Additional solar array and addition of a battery

[Ronski]

We have an existing 4kw array, using Solarworld 250W panels, and Soleredge inverter (SE4000-16A) and power optimisers, which was installed in December 2015, so we get reasonable FITS payments. This array takes up all suitable roof space on the house, there are two more roofs, but they are NW and NE facing, there's also a double garage with flat roof. We generate roughly 4300KWh a year, and use roughly half of that. Our annual usage is currently around 10,000KWh including what we use from solar production.

As mentioned above we have a flat roofed double garage that measures 6m x 6m, it does get some early morning shading, and late afternoon/early evening shading, but in between there is no shade. I think we should be able to get 12 panels on there, facing the same direction as the best performing panels on the main roof, roughly SW. So this could add another 4.8kw of solar, or there about.

I'm not sure on what our peak usage is, but have recently installed the Loop app, and can see from this that our usage peaks around 3.6kw at 16:00 on 5th December - so no solar production, there's no EV and no plans for one at the moment, no electric showers, no immersion heater, no electric heating, we do have an electric oven which is rated at 5.5Kw.

Given the rises in electricity costs, I'm now think it would be a good idea to have a battery or two, and this would mean more solar to charge it, and I'd also like to be able to charge using off peak when the weathers poor etc. It would also be useful to have the whole house powered off the batteries in the event of a power cut, although they are rare around here, so it would be a nice to have, rather than a necessity.

Given we have one array already, which can't be altered I think we need an AC coupled battery.

I don't have a lot of space in the house for batteries, dependant on size they could fit under the stairs, or in our cloakroom/shoe room/server room, or the other option is in the detached garage, or both locations (house + garage).

I'm not sure how this will all fit together, and I'm still waiting on quotes from various installers, seems they are all very busy, and there is long wait times just for a quote let alone for installation, or availability of batteries, so trying to get some info together in the mean time and understand things better.

Given a battery can only charge/discharge at a given rate I'd like a system that could cope with our current usage and perhaps be expanded in the future - as you've probably guessed I'm not sure on what we need.

From what I've read the DNO would take the two arrays, and the battery or batteries and add them all up when considering the export potential.

Is there an easy way to know what the DNO will allow us to connect in addition to our existing system?
What's the implications if they won't let us export more than we already do?

We're in Broadstairs, Kent - is there any pro's around this area?

 

[Berserkerboy]

I was told in our situation that an AC inverter would exceed our export limits.
Send in a G99 application and they will model the implications and either approve, or tell you that you need to pay for upgrading their transformer if you wish to proceed.

 

[binky]

The only way to find out what your DNO will allow is to make an application to them. You should be able to get permission with an export limited to zero if necessary.

 

[Ronski]

Thanks both. Will take a look at the forms.

 

[Ronski]

Instead of filling in the forms I contacted the DNO, and after a couple of emails, and a phone call I managed to get this info out of them.

Many thanks for your enquiry. I’ve reviewed your email and our records for the local network. Based on your close proximity to the substation (and therefore the low impedance of the circuit at your connection point) installing an additional 4.8kW of solar PV should not cause any voltage rise issues and your PV application ought to be approved without any problems.

I’m not sure whether there is any intention to export to the grid from the battery? If there is no intention to use the battery to export then you’d just need to submit a copy of the device’s G100 type-test certificate with the commissioning submission. If the battery is connected on the DC side of the inverter then we can disregard it as a potential issue as any export to the grid would be limited by the inverter size.

There may potentially be a voltage rise issue if the battery was connected on the AC side of the system and export from the battery coincided with that from the PV system. If you’d like the facility to use the battery for export to the grid at peak times then I’d suggest that a G100 compliant Export Limiting Scheme (set to the equivalent PV inverter rating) would be appropriate in this instance.

I hope that this makes sense but do contact me if you have any queries or would like further details on any of the points raised.

I'm pretty sure I'm going to need an AC connected battery, so the battery can be charged from both arrays, so what dos the fourth paragraph mean, installation wise? Is that fairly straightforward to achieve, or rather expensive?

