Future of the Australian Electricity Market

[truckjohn]

Right.

Nukes and coal plants are incredibly difficult to "turn down" and "turn up" with demand fluctuations. They are ultimately steam plants, and it takes a LONG time to generate that much steam.

And even better, the grid can't store energy, it can only supply it... All the extra has to go somewhere.

One of the "Interesting" business developments cropping up is electricity shedding devices which are installed and controlled and generate a side benefit of soaking up extra production. One that most people haven't heard about is specially designed hot water
heaters which are plumbed to sprinklers. They use excess electricity to heat water and spray it out... Yes - for real. This is not a small thing in solar heavy areas.

I think most would agree that simply turning down excess solar production is preferable to cooking up a myriad schemes to create of excess consumption on demand...

I always love to tease people that it's a shame Nature didn't sort out things which harness excess energy and use it to create renewable, consumable matter.... Oh yeah... Trees...

[Beardy]

I just fitted solar to my place and the power entering my property during the day is 256volts, I reported a fault to the authorities
We are at the end of the supply chain and the power at the node is 240v, by the time it gets to us it has jumped up that much from all the domestic solar feeding the system so they can’t do anything about it

[truckjohn]

Yep. Voltage rise due to wire resistance on a supply system is a real thing most folks don't understand. Newer solar installations are designed with voltage regulation so they don't over supply the grid in hot weather, but it's really a power line problem.

Luckily, most appliances can easily handle a wide range of voltage fluctuation. 16 volts is under 10% - so it should be ok, maybe even a little beneficial. Power consumption is Volts x Amps - so a 1500 watt appliance consumes 6.25A @240 volts, but only consumes 5.9A @256v. The lower current consumption causes less resistance heating in the circuitry - and things settle down. Going the other way is a worse problem, when you're 16v down on 240v system, you fall into the death spiral where everything consumes more current, which causes more resistance heat losses... Which causes more current drop...

[FenceFurniture]

by the time it gets to us it has jumped up that much from all the domestic solar feeding the system so they can’t do anything about it

Others more expert can comment better than I can, but this and other problems with the grid coping with scattered solar input is caused not so much by the rapid solar take-up, but by not having a grid that is suitable for it. We have a technology that is 80-100 (?) years old that was designed for energy supplied from a handful of sources (CF power plants) to go in one direction, and we are trying to force it to work with a brand new tech that is two way and scattered. It seems to me that there are band-aids everywhere.

We need a whole of Federation approach for a grid (et al) that is appropriate for the times.

[Optimark]

We have a reasonably sophisticated solar and battery system, one of the by products of this is the ability to see lots of recordings of various power figures. It doesn't mean I understand many of these figures, but they make interesting reading.

Beardy reported an excess of power in his measurements in the daytime, this does happen and I've seen it a bit myself. I did note when I was eating breakfast and musing on the state of charge of the batteries and where current solar was at around 08:00 this morning.

After reading Beardy's post, I checked out some figures from this morning.

As I was having breakfast this morning, I noted that the sun was shining very brightly; we were doing quite well in the generation department from the rooftop solar. Now after looking at some of the figures this is what I noted.

At 07:49 the street side of the meter was measured at 245.8V this was around the start of some serious sunshine appearing from nowhere. By 07:59 the voltage was now at 238.9V still with serious sunshine. I take from this that the system levelled out the higher voltage by itself, possibly as many toasters and coffee machines were being employed by the populace.

But I did find something quite interesting, something I wasn't looking for and only because I scanned the period from 00:00 11/03/2022 to around 10:30. At 02:29 the incoming voltage was 248.7V at 50.1Hz.

We haven't had any issues as we have been running solely on battery power for the whole of the night. At the time of the 248.7V street input situation, our house was consuming 99W from the batteries. As this is below a refrigerator running consumption and above our normal standby consumption, I'm assuming the missus was still up and reading with a light or two on.

By the way, nominal grid voltage in our part of Australia is 230V.

