How best to expand an existing PV system?

[Dillsue]

6 hours ago, richard_scotland said:

I just spoke to the designer and apparently it isn't - its a 50 kVa single phase transformer. They come in 3-phase and single-phase versions and this is a single phase version. 

Send the designer the photo as that's got 3 phases going in and 3 cables coming out of the back going to 3 isolators....looks pretty 3 phaseish to me.

 

SPEN upgraded our transformer last year to 25kva single phase just for us. If that's 50kva single phase for 4 houses then that sounds relatively underrated for an electrified future......unless it's actually a 3 phase unit.

 

Maybe they've got their records wrong! 

[richard_scotland]

11 hours ago, Dillsue said:

Send the designer the photo as that's got 3 phases going in and 3 cables coming out of the back going to 3 isolators....looks pretty 3 phaseish to me.

 

SPEN upgraded our transformer last year to 25kva single phase just for us. If that's 50kva single phase for 4 houses then that sounds relatively underrated for an electrified future......unless it's actually a 3 phase unit.

 

Maybe they've got their records wrong! 

They actually followed up this morning to ask me to send a photo of the transformer 'just in case our records are incorrect'. With binoculars I can read some of the values on the faceplate on the side and it suggests its 433V and 3-phase, with a 30 kva capacity (not 240V single phase). If its is 3-phase, that should make things a bit cheaper. 

[richard_scotland]

Turns out it is a 3-phase 50 kva transformer, which brings the 3PH connection cost down a bit- £3250+VAT, subject to a detailed quote. 

 

However, our 3PH supply would be limited to 30 kva to leave enough capacity for the other 3 houses.

 

I'm not sure what this means in practice. They said they would install 3x80A fuses, but we would have to have an agreement to limit total use to around 30 Kva - which they thought would be plenty for almost all domestic situations. Does that roughly equate to 120A?

 

So our options are:

 

upgrade from 60A to 80A single supply for no cost. 

or

pay £4k for a slightly less than full capacity 3PH connection (+ some internal electrical costs)

 

So the question becomes which is best:

 

at the moment we have 

12 Kw ASHP

7 Kw car charger

Induction hob

a dishwasher, washing machine and tumble dryer which are on constantly

4 Kw solar

and we frequently hit 11-12Kw import for hour+ periods

 

in the future (next 5 years)? we might want to add:

5 Kw invertor for battery storage

More solar (where this thread started!)

Sauna or hot-tub (the hot tub mainly for hyrdotherapy for my son). 

Possible garden annex (with kitchenette, electric shower, electric heating etc)

A second electric car (so more frequent use of the charger)

 

I think for all the wish list items we would be better off with 3PH, but perhaps we could do some of them just fine with an 80A single phase and careful use. 

 

Anyway, this thread has been helpful to explore options - thanks to all contributors 

 

[Marvin]

On 26/10/2024 at 17:58, Dillsue said:

We're at the end of a 1/2 mile long 11kv supply with a dozen or so properties including a couple of farms but I've no idea if that means we got export consent automatically. 

 

You can build as big a system as you want if you implement export limitation. That way you can use all the power your system generates but your inverter will throttle its output to limit export to whatever your DNO allows, if you're not using the power

Our DNO would only use the upper export limit of the Inverter in their calculation. Their opinion was that lower adjusted exporting limits on Inverters could be inadvertently altered and so certainty of requirements being followed. 

[Dillsue]

1 hour ago, Marvin said:

Our DNO would only use the upper export limit of the Inverter in their calculation. Their opinion was that lower adjusted exporting limits on Inverters could be inadvertently altered and so certainty of requirements being followed. 

Ask them what their own G100 spec is for.

[Marvin]

 

Hi @richard_scotland

 

Bear in mind that it is quite difficult to mix PV panels. 

 

Having investigated this when considering increasing the amount of panels for our home a couple of things came to light.

 

If you add PV panels to an existing system it's complicated to do unless the panels are exactly the same as the existing (not just the same manufacturer but voltage and amperage) as 1 different panel added to a string would effect the output from all the panels.

 

Unless you install a special system, if you have some panels shaded or facing a different direction from the others on the same string, the outputs of all the panels on the same string will be effected. 

 

Best of luck.

