This is a tale of 3 key numbers, that combine to paint a scary picture for consumers of electricity in the state of South Australia. In short, from 2018, the state will not have enough electricity available to it to reliably meet its periods of maximum demand.
Two of the key numbers are illustrated in the following figure, showing recent data for maximum electricity demand in the state (blue), together with the maximum available dispactable supply within the state (red):
Maximum Demand: 3400 MW
Maximum demand in South Australia occurs during summer heatwaves, and it reached its highest figure in 2011, at a value of around 3400 MW. Recent years have shown lower figures, but this may be due mainly to weather patterns, rather than to changes in consumer behavior. 2015 had 3 summer heatwaves, the first one in early January produced the highest demand, but it occurred during the Christmas/summer holiday period, so was lower than it could have been. There were two additional (2-day) heatwaves in February 2015, but they both occurred exactly at weekends, resulting in much lower demands than they could have done. 2016 had a relatively cool summer. There is no reason why maximum demands of 3400 MW or more will not recur in the near future.
Note that past negotiated demand reductions and rooftop solar contributions are already accounted for in the actual demand data.
Maximum Dispactable Supply: 2000 MW (from 2018)
The figure of 2000 MW is taken from a spreadsheet produced by the AEMO in March 2016; it is what they refer to as “Summer Aggregate Scheduled Generation”, but without the contribution from wind. The drop from the current figure of around 3000 MW is due to the closure of Northern Power Station (coal) in 2016, and Torrens A (gas) in 2017.
It is important to stress that this figure represents the MAXIMUM possible power that can be produced, the actual figure of available power is likely to be somewhat less. I’m no economist, but it seems likely that the dispactable supply is dropping towards the figure that the generators expect to be able to sell routinely; this figure is likely to drop even further in the future as more wind and solar are deployed.
Interconnector Capacity: 870 MW (when the Heywood upgrade is complete)
This is the maximum power that is expected to be available from the Heywood (650 MW) and Murraylink (220 MW) connectors, and is dependent on both of them achieving their design capacities, and on Victoria having that amount of surplus power available during periods of maximum demand.
The availability of 870 MW of surplus power from Victoria must be in doubt at certain times as it too has a maximum demand figure (10,490 MW) that exceeds its maximum dispactable supply figure (10,400 MW).
During periods of maximum and nearly-maximum demand, which typically last for several hours for each of several consecutive days, the deficit of dispactable power will be (at least):
3400 (demand) – max local supply (2000) – max interconnector supply (870) = 630 MW
Renewable sources of electricity in South Australia can sometimes provide 630 MW, but sometimes they cannot, and sometimes they produce essentially nothing, and this will be the case regardless of growth in their nominal capacity. The AEMO produced this plot in 2012 to illustrate the almost total absence of wind during a 2011 heatwave:
Thus, from 2018, South Australia must prepare for power cuts during summer heatwaves.
Demand data from CSV file available here: https://www.aer.gov.au/industry-information/industry-statistics/wholesale-statistics/seasonal-peak-demand-region
Supply data from spreadsheets available here: http://www.aemo.com.au/Electricity/Planning/Related-Information/Generation-Information