Mick.

[havabeer69]

Right.

Nukes and coal plants are incredibly difficult to "turn down" and "turn up" with demand fluctuations. They are ultimately steam plants, and it takes a LONG time to generate that much steam.

And even better, the grid can't store energy, it can only supply it... All the extra has to go somewhere.

One of the "Interesting" business developments cropping up is electricity shedding devices which are installed and controlled and generate a side benefit of soaking up extra production. One that most people haven't heard about is specially designed hot water
heaters which are plumbed to sprinklers. They use excess electricity to heat water and spray it out... Yes - for real. This is not a small thing in solar heavy areas.

I think most would agree that simply turning down excess solar production is preferable to cooking up a myriad schemes to create of excess consumption on demand...

I always love to tease people that it's a shame Nature didn't sort out things which harness excess energy and use it to create renewable, consumable matter.... Oh yeah... Trees...

You'd actually be surprised how quick the old coal clunkers and respond to load, obviously no where near instantaneous as a battery bank but some coal stations have about 10% "spinning reserve" of steam that can be used pretty much straight away.

On the last point of trees, its actually surprising the sheer volume of trees you actually need to burn to get the same amount of power from coal. And there is one other issue with it... throw a green log into your combustion fireplace, and you definitely know it compared to a well seasoned/dry one. its like a 1 to 5 or 6 ration. so for every ton of coal you can burn, you need 6 tons of wood and if you're station burns 8000T in a day of coal, you're getting close to 50,000T of wood.

So trying to dry and season a couple of hundred thousand tons of wood is a challenge unto its self, then it has to be processed so it can burn efficiently and not cover the whole area with smoke. There where a number of pilot plant ideas to try and pelletise wood for burning but it starts to get cost prohibitive when you need to pay for a fuel to provide heat to dry out your wood so it'll crush properly and actually burn in a boiler.

not to say you can't do it but it does get tricky trying to go large scale with it
Wood Burning Power Station at Wilton 10 - Power Technology

this place in the UK is a 30MW unit burning approx 300,000 tons of scrap wood and other such timber products all while meeting emission specs. shoving one down in the pine forests of S.A might make sense

[truckjohn]

Oh, absolutely, wood burning is one of those solutions that falls under "It's ok when one person does it, but becomes a catastrophe when everyone does."

Many of the huge older papermills and sawmills had their own cogeneration plant to burn scrap wood waste for electricity. Besides the smoke, they generate a giant amount of ash.

[Beardy]

The Endeavour Energy representative said they were trialling some stabilising devices to alleviate the higher voltage problem but it is happening everywhere
@truckjohn as you pointed out the systems have protection built in so as to not oversupply the system but the flip side of that is that when this happens you are not sell your power back to the grid.

[Bushmiller]

.


By the way, nominal grid voltage in our part of Australia is 230V.

Mick.

My understanding is that the nominal single phase supply was recently changed to 230V instead of the 240V we were all used to. As has been mentioned, the voltages can go higher than this nominal figure. When it was 240V those higher figures could cause damage to some machines. It is also a demonstration of the requirement for frequency control.

Regards
Paul

[BobL]

My cousin operates two 12 MW thermal generators powered by local sawmill offcuts and tree waste trimmed annually from tree overhangs on roads in the Italian Alps. They have relatively cheap hydro power so they don't really need the electricity from this system but read on to see how the whole system works.

The cooling system for the plants is a hot water and central heating heat exchanger that recirculates water to and from houses and businesses in a nearby town.

To be efficient the wood has to be collected within 30 km of the power plant otherwise the cost of diesel becomes too high.
The waste is chipped and transported and stored in large stockpiles at the plant.
There are heaps of roads snaking through the mountains that have to be trimmed of overhangs, plus there are a fair few falls collected after storms etc and there's a constant supply of sawdust from the 4 local sawmills.
Seeing as all this this stuff is just burned anyway it might as well do something useful.