 

M

 

 

[Marvin]

2 hours ago, Dillsue said:

Ask them what their own G100 spec is for.

You know more than me.. we obtained approval for our 6kW inverter so all's fine for us.

 

As I understand it G100 limits exportation: No export allowed (G100 applies) – this means all electricity produced by the embedded generation must be utilised on the premises. 

 

It may be that a different type of inverter or controls are required... you tell me.

 

M

 

 

[Dillsue]

23 hours ago, Marvin said:

You know more than me.. we obtained approval for our 6kW inverter so all's fine for us.

 

As I understand it G100 limits exportation: No export allowed (G100 applies) – this means all electricity produced by the embedded generation must be utilised on the premises. 

 

It may be that a different type of inverter or controls are required... you tell me.

 

M

 

 

Yep it's a G100 compliant inverter that's required to legitimately implement export limitation.

 

G100 is an industry spec produced by the ENA for all DNOs to use . If yours has said they don't trust the spec then they really need to go back to the ENA with their concerns. On the other hand it may only be the view of the the individual you contacted and if you pressed them they would(should) permit export limitation??

[Dillsue]

On 04/12/2024 at 20:17, Marvin said:

 

Hi @richard_scotland

 

Bear in mind that it is quite difficult to mix PV panels. 

 

Having investigated this when considering increasing the amount of panels for our home a couple of things came to light.

 

If you add PV panels to an existing system it's complicated to do unless the panels are exactly the same as the existing (not just the same manufacturer but voltage and amperage) as 1 different panel added to a string would effect the output from all the panels.

 

Unless you install a special system, if you have some panels shaded or facing a different direction from the others on the same string, the outputs of all the panels on the same string will be effected. 

 

Best of luck.

 

M

 

 

If you're using optimisers and likely micro inverters,  you can mix and match panels. We've got 310, 320, 335 and 405 watt panels all on the same inverter. There's a cost overhead, but optimisers have lots of advantages one of which is the ease of alteration/expansion.

[Marvin]

On 05/12/2024 at 21:06, Dillsue said:

If you're using optimisers and likely micro inverters,  you can mix and match panels. We've got 310, 320, 335 and 405 watt panels all on the same inverter. There's a cost overhead, but optimisers have lots of advantages one of which is the ease of alteration/expansion.

Hi @Dillsue

Of course your right. What sort of price are they to purchase for each panel?? It maybe something for us in the future. Am I right that they will protect the rest of the string if one of the panels is shaded? 

 

Another thought. can I use different rated Voltage/Amperage panels (I am looking at a very close range)?

 

Every day is a school day for me...

 

Thanks 

 

M

Edited December 8 by Marvin

[SteamyTea]

25 minutes ago, Marvin said:

Another thought. can I use different rated Voltage/Amperage panels (I am looking at a very close range)

You certainly can with single module micro-inverters, they just pump out AC at the correct voltages.

I am not sure about optimisers, they may have hard wired limits built into them.

[Dillsue]

10 hours ago, Marvin said:

What sort of price are they to purchase for each panel?? It maybe something for us in the future. Am I right that they will protect the rest of the string if one of the panels is shaded? 

 

Another thought. can I use different rated Voltage/Amperage panels (I am looking at a very close range)?

I use Solaredge and you can pick them up on Ebay for £15 upwards if you're prepared to wait. Otherwise £40? upwards. They have a 25yr warranty so I'm not bothered about buying privately. 

 

Optimisers/micro inverters are wired in a string the same way as panels can be wired. The panels plug into their optimiser but arent functionally part of the string. The difference is that where a faulty/shaded/lower powered panel in a conventional string can block or restrict the power coming from the rest of the string, optimisers don't. Each optimiser allows power from the rest of the string to pass through it unrestricted and adds any power it has available. If an optimiser has no power to add because its panel isnt producing any, the rest of the string carries on producing as normal. Each optimiser has an MPPT in it to get the most power out of its panel.

 

You can connect whatever panels you want to optimisers so long as the panels output is within the optimisers input range AND the optimiser is compatible with other optimisers in the string. If youre asking about mismatched panels in a conventional string then yes you can, but the lower rated panels will likely restrict the output of any higher rated panels. It's doable but alot more restrictive than using optimisers/micro inverters