Solar power question

[THE BARON]

Hi all, I have a question for someone who has a lot more knowledge of things electrical than I do. I have just been reading a news article in which it was stated that solar and wind generation is causing huge problems for the electrical grid. It seemed to imply that rooftop panels were responsible because they are feeding into the grid but that story was written by a journalist and they seem to have a knack of getting things wrong. My question is, do they? or are they only feeding into an area supplied by a single transformer? I read the comments beneath said article and it appears everybody is convinced power from your rooftop panels is being distributed up and down the eastern seaboard. I have a small amount of knowledge of electrickery such as why single phase is 230 and three phase is 415 and not 690 and I know that on a pole carrying multiple levels of wires the bottom are 230, next is 11000 and if there is a third it is likely 33000 but I don't know anything about solar power. I spent a working life in the water industry and I know its easy to reduce pressure but boosting it requires a lot of energy. And yes I did spend time on Google trying to find out but "feed excess into the grid" does not answer my question.

[DavidG]

Transformers change voltage either up or down.
Any electricity entering the system may be used anywhere in the system.

[THE BARON]

Thanks David, that was quicker than spending all night on the net trying to educate myself.

[elanjacobs]

Complete speculation, but perhaps the intermittent and somewhat unpredictable nature of how much power is getting fed back via wind and solar is giving their load monitoring systems trouble?

When it's station generated only, they can reasonably predict load requirements as the day progresses, but if you have tens of thousands of homes/businesses with solar panels that suddenly ALL need to take more out of the grid because some clouds have rolled in they'd have no way to anticipate the extra demand. Same the other way when the clouds clear up.

[Chris Parks]

It has been known for some years that the historic supply chain operation is being disrupted by the solar being installed causing operational issues. I am sure Bushmiller who works in the industry has a better explanation than I might attempt. If you go to Whirlpool forums/solar and do a search it has been discussed there as well.

[woodman-79]

The “issue” is that in order to push excess into the grid you need to exceed the electrical pressure (voltage) of the grid, or at least the line coming into your meter..

So when you have 10 houses in a row with solar, on a sunny day each successive one needs to increase the output voltage of the inverter just slightly above the input from the local line.
Australian standards which the power companies are supposed to abide by mean that the grid voltage should never exceed 253v (nominally 230v +10%).
This maximum is frequently exceeded by large margins in many areas of Vic “due to solar”

Why the quote marks... well it’s quite convenient for the lower companies when the grid voltage exceeds 253v because guess what happens.... everyone’s inverter shuts down and they can’t use their green solar anymore and are forced to buy dirty coal power from the grid...

In 2019 I find it impossible I believe that the technology does not exist to dynamically adjust local grid voltages in order to stick within the standards.


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[Bushmiller]

TB

There are many issues around this subject and a huge amount of misinformation. Some of that misinformation is deliberate and some is just by people who don't know. In every instance you have to carefully examine the source of the information to check both it's integrity and the possibility of hidden agendas. This latter aspect of agendas is the most insidious and reprehensible part.

As Chris Parks mentioned, I work in the industry and indeed I work in a thermal fired (coal) power station so I need to declare my connections and to some extent my own prejudices. My station was the second last to be built in Australia so arguably it is more efficient than most and will probably be one of the last stations to be shut down. At this point I will reiterate that there has to be a transition from fosil fuels to renewables. Only those people who are prepared to forego electricity should be advocating the immediate abolition of fossil fuelled stations.

Ok, having got the preamble out of the way, back to the question of solar and wind power causing disruption to the grid.The short answer is that there are issues. However, they are not quite as bad as some would make out and, to my mind, neither are they insurmountable.

Wind is primarily the preserve of wind farms, while solar can be commercial size solar farms or rooftop solar. If we take rooftop solar first, it simply feeds back into the existing grid. The issue here is that the system along your street (above ground or under ground) was designed to feed power into the household and not away from it. Also in many instances the infrastructure is old and was not maintained satisfactorily: That varies from company to company and area to area. Frequently a distribution company will complain that solar is causing them trouble, but it is quite likely that it is more to do with the equipment being old and possibly poorly maintained or updated. The company concerned uses solar as a get out of gaol free card to blame "issues" on the lack of adequate maintenance or upgrades. However, this is not necessarily the case everywhere and no doubt somebody will jump up and contest my statement. It may even be true for them. It does not mean that it is true everywhere. When the distribution (power lines and substations) was owned by the governments, they were the biggest culprits as they took the revenue but did not keep up to the maintenance. They quite happily sold those divisions off reaping a big cash inflow and not having to fork out large sums of money on overdue upgrades.