The savings are huge, around 100,000 litres of heating oil a year that normally provides the heat for the town.
They do have a back up oil powered generator that is used when it gets really cold and they happen to be doing maintenance on one of the generators but this is nominally being used at rate of about 10,000 litres a year.
So, much less money leaves the town to line the pockets of some Russian Oligarch or Middle Eastern Warlord.

The real bonus for the town is the snow on the surrounding ski resorts is no longer covered with a oil brown film from burning oil. The scheme is so successful its being rolled out to over 40 similar locations across the alps. The setup cost was funded by the local community plus some government grants and loans. Even the 90 year grandmothers were happy to chip in to make this work.

Oh yeah and the waste ash is used in road maintenance and construction sometimes by the crews on the council trucks collecting the overhangs.

[FenceFurniture]

My understanding is that the nominal single phase supply was recently changed to 230V instead of the 240V we were all used to. As has been mentioned, the voltages can go higher than this nominal figure. When it was 240V those higher figures could cause damage to some machines.

AFAIK, appliances, machinery etc must be able to operate on ±10% of the voltage. Now whether that is on 230V or 240V, I'm not sure, but that still only 1V difference in the variance range of 46-48V.

[FenceFurniture]

Seeing as all this this stuff is just burned anyway it might as well do something useful.

Yebbut surely the point is that this stuff shouldn't just be burned anyway, but left to decompose.

[russ57]

I may be wrong, but if i recall, the change from 240 to 230 was a 'nominal' change only. ie, no one actually went around and changed settings to deliver exactly 230v.
Rather, as noted above, its now normal for the supply to be over nominal (230) by 10v, or 8%.(240v). So long as it is between +10% and - 6% or 216-253, all is ok. (the 240v standard was +/-6%..
Today for example, the voltage did read 230 at about 4pm, but the rest of the day it was over 240, peaking @246.

[ian]

I may be wrong, but if i recall, the change from 240 to 230 was a 'nominal' change only. ie, no one actually went around and changed settings to deliver exactly 230v.
Rather, as noted above, its now normal for the supply to be over nominal (230) by 10v, or 8%.(240v). So long as it is between +10% and - 6% or 216-253, all is ok. (the 240v standard was +/-6%..
Today for example, the voltage did read 230 at about 4pm, but the rest of the day it was over 240, peaking @246.

Now we are really going back in time ...

My recollection is that the discussion around the 'nominal'change in supply voltage -- from 240 to 230 -- occurred sometime before 1981. My father retired at the end of 1981, but before he retired he had some role in the Australian Standards consultation around the proposed change. Dad ran what was then the only Government toxicology lab in NSW and was also an executive member of the Royal Society of NSW -- I don't know if dad's involvement was because he was associated with the NSW Royal Society or on account of his Government job.
Whilst the change in voltage might have been sold as a 'nominal' one, the background was that by the late 1960s electrical motors were increasingly sourced from Europe where the supply voltage was standardised at 230V. Motors designed for 230V would burn out if subjected to 240V plus whatever the then current over-voltage tolerance was. Changing the nominal supply to 230V (+10%, -6%), meant that domestic appliances could be connected to the Australian grid without any significant issues.

As an aside, at one time during the 1970s, Australian Standards was looking to modify the applicable Australian standard test for fridges and freezers to something like test the device's operation at 35*C. This thought bubble went away when it was pointed out that ambient temperatures in much of Australia regularly exceeded 40*C. Unfortunately, I don't know what the current Australian standard environmental test temperature is for fridges and freezers but some years ago, LG(?) was done for having fridges and freezers that would measure the ambient environmental temperature and thus determine if the device was being subjected to a Standards' compliance test and lower the fridge/freezer's power consumption accordingly to obtain a better star rating.

[BobL]

Yebbut surely the point is that this stuff shouldn't just be burned anyway, but left to decompose.

Either way it makes CO2.
The main reason it's burned is the volumes of waste are quite large so where are they going to put it, and if they did store it, over time it becomes a fire risk.