Wind output constrained in South Australia as it blows above 1200MW | RenewEconomy

Wind output constrained in South Australia as it blows above 1200MW

AEMO constrains wind farms in South Australia for first time because there were not enough “synchronous units” as wind output blew above 1200MW.


The output of wind farms in South Australia was constrained over two periods on Sunday on Monday after their combined output jumped above 1200MW and above new limits placed by the Australian Energy Market Operator.

The constraints were put in place for some 10 hours on Sunday, and another six hours early on Monday morning, both at times of relatively low demand, and at a time when the combined output of wind and gas power was significantly higher than state demand.

A ttimes, wind output in a state with some 1698MW of wind capacity jumped above 1400MW, but had to be constrained back to 1200MW, because there were not enough gas generators in the system under the AEMO’s new guidelines.

These new guidelines doubles the number of gas generators require to be online – in November it suggested only two were required, but in December in a separate document it lifted this to four.

output graph.This graph above (courtesy of the Climate and Energy College) shows the most dramatic intervention, at around 1.15am on Monday morning, when the second constraint was invoked, pulling the output of the wind farms back from more than 1400MW to 1200MW.

An AEMO spokesman confirmed: Peak wind output last night (2 July 2017) reached an unconstrained 1442 MW at 23:00. The 1200MW constraint limit was applied from 01:30 through to 06:50 this morning, Monday 3 July 2017.

The constraint applies to all turbines, but AEMO’s NEM dispatch engine reduces output of the wind in the most economical way, reducing from the most expensive first.

north brown graph.AEMO did not say which these were, but Dylan McConnell at the Climate and Energy College produced this graph which shows that the Waterloo, Bluff and North Brown Hill wind farms copped the brunt of it.

It had the effect of keeping prices high. Normally, when wind farms increase output, particularly at night, the pool price falls sharply, and sometimes goes into negative territory.

The trading rights of all three wind farms are owned by EnergyAustralia and AGL, the providers of much of the synchronous generation in the state. Neither company provided any comment by the time of publication. The Clean Energy Council also did not respond.

AEMO says the constraint – flagged in its National Transmission Network Development Plan (NTNDP) issued in December – is designed to maintain “power system strength, more specifically system fault current.””

As a result of that, it introduced new operational procedural changes, resulting in the requirements below:

  • When there is between 0 – 1,200 MW of wind generation, South Australia must have three capable synchronous generating units available and in the market to maintain sufficient power system strength.
  • When there is more than 1,200 MW of wind generation, South Australia must have four capable synchronous generating units available and in the market to maintain sufficient power system strength.

“In instances where there is not the required number of synchronous generating units available and in the market within South Australia, intermittent generation will be constrained to maintain a safe and secure fault current,” it says.

As it turned out on Sydney, only three “synchronous” units could be encouraged to bid into the market, meaning that the wind output had to be constrained at 1200MW.

AEMO says the measures are only interim as it decides on the best path forward, and pending the introduction of new requirements on wind and solar plants.  The introduction of battery storage will not directly affect the provision of fault current, but could serve to store the excess output.

“AEMO strongly believes this is a required and necessary initiative to maintain power system security during a period of rapid transformation,” a spokesman said in an emailed statement.

AEMO is assessing whether further Network Support and Control Ancillary Services (NSCAS) are required in the next five years. These are non-market ancillary services designed to maintain power system security and reliability, and to maintain or increase the power transfer capability of the transmission network.

In the 2016 NTNDP, AEMO identified an NSCAS gap to provide system strength in South Australia, and stated that the gap would be confirmed in 2017 following completion of more detailed analysis.

The industry is going through a period of rapid reappraisal of exactly how much security is needed in the system, particularly the level of synchronous generation, inertia and other grid services. These requirements are being rapidly re-assessed as the potential of new technologies and smart controls becomes evident.

“In instances where there is not the required number of synchronous generating units available and in the market within South Australia, intermittent generation will be constrained to maintain a safe and secure fault current.”



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  1. Ian 3 years ago

    If this is the norm going forward then there is a good case for pumped hydro, even if the water goes up one pipe into a pond and down another through a synchronous generator.

    • BushAxe 3 years ago

      This ultimately may be the answer, instead of unnecessarily burning gas for ‘system strength’.

