Solar swing state: From nearly too much grid demand to warnings of not enough in less than a day

On Monday at around 5 pm (AEST), Victoria posted a new high for operational demand for the state’s grid of 9,581 megawatts (MW) in the midst of a record-breaking December heatwave.

Despite having two of its coal generation units off line, the state had little trouble dealing with the surge in demand because renewables were also delivering a record level of output.

Within 24 hours, however, the Australian Energy Market Operator, having spent much of the day issuing lack of reserve warnings for NSW and elsewhere, was back on line issuing a market notice of a different kind: warning not of a lack of reserve but of a lack of demand (minimum system load) for Victoria for Saturday, December 21.

The sudden switch from nearly too much demand to nearly too little demand is symptomatic of the dramatic changes that are occurring on the grid, and one of the fundamental reasons why most energy experts thing the idea of shoe-horning gigawatts of inflexible nuclear power capacity into the grid would be nuts.

The best to deal with such fluctuations, the experts say, is with flexibility – both in demand and supply – and most of that can be delivered by providing incentives to change the times when electricity is consumed, and ensuring fast reaction and flexible power sources, such as big batteries, can be deployed.

The warning for minimum system load cited potentially insufficient demand for Victoria at around 1pm on Saturday, with sunny conditions, high rooftop solar output, mild temperatures and the lack of business activity contributing to low operational demand.

The MSL notices are issued so that the markets can prepare a response. There are various options, but at the last resort AEMO can issue instructions to big batteries in that state (like the Hazelwood battery pictured above) to stand by on empty and get ready to charge – i.e. creating demand – if conditions warrant.

If that fails, there is a solar switch off mechanism, although that has limited application and is not popular, with either households or politicians and is seen as very much a last resort.

The MSL notice from AEMO – like another that was issued in early December – cited a forecast minimum demand of around 1,643 MW. The one issued for December 8 expected minimum load of around 1,250 MW.

This fits in with Tesla’s observations, in a submission to the federal nuclear inquiry, that most states in Australia, including Victoria, would struggle to support even 1 GW of baseload, or “always on” power because of the growing impact of renewables, and rooftop solar in particular.

It has warned that the federal Coalition’s nuclear power plan would result in “severe” constraints on rooftop solar – not just the occasional partial switch off in events like those cited above, but almost on a daily basis to accommodate nuclear power that does not like to ramp up and down.

“Given Australia’s world-leading solar and wind resources, and leading rates of rooftop solar PV, the power system’s minimum operating demand threshold becomes an upper ceiling for baseload supply to operate the power system in a secure and reliable state,” Tesla wrote in its submission.

“Increasing renewable penetration at these times further displaces baseload generation, reducing capacity factors and increasing the cost of supplying energy to consumers.

“The practical sizing of baseload generation is now significantly less than the minimum operating load.”