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Generally the voltage is a bad signal for grid load, it varies from too much from one part of the grid to another. It makes to have a safety cut-out if it goes too far out of bounds, but if it trips the grid is likely already quite over-supplied and other problems have happened first.

The main signal that's generally used to evaluate grid load is instead the frequency: it's the same everywhere on a synchronous grid, and because of inertial generation it will increase when there's more supply than demand, and decrease when there's more demand than supply, and that's what grid operators monitor to adjust the supply to meet demand.

Though it's worth noting, there's nothing that fundamentally stops an inverter from emulating an intertial generator: solar panel inverters can smoothly output anywhere from 0 to 100% of the power available from the solar panel (the remaining energy just gets dissipated as heat inside the panel, which doesn't harm it since it's at most an increase equal to the efficiency of the panel in the first place). A grid which has enough spare capacity in solar panels could operate stably off of them alone, while there's enough margin, if enough of the inverters were doing this emulation (OK, it would be slightly more complicated, you would still need some central control of generation to keep power flows balanced in the grid)

But in general home solar inverters don't implement this, there would still need to be some standardisation on how the grid controls them, and you probably still want some battery storage anyway as they can do it much more efficiently (solar inverters doing this emulation would necessarily not be running near 100% output), and it may be cheaper and easier to mostly delegate it to them.

The plan here for urban Australia is a lot more battery parks and a lot more peak solar supply usage via smart grids and industry:

    According to Ms Hunt, building more batteries to cope with the surge in solar was only part of the solution to the minimum demand problem.

    She said another, arguably better option, was to increase demand for electricity during the middle of the day when solar output was highest.

Currently there's effectively near zero of the supply going toward transport energy; there's barely any electric vehicles compared to the fossil fuel vehicle numbers.

Ideally in the coming decades Australia sees a majority of EVs that are largely being charged durk peak solar supply hours.

> The plan here for urban Australia

I'm not sure they have a concrete plan beyond "don't shut down the fossil generation until we have installed a replacement". Yes, currently they hope an huge uptake in EV's will make a lot of battery capacity available. Maybe it will. But right now, EV's with V2G are a rarity. If that doesn't work out, then maybe will be using a lot of the sites the Uni of Melbourne identified for pumped storage. (I'd be a lot more comfortable with that if they were subsidising building a few small ones to see how it worked out.). Or maybe all those transmission lines they are saying they need will save the day. Or maybe flow batteries are the go.

I'm pretty sure their crystal ball isn't much better than ours. If they have a plan, it looks to "let the capitalists build what they see fit, and if it doesn't work the market will correct it". They probably don't have a lot of choice in that, but letting that happen while ensuring the network doesn't collapse when in the face of the inevitable failures isn't a tight rope I would want to be guiding the nation along. Which is probably why they want guard rails like "let us turn off solar" even if they don't have a plan to use it right now. The more guard rails the better.

The one and only thing they look to have ruled out is nuclear. Not because it costs too much, but because by the time the first one is up and running it will all be over.

> I'm not sure they have a concrete plan

Which "they" .. the Coalition in Opposition, the Labor Government, the various multi billion dollar private sector players (Santos, Fortescue, Rio Tinto, et al)?

In the time frame through until 2050 all will get a chunk of the decision making and execution.

The greatest driver for massive large scale solar and battery (off peak energy storage for use) technology is already the mining industry - fleets that move a billion tonne per annum use a lot of guzzleline.

> sites the Uni of Melbourne identified for pumped storage.

https://energy.unimelb.edu.au/__data/assets/pdf_file/0003/15...

These form one type of battery that is viable to varying degrees in some locations; great in the Snowy mountains and Tasmania, more difficult to execute elsewhere and they have their own pros and cons - thankfully there's a spectrum of "batteries" to draw upon - thermal heat storage and less mass efficient (ie. not suitable for cars but great for fixed locations) iron and other non lithium variations still have untapped potential.

> If they have a plan, it looks to ..

Politically there's not much planning from either party .. what is more probable is the policies will flow from both industry and scientists in the public sector, the pollies on either side are flopping about like landed fish at the behest of various traditional mining and energy sectors.

> The one and only thing they look to have ruled out is nuclear.

If "they" is the current crop of pollies then they have the "ruling out" grandfathered in already:

    Nuclear power is prohibited in Australia, principally by two pieces of Federal legislation - the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act); and the Australian Radiation Protection and Nuclear Safety Act 1998 (ARPANS Act). These laws effectively prevent the construction or operation of nuclear facilities for power generation, as well as facilities for the fabrication of nuclear fuel, uranium enrichment and the reprocessing of nuclear waste.