Wind and solar generally have a big failing. It is that they are unable to provide voltage control. Around Australia it is the thermal stations and particularly the hydro stations that provide this control aspect. That is not a reason to not go down the renewable path, but it is an issue and will need to be addressed in the future as coal stations are phased out. Interestingly the Tesla battery's (there are other batteries too, but less prominent in the public's mind as they did not have a flamboyant Elon Musk touting their worth) main value is in the area of voltage control at which it is supreme and faster even than the hydro stations in this regard: Actually many times faster. As a storage battery it was an exercise and really a joke, although arguably a necessary joke to demonstrate potential. Why I say that is that SA has a small electricity demand compared to the other states. An average might be around 1800MW. Other states 5000MW to 8000MW (I'm talking averages here and not peaks). The Tesla battery can produce 100MW: FOR ONE HOUR ONLY.

Some more general information is that the eastern seaboard is linked electrically. All the states except WA and NT are connected to this. There are a few communities still on their own such as Mt Isa and others. There are "interconnectors, which are a little like giant extension cords, but they are limited and power from Queensland does not go directly to victoria or Tasmania. One state can provide "limited" electrical supply to another.

Just back to the street for a moment: The supply coming down the street is 415V, but the single phase supply comes from one of the three 415V wires. Some house come from one phase while others come from another. it has to be balanced. Similarly, power going out from solar rooftop has to be balanced too. If one third of the houses in a street install solar, but they all happen to be on the same phase, an out of balance situation would occur. it would not be allowed.

Lastly I would sing my old chorus, which is the main bugbear of solar, and it is that you have to have at least three times the amount of solar to replace thermal power (actually it is more than that as I have not factored in cloudy days) because solar really only generates for a maximum of eight hours. On top of that you need somewhere to store electricity for sixteen hours worth of storage.

I am a big fan of solar, but it is not without problems. I maintain that in today's world there is not a single form of energy supply that does not have a fundamental flaw: It is a problem.

Regards
Paul

[Pete57]

Great info Bushmiller.
My understanding is the grid was designed for power flow from big power stations, through transmission systems, distribution then to the consumer. Not we have the consumer trying to send back into the grid and potentially reverse flows through the distribution system. Work is being done in this area so stay tuned.

[THE BARON]

Thanks Paul, another very informative post. I can almost forgive you for causing me to completely rethink my support for going to nuclear power. One post on a thread from years ago changed my whole understanding of the issue and now when I hear other people blaming Greenies for stopping nuclear power, I shoot them down using arguments based on your facts. I hope you don't mind.

[Bushmiller]

TB

No I don't mind at all.

My objective in these discussions is to make sure people have good information on which to base their own judgements. I would also explain that some of the finer electrical considerations are beyond me as I am not an electrician. Pete is correct when he states the existing grid was designed as a one way system. The world is changing. So must electrical supply.

The nuclear question is very controversial and probably could have it's own thread. However, Nuclear power suffers from the same issue as solar in that nobody is prepared to throw enough money at it for development. Thorium could be a possibility, but it lacks the incentive to develop without the ability for governments to make bombs! While ever governments procrastinate with their direction there will be a reluctance by private enterprise to invest in what they will see as a risky venture: Be it Nuclear or Solar. Nuclear stations have to be large to be viable. I am not sure that the Australian market can support a station of sufficient size even if all the safety and waste disposal issues were solved. Having said that, I think I read that some "pocket size" technology was being developed, but I don't know what stage it is at.

Regards
Paul

[yvan]

Thank you for your explanation Paul. We have 5kW solar array. I am intrigued that, on the one hand various state governments are encouraging home owners to install a solar system by subsidising the price of the power buy-back and, on the other, electricity utilities suggest that solar systems generate additional costs which are ultimately borne by "non-solar" consumers.

In Tasmania, the generous buy-back price of 26c/kW - for systems installed before 30 June 13 - has now dropped to 13c/kW and, in some 18 months or so, will finally settle to 8c/kW. For new installations, the buy-back price is 8c.

