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 Solar Panels and Grid Instability
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 Return to top of page · Post #: 1 · Written at 6:55:30 PM on 20 May 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

A while back an electrical engineer was debating me in conversation on this subject. He strongly asserted that there is no issue of instability with private solar generators being connected to the grid and told me in no uncertain terms that, despite what I had read, there was no evidence of it.

Well, seems I need to draw this article to his attention. Some quotes:

QUOTE: Since 2010, the number of panels across the nation has grown from 100,000 to 2.2 million.

But the proliferation is at times leading to grid instability, prompting the Australian Energy Market Operator (AEMO) to call for the switch-off measure.

"When we have way too much solar there's so little load we can't even manage to keep the balance with the generators, and in that context there's always a risk that the system could fail and will go black."

Solar operates "behind the meter" or out of control of the authorities. As the level of solar is unpredictable it poses challenges for frequency and voltage. AEMO said South Australia was particularly at risk if it became disconnected from the national electricity grid.


https://www.abc.net.au/news/2020-05-20/concerns-over-plan-to-switch-off-household-solar-panels/12267162


 
 Return to top of page · Post #: 2 · Written at 7:26:04 PM on 20 May 2020.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7290

Domestic solar can create instability. It can also overload street distribution networks. Street distributor networks were never designed to act as a feed in system and they are the weakest point in the path from power station to retail consumer.

The trick with solar is that if there is a suburb with lots of solar installed but all the occupiers of dwellings are at work and school, the power consumed travels back along the street distributors, back through pole top or kiosk substations and along 11kV lines to shopping centres, schools, factories, rail lines, etc and there is grave risk of local network overload.

I call bullsh-t on the 'no evidence' mantra. It isn't an issue of needing to gather evidence. It is common sense. Additionally, if there is an over-representation of solar feed-in on 1 or 2 phases with the third phase under represented then that is an even bigger problem, especially if there is a large balanced load in the area such as a water board pumping station. This 'engineer' can't be worth his salt if he is advocating any of this. Feel free to show him this thread. Wink

Then, at night, when solar panels are doing 2/5ths of sweet foxtrot alpha, bearing in mind that they just don't work when the sun doesn't shine on them, power is being drawn from centralised supplies as the grid was designed, all that infrastructure is unused and thus giving no return on investment.

Both SA and VIC are particularly ar risk given that these states have closed down power stations in the last five or six years. NSW is somewhat at risk but is managing for now. Wallerawang, Munmorah and Redbank power stations are just gathing pigeon poop whilst governments just dither on the issue.

Regardless of whether they be Left or Right leaning - all our politicians seem blind to the folly. If there isn't a reversal of policy on electricity generation with a renewed focus on baseload generation then the electricity network on the eastern seaboard is going to be rendered useless within ten years.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 8:56:13 PM on 20 May 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

It isn't an issue of needing to gather evidence. It is common sense. ... This 'engineer' can't be worth his salt if he is advocating any of this.

I worked with/for electrical engineers for a few years in my 20's and I very quickly learned that were basically two types: Those who believed that they were born knowing everything and those who accepted that they weren't. In this case it became evident that he was a Type 1 so I didn't press the issue at the time, but I will happily send him this article.

I hasten to add that I learned a lot from Type 2 engineers. One of those for whom I had a lot of respect once said to me regarding project management: "In a room full of people all spouting estimates for completion of a proposed project, listen to the one who gives the most pessimistic time estimate because he is the expert."


 
 Return to top of page · Post #: 4 · Written at 9:21:40 PM on 20 May 2020.
Brad's avatar
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 Location: Naremburn, NSW
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It's like any profession, I reckon. The humble ones tend to know more. The ones that bignote themselves usually have a good reason for operating that way - it is the only way they can be noticed. The type twos end up getting more done.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 5 · Written at 4:14:06 AM on 21 May 2020.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 830

My local power company Pubic Service Electric and Gas, installed lots of small solar panels on their telephone poles throughout their service area. These probably only produce only several percent of the electricity in the network. But what likely happens is that during the Summer the electricity these panels produce gets consumed locally (air conditioners), and not loading the high tension lines from the big power plants.

Problems can happen if there are enough panels out there that produce more electricity than there is demand for. But demand is usually higher during the day (when the Sun is in the sky), demand by industry and office buildings. During the night, when people are asleep, there's no Sun and less demand. But there is an upper limit on panels, that the power company controllers can manage the system and keep it stable. And then there is the expense of having the regular power plants to fill in for when the panels shortfall.


 
 Return to top of page · Post #: 6 · Written at 10:16:54 AM on 21 May 2020.
Irext's avatar
 Location: Werribee South, VIC
 Member since 30 September 2016
 Member #: 1981
 Postcount: 470

It will be interesting to see if the problem is better or worse with the systems using battery storage which can be off grid at certain times and only connected to the grid when required.
I think that ultimately that's where solar installations will be heading as battery technology improves and the cost becomes affordable.


