A Problem Nobody Anticipated – Excess Solar Energy

[Visitor]

With 35% of homes in Southern Australia having solar arrays, there's an unanticipated problem. On sunny days, 'independent' solar arrays can supply more than 100% of the demand for power. Utilities currently have no way to control this independent production, which can lead to very bad things happening.

If more power is supplied to the grid then is being used by the grid, the voltage rises. Electronics and machinery may be damaged. At some point, the safety systems on the grid-tie inverters will trip on overvoltage en masse, with utilities unable to respond quickly enough to this step-increase in generation required, resulting in blackouts.

100% of power needs supplied by solar! A huge win! Nope, not quite....

South Australia Vs. Too Much Home Solar

Once upon a time, the consensus was that renewable energy was too expensive and in too sparse supply to be a viable power source to run our proud, electrified societies on. Since then, prices of so…

hackaday.com

 

[shortbus=]

Great for you Aussies At least with solar you don't get cancer from the windmill noise. Some one much loved here said that, the CheetoJesus, he is still worshiped by some.

 

[Visitor]

(Sad because the comment is true, not because of the comment.)

 

[AnalogKid]

the CheetoJesus

l.i.k.e.

 

[gophert]

The same problem has existed in Germany for some time. Some years ago, Germany had to "sell" their excess power to Poland to accommodate all the obligations the country had made with wind-turbine owners. They were "selling" so much power to Poland that Germany was PAYING Poland to take the power back in 2016.
Looking into more recent reports show similar issues still exist... along with a weak grid that allows wind energy made in the North to be pushed to industrial centers in Southern Germany.

Germany’s Maxed-Out Grid Is Causing Trouble Across Europe

The growing mismatch between Germany’s renewables capacity and the strength of its electricity network is leading to curtailment, crazy pricing and challenges for neighboring nations.

www.greentechmedia.com

 

[Diver300]

There have been issues like that in the UK, with too much wind power overnight.

The nuclear power stations don't like to vary the power. The wind turbines don't have fuel costs so they will keep running until the price goes negative in order to encourage them to turn off. Any power station that pays for fuel, or can store fuel, and can turn off quickly, will have shut down.

Dinorwig Power Station was happy to be paid to take electricity from the grid, and then sell 75% of it back again when the price was positive. The problem is that finding somewhere to store 7 million tonnes of water, 600 m up a hill, is quite difficult.

Electric cars can help smooth out the electricity supply, especially if they have vehicle to grid (V2G) capability, but waiting until the price is cheap before charging can make a big difference if there are enough.

Of course, odd things can happen in any oversupply situation. It was a year ago when this happened:- https://www.bbc.co.uk/news/business-52350082

 

[augustinetez]

And they also want to charge us for exporting excess energy to the grid (Australia).

Most of the problem has been caused by the lack of foresight of both government and the electricity companies - they knew it would happen years ago and did nothing about it.

Reasonably simply solution to the problem is distributed battery banks around the state to absorb the excess energy and feed it back in overnight - pity the shiny suit brigade can't see simple.

 

[gophert]

Reasonably simply solution to the problem is...

Or to just disconnect the grid-tie when there is over-production. It's not like a solar panel has startup/shutdown expenses like a coal or nuke plant.

 

[AnalogKid]

Reasonably simply solution to the problem is distributed battery banks around the state to absorb the excess energy and feed it back in overnight

Doesn't smell right. TCIO of that many batteries would eat up any returns for 10-20 years.

 

[Externet]

What happens on a not grid-tied solar generation when the batteries reach full charge ? The surplus generation is not used, the solar panels feed nothing. There is no energy 'waste' but the investment is useless.
Am installing 4KW grid-tied generation on my roof now, with lots of learning in front of me about future behavior of the power company.

 

[augustinetez]

Once we have saved enough extra pennies - batteries, wind generator and standby diesel generator and then going to tell the electricity company to go suck eggs.

Bad enough that we have almost the most expensive electricity cost /kWh in the world, they want to rip us off further.

Doesn't smell right. TCIO of that many batteries would eat up any returns for 10-20 years.

Still cheaper than what they are proposing.

 

[gophert]

Still cheaper than what they are proposing.

the joy of living in a sparsely populated country has the hidden costs of sprawling infrastructure a few people to pay for it. Adding even more, small-scale widely dispersed infrastructure simply adds more cost to an already expensive delivery system. Unless you and all of your neighbors are going to completely disconnect from the grid, your solution is nonsense. All your neighbors must also disconnect and then pay all future maintenance costs yourselves because, if only you or a few disconnect,BigBrother will step in to make things "fair" and use your tax dollars to supplement the cost of your neighbor's electricity since it is now even more expensive for them since you are no longer helping dilute the cost with a monthly power bill.