Yvan

[NCArcher]

Lets get a couple of things sorted out here. There is no 'reverse flow' or 'having to generate a larger voltage to be able to overcome the line voltage' it doesn't work like that. The grid is just a network of wires that distributes electricity to where it is needed. One thing to remember, there is no storage (apart from SAs battery) the power stations basically generate power on an as needed basis. There are very sophisticated distribution control centers that work out where the power is needed and how much at any time. The generators in a power station are constantly altering their output to match the required load. Although there are safety interlocks to prevent it, a blackout can be caused by one generator going down, due to a fault or failure, when the other generators see that loss of power to the grid they ramp up very quickly to try and get the power back up to the required level. The sudden surge can cause a generator to trip on over load and then you have an even bigger hole in the power requirements, so the remaining generators ramp up and so on and so on. Although that has nothing to do with solar power on houses it sort of explains what is happening with the grid. When you turn on an appliance, current flows through either an element or a coil and heats it or makes it spin. In Australia that current flow reverses 50 times a second so reverse flow is not a thing. When you feed power into the grid you are adding current flow not changing the voltage. The voltage is set and the control systems work very hard to keep it where it is.The voltage will vary by relatively small amounts but if it goes outside certain limits it will cause protection systems to trip and shut everything down.
I'm not sure how solar systems cost the generators more money but i suspect it's more political than operational. The generators sell electricity at a regular rate and then an exorbitant peak rate. I suspect the solar input is cutting into the peak rate revenue but that's just a guess.

[Chris Parks]

It is fairly obvious that those who can't have a solar array because either they simply can't afford it or live in a situation where it is not possible such as renting or an apartment will have to put up with paying more for electricity as the retail market shrinks or at least stabilizes. Businesses are now getting into the solar panel installation game and putting huge arrays on their roofs as well. I have family connections to one such installation and it is going to be huge and is being done for the obvious reason of saving money though the upfront costs are very large.

Then we have the peer to peer scenario where those with solar will sell directly to those who don't and this idea must terrify the power companies. Solar farms are seen as another way for those who can't have solar to invest in and receive a return that will offset the electricity costs as it inevitably goes higher due to less retail consumption. Some solar installations have a cap that reduces the amount of power that can be returned to the grid so the owner does not get a full return on their investment. All very interesting and the electricity companies business plan has been turned on its head, the governments privatised the electricity suppliers and then proceeded to put in place a policy that damaged their business model which can't make them happy.

[rrich]

Allow me a bit of sarcasm if you don't mind. Here we occasionally run across "articles" in print, on the evening news and on the web purporting how bad solar and wind energy is for the grid. As we dig into those articles, many can be sourced to a group financed by a public utility organization. Interesting to say the least.

There is an un-named automaker that is also selling solar panels and solar roofs. This particular company has a one/five reputation. They are rated by their customers as a one or a five with almost nothing in-between. This company also sells a "roof" that looks like a New England slate shingle roof. I was exceptionally interested in this roof as it is interconnected glass shingles that are very close to the character of my neighborhood. I did notice that the ridge cap is missing in all of the pictures of this roof installed. After a lot of hours of digging and finally reading the installer instructions I discovered it is not a roof. They are solar panels that are made to look like a roof and installed over an existing roof on an aluminum framework.

There is another product that are almost attractive panels with black (anodized?) aluminum frames. These panels are much thinner than most of the others. I don't know if they are reliable or not.

A bit more than 10 years ago we added an additional 500 square feet (46 Square Meters) to the house. We had who is considered to be one of the best general contractors in the area. I wanted to put solar on the south facing roof which is in the back and not visible from the street. After several weeks of the general looking for a solar installer he told me that the ones he found he wouldn't let their dog poop within a mile of his house. He went on to say that solar was just too new and the flakes hadn't been weeded out yet. From what I've seen recently, we're pulling weeds as fast as possible but three new ones take the place of every one pulled.

[Pete57]

Lets get a couple of things sorted out here. There is no 'reverse flow' or 'having to generate a larger voltage to be able to overcome the line voltage' it doesn't work like that. The grid is just a network of wires that distributes electricity to where it is needed.
Just be careful what you read especially on the internet. I am not an electrical engineer but have worked with plenty and they all say the same as Bushmiller.
If you are interested there are some very interesting trials coming up in this area.

[Bushmiller]

