[JMTQp8lwXL]

An explanation of the mechanics of how I'd have to pay somebody else to take my electricity (e.g., a negative rate) would be helpful.

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.

[apendleton]

Anything you could do it with it would have capital costs. Maybe it's transient enough that that money would be better invested elsewhere. Like, if you only run your cryptocurrency mining when the price is negative, your capital is stuck in an idle asset most of the time, and if you run it all the time, it's the average price you want to consider, not the minimum price (even if the minimum price is negative), and my guess is that Australian electricity isn't cheaper on average than other kinds of power other places (especially places with lax environmental regulation).

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.

[_AzMoo]

> and my guess is that Australian electricity isn't cheaper on average

South Australian electricity is actually some of the most expensive in the world due to incredibly high transmission costs.

[jussij]

Historically South Australia has generally had the most expensive electricity in Australia.

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.

[londons_explore]

Multi-megawatt electric heaters don't cost much. In fact, I could make a backyard megawatt power sink in an afternoon for just a few hundred bucks. 1 mile of 22 AWG bare copper wire strung through the air should do the job. When turned on, watch the whole lot glow red hot like a big space heater.

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.

[solotronics]

There are older bitcoin ASIC miners that aren't nearly as efficient but if you are getting totally free electricity... definately an opportunity here.

[bseidensticker]

Yes this happens.

[iknowalot]

Yea shutting off anything that is producing free electricity to keep a market price stable is moronic....

[Leherenn]

It's not to protect market price, it's to protect the grid. You basically need to use as much power as you produce, if this becomes imbalanced, you damage the grid.

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.

[manicdee]

Executive Summary (drastically oversimplified):

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.

[JMTQp8lwXL]

Why do they have to pay someone to take the electricity? I could take a dollar bill and rip it in half (perhaps not legally, but besides the point). I understand there's costs to shutting down a system. So, they might keep it running.

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?

[donw]

I'm going to hazard a guess.

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).

[peteretep]

> that's enough to boil an Olympic-sized swimming pool in about 25 minutes

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?

[flukus]

More desalinated water would be handy, but typically it's not needed anywhere near the salt water and where it is needed more electricity isn't.

[mcv]

So use the energy to pump the water to where it is needed. Use it to generate hydrogen or methane or something to sell as fuel. Mine bitcoin even. It seems weird and wasteful to just shut off free energy.

[donw]

But can't those plants just pull from the (now cheaper) power on the grid?

[hanniabu]

> Dumping that kind of power is... hard.

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.

[teraflop]

Because that nearby neighborhood already has enough power being generated to meet its demand. You can't just send the power somewhere without either increasing demand or reducing other suppliers.

[hanniabu]

> reducing other suppliers

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.

[Scarblac]

What, how? Increase the voltage and damage people's electronics?

[viraptor]

Not at that levels of output. With large enough machines it's "we're going to spend X to spin everything down, do maintenance checks, spin back up" vs "we're going to pay you X/2 so you take the output and we can keep going". The X may be spent on extra workers, on extra maintenance, on replacement for posts that wear out faster, etc. It's the cost of unusual operation.

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.

[Udik]

This makes me wonder how do you stop generating with a solar farm that is made of PV panels. They're entirely passive, right? The light hits them and they output electricity. How do you stop them?

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?

[imtringued]

Photons excite electrons. If a photon doesn't have enough energy it will be reflected.

[beachy]

It's electricity. Break the circuit and it stops flowing.

[Udik]

When I stop a turbine I'm not simply breaking the circuit- I stop converting some fuel into energy, and keep it for later. If I break the circuit on a solar panel, the "fuel" keeps hitting the panel anyway. I guess the panel just reaches a different thermal equilibrium. Which is the same as dumping the energy in the ground, only more distributed.

[gumby]

Some baseload devices can’t really be realistically switched off. Some of these turbines run for decades.

[james_s_tayler]

If I remember correctly there are rules that the estimated demand and actual generation have to match pretty closely and the overage can only be within a few percent tolerance. You're not allowed to just generate electricity that there isn't demand for.

