The demand profiles on 24 and 25 January are quite different. The profile on 25 January is impacted by voluntary and involuntary load shedding and then the cool change coming through.
Importantly however, it was also affected by the cumulative impact of the hot weather where the minimum overnight temperature was 30 degrees Celsius in the early morning of 25 January.
This means that the air- conditioning and refrigeration load was much higher than would otherwise have been the case in the morning. If we were to add back the impact of the voluntary and involuntary load shedding and adjust for the impact of the cool change, then Victorian demand would most likely have been more than 12,000 MW.
Innovative peak demand policy options for next summer
Roof-top solar PV is making a significant contribution in reducing and delaying peak demand so that the system peak now occurs when the level of PV generation is reduced to very low levels (eg. around 6:00 pm), as occurred on 24 January which might be the more typical profile.
It’s now clear that we need to complement solar with additional demand-side solutions that act to reduce demand in the afternoon and evening. Building extra conventional generating capacity is unlikely to be sensible, given its very high capital cost can only be offset over a very narrow time window, not to mention its carbon emissions and high fuel costs.
It is estimated that the level of rooftop solar PV to be installed in Victoria in 2019 will be 500 MW (Green Energy Markets, STC Modelling Report, January 2019).
Supported by the Victorian Government solar rebate program, we have assumed that an average of 500 MW of rooftop solar PV will be installed each year over the next 5 years. This means that by the end of 2023 a total of 4,000 MW of rooftop solar PV will be installed in Victoria (2.5 times the amount installed at the end of 2018).
To see what Victorian demand might look like under this scenario, we have reconstructed the demand profile that occurred on 24 January 2019. To account for the growth in rooftop solar we have merely multiplied by 2.5 times the actual level of solar generation on 24 January to reflect 4,000 MW of expected rooftop solar (refer to Figure 4).