Lets get a couple of things sorted out here. There is no 'reverse flow' or 'having to generate a larger voltage to be able to overcome the line voltage' it doesn't work like that. The grid is just a network of wires that distributes electricity to where it is needed. One thing to remember, there is no storage (apart from SAs battery) the power stations basically generate power on an as needed basis. There are very sophisticated distribution control centers that work out where the power is needed and how much at any time. The generators in a power station are constantly altering their output to match the required load. Although there are safety interlocks to prevent it, a blackout can be caused by one generator going down, due to a fault or failure, when the other generators see that loss of power to the grid they ramp up very quickly to try and get the power back up to the required level. The sudden surge can cause a generator to trip on over load and then you have an even bigger hole in the power requirements, so the remaining generators ramp up and so on and so on. Although that has nothing to do with solar power on houses it sort of explains what is happening with the grid. When you turn on an appliance, current flows through either an element or a coil and heats it or makes it spin. In Australia that current flow reverses 50 times a second so reverse flow is not a thing. When you feed power into the grid you are adding current flow not changing the voltage. The voltage is set and the control systems work very hard to keep it where it is.The voltage will vary by relatively small amounts but if it goes outside certain limits it will cause protection systems to trip and shut everything down.
I'm not sure how solar systems cost the generators more money but i suspect it's more political than operational. The generators sell electricity at a regular rate and then an exorbitant peak rate. I suspect the solar input is cutting into the peak rate revenue but that's just a guess.

Thanks Tony

I probably should have gone into those aspects but did not. Besides which you have explained it better than I would.

The advent of increased solar power (and wind power) has changed the dynamic of how the traditional thermal power stations operate. Until now the periods of high demand have been winter and summer. Winter used to be the high point but in recent years, thanks to increased air conditioning, summer is the highest point. On a day to day basis night time was a period of low demand and low prices. As solar generation increases, the day time prices are not so high or so volatile and night time prices are higher than they used to be. As a consumer you are used to a fixed price for your electricity, but the wholesale market has a constantly varying cost apart from fixed contracts. The wholesale cost varies every five minutes and this is dictated by a complicated bidding process submitted in advance of the day. Overall these are the average prices for this year to date across the Eastern states.

QLD 7.2c
NSW 8.5c
VIC 12.3c
SA 10.5c

For some reason I don't have the figures for Tassy, but they too are part of the grid (there is a DC link under Bass Straight) and I would guess will be similar to SA and VIC.

I expect most of us are paying around 28c/KWH for our power and a little less for off peak water heating. Only a few years ago the average wholesale prices were around 5/6c. Although retail prices have increased they are probably less than the wholesale increases proportionately. I would also guess that much of the increased power bills are down to increased usage. (I have just donned my flak jacket on that one!). It is true to say that the wholesale prices of just a few years go were unsustainable. There was one year that every QLD generator forecast a loss.

Tony mentioned the exorbitant peak rates. They can be: up to $14/KWH!! However, this is rare and increasingly so. When it happens, it lasts for five minutes. What is more frequent is when the cost goes to - $1/KWH . Yes, that is a negative figure. Actually what we see at work is a MW cost, so -$1000 and between the two units that is a cost to us of $800,000 per hour. Of course we commence reducing load, but that takes time: It is not quite like braking in your car. To reduce load in a controlled fashion may take hours. Normally, the price reverts to normality way before we have to go too far as the Gas Turbine stations can just switch off. I mention this purely to highlight that the generators do not have the cushy position many parties out there assume.

Regards
Paul

[NCArcher]

For some reason I don't have the figures for Tassy, but they too are part of the grid (there is a DC link under Bass Straight) and I would guess will be similar to SA and VIC.


The Tassie link was cut a couple of years ago. I can't remember how it happened but it was almost impossible to hire a decent sized diesel generator for about 3 months as they were all shipped to tassie to make a massive diesel generator power station while the cable was repaired. Tassies power consumption is tiny. There are only 500k people in Tas.

[Bushmiller]

Tony

The link was indeed broken and I can't remember the details of how either. It has been repaired for some time now and it appears on our maps of the grid along with the other states. I don't know why it was not in the list of average prices. It is less than SA but still significant. It was constructed to insulate Tasmania against a drought as a large proportion of their power is Hydro. When the line broke they had been freely selling off their power to the mainland and the dams were low. Consequently they were up a creek and no paddle.

It took months to repair the line during which time there was, as you say, a very good market in diesel generators.

Regards
Paul

[pintek]

'as you say, a very good market in diesel generators.'

I believe the diesel generator market was propped up further in the summer after Hazelwood closed the doors when the AEMO contracted a hire company to install them at the old Morwell power station for grid top up. Same year they requested some industrial plants to close over the summer period to reduce load requirements. Crazy stuff. I wonder if it will take a system black for people to see the fragility being forced into the grid.

[RossM]

Tony mentioned the exorbitant peak rates. They can be: up to $14/KWH!! However, this is rare and increasingly so.

The park spot price actually has a cap - it's set at $12,500/MWh ($12.50/KWh) This is less rare than you may think, as it can be invoked by the market operator at any time to force load shedding during peak demand.

