Monday, March 2, 2020

A Frequency Control Ancillary Services story

Frequency Control Ancillary Services (FCAS) has not been the hot topic in public discussions of the electricity sector, but recent events in South Australia made "Don't Forget About FCAS!", by Allan O'Neil at WattClarity, the most interesting article I've read in some time.

The grid in South Australia has one major interconnector to another grid, which was taken out of service by a storm on January 31st, 2020, essentially "islanding" the state's system. I first noticed discussion on events from a tweet listing generators (mostly wind) that would be "ramped down and constrained to zero" when "operational demand in South Australia falls below 800 MW". Operational would mean demand from the grid, which in South Australia is lessened significantly during the day as 1 in 3 houses are reported to have solar panels. For perspective, average consumption in the state is less than 1400 MW; demand following below 800 MW has been rare but occurences are growing (now 200+ a year).

The state was better prepared for the loss of transmission the year than it had been in 2016, when it suffered a full blackout. In part driven by changes made after the 2016 blackout the state has become a net exporter. Operational system peaks have been around 3,000 MW (now occurring after solar's productive hours), and the state's gas capacity  (~2700 MW) is capable of meeting about 90% of that. The state also has about 2,700 MW of wind capacity, so stories coming out claiming the state survived the loss of the interconnector include phrases like "renewables saved the day" - although we know many wind generators were constrained off, natural gas climbed to 60% of production (it's usually about 50%), and demand wasn't high (averaging ~1,250 MW).

All sorts of interesting aspects to be explored, but for me the most interesting was this: during the loss of the interconnector FCAS became more valuable in South Australia than "energy" (the production from generators).

There's something in the Watt Clarity article for many different audiences - including battery performances from both the large grid-connected units and the appearance of FCAS being provided by aggregators of residential units.


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