The volume-weighted average spot price (in nominal dollars) for South Australia wind generation over
each 12-month period is also displayed (as a horizontal line) on each graph for reference.
Excluding very high and very low prices, most prices cluster around the mean, and decrease as
generation output increases. Very high prices tend to occur when wind generation is low, while low
prices tend to occur when wind generation is high.
Figure 17

South Australian 30-minute spot prices and average wind generation (positive market prices)

Note: Logarithmic axis

© AEMO 2015

33

 SOUTH AUSTRALIAN WIND STUDY REPORT

3.4

Negative spot price trading intervals

Figure 18 shows only the negative spot prices for the South Australian region and the corresponding
average wind generation levels for each 30-minute dispatch interval from 2010–11 to 2014–15. Spot
prices are plotted on a logarithmic axis to better represent the variance.
Of note is the number of negative spot prices, which has increased in 2014–15. A correlation is
observed between the occurrences of negative prices and higher levels of wind generation.
Figure 18

South Australian 30-minute spot prices and average wind generation (negative market prices)
South Australian wind generation (MW)

South Australian wind generation (MW)
0

200

400

600

800

1,000

1,200

0

1,400

2014-15

400

600

800

1,000

1,200

1,400

-0.3
-1.0
-4.0
-16.0
-64.0

2013-14

-0.1

SA spot price ($/MWh)

SA spot price ($/MWh)

-0.1

-0.3
-1.0
-4.0
-16.0
-64.0

-256.0

-256.0

-1,024.0

-1,024.0

South Australian wind generation (MW)

South Australian wind generation (MW)
0

200

400

600

800

1,000

1,200

0

1,400

200

400

600

800

1,000

1,200

1,400

-0.0

-0.0

2012-13

-0.1

SA spot price ($/MWh)

-0.1

SA spot price ($/MWh)

200

-0.0

-0.0

-0.3
-1.0
-4.0
-16.0
-64.0

2011-12

-0.3
-1.0
-4.0
-16.0
-64.0

-256.0

-256.0

-1,024.0

-1,024.0

South Australian wind generation (MW)
0

200

400

600

800

1,000

1,200

1,400

-0.0

SA spot price ($/MWh)

-0.1

2010-11

-0.3
-1.0
-4.0
-16.0
-64.0
-256.0
-1,024.0

Note: Logarithmic axis

© AEMO 2015

34

 SOUTH AUSTRALIAN WIND STUDY REPORT

Negative spot prices by time of day
Figure 19 shows the time of day and average wind generation level for negative spot prices in 2014–15.
Most negative spot prices occurred either early in the morning or during the middle of the day, when
wind generation was relatively high. As discussed in Section 2.6, highest average penetration values
occur early in the morning and the maximum value in 2014–15 occurred during the middle of the day.

300

-20

200

-30

100

-40

0

-50

12:00 AM

-10

11:00 PM

400

9:00 PM

0

10:00 PM

500

8:00 PM

10

7:00 PM

600

6:00 PM

20

5:00 PM

700

4:00 PM

30

3:00 PM

800

2:00 PM

40

1:00 PM

900

12:00 PM

50

11:00 AM

1,000

10:00 AM

60

9:00 AM

1,100

8:00 AM

70

7:00 AM

1,200

6:00 AM

80

5:00 AM

1,300

4:00 AM

90

3:00 AM

1,400

2:00 AM

100

1:00 AM

1,500

South Australian spot price (nominal $/MWh)

Negative South Australian spot price and average wind generation by time of day (2014-15)

12:00 AM

South Australian wind generation and capacity (MW)

Figure 19

Time of day
Wind generation (during negative prices only)

Wind total registered capacity

Spot price (during negative prices only)

