[ryan_j_naughton]

I agree. Negative prices make perfect sense in electricity markets, and journalism does a bad job at explaining it.

Supply and demand must always be in equilibrium in real time with electricity (forgetting storage / batteries for a second). If there is more supply than demand or vice versa, then you have instability in the grid and can have blackouts. Those electrons have to go somewhere. This is in contrast to virtually any other good where you can store the good in a warehouse and smooth it supply intertemporaly.

Thus, if there is a big drop in demand or it's simply too sunny / windy of a day, there can be too much supply.

To incentivize reducing supply quickly enough, sometimes prices have to go negative. This is in part because some supply simply cannot reduce quickly (e.g. nuclear) and are still happy to operate in zero price situations bc either they have no marginal cost of generation (solar, wind) or the cost of reducing generation and increasing it back up is high (nuclear, coal).

Thus, there simply might not be enough plants that have the characteristics where they can scale down quickly AND have a marginal cost of generation such that they would turn off when prices go to zero (e.g. combined cycle natural gas plants can turn on and off very quickly and don't want to be on when the price falls below the cost of the gas used to generate electricity, but Australia doesn't have enough of them to absorb a supply decrease as prices fall). Alternatively, the subsidies that you mention shift the break even point into negative prices territory.

Either was, negative is needed to incentivize solar and wind to turn off or else there would be a blackout from oversupply.

Thankfully, this all gets solved with energy storage and all the slow, dirty systems that stay on will be priced out by more nimble renewables and rapid energy storage. Bc then that excess supply is stored and arbitraged to higher price times (when the sun isn't shining and wind isn't blowing). Then prices should always be positive (so long as there is available storage). If the storage is full though, prices could again go negative. Without a place to put those electrons, they quickly go from a good to an externality. It's almost like how we'll pay a musician to perform, but if your neighbor is blasting music at 3am. Without someone willing to consume and pay for those electrons, they literally are just causing trouble for all the other electrons that we do want to consume.

It in part why you can't simply just create significant generation and hook it into the grid anywhere without working with the grid operator. AC power, dude. We don't control where those electrons flow directionally. So you adding too much power somewhere can really destabilize the system.

[Reason077]

> "combined cycle natural gas plants can turn on and off very quickly"

Response/ramp times for CCGTs are not particularly quick. Typically they need 15 minutes notice to initial grid synchronisation, a further 60-80 minutes to reach full power output from a "warm" start, and up to several hours from a "cold" start. That's much better than coal-fired plants which need many hours of notice, but still likely to be too slow to respond to unexpected grid imbalances without additional support.

Natural gas "peaker" plants typically use less-efficient but faster responding OCGTs for that reason.

[tremon]

some supply simply cannot reduce quickly (e.g. nuclear)

What is it about nuclear that makes it impossible to reduce as fast as gas or coal? From my layman's point of view, they all use comparable (steam) turbines to power the actual generators, so I would expect them to be equally capable of disengaging the generator from the turbine.

Is this perhaps due to design decisions, or simply a size problem? A foolish question perhaps, but I don't have more knowledge to draw from.

[_ph_]

The nuclear part of the reactor is slow to react to control input. Even when completely switched off it produces hundreds of megawatts of thermal energy. This is what doomed the Fukushima reactor. After the earthquake it was technically switched off, but required a lot of cooling as the nuclear reactions continue to go on even with the control rods completely extended. But with the failure of the power supply there was not enough cooling and the reactor eventually melted. Theoretically it should have been possible to passively cool this reactor, but due to operators mistake, one important valve was in the wrong position for that.

Beyond shutting down slowly, nuclear reactors are even slower to start up again. So after a complete shutdown it can take up to two weeks to put a reactor back into full production.

It is conceiveable to build nuclear reactors which are a bit quicker to ramp up and down - I guess more like the reactors of nuclear submarines, but our existing reactors are not suiteable for that, as this was not a requirement when they were designed. They were designed to be combined with quicker providers like gas and water plants.

[redblacktree]

I don't think you answered the question. The way I read it was "Why can't the nuclear power plant simply vent the steam they create instead of turning turbines with it?" In order to switch off power generation, even if the reactor is still creating thermal energy.

[_ph_]

That could possibly done, but then, no one had created such a design yet. It is also not trivial to cool in the gigawatt range. Actually, many power plants even run into cooling issues in some time of the year, as they often rely on local rives to provide the cooling and the water supply as well as maximum water temperatures (animal and plant live) limit their cooling capacity in normal operations.

In Belgium there were even streetlights being installed along all highways to use up nuclear energy when the grid was not consuming it.

[mikekchar]

So extrapolating from what you said, these negative price events should incentivise energy storage solutions. Which arguably seems to be a good thing for the network. I suppose it should not be a surprise that the use of a thing incetivises the infrastructure necessary to make it more efficient, but it still does surprise me ;-)