  2. Mark Roest 3 years ago

    240 MW of battery storage for six hours at US$100/kWh by late 2020 would cost US$24 million, and could last decades. Given the amount of production likely to be curtailed going forward if the rule is rigidly enforced, how long would it take for such battery capacity to pay for itself? How long would it take for ten hours capacity to pay for itself?

    Put another way, what would the conversion value of these two scales of installations be, if they can provide 10,000-cycle lifetimes? And what if they are good for 20,000 cycles?

    • Gus Griffin 3 years ago

      It’s extremely difficult to invest in capacity when the competition is also pulling the strings of the rule-makers. What’s really needed is a people’s crusade to change the political landscape of our fair nation.

    • neroden 3 years ago

      It looks to me like it would take 2 to 4 years to pay for itself. Quick ROI.

  3. Rod 3 years ago

    Thanks Giles,
    I saw the notice on the NEM website and my first thoughts were WTF? and you have confirmed my suspicions.
    If this had been in place during our one in a hundred year storm last year we may have averted the system black but I have my doubts.
    To have curtailment for every time the wind reaches 35KM/h is ludicrous.
    The other effect this has is ensuring spot prices stay high.

  4. Peter F 3 years ago

    So now the logical thing for the wind generators to do is to install storage either collectively for pumped hydro or individually for batteries. Then the power which has zero value can be sold later for $150-300/MWhr. Once they have even 30 minutes at 25% of generator rating of batteries installed they can participate in the FCAS market. That alone would make a significant contribution to the cost of storage then price arbitrage will rapidly become profitable. In low wind times they could even charge their batteries from must run gas or coal plants. Isn’t that delicious wind plants making a profit on gas generation.
    Then with synthetic inertia and batteries the requirement for synchronous gas plants will be relaxed

    • George Darroch 3 years ago

      I wonder: should wind generators be buying hydro generators?

      • Peter F 3 years ago

        or the hydro generators buying wind farms

    • neroden 3 years ago

      Yep. With batteries the wind farms can stay under the arbitrary limit and flood the grid later when electricity is more expensive.

      Instead of the gas generators being shut off during the wind peak hours, they’ll be shut off afterwards — during the more expensive hours. This should be even worse for gas generators.

  5. John Saint-Smith 3 years ago

    So, once again the trogs will blame renewables for the added cost of electricity in South Australia.

    This game is so stupid, it’s a good thing the fate of the planet doesn’t depend on the outcome….

  6. Paul McArdle 3 years ago

    Thanks Giles (and Dylan),
    The increased incidence of constraints on wind farms in the past 6 months (in SA – but not VIC, NSW or TAS I think) will have contributed to the amazingly low output seen in June I noted last week here:
    Will post more analysis on WattClarity as time permits.

    • Rod 3 years ago

      I’ve been watching SA in particular and we have had our second lowest rainfall for June and lots of sunny and calm days.
      Great for riding the bike or rowing but not good for a State with a high percentage of wind generation and an election on the horizon.

    • BushAxe 3 years ago

      SA had very little wind during June (and rainfall as Rod mentioned).

  7. Malcolm M 3 years ago

    AEMO need to explain what their pathway to resolution is to this constraint, and whether batteries will be tested in the same way as spinning turbines. There was an ElectraNet/AEMO project to increase the SA/Vic inter-connector capacity via Heywood to 650 MW, but it is still constrained by AEMO to 500 MW from SA to Vic. Will this project ever be delivered as promised ?

    • BushAxe 3 years ago

      The Heywood upgrade was completed last year, but after the September blackout the inter-connector is limited to 500MW. I agree that AEMO needs to come up with something fast as this is just another rule the incumbents can exploit and with Hornsdale 3 and Bungala Solar coming online the 1200MW limit is unrealistic in the long term.

  8. Malcolm M 3 years ago

    A few hours before the constraint was imposed, the price forecast on the AEMO website was for a spot price of -$45 from about 2 am to 5 am. However the actual price was around $90/MWh. So the wind farms that were not constrained would have done well out of it.

    • Rod 3 years ago

      Can’t have negative prices can we.
      I’ll bet the FF generators saw that forecast and reached for the hot line.
      Wind in SA at about 1000 MW as I type and $117/MWh. Where do I buy shares in a wind farm earning those numbers.