© AEMO 2015

35

 SOUTH AUSTRALIAN WIND STUDY REPORT

Frequency of negative pricing events
Figure 20 shows the frequency of negative South Australian market prices from 2010–11 to 2014–15.
The magnitude of each event is also indicated by colour.
The number of negative price intervals for 2014–15 (at 154) is higher than the previous three years, but
not as high as the total in 2010–11 (177). However 2014–15, as in 2013–14, saw the value of negative
prices restricted to the $0/MWh to –$100/MWh band only.
Figure 20

Count of negative price trading intervals per year

200
180

Number of trading intervals

160
140
120
100
80
60
40
20
0
2010-11

$0 to -$100

© AEMO 2015

2011-12

-$100 to -$300

2012-13

-$300 to -$500

2013-14

-$500 to -$700

2014-15

-$700 to -$1,000

36

 SOUTH AUSTRALIAN WIND STUDY REPORT

Negative price duration curves
Figure 21 shows the price duration curves for negative price events, indicating the increased frequency
but similar magnitude of negative events in 2014–15, compared to 2013–14.
Figure 21

South Australian spot price duration curves, negative values only
$0

South Australian spot price (nominal $/MWh)

-$100
-$200
-$300
-$400
-$500
-$600
-$700
-$800
-$900
-$1,000
99.5%

99.6%

99.7%

99.8%

99.9%

100.0%

Cumulative percentage of the financial year
2010-11

© AEMO 2015

2011-12

2012-13

2013-14

2014-15

37

 SOUTH AUSTRALIAN WIND STUDY REPORT

Generation mix during negative spot price intervals
Historically, negative spot prices have occurred during periods of relatively low demand, periods of
high wind, and restrictions on interconnector flow from South Australia to Victoria. At these times,
negatively-priced generating capacity can exceed demand.
During 2014–15, negative spot prices for South Australia occurred for 154 trading intervals, with no
events below –$100/MWh, as highlighted in Figure 20.
Figure 22 provides details on the mix and magnitude of South Australian generation and net
interconnector import during 30-minute periods that had negative prices. As all 154 events occurred
across 33 days, only the most extreme negative pricing event is shown for each day.
The negative pricing events analysed in Figure 22 suggest that in 2014–15, most negative prices
occurred during times when wind energy penetration was above average (the annual value for the year
being 33% as presented in Table 7), and typically when South Australia was net exporting electricity
to Victoria.
Supply summary at selected times of negative South Australian spot price during 2014–15

1600

110%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
-10%
-20%
-30%
-40%
-50%
-60%
-70%
-80%
-90%
-100%
-110%
-120%
-130%
-140%
-150%
-160%
-170%
-180%
-190%
-200%
-210%
-220%
-230%
-240%
-250%
-260%

1500
1400
1300
1200
1100

Energy supplied to South Australia (MWh)

1000
900
800
700

600
500
400
300
200
100
0
-100
-200
-300
-400
-500

Gas

© AEMO 2015

Wind

Coal

Other

Net interconnector flow

22/06/2015

08/06/2015

07/06/2015

31/05/2015

11/05/2015

10/05/2015

09/05/2015

06/05/2015

07/04/2015

06/04/2015

23/03/2015

19/03/2015

01/02/2015

28/01/2015

25/01/2015

24/01/2015

29/12/2014

25/12/2014

18/12/2014

16/12/2014

07/11/2014

04/11/2014

01/11/2014

27/10/2014

26/10/2014

18/10/2014

29/09/2014

28/09/2014

23/09/2014

31/07/2014

29/07/2014

17/07/2014

05/07/2014

-600

South Australian wind energy penetration (%)

