Another way to think about it: uses like those you propose that can soak up excess energy in the grid are exactly why energy markets are allowed to float, and even to go negative. If there's a surplus, they want you to use it, and if it were economical to store it and sell it back to the power company later, both they and you would benefit. That this isn't common suggests that it isn't economical.
South Australian electricity is actually some of the most expensive in the world due to incredibly high transmission costs.
The Australian Energy Minister, Mr Frydenberg has even placed some of that blame on the SA Government's and it's "self-inflicted wounds" on deciding to transition away from coal to clean energy.
However, in the article above has there is a link to this page:
https://reneweconomy.com.au/south-australia-had-lowest-cost-...
which states:
The renewable energy state of South Australia recorded the lowest prices in Australia’s main grid in October, a month when it sourced well over half of its it's electricity supply from wind and solar.
That would suggests that transition to clean energy is working out just fine.
The reason people don't do this is that the cost of a grid interconnect (the paperwork, approvals, etc.) outweighs the profit from the very short periods of time the price really is negative.
In this case, demand is lower than supply, so either you decrease the supply (shutting down the solar farm here), or increase the demand (lower the price). Because this is transient, and some powerplants (e.g. nuclear) take time and effort to shut down, for those operators it is cheaper to pay you to use their energy during those times (negative prices), than to shutdown/restart when needed.
In a wholesale electricity market we have a market operator who estimates the demand for the near term future and opens the market up to bids for supply.
Suppliers bid a certain capacity for each period, with the operator typically accepting firm supply offers, contingency supply offers, and ancillary service offers in advance. Since some suppliers are “baseload” (ie: unable to adjust output to suit the current level of demand) they will typically bid low to always be paid for their supply. Everyone else will be affected by these bids because the “baseload” operators are typically not only inflexible but also have huge capacity.
In periods where total demand is low relative to total supply capacity, the wholesale bids will drop to low prices. For the baseload suppliers, they would prefer to pay for someone to use their excess power rather than damage their equipment by either turning it off or reducing output below certain minimums. A baseload supplier might, for example, be facing a maintenance cost of a million dollars versus paying the market a hundred thousand to create extra demand for surplus energy. So rather than turn off equipment they will bid negative prices on the wholesale market.
A second cause of negative wholesale prices is established players with large war chests waging economic war against new entrants. They know solar farms have razor thin margins, so it is worth spending a few tens of million dollars to drive the solar farm bankrupt. Enough negative pricing periods during peak solar capacity means the solar farm is not making any money. If the baseload operator knows roughly the breakeven point for the solar farm, they will know how much they have to spend in order to shut the solar farm out of the market and bankrupt them. There are no rules against this kind of activity in the Australian energy market.
But what I don't get: the electricity producer has to pay someone to take the excess electricity off their hands? The producer can't route the excess to, well... nowhere?
If we assume the numbers for a sort of medium-size nuclear plant, we've got a total power generation of 500MW.
Dumping that kind of power is... hard.
If I haven't missed an order of magnitude, that's enough to boil an Olympic-sized swimming pool in about 25 minutes (500MW to boil 2.5ML of water, assuming STP).
So you'd either need to build and maintain the infrastructure to burn that kind of energy when it isn't needed (not cheap) or just sell the power at a loss (likely cheaper).
This is in a country that — as I understand it — could definitely do with more desalinated water. How capital intensive can putting a huge kettle element in the sea with something to catch the vapour be?
Why not route it to a nearby neighborhood? It's free it doesn't matter if a lot is lost in transmission and you don't need to pay somebody to take it.
This would be the case, what's wrong with this? It's better than paying people to take your electricity and isn't this how business works? I don't see why they shouldn't be able to increase supply (And hence reduce other suppliers) just because it would ruin the profit margins of others. Unless there's something I'm missing here or not following correctly.
And once you're generating there's no great way to just "disconnect" in many cases. If you disconnect the load, the charge still has to go somewhere. Preferably not into nearby equipment. Even the safety switches are non-trivial when dealing with high power - if you break a cable connection, the electric arc will still keep them connected.
I guess the process is somehow invertible, and once reached a certain static charge each panel stops absorbing energy?
In which case you're sort of already dumping the (non)produced energy in the environment- as heat, on each single panel?