It's been ruled out for more than a quarter of a century.

The pragmatic economic feasibility of overturning that past legislation is twofold, both

* it costs more than other options, and

* by the time the first one is up and running it will all be over

are both in play here (see the most recent CSIRO energy futures report)

> Which "they" .. the Coalition in Opposition, the Labor Government, the various multi billion dollar private sector players (Santos, Fortescue, Rio Tinto, et al)?

AEMO. AEMO are the only ones who are tasked with keeping the grid running at the least cost.

The private players are playing "how can I use this crisis to make money" game, the pollies are playing some game akin to "whats the best way to buy votes using the voters own money".

AEMO handles the private players by attempting to create a market aligning the profit motive with their task. That's hard enough when the technology is stable. Right now it must be near impossible. I have no idea how they handle the pollies. It's probably a case of "keep your head down and hope they go away".

AEMO, here at least, outside of it's core Eastern and Southern regions, is reactive rather than leading with plans .. it manages what exists and comes into existance and functions as a reference for questions on energy policies that are set elsewhere.

The private players have many goals, a sizable part of those goals are driven by "how can we save money that we are already spending" - hence the interest in R&D from the likes of Rio Tinto and Fortescue in Infinity trains, solar farms, electric and other renewable renewables etc. in a sectors with some serious draw down on fossil fuels.

Other players, eg. Santos, are motivated by green washing existing practices .. having the worlds largest carbon capture and sequestration project is small beans given a) it's piddling success so far and b) tiny impact compared to the magnitude of the larger operation that's releasing greater amounts of carbon than are being captured.

AEMO is one part of what I generally referred to as "policies will flow from both industry and scientists in the public sector", it serves to coordinate a multitude of schemes pushing forwards, some of those schemes being hollow tin cutouts of no real substance.

You don't need V2G to soak up excess solar. You just need smart charging and/or pricing that reflects supply.

And they ruled out nuclear both on cost and timescale. Cheap carbon free energy in a decade or two would be worth investing in. Expensive carbon free energy in a decade or two much less so.

> Ideally in the coming decades Australia sees a majority of EVs that are largely being charged durk peak solar supply hours.

Better to drive at night. The streets are not so crowded. /s

Better to fastcharge and charge while parked.

Inertia is stored energy. To emulate an energy storage, you need to be able to get energy from "somewhere". That's just physics. Plus, it works both ways: If there is excess power, you also need to dissipate power from the grid.

But an individual solar inverter fluctuates wildly, and has no significant amount of energy stored (e.g. in capacitors). It also has no place to put power (okay, you can put it in the PV panels to produce heat, but they won't like that during a hot summer day).

That's why they are using batteries to emulate inertia: They are energy storage, and thus can act like inertia. Both putting energy into the system and "removing" it. The power industry is slow moving, so we're only seeing it now.

(Not an EE, but I think the reasoning is sound. Proper EEs feel free to teach me)

> It also has no place to put power (okay, you can put it in the PV panels to produce heat, but they won't like that during a hot summer day).

Actually solar can vary it's output fairly easily. The inverters are constantly monitoring the voltage from the panels, and rasing or lowering their impedance to extract the maximum energy from them. It is trivial for them to deliberately extract less power by varying that impedance, and that's exactly what happens with solar battery chargers. They have to match what the battery can accept. But from the grid's viewpoint though it would be a pointless additional complexity. The contribution from each household is so small they can achieve the same effect by shutting on and off an entire household, or more likely a suburb.

To put it another way they are saying they want to power off solar to ensure grid stability. But at the times you might want to power off solar there is excess capacity. Yes it's not stored, but it's just there, waiting to be turned on or not.

Keeping the grid locked to phase is much harder. The inertia of spinning iron does it automagically for a short while, without any complex control systems or fancy programming. They each pull the others into sync. But if the grid falls apart the magic is gone, and it the grid has to be brought up one generator at a time somehow manually syncing each one. That's hard enough when there are 100's of coal fired plants around the country, but can you imagine what it would be like if there are a millions of solar powered homes all trying to have their say in what the phase should be.

Maybe this has something to do with that, or maybe not. I'm not a power EE.

Interest factoid: most solar + battery setups will not power the house from the battery if they lose grid supply. The reason is the inverter refuses to switch while it doesn't have a grid to sync phase with. If was switched on and then the grid came up at a different phase a lot of smoke would result. You can get setups that will work while there is no grid, it's just that unless you specifically ask for it you may not get it.