Figure 22

Wind penetration

38

 SOUTH AUSTRALIAN WIND STUDY REPORT

3.5

Wind forecast performance

This section presents information on the forecast accuracy of the Australian Wind Energy Forecasting
System (AWEFS) for South Australian wind farms.
Under National Electricity Rules clause 3.7B(a), AEMO is required to prepare forecasts of the available
capacity of semi-scheduled generation to schedule sufficient generation in the dispatch process. This
system aims to improve the efficiency of overall NEM dispatch. Greater AWEFS accuracy results in
more accurate and efficient scheduling of other forms of generation.
South Australia has the highest wind penetration in the NEM, so AWEFS accuracy in forecasting South
Australian wind generation may affect the market by contributing to determination of pre-dispatch levels
at different forecast time horizons.
AWEFS produces wind generation forecasts for all NEM wind farms above or equal to 30 MW, for all
NEM forecasting timeframes as follows:
 Dispatch (five-minutes ahead).
 Five-minute pre-dispatch (five-minute resolution, one hour ahead).
 Pre-dispatch (30-minute resolution, up to 40 hours ahead).
 ST PASA (30-minute resolution, seven days ahead).
 MT PASA (daily resolution, two years ahead).24
AWEFS accuracy is most commonly measured as the normalised mean absolute error (NMAE) of the
forecast. The NMAE is calculated as the absolute difference between forecast and actual output,
divided by the nominal capacity.
AWEFS accuracy is monitored for compliance with performance standards at the NEM level.
Performance standards are also monitored at regional level, although this is not mandated.
Figure 23 shows monthly average NMAE figures of the AWEFS forecasts for South Australian wind
farms. Forecast accuracy decreases as the forecast horizon extends, in line with the decreasing
accuracy of the input weather models.

24

Further information available at: http://www.aemo.com.au/Electricity/Market-Operations/Dispatch/AWEFS.

© AEMO 2015

39

 SOUTH AUSTRALIAN WIND STUDY REPORT

Figure 23

Normalised mean absolute error of AWEFS forecasts for South Australia 2014-15

South Australian AWEFS normalised mean absolute error
(monthly average)

25%

20%

15%

10%

5%

5 mintues

© AEMO 2015

1 hour

4 hours

12 hours

24 hours

40 hours

Jun-15

May-15

Apr-15

Mar-15

Feb-15

Jan-15

Dec-14

Nov-14

Oct-14

Sep-14

Aug-14

Jul-14

0%

6 days

40

 SOUTH AUSTRALIAN WIND STUDY REPORT

APPENDIX A. WIND FARM STATISTICS
A.1

Wind farm capacities

Table 12

Registered capacities of South Australian wind farms

Wind farm

Dispatchable unit
identifier (DUID)

Canunda Wind Farm

CNUNDAWF

Cathedral Rocks Wind Farm

Registered
capacity (MW)*

Classification

Area for SAWSR
analysis

46

Nonscheduled

South-east

CATHROCK

66

Nonscheduled

Coastal peninsula

Clements Gap Wind Farm

CLEMGPWF

57

Semischeduled

Mid-north

Hallett 1 (Brown Hill)

HALLWF1

94.5

Semischeduled

Mid-north

Hallett 2 (Hallett Hill)

HALLWF2

71.4

Semischeduled

Mid-north

Hallett 4 (North Brown Hill Wind Farm)

NBHWF1

132.3

Semischeduled

Mid-north

Hallett 5 (The Bluff) Wind Farm

BLUFF1

52.5

Semischeduled

Mid-north

Lake Bonney 2

LKBONNY2

159

Semischeduled

South-east

Lake Bonney 3

LKBONNY3

39

Semischeduled

South-east

Lake Bonney Wind Farm

LKBONNY1

80.5

Nonscheduled

South-east

Mount Millar Wind Farm

MTMILLAR

70

Nonscheduled

Not included in
areas analysed

Snowtown Stage 2 Wind Farm North

SNOWNTH1

144

Semischeduled

Mid-north

Snowtown Stage 2 Wind Farm South

SNOWSTH1

126

Semischeduled

Mid-north

Snowtown Wind Farm

SNOWTWN1

99

Semischeduled

Mid-north

Starfish Hill Wind Farm

STARHLWF

34.5

Nonscheduled

Coastal peninsula

Waterloo Wind Farm

WATERLWF

111

Semischeduled

Mid-north

Wattle Point Wind Farm

WPWF

90.75

Nonscheduled

Coastal peninsula

* Registered capacity sourced from AEMO’s NEM Registration and Exemption List, 7 October 2015. Available: http://www.aemo.com.au/About-theIndustry/Registration/Current-Registration-and-Exemption-lists. Viewed: 16 October 2015.