> Electric power is the product of voltage and current. If there is no external circuit, there can be no current and thus no electric power can be delivered by the panel, i.e., the "electricity" is never developed and thus, there is no need to consider "where it goes".
There's also an interesting discussion in the linked post in more depth about electron hole-pairs.
My takeaway is that the temperature in the panel will not rise due to it absorbing any power that would otherwise go down the wires were the circuit complete.
"The equilibrium temperature of the connected panel should be slightly lower than the disconnected panel, because those hole recombinations introduce heat. But the efficiency is only something like 12% to begin with. So the temperature difference isn't like the difference between a white and black surface. More like the difference between a dark and slightly darker surface"
In practical terms the energy has to go somewhere. Maybe they could build massive dump resistors to burn off the energy that way but doing so would only increase load on everything (shortening component lives) for no gain.
(The heat being dumped is usually low-temperature waste heat, not final output.)
The negative bids aren't coming from suppliers who can easily turn off, they have already turned off at this point.
And, cooling towers don't work by pumping hot water back into a lake. No need for a tower for that. They work by evaporating it, which lets you dump both the heat up to 100C, plus the latent heat of liquid -> gas.
There is a bit of leeway in that turbine power stations will run a little bit slower or faster depending on exact use (resulting in a grid frequency a little bit faster or slower than 50Hz) but the difference has to be made up quickly.
(not an expert, this is badly remembered from Internet articles so probably hurts to read for real experts, I'm sorry. But I hope I got the gist sort of right.)
There are people that arbitrage this--moving water up a hill is actually how many of them do it.
This stuff is really confusing. My brother trades electricity and has explained it to me numerous times and it's still a little fuzzy.
Sure. Let's say you have a million people producing a glut of electricity on sunny days from 11am to 2pm, when there is not a lot of demand. So there's massive overproduction and you need to create a financial incentive to incentivize the overproducers to pull back. So you have negative rates. It's as simple as that.
How much you can charge has nothing to do with your cost. Your amortized cost of providing excess power every sunny mid-day might be extravagant. That is no matter as far as the market is concerned.
Solar energy production still costs a lot. But there's tons of articles claiming that it's now cheaper than pretty much every other energy source. Yes, it's cheaper to buy at noon in sunny areas during some months because of economics. That doesn't mean it's cheaper to produce and supply though.
If you produce more than your share, someone else needs to shutdown.
Shutting down certain power sources (e.g. coal) comes at a non zero cost. Someone still has to pay the power plant that needs to shutdown or send people home unexpectedly. These plants might be have pre secured contracts to sell at a given price over a given time period further adding to the cost of shutting off their supply.
Some more info here:
https://www.epexspot.com/en/company-info/basics_of_the_power...
FTA: "Tailem Bend is also considering a battery storage..." and links to https://reneweconomy.com.au/tailem-bend-solar-farm-officiall... which adds "Vena Energy also has plans for a Tailem Bend Battery Energy Storage Project."
The crypto one won’t work because there would only be free electricity half of the time, and the water idea is good but it takes immense capex and time to make
Water storage would only work if there is a steep mountain or big hill nearby.
Another way to look at negitive pricing is the grid is paying industrial users to burn as much power as they can.
If your solar panels are on an open circuit with no way to generate electric power, I guess the amount of heat produced in the panels would be roughly equivalent to the heat produced by other dark objects -- which may or may not be too hot. If you keep turning the sunlight into power to route some of that energy into the ground, that may be a lot if you're doing that in a single spot, but I don't think it would be impossible to come up with a workable grounding system.
That said, I'd be very interested to hear how a large solar farm like this turns off their panels.
Essentially, electric load is what brakes electric generators, if you take off the brakes but keep the motor running, they'll speed up.
So it doesn't help in any significant way, you have to set up a more complicated grid with very expensive transformers, and it requires you to design all your turbines to be twice as strong.
Yes they can and should and that's why they have to pay since there is a mitigation cost to handling the excess.
> Why do they have to pay to send it into the grid?
Because it's bad when there is a glut of overproduction.
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.
So in what system wouldn't this happen?
In any system designed by half-competent engineers, instead of by politicians who hate renewable energy for ideological reasons.
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.
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.)
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.
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.
As prices approaches 0, I could take the excess electricity and say, mine cryptocurrency. Is nobody considering the arbitrage opportunities here? Take the 0-cost electricity, move water up a hill, and convert it back to electric when it's needed, etc.