Submission to Senate Select Committee on Wind Turbines

Submission to the Senate Inquiry into Wind Turbines

Peter Bobroff, AM



This submission addresses the any related matter aspect of the Terms of Reference and offers information relating to the question Should more wind farms be built?

This submission is based upon a personal analysis of the 5 minute data from the Australian Energy Market Operator (AEMO) for every day of 2014 which comprises:

  • Demand power for each state
  • Regional reference price for each state which is assumed to be the wholesale spot price.
  • Dispatch power for every generator.
  • Dispatch power for each of the interconnectors between states.
  • Technical data on each generator including its registered capacity and data to allow a simplistic estimate of CO2 Emissions.

The Fuel Class: WindSolar currently contains only one solar generator – Royalla1, but no dispatched power was detected in 2014. Roof top solar is not dispatched by AEMO so is not included within analysis. Western Australia and the Northern Territory are not connected to the Grid. The Australian Capital Territory is considered part of NSW.

This submission was prepared as a blog posting and it was intended that the images should link into the interactive database that prepared the images. The database is not yet robust enough to allow public access.

Wind contribution to the whole grid during 2014

screenshot-gridyear publicknowledge com au 2015-02-25 12-35-20The pie chart is based on the 5 minute dispatch power of every generator for the Whole Grid in 2014.

As far as the current whole grid is concerned, wind is irrelevant. Other existing generators could instantly replace wind if wind’s special status were removed.

 Dispatched power into the Whole Grid for 2014

The histograms are all formatted with probability on the y axis. The 2 digits of fractional probability can be read as the percentage occurrence within one bar.

  • screenshot-localhost 2015-02-27 17-40-40Coal fired generators dispatched between about 12 and 20 GigaWatts (GW) with an average of 16.6 GW
  • Gas fired generators dispatched between about 2 to 4 GW with an average of 2.9 GW
  • Hydro generators dispatched about 1 to 3 GW with an average of 1.6 GW
  • Wind generators dispatched less than 3 GW with an average of 0.96 GW

The histograms show that coal dominates the grid. It provides the base load power, never less than 12GW. Gas and hydro provide the peak loads with their reliable quick responses. Sometimes only a little peaking is required, but their rapid responsive reserve is always needed for overall grid reliability. Wind, with all it’s special privileges,  has over 40% probability of producing almost nothing.

Whole grid on calm days

screenshot-localhost 2015-02-26 11-02-19There were 45 days when the average wind power throughout the day was less than 2% of the grid demand and 7 days when less than 1%.

2014-03-29 is an example of a particularly calm day across the whole grid.

The whole grid does not require any wind power for its reliable operation.

Whole grid on windy days

screenshot-localhost 2015-02-26 11-12-55There were 18 days when the average Wind power throughout the day exceeded 10%.

2014-09-28 is an example of a particularly windy day across the whole grid.

South Australia as a portent?

screenshot-localhost 2015-02-25 15-18-14

The present conditions of the SA grid might give some indication of the future of the eastern states’ grids if wind capacity is greatly increased and fossil fuel capacity  greatly reduced. The pie chart is for dispatched power separated by Fuel Class.

In 2014 South Australia generated about 45% of its power by Gas, 33% by Wind and 22% by Coal. Some of the wind power was exported, sometimes up to 8%. Often power was imported from Victoria, sometimes up to 20% of SA requirements.

How did South Australian Wind perform in 2014?

In terms of power dispatched

screenshot-localhost 2015-02-27 17-48-17Over the year 2014 South Australia’s wind farms produced anywhere from 0 MW to about 1200 MW with an average of 447 MW. Below 100 MW was the most common output, with 1200 MW being very rare.

In terms of whole state capacity factor

Capacity Factor is the power produced compared to the maximum possible (Registered Capacity).
screenshot-localhost 2015-02-27 17-55-56As would be expected, all the SA wind farms never reached full output simultaneously. They did occasionally exceed 80%. Far more commonly they produced less than 10%. Wind turbines can only produce their maximum power at a particular wind speed. If the wind gets stronger, the turbine must feather it’s blades to prevent damage.

In terms of individual farm capacity factor

screenshot-localhost 2015-02-27 18-03-25Looked at individually, the wind farms more frequently approached 100% capacity. However four times more frequently, they had to draw power from the grid to prevent damage to their main bearings during calms.

Windy days in South Australia

screenshot-localhost 2015-02-26 11-19-30There were 4 days when the average Wind power throughout the day exceeded 100% of the state demand. Power is often exported on windy days.

2014-09-28 is an example of a windy day in South Australia.