[taneq]

1. Energy can neither be created nor destroyed.

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.

[iguy]

Those giant cooling towers that are most people's image of a power station are almost exactly this. They are a giant system for dumping heat into the air, usually (but not always) by evaporating water.

(The heat being dumped is usually low-temperature waste heat, not final output.)

[taneq]

Those giant cooling towers are pretty expensive and the water to run them can cause significant damage to the local ecosystem if it raises the temperature of whatever water body they draw from. It's a lot easier to just turn off the energy sources (such as solar) that can be turned off without ill effect.

[iguy]

Sure they are expensive. That's why the coal plants are willing to bid a negative price for their power, to have someone else deal with it. Rather than paying to build another tower.

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.

[Scarblac]

No, electricity can't be routed to nowhere, that's not how the grid works. The amount produced and the amount used have to stay in balance.

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.)

[steve_gh]

And what happens when a solar farm goes bankrupt? Its major operating overhead is servicing the loans for the initial capital cost. So all that will happen is that the bank will take possession of the solar farm. It will still be producing cheap power, and it will now be owned by an organisation with very deep pockets!

[glamp]

On the grid there are lots of different types of producers (solar, diesel, wind, nuclear, etc.). Each has its strengths/weaknesses. A big weakness of nuclear plants is that it's very expensive to turn them off. So much so that when electricity demand temporarily goes down (and with it prices), it is actually more profitable for them to continue keep the plant running but pay someone to offset their excess production.

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.

[dv_dt]

The problems are also not always technical. In CA I've read articles with descriptions of similar moments where power needs to be shutoff from renewable sources and/or offloaded from the grid, but in part because contracts locked in priority for some fossil-fuel peaking plants over renweable sources.

[droithomme]

> An explanation of the mechanics of how I'd have to pay somebody else to take my electricity (e.g., a negative rate) would be helpful.

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.

[wisdomdata]

South Australian here - In South Australia keep in mind commercial scale solar is also generating against residential rooftop solar which is sold back via a feed in tarrif to the generator at a contracted fixed rate. The generators have to pay for (and take) this power. In some cases 20 year contracts where signed some time ago with feed-in tariffs much higher than what they ever should have been. This has resulted in early adapters making thousands in cash every year from residential solar (and still doing so). Everyone else is paying for it of course. Feed-in tarrifs available for contracts signed today are much lower, but some of these contracts still have a few years to run. Without more storage solar will continue to reduce reliability and add costs.

[DevoidSimo]

People do, we have snowy hydro who normally correct these negative prices by pumping water uphill into a dam. They then double dip on profits by generating when the cost is positive. Very profitable operation although the initial infrastructure cost is high.

[lugg]

The grid needs to maintain supply within certain levels.

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...

[pabs3]

The article mentions there are pumped hydro projects that could be used soon and others that are coming online. OTOH perhaps you are talking about smaller-scale pumped hydro on individual farms with access to enough water. I suppose the viability of that would depend on how easy it is for the farms to access real-time prices and turn on the pumps based on prices.

[Terretta]

> convert it back to electric when it's needed

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."

[nabla9]

It happens when high inflexible power generation meets low demand. Some power sources can’t be shut down and restarted in a quickly and cost-efficiently. If the cost of stopping and restarting their plant is higher than the costs of selling energy at a negative price for some time, prices go negative.

[ramraj07]

Did you read the article? It goes into reasonable detail on why they don't necessarily do that.

[wyxuan]

Can’t they discharge it for free? Why do they have to pay to send it into the grid?

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

[steve19]

The grid has to finely balance supply and demand. You can't just dump power into the grid. If you did the grid frequency would increase out of spec and it could damage connected equipment and machinery.

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.

[thaumasiotes]

I think the dominant question here is, "I have this machinery that produces electricity, and it's hooked up to the grid. Why can't I also hook it up to the ground, and -- during periods of negative prices -- send the electricity into the ground instead of the grid?" Nobody charges you to ground your wires.

[duckymcduckface]

The ground is a poor load and also there's a finite amount of energy you can dump into it because every watt that goes in gets turned into heat, you'd liquify the ground very quickly at the multi MW scale.