 

[binky]

Solis and Solax, and other makes have export limitation settings that can be tweaked as necessary and set as low as zero export. This is achieved by installing a meter that monitors energy flow in and out of the building to your meter tails. Cat 5 cable from the meter can then be run to the battery inverter.

 

[Ronski]

So that would be classed as an export limiting scheme, I was thinking they wanted some sort of fail safe device in case the system developed a fault?

 

[binky]

So that would be classed as an export limiting scheme, I was thinking they wanted some sort of fail safe device in case the system developed a fault?

Nope, just export limitation. I've never found out what happens if it fails

 

[Ronski]

Acytually if I had a Victron Multi Plus II as an inverter/charger, the batteries would be DC coupled wouldn't they?

 

[binky]

Acytually if I had a Victron Multi Plus II as an inverter/charger, the batteries would be DC coupled wouldn't they?

Yep

 

[Berserkerboy]

Solis and Solax, and other makes have export limitation settings that can be tweaked as necessary and set as low as zero export. This is achieved by installing a meter that monitors energy flow in and out of the building to your meter tails. Cat 5 cable from the meter can then be run to the battery inverter.

Hi Binky. Just wondering about your post here.
I am waiting to hear from the DNO on a G100 application. My diagram to them doesn't include a meter monitoring the energy flow. I thought that the G100 compliant Solis used a CT clamp to monitor the energy flow and react accordingly. Do I need to include a further monitor in the application? Maybe, that's why they haven't responded yet.?

 

[binky]

Hi Binky. Just wondering about your post here.
I am waiting to hear from the DNO on a G100 application. My diagram to them doesn't include a meter monitoring the energy flow. I thought that the G100 compliant Solis used a CT clamp to monitor the energy flow and react accordingly. Do I need to include a further monitor in the application? Maybe, that's why they haven't responded yet.?

Sometimes they supply a clamp, sometimes a meter, just depends what turns up with the box. It's fair to say the last few Solis I've fitted have been hybrid with a meter. Clamps are a lot easier, but no need to change your application.

 

[Berserkerboy]

Ah, that makes sense. Cheers Binky.
Confirmation of receipt of my G100 application received today. The person who is dealing with my application is a trainee planner........

 

[Ronski]

I'm still getting some quotes, but one company seems to extremely thorough, they even want to do a site visit before quoting - scheduled for the 24th.

I don't mind thorough, but they now want me to sign some paperwork so they can apply for a G99 on my behalf, surely that's not normal, and I don't even know what they are applying for.

Do you think I'd be better off sending in my own application? Presumably if equipment changes then thats not an issue as long as the declared kw isn't exceeded?

 

[binky]

I'm still getting some quotes, but one company seems to extremely thorough, they even want to do a site visit before quoting - scheduled for the 24th.

I don't mind thorough, but they now want me to sign some paperwork so they can apply for a G99 on my behalf, surely that's not normal, and I don't even know what they are applying for.

Do you think I'd be better off sending in my own application? Presumably if equipment changes then thats not an issue as long as the declared kw isn't exceeded?

Everyone should do a site visit before quoting.

 

[Ronski]

I totally agree, as how else can they give an accurate quote, I suspect most just bump the quote up to cover the unknown.

What do you thing about the G99 application?

 

[Berserkerboy]

I'd be inclined to inform the DNO if there are any equipment changes. They need the G99/100 certification forms for the installed equipment.
If something goes wrong and it's down to you...Better to just be transparent about everything.

 

[Ronski]

@Berserkerboy I think you misunderstand. I fully intend on doing the G99. The question is whether I let a solar company that's only doing a quote apply, or whether I send the form in listing my ideal hardware.

I've no idea what the solar company is going to apply for, and I've no idea if it will cause complications if I go with a different company - remember the company that wants to apply hasn't even given me a price yet, it feels more like they are trying to lock me in, and make me feel I have to go with them.

 

[binky]

When I was installing solar, doing the paperwork was part of the package. If there was a need to pre-apply then there was never an obligation to use my company, and it doesn't lock you into that company with the DNO either.

 

[Berserkerboy]

I'm just saying that if the company do the application for you and you subsequently decide to do your own installation, let the DNO know what different equipment you intend to install.