Another milestone in Australia this week with the last coal fired power station in South Australia closed down. Going to be an interesting experiment moving forward as some are claiming that it's bright light news, others looming disaster. Have been accused of bias before (Tasmania discussion), so will try to even out the spread of information from a couple of directions, however I'm leaning towards the latter outlook. First off, how that place is situated in the Australian grid. Oldish pic below, but it's not really changed that much except in capacity. For reference, Oz is about the same size as the US (excluding Alaska), so you should have a mental frame of reference. South Australia is that bit in the lower middle (capital Adelaide), and is connected to the eastern Seaboard by two interconnector paths. (the dotted line to Tasmania is THEIR interconnector, it's still broken, after nearly 6 months, and they are running diesel gen sets to keep the lights on). South Australia has been installing masses of wind turbines, more than enough nameplate capacity to keep the state running when the wind is blowing. When the wind IS blowing there's often export to the RHS of the country. Wind, being bid in at $0 as it's harvesting energy, and not able to react to the market pushes the prices down when it's blowing. Under very high wind conditions, the prices go negative, with the traditional generators having to pay money to generate (takes about $50-$100k of fuel to fire up a coaler, so brief negatives will be ridden through)...funnily, the wind has been blowing too hard lately at times and they have to get shut down. AC power is a funny thing. Voltage can be raised and lowered through transformers, or generator excitation. Different loads shift the link between voltage and current, the "power factor" is the percentage of the theoretical power that you can actually get out of the volts and amps that you have due to the "phase shift" between them...get the phase shift way out, and the volts and amps available can be completely out of phase and the available power is zero...the big generators (hydro, nuke, coal, big gas) have VAR (volts Amps Reactive) import and export capabilities to fix the power factor locally...can be done grid side with capacitor banks (Static VAR compensation), or synchronous condensers (generators run without a power source). AC does some crazy things over long distances, with things like the Ferranti effect meaning that the voltage at the far end of an energised line can be significantly higher then the voltage at the power end...system design is crucial. Every synchronised generator runs in lock step with each other. Load goes up, and frequency drops, and the generator governors initially compensate and then the controls systems load up and follow. Load drops, frequency rises, governor drops off load, and the control system follows. These wind and solar systems are "asynchronous", they aren't regidly connected to the grid like the big gens are, they are akin to electric induction motors that are driven faster than the grid frequency and thus pump POWER into the grid, but not any of the other things. They require the grid to be there in order to generate anything. Like a "reverse" load, when they power up, the generators see that like a load drop, frequency goes up, and the synchronous machines compensate. Their load drops, frequency drops and the synchronous machines bump their gen up a bit to compensate...Again, these asynchronous machines provide no grid stability features other than power. Sitting in the control room, you can see how this influx of power affects the grid...Units are being ramped up for say the evening peak, then a gust comes through the system and the governor responds down to a frequency event, only to have leave the machine short of target once the gust is gone...same with clouds over the solar farms etc. Now back to South Australia...as can be seen, it's at the end of two long transmission lines that link it to the main Eastern Seaboard of Australia. S.A. had a mix of power sources, gas thermal (I used to fish around their outfall when I was a kid), gas turbine, coal (brown, and a little black) and increasingly now wind. There's been an emergence of diesel generators as the wineries need a reliable supply for their operations, and have installed diesel gens for security, which do get called on at times. Due to the disruption of wind, and the Oz gas price hikes (we are exporting our gas to improve the greenhouse performance of other countries), the gas and coal have become non-viable, and there are mothballed plant all over the place. Northern closed last week. Torrens Island A (gas thermal) is slated for next year, leaving Torrens Island B as the only big machines, mostly on line. The wind blows, and supplies the state with power, it doesn't and they get it from the brown coalers, which include Hazelwood (google Hazelwood power station, it's another story). Go up a few paras on what grids need for stability. The state is losing that capacity at their end of the line. Late last year, the southern most of the two lines was scheduled for maintnance, leaving only a single contingency. The regulator considered the risk of separation of S.A. from the grid was a "credible" contingency, and started to make arrangements with the generators to be able to supply "FCAS" (Frequency Control Ancillary Services with the generators who were able to provide it...bidding war erupted which made those services massively expensive (it's a free market, and opportunity was there, so why not). State DID get disconnected, and frequency was berserk, as the synchronous machines were required to counter the variability in the isolated grid, while being a much smaller part of it...balancing a broom on your finger. (Funnily enough one of the Eastern seaboard generators got slammed financially for the costs of controlling that event even 'though they weren't connected to it). Here's the regulator's report on the event. and to provide balance, an alternate view of the event from a totally unbiased source. . Well last week they've lost another 500+MW of schedulable power at their end. To compensate, another 500+MW of wind is being installed, and one of the interconnectors to the eastern seaboard is getting a 190MW upgrade. Why post all this ? a) to show that it's not as easy as plugging another wind turbine into the grid in Iowa. b) it's actually an interesting experiment happening in real time as to how to decarbon the grid and keep it running. Personally, I see South Australia heading for virtually a state wide blackout at some point in the not too distant future.... Happy if they don't, happy if I'm wrong, but that state already has the highest cost, least reliable electricity in the market.