[qiqitori]

Well, I don't know. Let's think about how you would turn off solar panels. I remember hearing about solar panels (~10 years ago?) that would actually break under very-sunny-but-zero-load conditions, so I did some research using queries like 'solar panels without load' and am led to think that this isn't usually a huge problem (with regular/modern panels?). But physically speaking, unless you cover the solar panels with a blanket, the amount of incoming sunlight won't decrease, and when you aren't turning that into electric power, it'll turn into some more heat.

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.

[seized]

Likely if they need to most of them can turn the panels away from maximum sunlight and that would take care of the turning off/full light no load problems. Same with the molten salt tower systems, just just the aim on the mirrors.

[thaumasiotes]

We routinely dump lightning bolts right into the ground and they go well beyond multiple megawatts. They're very brief, but if lightning took ten seconds to strike, it would still provide several dozen megawatts of power. How quickly would we be melting the ground at the multi-MW scale? How many lightning bolts would it take before the ground around my house melted and flowed downhill?

[Scarblac]

Lightning bolts do in fact melt the ground (see fulgurite), and they take at most about 0.2 seconds.

[eecc]

Yes very localized and for a very short amount of time and most of the energy radiated away into the surroundings, including the atmosphere

[swinglock]

At that point, isn't it cheaper, safer and easier to turn off the machine? The machine being on has no value, only producing energy being consumed on the grid has value.

[thaumasiotes]

The value of the machine being on is precisely that you avoid the costs of turning it off and then turning it back on. Those can be considerable, depending on what machine you're talking about.

[coin]

How does excess electricity impact the frequency?

[zAy0LfpBZLC8mAC]

It's not really excess electricity, but excess energy, and it's an artefact of how traditional power generation works: You generate electricity by creating rotation and using that rotation to drive a generator. Now, it's basic physics (conservation of energy) that if you add energy into a rotating system, it will spin faster and faster with every bit of energy you add, because the energy is transformed into kinetic energy of the rotation. The only way to prevent that speeding up of the rotation is to take energy out of the system--which, in the case of an electric generator you would usually do by connecting it to an electric load, i.e., the grid. But if demand is too low, you are removing energy from the rotation at a lower rate than it is added back from the mechanical drive side, so the net energy in the rotation increases and thus the speed of the rotation increases and thus the frequency of the electricity output increases.

Essentially, electric load is what brakes electric generators, if you take off the brakes but keep the motor running, they'll speed up.

[eecc]

My guess is that load acts as an inertial mass that adds drag to the turbines. Think of cycling downhill at the same power used when going uphill: you’ll spin like a crazy fool

[jonathonadler]

I thought voltage needs to increase because a differential is required to add power to the network.

[eecc]

Hmm has anyone experimented with variable frequency transmission and solid state frequency synthesizing power transformers?

[Dylan16807]

So you might be able to increase all the turbines from 50 to 70. That will absorb the excess power for a moment. Then you're maxed out and still need to shed just as much power as before.

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.

[droithomme]

> Can’t they discharge it for free?

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.

[dwd]

They mentioned moving water uphill with the Wivenhoe pumped hydro which is about 3000km away in Qld. This is also where the NSW interconnect will help as most pumped hydro is in NSW.

[Iv]

tl;dr: the Australian grid is working on a faulty system because of politics. This is not a technical limitation there.

[synchro77]

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.

So in what system wouldn't this happen?

[mhandley]

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.

[Dylan16807]

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.

[jabl]

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?

[mhandley]

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.

[perilunar]

> 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.

[Dylan16807]

Be specific. How would it work differently? (Assume the designer of the system is trying to deliver reliable power without wasting a lot of money.)

[Iv]

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.

[iguy]

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.)

[Iv]

> 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.

[zAy0LfpBZLC8mAC]

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?

[iguy]

"dissipate heat in well ventilated radiators": you've just invented a https://en.wikipedia.org/wiki/Cooling_tower , often the largest building at a power plant.

[zwaps]

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.