Graph of the Day: Rooftop solar is eating big solar’s lunch

Queensland has more solar than any other state in Australia, but it seems that even in the Sunshine State not all solar is equal.

This fascinating graph above – courtesy of NEM Review and sent through by Energy Insiders co-host and ITK principal David Leitch – shows the output of large scale solar farms in Queensland so far in October.

Normally, the output of large scale solar should resemble a reasonably flat dome, with a consistent peak in the midday sun, but something has taken a big bite out of its production profile, and it’s not a big cloud that appears at the same time each day.

It’s actually because large scale solar is struggling to find room in the grid. Rooftop solar – there is more than 4GW of it in Queensland – takes up a lot of daytime demand, and prices regularly fall below zero as coal generators compete and bid prices low to avoid being switched off.

Most large scale solar farms have contracts with other parties that require them to shut down when the prices go below zero. And that seems to be what is happening. Over the month, the peak in large scale solar output is around 4pm rather than the middle of the day.

According to Leitch, the average pool price for utility scale solar in Queensland so far in October is $4.90/MWh.  It’s actually worse in Victoria, where the average price so far this month is minus $8/MWh.

More storage will help address that issue. Queensland’s first big battery is now going through commissioning, and Genex is building the Kidston pumped hydro plant in north Queensland and another big battery at Bouldercombe.

The only main storage facility in Queensland right now is the Wivenhoe facility, but one of its two turbines is off for maintenance now. In Victoria, the biggest battery in the country, the 300MW/450MWh Victoria Big Battery is going through commissioning after a delay caused by fires in two of its Tesla Megapack containers.