As we’ve briefly noted here on WattClarity, South Australia experienced an extended period of high prices last night, as historically high temperatures drove elevated market demand to within a couple of hundred megawatts of the region’s long-standing demand record.
Whilst my to-do list is overflowing after coming back from the public holiday, curiosity got the better of me this morning, prompting an initial look at how the region’s growing utility-scale battery fleet responded through yesterday evening.
Aggregate Stored Energy
In our trends editor widget within our ez2view software, we’ve recently added the AEMO’s new energy storage data field — so in the screenshot below I’ve plotted the aggregate stored energy value across all registered battery units in SA between 4:00pm yesterday and 4:00am this morning (NEM time). It highlights that during this window, stored energy peaked at 1,325 MWh at 17:05 yesterday afternoon (NEM time), prior to when prices accelerated, before rapidly draining through the high-price window to a low of just 66 MWh at 21:45 last night.
Source: ez2view’s Trend Editor widget
This outcome is perhaps unsurprising given that much of the region’s battery fleet contains around two hours of duration, while the period of sustained high prices extended for more than three hours, pushing many batteries toward their energy limits as the evening wore on.
Aggregate Bid Availability
That tightening energy position was evident not just in the aggregate MWh stored, but also in how bid availability evolved as the evening progressed. The screenshot from our Bids and Offers widget below, filtered to South Australian batteries, shows availability steadily declining alongside changes in the distribution of bid volumes. This contraction became particularly pronounced once prices surged to the Market Price Cap at around 8:30pm NEM time (9pm local time), at which point, offered availability fell away sharply.
Source: ez2view’s Bids & Offers widget
The impact was particularly evident at the region’s two largest batteries, with both the 250 MW Torrens Island BESS and 200 MW Blyth BESS becoming unavailable from around 8:40pm NEM time (9:10pm local time) while prices were sitting at the Market Price Cap of $20,300/MWh.
At Torrens Island, availability fell to 0 MW from the 20:45 dispatch interval, with the unit reporting that 20 MWh of stored energy was being maintained. Similarly, Blyth dropped to 0 MW of availability from the 20:40 dispatch interval, while retaining approximately 10 MWh of charge at the time.
Source: ez2view’s Unit Dashboard widget for the Torrens Island BESS (TIB1)
Source: ez2view’s Unit Dashboard widget for the Blyth BESS (BLYTHB1)
This suggests that much of the residual stored energy visible at the low point in the first chart reflects minimum state-of-charge being maintained on site, rather than energy that was genuinely available to the market. However, as we saw earlier in the Bids & Offers view, availability across the fleet never quite fell to absolute zero — as we can see that the Mannum BESS briefly recharged and offered a small amount of capacity again from around 8:30pm NEM time. For most of the remaining high-price window after this point, effective discharge capability across the fleet had largely evaporated until after the period of extreme prices had ended.
Accumulated aggregate state of charge is a good metric.
I expect that when EnergyConnect is fully commissioned the SA volatility will flow into all the other states. Will be interesting to try and track that.
Ben,
Been said before – the state that can’t(SA) will be used to put the finishing touches to those that (barely) still can.
And very high power prices