Case Study / Generators
Automated negative-price curtailment for a 5MW solar farm
A 5MW South Australian solar farm exposed to wholesale spot pricing was paying to generate whenever the spot price went negative — until automated curtailment removed the exposure entirely.
Snapshot
No human in the loop
The system monitors the live market, curtails the plant when generating becomes uneconomic, and restores full output the moment it isn't. The owner sets the policy; the system executes it around the clock.
Highlights
The challenge
Context and operating problem
The farm operates in South Australia — the region with the highest negative-price occurrence in the National Electricity Market, where negative spot prices now occur in more than half of all daytime dispatch intervals, and in some quarters nearly nine in ten. An uncurtailed solar farm in this market pays to generate for a substantial share of its producing hours. Manually watching the market and curtailing the plant was not a viable operating model.
The solution
How Autonomy Power helped
Autonomy deployed a control system that continuously monitors the wholesale market and automatically curtails generation when running the plant becomes uneconomic — then restores full output the moment it isn't. The trigger is not a simple zero-price threshold: the system calculates the farm's true net revenue per megawatt-hour, factoring in both the spot price and the value of large-scale generation certificates, and curtails only when generating genuinely costs the owner money. A flat zero-dollar cutoff would shut the plant down too early and forfeit certificate revenue; the net-revenue trigger captures every profitable interval and avoids every loss-making one.
The threshold also adapts as the market moves. With LGC prices having fallen sharply over recent years, a fixed threshold set two years ago would now curtail at the wrong price — the net-revenue calculation reprices the breakeven every interval, so the curtailment policy stays correct as certificate values change. The owner sets the policy; the system executes it interval by interval, around the clock, with no human in the loop.
The outcome
Operational and commercial result
The farm no longer pays to generate. Negative-price intervals that previously turned the asset into a cost are now sat out automatically, and generation resumes the moment the market makes it worthwhile. Automated curtailment is estimated to avoid costs in the tens of thousands of dollars annually for a plant of this size at current market conditions — converting a manual, unwinnable monitoring task into a standing automated policy.