  9. WR 3 years ago

    What was the reason for the policy change? Has the AEMO lost faith in their management of the interstate transmission lines?

  10. WR 3 years ago

    Storage isn’t really the answer here. This is an event that is going to happen only a few times a year at current wind capacities. So the storage wouldn’t see much use and would therefore be very uneconomic until wind and solar capacities increase by a fairly large margin.

    The current storage tender for SA is basically the equivalent of a peaking-plant that will rarely see use. It is intended to provide extra electricity for evening peaks caused by heat-wave conditions in summer. During the heat-waves, there is very little wind-generated power. So the proposed 100 MW of battery storage is almost certainly going to be recharged primarily by gas-generated electricity during off-peak, late night hours following the evening use.

    • Rod 3 years ago

      1400MW (wind) installed atm. Curtailment at 1200MW and restrictions on the interconnector will combine to make this a regular occurrence.

      I”m not sure where PV sits in all this but as we have seen, voltage excursions that disconnect every rooftop PV system causes serious “curtailment”
      Maybe we will have wind curtailment when the sun is shining too much!

      The various large scale tracking PV coming on line will eat into that Summer evening peak.

      • WR 3 years ago

        To get a return on investment, you want the storage to be charged and discharged 250+ times a year. Wind power is never going to produce that pattern of use.

        Instead, storage is best suited to complement large amounts of solar capacity where you can guarantee there will be excess supply most days while the solar is generating and excess demand most nights while the solar is dormant.

        • Rod 3 years ago

          Agreed, wind excess or more suited to pumped hydro.
          At least the sun comes up every day.

        • neroden 3 years ago

          Really? I’m pretty sure wind does produce that pattern of use. There are a lot of places where wind peaks in morning and evening and lulls at noon and midnight.

      • Greg Hudson 3 years ago

        Why would they restrict the interconnector? Victoria needs all the extra power it can get !

        • Rod 3 years ago

          One of the issues during the SA system black was the interconnector was near it’s limit. When the transmission lines from the wind farms were knocked down the loss of generation caused the interconnector to trip. Leaving some room to move is deemed necessary by AEMO to avoid a similar event.

    • neroden 3 years ago

      Storage is really the answer here. With over 1400 MW of wind installed and an arbitrary curtailment at 1200 MW, storage becomes quite obviously valuable to any wind farm owner.

      The electricity to fill the batteries is literally free — it would have been curtailed otherwise. At Tesla’s prices, for 10 years the cost per kwh delivered from the batteries would amount to US$50 – US$70 / Mwh. At Australian grid prices over AUD$100/Mwh, this is definitively and indubitably profitable.

      Of course, with all the wind farms having batteries, they will be “baseload”. So much for gas generators.

  11. Mike Dill 3 years ago

    As I have said elsewhere, a wind farm operator should build a small (50MW)
    peaking gas generator with a lot of storage near a load center. Buy the curtailed power for
    almost nothing, sell it as part of a ‘gas generation plant’. Probably need to have 4 hours of gas on hand just to prove that it is a ‘gas generation plant’

    • Miles Harding 3 years ago

      It’s putting the cart before the horse in that this level of backup is only needed as the 100% renewable point is approached, say around 2040.

      In addition to gas peakers (which will also burn just about anything) this future point will be characterised by an entire spectrum of options and strategies, such as demand management, deferral or curtailment, some bio-liquids, pumped hydro, batteries and an over-build renewables to feed the storage and reduce the times when fuel is required.

      We have 25 years to get there, which is difficult and won’t be achieved with these trolls under every bridge.

  12. Nemo 3 years ago

    Am I wrong in reading this as AEMO forcing gas online to ensure no spikes of $1000+ plus, the problem is to get those plants online you need to get over their SRMC which is about $110-130 with current gas prices. So, net net AEMO has railroaded AGL et al into selling caps into the market at $50 in exchange for reduced silly buggers on gaming auctions?

  13. neroden 3 years ago

    So this is basically a direct subsidy to gas generators, to keep them running when cheaper wind is available.

    Disgusting. Hopefully enough batteries going in will make this sort of nonsense non-viable.

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