DNO limitation and potential workaround

[binky]

Overthinking it is an understatement

 

[bladerunnerpv]

Hey Bob
I get what you're saying I think, you're basically trying to even out the export of your excess generation over the 24h such that DNO limit is not exceeded.

It presumes the DNO is a hard limit.

But IIUC the 3.68kW limit can be exceeded with DNO agreement, via G99(?) which is applied for in advance of install

Why not contact your DNO for some advice? I'm sure you won't be the first trying to do a 15kWp system.

I would imagine most DNOs would be glad of the of the extra generation in the current climate

 

[Bob Smith]

Hey Bob
I get what you're saying I think, you're basically trying to even out the export of your excess generation over the 24h such that DNO limit is not exceeded.

It presumes the DNO is a hard limit.

But IIUC the 3.68kW limit can be exceeded with DNO agreement, via G99(?) which is applied for in advance of install

Why not contact your DNO for some advice? I'm sure you won't be the first trying to do a 15kWp system.

I would imagine most DNOs would be glad of the of the extra generation in the current climate

That was the idea. You are correct. For DNO it is free up to 3.68. I have that already. Then they can be generous and allow you a bit more for free but then depending on many obscure reasons (I did ring the DNO but they could not give me a straight answer as I could not give them some of the info they wanted and it depends on the state of the grid where I am etc....). they may charge you to be allowed that extra power and if I think the charge is too much I will need to figure out what to do. I do not want to downsize my system. To pay people to come I want to make the most of them being here and cover the house with panels I'll be "The house with the PV" lol

 

[binky]

That was the idea. You are correct. For DNO it is free up to 3.68. I have that already. Then they can be generous and allow you a bit more for free but then depending on many obscure reasons (I did ring the DNO but they could not give me a straight answer as I could not give them some of the info they wanted and it depends on the state of the grid where I am etc....). they may charge you to be allowed that extra power and if I think the charge is too much I will need to figure out what to do. I do not want to downsize my system. To pay people to come I want to make the most of them being here and cover the house with panels I'll be "The house with the PV" lol

The exporting scenario was only of any importance when the FIT was available, and you didn't want to be limiting generation from your panels because that meant losing potential income. Now it's fairly irrelevant, the target is reducing your bills and self consumption of the energy generated.

 

[Bob Smith]

The exporting scenario was only of any importance when the FIT was available, and you didn't want to be limiting generation from your panels because that meant losing potential income. Now it's fairly irrelevant, the target is reducing your bills and self consumption of the energy generated.

It depended on what type of FiT you had. My export is based on a "assumed" 50% export. This is because, as you surely know well, what I export cannot be measured, So the higher benefits is when nothing is exported and I still get paid 50% of my generation as export leccy

I agree with your target but if you generate more than what you need (even with batteries) then exporting is next. If you are limited to what you can export and still have excess then what?

You surely remember I wrote that originally, I thought I'll have a very very large battery to store plenty leccy in summer and to use it in Winter.
Unfortunately, this is not practical. For cost. Having a 100 or 200kWh battery is very expensive, and then there is also technical limitation. There is a daily loss. That is, when unused the battery will lose daily a bit of the store energy. So if one battery is full in July in the hope you'll use it in Winter, then you would have lost a fair bit. I once read on a specs that the loss can be 5% per day. The rate depends on the ambient temperature.


To give more info

I currently buy for 5500kWh per year. My panels generate 3850kWh but some are exported at the moment (when not used for the hot water, and I do not currently have batteries).
With the new panels it is estimated that I will generate between 8 to 10MWh extra, so let's say for sake of argument a total of 12MWh with my existing system..

in theory I could be in a situation that I never have to buy electricity again. Unfortunately this is not true. The batteries in Winter will get emptied and the panels may not produce enough in the day for the house + charging the batteries.

In summer. I expect I will hardly empty much the batteries (I use 3-5kWh/24hrs in summer). so I will have plenty of excess of leccy. If I have no limitation from DNO not a problem, I'll export. If there is a DNO limitation, what can I do in order not to waste what the panels could be generated extra.

 

[binky]

It depended on what type of FiT you had. My export is based on a "assumed" 50% export. This is because, as you surely know well, what I export cannot be measured, So the higher benefits is when nothing is exported and I still get paid 50% of my generation as export leccy

I agree with your target but if you generate more than what you need (even with batteries) then exporting is next. If you are limited to what you can export and still have excess then what?

your Fit is based on total generation, so limiting generation was always a bad idea. From the total generated it was assumed 50% got exported for which you received an additional 4.5p per kwh.

If yuo want to make use of exported energy in summer/ spring/ autumn, then you need to look at the flexible tariffs such as Octopus go - there's lots of info on that in the posts on here already.

 

[Joules]

Hello

I would like to share with you some thoughts and that you let me know what you think and what else I should consider.

The set: PV System 15kW. For simplicity let's assume 5kW facing East, 5kW facing South and 5kW facing West.
DNO does not authorize additional power to the grid and therefore 3.68kW is the only authorized power to be exported and the inverter will limit the export accordingly


Size the battery to store all the excess power which has not been consumed by the house (including heating hot water) and cannot be exported due to the limitation.
Then later when the panels no longer produce enough power and the house has enough power from the battery, the excess stored in the battery will slowly be exported to the grid (respecting the limit).

In other words, does it make sense with such an export limit and large system to send some of the electricity stored in the battery to the grid at night? Keep enough for you and export the rest.

Thank you for your insight

Think outside of the box. Your at full power has say a 60kW engine but more often than not it runs at a fraction of this whilst driving. The reason is that you are able to control its power and hence speed by use of the accelerator pedal.

You have too much Accept that you need to limit that power so for solar power zero export solutions and discover your solar ‘accelerator pedal’. Enhance the National Grid by not stressing its DNO infrastructure.

 

[Kot]

what can I do in order not to waste what the panels could be generated extra.

EV ? Storage heater?

 

[Bob Smith]

what can I do in order not to waste what the panels could be generated extra.

EV ? Storage heater?

Hi

I currently do not have EV and don't except one before a couple of years.
Storage heater. That's an idea Thanks

 

[binky]

Hi

I currently do not have EV and don't except one before a couple of years.
Storage heater. That's an idea Thanks

You can buy storage heater specifically designed to work with solar, although I can't remember who makes them

 

[bladerunnerpv]

What to do with the extra ?
Sunamp or iBoost for water heating?
Air conditioning for the summer?