© AEMO 2015

41

 SOUTH AUSTRALIAN WIND STUDY REPORT

A.2

Wind farm capacity factors

Table 13

Capacity factors of South Australian wind farms25

Wind farm

DUID

2010–11

2011–12

2012–13

2013–14

2014–15

Canunda Wind Farm

CNUNDAWF

27.4%

30.5%

28.0%

30.7%

28.9%

Cathedral Rocks Wind Farm

CATHROCK

30.6%

31.8%

30.2%

34.0%

29.4%

Clements Gap Wind Farm

CLEMGPWF

33.8%

35.1%

33.6%

35.3%

33.7%

Hallett 1 (Brown Hill)

HALLWF1

38.8%

40.0%

40.1%

42.3%

37.3%

Hallett 2 (Hallett Hill)

HALLWF2

39.2%

40.8%

41.1%

41.1%

37.4%

Hallett 4 (North Brown Hill
Wind Farm)

NBHWF1

27.6%

39.5%

36.8%

40.9%

36.3%

Hallett 5 (The Bluff) Wind
Farm

BLUFF1

-

28.9%

33.7%

36.4%

29.5%

Lake Bonney 2

LKBONNY2

26.0%

27.6%

27.5%

30.2%

28.7%

Lake Bonney 3

LKBONNY3

24.9%

25.4%

28.0%

29.9%

27.6%

Lake Bonney Wind Farm

LKBONNY1

26.0%

28.5%

27.0%

29.2%

27.1%

Mount Millar Wind Farm

MTMILLAR

29.7%

30.6%

30.2%

33.2%

30.5%

Snowtown Stage 2 Wind Farm
(North and South total)

SNOWNTH1 and
SNOWSTH1

-

-

-

-*

34.8%

Snowtown Wind Farm

SNOWTWN1

40.0%

43.3%

43.3%

45.1%

38.6%

Starfish Hill Wind Farm

STARHLWF

24.4%

28.1%

22.4%

31.1%

28.2%

Waterloo Wind Farm

WATERLWF

27.3%

32.0%

32.2%

34.9%

30.2%

Wattle Point Wind Farm

WPWF

32.8%

34.0%

31.1%

37.0%

33.2%

* A capacity factor is not shown for Snowtown Stage 2 Wind Farm for 2013–14 since it did not meet the analysis criteria of first generating 90% of
registered capacity until mid-June 2014; analysis over such a short part of the 2013–14 financial year would not be sufficiently representative of an
annual factor.

25

Data taken from the 2015 South Australian Historical Market Information Report (SAHMIR). Available:
http://www.aemo.com.au/Electricity/Planning/South-Australian-Advisory-Functions/South-Australian-Historical-Market-Information-Report.
Viewed: 6 October 2015.

© AEMO 2015

42

 SOUTH AUSTRALIAN WIND STUDY REPORT

A.3

Wind generation variation

Table 14

Key statistical characteristics and five- and 10-minute wind generation variation for 2014–15
Mid-north
area

FY 2014–15

5-minute

South-east
area

10-minute

5-minute

Coastal peninsula
area

10-minute

5-minute

10-minute

South Australian wind
farms
5-minute

10-minute

Key statistical characteristics of absolute variation (% of registered capacity)
Mean