When the wind blows strongly and consistently, the dispatched power data looks good.

Calm days in South Australia

screenshot-localhost 2015-02-26 11-22-19There were 37 days when the average Wind power throughout the day was less than 10% of the state demand. Power is imported from Victoria on calm days.

2014-08-02 is an example of a calm day in South Australia.

Wind was almost non-existent except for a slight breeze during the night.

Contrasting windy and calm conditions in SA

Coal output in SA is relatively unaffected by wind conditions. However as the wind increases, the gas turbines and import interconnectors start to shut down.screenshot-localhost 2015-02-28 12-44-12 With no wind, the gas is almost at maximum. As the wind increases, gas decreases but never much below 20% of demand. There are times when gas is around 20% of demand when wind is also very low. The effects of imports and exports are not included in this plot.

The gas and imports are needed on wind-free days. There are no gas-free days when wind is need. This submission did not investigate whether the extra capital costs of wind generators are justified by the savings in fuel cost of gas generators on windy days.

Prices on a windy day

screenshot-localhost 2015-02-28 13-31-02On a windy day without any drama, the Regional Reference Price tends to fall with increasing wind power dispatched.

On 2014-10-06 prices varied from $45/MWh down to $6/MWh. With their special status and extremely low marginal costs, there seems little to prevent wind companies undercutting themselves in a downward spiral. Better to get a low price than no price.

screenshot-localhost 2015-03-01 16-40-282014-10-27 provides an example of this spiral resulting in negative prices.

Prices on calm days

screenshot-localhost 2015-02-28 13-34-30On calm days the price changes can be more dramatic. 2014-07-01 shows prices rising to 150 $/MWh during very calm periods. During this period there was a price spike to 11,000 $/MWh, which as been omitted so the lower price changes can be seen.

In this document the term PriceDeSpiked refers to the Regional Reference Price limited to the range -50 to 150 $/MWh

Price vs Wind % South Australia 2014-01-15

screenshot-localhost 2015-02-28 19-44-08A more extreme day was 2014-01-15 when spot prices rose to 13,000 $/MWh and fell to -1,000 $/MWh. This sort of price would seem to be an abberation.

Negative prices

screenshot-localhost 2015-02-28 19-51-56It is difficult to understand a market with negative prices. How can a seller pay customers to take a product? This seems to be a characteristic of electricity markets that include significant amounts of wind and solar. It is apparently quite common in Germany.

The two scatter plots to the right have their prices limited to the range +150 to -50 $/MWh with spikes being limited. Otherwise the detail in this range is lost if the spikes are shown linearly. Negatives are a bit of a problem with log scales.

In South Australia the negative prices can occur at any wind percentage but seem more common in higher winds. Above about 40% wind the floor of the scatter plot goes negative.

In New South Wales negative prices are far less common and the floor of the scatter plot remains positive.

It would take a fast talking Keynesian economist or a merchant banker to explain how such a market can be healthy in the long term.

An Austrian economist would probably say that such aberrations are inevitable when governments interfere in markets.

The Germans are apparently considering a scheme where generation companies must supply contracted power whether the wind blows or not. This moves the brown-out risk from the market operator to the contracting generation companies. This may improve the market health.

 Is Wind power cheaper?

The plot below compares the average price of power per day in each state for 2014.

South Australian prices don’t seem noticeably lower than other states who have less wind power. Wind power does not seem to be free.

A generation company cannot survive in the long term if the short term price it receives for its power is insufficient to cover its long term capital, operations and maintenance costs. The German proposal for contracting companies to supply power at a particular price irrespective of wind conditions, might help.

This submission does not address the long term viability of power generation companies.
screenshot-localhost 2015-02-25 16-29-09

Does wind deliver its registered capacity?

screenshot-localhost 2015-02-27 18-11-25Actual Dispatched Power divided by the Registered Capacity is known as the Capacity Factor and is usually expressed as a percentage.

This set of histograms averages all the units of a Fuel Class for each 5 minute period. When a generator is not delivering any power, it is assumed not to be required and that period is excluded from the samples, except for Wind which is assumed to be delivering zero power.

  • The most probable Capacity Factor of the whole SA wind class is only a few percent of Registered Capacity. The probabilities decrease to only a small probability of exceeding 80%.
  • SA usually relies on imports to some extent. The interconnectors operate when required, usually at between 10-60% of their Nominal Capacity.
  • SA has a lot of Gas generators which run a Capacity Factors from 5-60%
  • SA occasionally exports power, rarely getting up to 40% of the available interconnector capacity.
  • SA coal fired generators run at between 20-70% capacity with 40% being the most probable.