 

[Nigel Goodwin]

I don't see an issue? - certainly with wind power they simply shut down unwanted wind turbines when they don't need their power - there's a smallish turbine at a farm just behind where I live, and apparently that's actually controlled from Ireland?.

Same with solar - if you don't want the power then don't take it.

 

[Visitor]

Same with solar - if you don't want the power then don't take it.

Currently, there is no mechanism to "don't take it" - this isn't power from large wind farms. This power is produced by about 288,000 homes with solar arrays in South Australia. More than a quarter of a million independent producers of power feeding it into the grid with no mechanism of "simply shutting it off." When supply exceeds demand on the grid, the voltage rises and bad things happen.

As the article discusses, various remote control schemes are being developed so that the utilities can regulate these quarter of a million power producers to regulate supply.

 

[Pommie]

A simple solution would be to have a max voltage that power can be fed into the grid. Nominal voltage here is 230 so maybe have a gradual cutoff point up to 240V . The government here are talking about producing hydrogen with any excess energy but that seems incredibly inefficient. I suppose you could combine it with Carbon Dioxide to make butane and burn that as it would end up carbon neutral.

Mike.
Edit, one other thing, when the sun is at max there is normally a power shortage due to aircon use. The blackout mentioned in the article above was due to a huge storm causing damage to infrastructure - maybe Terry (from S.A.) will know more on this subject.

 

[Nigel Goodwin]

Currently, there is no mechanism to "don't take it" - this isn't power from large wind farms. This power is produced by about 288,000 homes with solar arrays in South Australia. More than a quarter of a million independent producers of power feeding it into the grid with no mechanism of "simply shutting it off." When supply exceeds demand on the grid, the voltage rises and bad things happen.

As the article discusses, various remote control schemes are being developed so that the utilities can regulate these quarter of a million power producers to regulate supply.

Presumably Australia has solar farms?, as the UK does, which I would expect to have facilities for shutting them off - probably in sections.

 

[Nigel Goodwin]

A simple solution would be to have a max voltage that power can be fed into the grid. Nominal voltage here is 230 so maybe have a gradual cutoff point up to 240V .

As the UK mains is 240V you certainly don't want a 240V cut-off - the 230V specification is for EQUIPMENT, not the actual mains voltage, which is still 240V in the UK and 220V in most of the rest of Europe. The 230V 'specification' has different tolerances to compensate.

Historically, back in the valve TV days, we used to occasionally get issues with low mains voltage and had to report it. One particular area was due to having extended a road and built a large number of extra houses, which was never planned for, and the cable feeding that road was too small for the load. The cure, obviously, was major roadworks to replace the underground cable with something more suitable.

But I don't think there's any issue here?, they simply shut down the parts they don't need if supply exceeds demand (and the stored power facilities - like Dinorwig - can't take the excess). Certainly when you look at wind farms it's VERY rare to see them all going round - I was talking to a maintenance guy the other year so asked him about them. Apparently it's because either they are faulty, shut down for maintenance, or shut down due to lack of demand.

 

[fourtytwo]

As far as I understand it all generating equipment up to 12Kw connected to the grid in the UK must conform to G83 and the protection settings are :-
Table1 ProtectionSettingsProtection FunctionTrip SettingTrip Delay Setting (Time)
U/V stage1Vφ-n†-13% = 200.1V2.5s
U/V stage2Vφ-n†-20% = 184V0.5s
O/V stage1Vφ-n†+14%= 262.2V1.0s
O/V stage2Vφ-n†+ 19% = 273.7V30.5s
U/F stage147.5Hz20s
U/F stage247Hz0.5s
O/F stage151.5Hz90s
O/F stage252 Hz0.5s
Loss of Mains*¶(RoCoF)1.0 Hzs-10.

For larger units more severe constraints would apply, this is to ensure the situation you describe (overvoltage by uncontrolled overproduction) does not occur. Also permission to connect has to be sought from the local distribution company ensuring they can keep track of feed network impedance issues.

 

[Visitor]

Presumably Australia has solar farms?, as the UK does, which I would expect to have facilities for shutting them off - probably in sections.

Yeah, but this article and the problem it addresses is with solar panels on homes. More than a quarter million homes that have the ability to pump more power into the grid than is needed.

 

[Nigel Goodwin]

Yeah, but this article and the problem it addresses is with solar panels on homes. More than a quarter million homes that have the ability to pump more power into the grid than is needed.

Presumably, as usual, it's just a made up newspaper story and complete nonsense - you simply shut down part of the larger producers, like the solar farms.