DNO limited export, oversize array storage options - Solar Immersion Diverter or battery 1 September 2022 at 11:00AM in Green & ethical MoneySaving 10 replies 238 views

rc28

Hi,

Just after some practical advice please as i'm struggling to find info online.

Our export with the DNO is limited to 3.68kwh. we are a large family and would like a bigger array, so am wondering what options there are to store excess.

We're proposing an 8kw array (all on the same orientation) that would be clipped to 3.68kw export, if we're generating over 3.68kwh what storage options are available that could use the pre clipped energy on the DC side?

Is there an immersion diverter that will use this? e.g. if the array was generating peak circa 8kwh and we were self consuming the inverted AC 3.68kwh, could the immersion diverter use the remaining output? or would it be lost without a battery?

I understand that a hybrid inverter with battery could be used that would store in DC, we dont really want to go down that route at the moment as we have a 500 litre unvented cylinder that has potential.

Thanks 

DougMLancs

With that size of array I would be wanting to apply to the DNO for a larger export limit

QrizB

rc28 said:

We're proposing an 8kw array (all on the same orientation) that would be clipped to 3.68kw export, if we're generating over 3.68kwh what storage options are available that could use the pre clipped energy on the DC side?

If you wish to store on the DC side, you're looking at a hybrid inverter (or an add-on DC battery that achieves the same result).

I understand that a hybrid inverter with battery could be used that would store in DC, we dont really want to go down that route at the moment as we have a 500 litre unvented cylinder that has potential.

You can get hybrid inverters that monitor your export (after any house loads are satisfied) and clip accordingly. This would let you heat your cylinder withour eating into your export limit. I think Reed_Richards has one.

ispookie666

The tech has come a long way and you can just limit export to 3.68 and have unrestricted generation.  It can be any variant DC, AC or hybrid. 
Export limitation would be usually G100, I would look for inverters which are already certified for G100. 

rc28

QrizB said:

rc28 said:

We're proposing an 8kw array (all on the same orientation) that would be clipped to 3.68kw export, if we're generating over 3.68kwh what storage options are available that could use the pre clipped energy on the DC side?

If you wish to store on the DC side, you're looking at a hybrid inverter (or an add-on DC battery that achieves the same result).

I understand that a hybrid inverter with battery could be used that would store in DC, we dont really want to go down that route at the moment as we have a 500 litre unvented cylinder that has potential.

You can get hybrid inverters that monitor your export (after any house loads are satisfied) and clip accordingly. This would let you heat your cylinder withour eating into your export limit. I think Reed_Richards has one.

Perfect thanks, sounds like i need to research that specific type of hybrid inverter. Am finding it a bit of a minefield (new to solar pv) as were sourcing the components ourselves for a self build there's no point of contact to ask questions.

Batteries may be an option for the future, for now immersion storage seems like the most economical thing.

ispookie666

@rc28 without applying to DNO how do you know the export is limited to 3.68?

rc28

Im not 100% it will be limited but 3 neighbours directly adjacent to me have 4kw systems (all installed many years ago). One of the neighbours said western power limited them to 4kw.

I suppose i will have to apply to be sure.

Thanks for the advice on the inverters, atleast i know it's possible to oversize (over export limit) and still use all generation.

ispookie666

I would probably go with the usual application process.  The outcomes could be 

• Unrestricted export - Your full generation/Inverter output capacity
• G98 limit of 3.68
• Limited export - Any value depending on the local grid 
• Zero export - Depending on your local grid.  

I hope the DNO lets you export at least 3.68.  

70sbudgie

ispookie666 said:

I would probably go with the usual application process.  The outcomes could be 

• Unrestricted export - Your full generation/Inverter output capacity
• G98 limit of 3.68
• Limited export - Any value depending on the local grid 
• Zero export - Depending on your local grid.  

I hope the DNO lets you export at least 3.68.  

I'm not sure the DNO can limit the export of a domestic property below 3.68kW? Because up to 3.68kW is G98 notification and you don't apply in advance for that.

So I think your third possible outcome should be "Any value above 3.68kW, depending on the local grid."

And the 4th outcome is not a possibility. 

(This is only applicable if you are a domestic property. If you are a commercial property, ignore everything I just said and @ispookie666 's comment stands in full)

ispookie666

Good point. I would not be surprised with a limit lower than 3.68 is applied by DNO. 
G98 is notification after completion of works, I presume this does not mean automatic approval from DNO. 

If I was DNO, with the scrutiny on finances and having to eat profit - I'd look at low hanging fruit a and domestic generation looks very appealing 🤐. 

70sbudgie

ispookie666 said:

Good point. I would not be surprised with a limit lower than 3.68 is applied by DNO. 
G98 is notification after completion of works, I presume this does not mean automatic approval from DNO. 

If I was DNO, with the scrutiny on finances and having to eat profit - I'd look at low hanging fruit a and domestic generation looks very appealing 🤐. 

This is why they are so heavily regulated. As long as you meet the prerequisites (like MSC cert, max 3.68kWhr inverter, safety cut out etc etc), then I don't think they are allowed to say no to G98. If they do, I would be having words with my installer as it means info is missing. I think they would also tell you why its been refused, so it can be sorted.