0.9%

1.4%

1.4%

2.3%

1.6%

2.3%

0.7%

1.2%

Median

0.6%

0.9%

0.7%

1.2%

1.0%

1.5%

0.5%

0.8%

Standard deviation

1.0%

1.6%

2.2%

3.5%

1.9%

2.8%

0.8%

1.2%

Key statistical characteristics of absolute variation (megawatt equivalent)
Mean

7.8

12.6

4.7

7.5

3.0

4.4

10.7

17.1

Median

5.1

8.4

2.4

3.8

1.9

2.8

7.3

11.8

Standard deviation

9.2

14.3

7.0

11.2

3.6

5.3

11.5

18.0

90th percentile

0.1%

0.1%

0.0%

0.1%

0.1%

0.2%

0.1%

0.1%

10th percentile

2.0%

3.3%

3.6%

5.7%

3.7%

5.4%

1.6%

2.6%

5th percentile

2.7%

4.3%

5.2%

8.4%

5.0%

7.4%

2.2%

3.5%

4.7%

7.3%

10.1%

16.9%

8.6%

13.2%

3.7%

5.7%

32.5%

36.4%

42.3%

64.0%

38.2%

43.8%

16.3%

21.5%

Absolute variation

1st percentile
Maximum

Table 15

Key statistical characteristics and five- and 10-minute wind generation variation for 2013–14*

FY 2013–14

Mid-north
area
5-minute

South-east
area

10-minute

5-minute

Coastal peninsula
area

10-minute

5-minute

10-minute

South Australian wind
farms
5-minute

10-minute

Key statistical characteristics of absolute variation (% of registered capacity)
Mean

1.1%

1.7%

1.5%

2.4%

1.7%

2.5%

0.8%

1.3%

Median

0.7%

1.2%

0.8%

1.3%

1.1%

1.6%

0.6%

0.9%

1.2%

1.9%

2.2%

3.5%

2.0%

3.0%

0.9%

1.4%

10.1

16.2

Standard deviation

Key statistical characteristics of absolute variation (megawatt equivalent)
Mean

6.8

10.9

4.9

Median
Standard deviation

7.9

3.3

4.8

4.6

7.3

7.7

12.2

2.6

4.2

2.1

3.1

7.0

11.4

7.0

11.4

3.9

5.7

10.6

16.7

Absolute variation
90th percentile

0.1%

0.1%

0.1%

0.1%

0.1%

0.2%

0.1%

0.2%

10th percentile

2.5%

4.0%

3.6%

5.8%

3.9%

5.8%

1.8%

3.0%

5th percentile

3.3%

5.3%

5.3%

8.7%

5.4%

8.0%

2.4%

3.9%

5.7%

8.9%

10.4%

17.2%

9.3%

14.3%

4.1%

6.5%

25.0%

37.7%

55.5%

62.2%

45.0%

50.4%

16.1%

23.1%

1st percentile
Maximum

* Values for some cells are different to those published in the 2014 SAWSR due to improved time-alignment between non-scheduled and semischeduled wind farm data.

© AEMO 2015

43

 SOUTH AUSTRALIAN WIND STUDY REPORT

MEASURES AND ABBREVIATIONS
Units of measure
Abbreviation

Unit of measure

$

Australian dollar

GWh

Gigawatt hour

hr

Hour

min

Minute

MW

Megawatt

MWh

Megawatt hour

Abbreviations
Abbreviation

Expanded name

AEMO

Australian Energy Market Operator

ASEFS2

Australian Solar Energy Forecasting System Phase 2

AWEFS

Australian Wind Energy Forecasting System

DUID

Dispatchable unit identifier

MD

Maximum demand

MT PASA

Medium-term Projected Assessment of System Adequacy

NEM

National Electricity Market

NER

National Electricity Rules

NMAE

Normalised Mean Absolute Error

PV

Photovoltaic

SA

South Australia

SAER

South Australian Electricity Report

SAEMETR

South Australian Electricity Market Economic Trends Report

SCADA

Supervisory Control and Data Acquisition

ST PASA

Short-term Projected Assessment of System Adequacy

© AEMO 2015

44

 SOUTH AUSTRALIAN WIND STUDY REPORT

GLOSSARY
The 2015 SAWSR uses many terms that have meanings defined in the National Electricity Rules
(NER). The NER meanings are adopted unless otherwise specified. Other key terms used in the 2015
SAWSR are listed below.
Term

Definition

Absolute variation

The total variation, regardless of whether it is positive (an increase) or negative (a decrease).