This link has a full run-down on the grid and it's operation (https://www.abc.net.au/mediawatch/transcripts/1234_aemo2.pdf)

[Bushmiller]

The park spot price actually has a cap - it's set at $12,500/MWh ($12.50/KWh) This is less rare than you may think, as it can be invoked by the market operator at any time to force load shedding during peak demand.

This link has a full run-down on the grid and it's operation (https://www.abc.net.au/mediawatch/transcripts/1234_aemo2.pdf)

Ross

That is a good link and goes a long way to explaining some of the intricacies of electrical generation as it exists on the eastern seaboard. It is however a little out of date (2010) and some aspects have been revised. Load shedding does not occur because the price has gone high. It occurs because there is insufficient generation capacity to support a stable system. The market operator, AEMO, can invoke load shedding if they feel the stability of the system is being compromised or likely to be compromised, but they don't do this by raising the cost. The cost varies by the bidding process in which the generators participate. Load shedding varies from state to state. The first to go in the southern states are the industrial consumers, but in QLD industry is preserved and it is the domestic element that is the first to be shed.

I thought you may be interested to see some snapshots of the variance in power generation. These prices and loadings occured on Saturday 5/10/2019.

0700hrs. At this time in the morning Solar is active.Tasmania being a colder climate looks as though it has similar generation demands to SA. Tasmania is actually closer to half that of SA when the latter state wakes up and switches on their air conditioners!

462605

0701hrs. Solar is really kicking in and the price has gone negative. Just one minute later (remember it is adjusted every five minutes)

462606

1249hrs.

462607

1817hrs. Completely different scenario. The solar is pretty much out of the equation and prices are higher everywhere.

462608

I have to reiterate that this is just a fairly random series of snapshots, on a weekend and in Spring. I have shown them only to show the range of prices and how quickly at times the price can fall. I should also point out that this is not the only products for which generators are paid so it is by no means the whole story. Also most thermal generators have some fixed contracts with large consumers so not all electricity is sold on the spot market. The above should only be seen as a guide to market trends.

The prices above are for MWs so divide by 1000 and you have the Kwh price you see on your domestic bills.

The picture would be very different today, being a week day with industry in full swing and a very hot day as well (33degs C here by 1100hrs. Almost 37degs C at 1300hrs ).

Yesterday we spent hours with the price at $0.00! I met a man on Saturday evening who commented on how expensive solar power was making our electricity. There is an element of that from the early days where incentives were offered to establish solar power (primarily rooftop solar PV), but as you can see that is being significantly counteracted with the effect on traditional thermal generators at certain times. I would have liked to have shown him those snapshots above.

It is a complex issue and very easy for interested parties with agendas to cherry pick.

This is another link that may be of interest to the solar watchers:

Australian Photovoltaic Institute • APVI Solar Maps (https://pv-map.apvi.org.au/)

This is the AEMO website which is live and everybody can see an instantaneous spot price.

Access the latest news, perspectives and backgrounders on energy here. – Australian Energy Market Operator (https://www.aemo.com.au/)

A moment ago just for information:

NSW: $53
QLD: $0
VIC: $92
SA: $ -292 (yeah, negative)
TAS: $97
WA: $27 (Not on our grid and 3 hours behind)

Regards
Paul

[forrestmount]

Not sure if I should post a response on this topic as I am not an expert in power distribution, but I was told by friends who are in the industry the single biggest issue solar power presents to the network is when a large cloud coverage takes out a lot of houses feeding power into the grid without warning for short periods of time. This scenario rings true to me.


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[Bushmiller]

forrestmount

There is always a "rolling reserve" in the system to take up any shortfall (at least mostly). Generators place their bids in price bands so they are mostly not at full load. It is difficult to imagine cloud cover "suddenly" materialising. Cloud moves across the sky in a controlled manner. I would need to hear corroboration of that type of scenario. My gut feeling is that it is anecdotal and no different to any sudden demand. People tend to imagine how the system works rather than knowing. See NCArcher's earlier post on the way electricity feeds along the lines. (Post #12).

It is important to remember that electricity is not stored. Whatever is generated is used. The voltage needs to be regulated so machinery and equipment is not damaged. Electrical protections are in place so the systems do not destroy themselves. This is what happened in the SA storms when the power lines blew down. The interconnector from Victoria shut itself down so it was not overloaded and in doing so contributed to the problem short term. Without that protection serious damage may have occurred that kept it out of service for weeks rather than hours.

Regards
Paul

[rrich]

Ah yes! Mr. Kirchhoff and his laws rear their ugly heads again. Anyone who has studied electronics has suffered through the chapter on Kirchhoff's Laws.