I'm not sure I understand, in what system would this not happen?
You can say that the goverment should store the extra electricity but that's not as easy as it sounds. Most things need very specific geographical or technical conditions for pumped hydro, compressed air energy storage, boreholes, hydrogen, molten salts.
If you have a way for consumers to bid for zero-price electricity, there are many things that can increase demand now and give reduced demand later when prices are higher. Everyone has a domestic freezer. If the freezer is smart, when prices reach zero, it can switch on and decrease the temperature another 10C. When prices are higher, it won't need to run as it warms up slowly. Similarly with domestic hot water - just run the temperature up another 10C. People are creative: if you given them intermittent free electricity, they'll find a use. The main problem though is that this reduces demand when prices are above zero. While this is good for the environment, it's not good for the electricity industry.
How much money does it cost to build this out to every house, compared to what it saves? And do people want their electricity prices to vary over the day? If you have a lower cost part of the day then you have to charge more the rest of the time, all else equal.
These spot price contracts for end users do exist in many places (don't know about SA specifically). They haven't been particularly popular; I guess most people are scared about the other side of the coin, will I accidentally drain my bank account if I do my laundry when prices are at the roof limit?
It probably works best when you only have some sockets in a home that are on spot price contracts. And on those sockets, you have plugged in a washer/freezer/AC that is smart enough to receive spot price information and turn on and off as prices rise or fall. We're not quite there with all the pieces of the puzzle, but it's all technically possible now and likely much cheaper than using batteries to load-shift.
If you suppose a well-designed grid, I really doubt that free electricity is something that clients would refuse. Electricity is valuable, at any time of the day. There is no reason for it to go below zero.
Sure, storing energy is hard but spending it is easy.
Hell, give me free electricity and I will be running a pyrolysis rig, making biofuel for free.
No, it's not always valuable. If you get free electricity for an hour, some days of the week, then your giant biofuel plant spends a lot of time sitting idle.
It's not obvious that your mostly-idle plant is a better business than a much smaller one which runs all the time. The costs of building and maintaining the thing are real too. (Not to mention needing to design the plant to ramp up to full production in minutes, while a more traditional one might spend a day warming up all the pieces to operating temperature.)
> It's not obvious that your mostly-idle plant is a better business than a much smaller one which runs all the time.
This process is usually not profitable because of the energy cost it requires. This is why I am proposing it as a way to absorb energy surplus. But I am only talking about what would happen if you got electricity at zero cost. At negative costs, even crazier things would happen.
The reality, is that, to my knowledge, the Australian grid does not "sell" electricity for negative prices, it only "buys" it. If it were to pay clients to absorb electricity, I would just dissipate heat in well ventilated radiators, make a ton of steam, and make a show of giant tesla coils. Radiators can be made out of scrap metal, it really is a small investment that can lie dormant at no cost if negative electricity prices only happen 5% of the time.
Could you please show the calculation of what it costs to build and maintain such a scrap metal radiator thing, and how much money you would have made with such a device over the last 12 months?
There are economic involved. Long term, it pays to have many variable load generation in the grid, because they are cheap and environment friendly.
But a net needs to be handled exactly to match supply to cost, and demand has a large random component that no-one foresee perfectly.
Hence, negative prices are a normal feature of balancing demand and supply, which is a technical necessity not to have black-outs and brown-outs or, in this case, damage expensive base-load powerplants during emergency shut-downs.