ASEFS2

Australian Solar Energy Forecasting System Phase 2 (Small scale PV Forecasting). An indevelopment AEMO system that will produce forecasts up to 8 days ahead of distributed
rooftop PV generation.

AWEFS

Australian Wind Energy Forecasting System. A system used by AEMO to produce wind
generation forecasts ranging from five minutes ahead to two years ahead.

Capacity penetration

The ratio of registered wind capacity to registered total generation capacity, excluding
generating units that were effectively mothballed for at least the last six months of the financial
year in consideration. This gives a relative measure of wind generation potential compared to
the rest of the generating systems.

Cleared supply

The National Electricity Market Dispatch Engine (NEMDE) dispatches generation at
five-minute intervals. Cleared Supply represents the dispatched supply values.

Energy penetration

The ratio of annual wind generation to annual total consumption from the grid (excludes any
net interconnector exports).

Maximum demand

An absolute value (MW) of demand, observed to be the maximum during a specified time
period. Generally the maximum demand is the maximum over an annual or summer period,
though any period (e.g. daily) can be defined.

Maximum instantaneous
penetration

The maximum observed ratio of wind generation output to demand during the year. This
captures the extreme of wind generation relative to other generation, including interconnector
exports.

Maximum possible
instantaneous penetration

The ratio of maximum possible wind generation output (registered capacity) to minimum
demand, assuming zero interconnector exports. Wind capacity is the total registered at the
time of minimum demand during the year.

MT PASA

Medium-term Projected Assessment of System Adequacy. The projected assessment of
system adequacy covering two years and in a daily resolution.

Mothballed

A generation unit that has been withdrawn from operation but may return to service at some
point in the future.

Nameplate capacity

The maximum continuous output or consumption in MW of an item of equipment as specified
by the manufacturer, or as subsequently modified.

Operational

Operational reporting includes the electrical energy used by all residential, commercial, and
large industrial consumption, and transmission losses (as supplied by scheduled, semischeduled and significant non-scheduled generating units). Significant non-scheduled
generating units in South Australia are Angaston, Port Stanvac 1, Port Stanvac 2 and all nonscheduled wind farms. It does not include the output of small non-scheduled generating
systems, typically less than 30 MW capacity.

Peak demand

The time period over which demand is observed to peak above a nominal value, during the
total time period specified.

SCADA

Supervisory Control and Data Acquisition. A system that gathers real-time data from remote
terminal units and other communication sources in the field and enables operators to control
field devices from their consoles.

ST PASA

Short-term Projected Assessment of System Adequacy. The projected assessment of system
adequacy covering seven days ahead and in a 30-minute resolution.

Spot price

The price in a trading interval for one megawatt hour (MWh) of electricity at a regional
reference node. Prices are calculated for each dispatch interval (five minutes) over the length
of a trading interval (a 30-minute period). The six dispatch prices are averaged each half hour
to determine the price for the trading interval.

Summer

For the purposes of the analysis in this report, 1 November to 31 March.

Summer peak

The top 10% of demand over the summer period on a five-minute basis.

Wind penetration

The relative amount of wind energy or capacity compared to total energy or capacity. This can
be measured in a number of different ways (see Section 2.6). Also see glossary entries for
Capacity penetration, Energy penetration, Maximum instantaneous penetration, and Maximum
possible instantaneous penetration.

© AEMO 2015

45

 SOUTH AUSTRALIAN WIND STUDY REPORT

Term

Definition

Winter

For the purposes of the analysis in this report, 1 June to 31 August.

Winter peak

The top 10% of demand over the winter period on a five-minute basis.

© AEMO 2015

46