 
 Return to top of page · Post #: 7 · Written at 10:33:10 AM on 21 May 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2363

NSW has a lot of pumped hydro. Hence the massive transmission lines from the Hunter Valley base load coal to the south coast and Snowy Mtns. This means they can have a fairly stable and controllable load on the coal fired stations.

Solar impacts downstream from all this so the base load stability afforded by the hydro - coal combination doesn't always help. However, the use of aircon on hot days should help level things out. I believe latest aircon systems can be controlled centrally. I wonder to what extent this is done?


 
 Return to top of page · Post #: 8 · Written at 11:53:42 AM on 21 May 2020.
Brad's avatar
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 Location: Naremburn, NSW
 Member since 15 November 2005
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I believe latest aircon systems can be controlled centrally. I wonder to what extent this is done?

Newer systems designed for domestic and light commercial installations will soon have a device fitted which can be controlled remotely by the supply authority - similar to how an off-peak HWS is. Whether this has started happening or not is another matter. The supply authority (with the owner's permission and a slight discount on electricity to entice participation) would be able to turn AC units on or off or limit them to a specified temperature. Gone would be the days of buying an undersized AC unit and setting it to 16 degrees and run it red hot right through a 45 degree summer day.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 9 · Written at 5:42:28 PM on 21 May 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

Utility-controlled load shedding switches attached to aircon units is not uncommon in the USA. In fact, in some areas I think installation may be compulsory.


 
 Return to top of page · Post #: 10 · Written at 9:36:00 AM on 22 May 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1245

The one thing the solar panel "experts" do not seem to understand is that: if there is no stable grid then their solar panel array will not work!
With all the BS that goes on about how wonderful a roof full of panels is, just ask a panel supplier if a house can run off the roof panels IF the mains is disconnected?
The answer is of course NO.

Try running your air con or your fridge straight off your roof panel invertor!
You need the low impedance of the grid to provide the start up inrush surge of inductive loads like motors and transformers and to provide a reference level of Volts and Hz to syncronise to .
Your roof panel invertor will just drop dead by itself.

Yes I know what I am talking about because I worked in the power generating industry suppling plant of 500 Kva and less for standby and farm use.
I had my own rooftop bank of solar cells running my workshop, BUT, there was a big thing called a BATTERY BANK in the shop that ran the AC invertor as well. THAT provided the balls to shift start up loads or sun out/ night time running. I could also mix my balance of mains to solar draw if the battery bank was getting discharged. If you are running stand alone, THEN you have to shed loads or start the standby genset (petrol or diesel) to supply the balls or recharge the batteries.

Acres of uncontrolled roof top invertor solar supplies back feeding into the grid scares the hell out of me!
No wonder I see funny waveshapes and Hz/Volt levels in my locality!

Fred.


 
 Return to top of page · Post #: 11 · Written at 12:51:28 PM on 22 May 2020.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7290

Domestic solar (the feed-in type) also has an anti-islanding feature built in to stop linesmen being electrocuted when they are working on dead street distributors. This means that when there is a blackout, the inverter will automatically stop working until power is restored. It will then use the mains frequency as a reference to parallel correctly once the mains supply is back on.

Large solar and wind installations don't anti-island but they also require baseload generation to act as a frequency reference in order for those installations to parallel with the grid correctly.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 4:28:34 PM on 22 May 2020.
Irext's avatar
 Location: Werribee South, VIC
 Member since 30 September 2016
 Member #: 1981
 Postcount: 470

Do we trust the auto islanding on an inverter made in China? Hmmm.


 
 Return to top of page · Post #: 13 · Written at 4:36:56 PM on 22 May 2020.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7290

It matters little, linesmen are trained much the same way as electricians - treat everything as if it is live and if an inverter doesn't isolate itself then it'll probably get blown up when the workers are on the job as dead conductors are often bound to earth when they are being worked on. This would short out any wayward inverters.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 14 · Written at 7:22:00 PM on 25 May 2020.
Tinkera123's Gravatar
 Location: Melbourne, VIC
 Member since 5 October 2009
 Member #: 555
 Postcount: 465

Fred ... spot on.


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Cheers, Ian

 
 Return to top of page · Post #: 15 · Written at 7:09:33 PM on 26 May 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1245

Ian I do not reckon many electrical "experts" that come from universities and keep tapping away at their dumbphones to fix a problem have any practical experience in power generation.
You have to have either worked at manufacturing level in industry, or, worked at the laboratory level at uni to have any idea about a subject like electricity its uses and application in the real world. Computer trained engineers do not have a clue, hand them a problem involving actual Volts and Amps and they are lost.
Fans in the sky and sheets of glass in the sun don't have balls.
What we need is atomic energy to make electric power direct, not make different ways of boiling water to run 19th century generators.
Failing that make 19th century generators that are latest generation ie 21st century.
Over to the latest generation of lab engineers to get weaving and stop farting about.

Fred.


 
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