Graph of the Day: How AEMO saw rooftop solar in heatwave

Last week’s heatwave sparked a huge interest in the role of renewables, and in particular solar, in dealing with the huge increase in electricity demand as consumers across the southern-states flicked on the air-conditioning.

RenewEconomy was one of the first to point out how solar had stolen some of the revenue, and a little of the thunder, from the fossil fuel generators by making a significant contribution to day-time demand. This was followed up by an analysis from the RAA, which suggested that wholesale electricity prices were just a fraction of the similar heatwave that hit the (then largely solar-free) southern states in 2009. It drew on some fascinating graphs from the APVI.

Mainstream media, on the other hand, swallowed the line from the incumbents that the only criteria on which solar and wind should be judged was its ability to meet peak demand. Apparently, they said, not very well. This ignored the fact that solar (and wind) had helped to shift those peaks, and reduce overall need for peaking plant. This was well described by CEC deputy CEO Kane Thornton in a piece in the AFR this week.

But what did the Australian Energy Market Operator really see? The same thing as the APVI? RenewEconomy put the question to AEMO last week. It has taken six days – testimony to the difficulty of estimating the output of solar PV consumed behind the meter, but we finally have an answer.

These tables were sent to RE yesterday. They give a snapshot of the output of rooftop solar PV in South Australia and Victoria, the states hardest hit by the heatwave, over five days from January 13-17.

At 1pm, the solar systems in the two states were contributing up to 600MW, and always well over 500MW, before easing down to around 350MW (and a high of more than 400MW) at 3pm.

On two of the five days in Victoria, solar PV was contributing roughly two third of its 1pm output at the time of the maximum peak – at 3.30pm. That is the equivalent of several smaller gas peaking plants, which did not have to be switched on. The same thing happed in South Australia. On other days, the maximum peak was punted to the early evening.