Capacity factors – treating units individually

screenshot-localhost 2015-02-27 18-06-12This set of histograms treats each generator separately. Each histogram therefore shows the probability of an individual generator of that Fuel Class operating at  the particular Capacity Factor.

  •  The interconnectors used for imports operate when required at desired factors of 0-100%
  • The Gas turbines operate when required at desired factors of 0-110%
  • The interconnectors used for exports are not often required to run at high capacity.
  • Coal fired generators are almost always in use, running at 50-100% capacity.
  • Individual wind turbines sometimes consume power to prevent damage to bearings in a calm but also occasionally deliver their rated capacity.  The most common output is almost zero.

Comparing windy and calm days.

screenshot-localhost 2015-03-01 16-47-17Here we are comparing a windy day with a calm day that had a similar demand curve. Sets are from South Australia.

Prices are cheaper on the windy day as wind generators have low marginal costs.

Prices generally appear to rise as the demand increases.

The low negative price spikes seemed to occur on windy days. Perhaps these are attempts by the market operator to shed excess capacity.

Variability of individual wind farms

screenshot-localhost 2015-02-27 10-42-07The output of an individual wind farm throughout the day is often quite variable. The short term variation (between 5 minute periods) as measured by the Variate Difference method is no greater than other Fuel Classes, however the dispatched power can disappear over 15 minutes.

Variability of wind across South Australia

screenshot-localhost 2015-02-27 10-55-03The plot shows standard deviations by the Variate Difference Method for each Fuel Class for each day in 2014-Q1. Wind is more variable than coal. Gas variability is probably due to balancing wind variability.

The wind variability is seldom over 2% of the dispatched power.

CO2 Emissions

The plots below are of daily averages for the year 2014. The weekly ripple is evident. Import and Export of power via the interconnectors between states is not being considered. South Australia often imports Brown Coal power from Victoria.

screenshot-localhost 2015-02-27 09-46-17The CO2 Emissions ( tonnes/hour )  don’t vary much with the change of demand throughout the year. Perhaps the seasonal demand increases are handled by gas turbines which emit less than coal fired ones.

The CO2 Intensities (tonnes/MWh) of the states reflect their dominant Fuel Class

  • VIC – brown coal
  • NSW and QLD – black coal
  • SA – wind
  • TAS – hydro

Could unilateral action to reduce emissions by South Australia significantly reduce Australian emissions?

VIC, NSW and QLD are the big  emitters and they determine Australia’s emissions. Similarly China, India and USA are the big emitters and they determine the Earth’s emissions.

Summary of the advantages of wind power

  • On windy days the wholesale price of electricity may fall. This might have some influence on the long term price to consumers;
  • Less CO2 is emitted, if you consider this an advantage.

Summary of the disadvantages of wind power

  • Wind generators do not replace existing generators as calm periods often occur. Even enormous numbers of wind farms can only reduce the probability of no wind output – not eliminate it. The big states (NSW, VIC, QLD) rely almost entirely on fossil fuels and have large reserves. It would be totally unaffordable to build enough wind farms to supply most of the demand most of the time. Even then the existing generators would still be required on occasions.
  • Increasing use of wind appears to result in large positive price spikes and periods of negative prices. These don’t seem to indicate a healthy market.
  • Less CO2 is emitted, if you consider this to be a disadvantage.

Final Observation

This inquiry has an unstated assumption:The world is in danger of Catastrophic Anthropogenic Global Warming and the most cost effective solution is to build wind and solar farms.

If the assumption fails, this inquiry is irrelevant. Another inquiry is needed into:

  • Have the climate models been accurately predicting the future?
  • Is the predicted future so bad that CAGW out ranks all other human problems?
  • Will China and India stop building fossil fuel powered power plants and replace all existing ones with nuclear, hydro, wind or solar?

2 thoughts on “Submission to Senate Select Committee on Wind Turbines

  1. “As far as the whole grid is concerned, wind is irrelevant. Other existing generators could instantly replace wind if wind’s special status were removed. This is not the case for South Australia.”

    – What is not the case in SA ? To Complex, to many points

    “with the most likely output being …”

    – Leave out, does not add much, or stateaverage

    – Alternatives, efficiency and nuck


  2. Peter, an excellent summary. In the first section, fourth dot point, “it’s” should be “its”. A little further down (‘Wind contributed little…’) you say: ‘…for South Australia which has little coal capacity and can currently supply a much larger proportion of its demand than the larger states.’

    I think you mean, ‘for South Australia, which has little coal capacity, and for which wind can supply…’

    If not, then something is missing.


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