I have a three-phase supply and am looking to install solar panels and a Home Energy Storage battery. Would I need a Single-phase or Three-phase inverter?

Hiya!

Did you mean the Aclara SGM1433-B by any chance? If so, that's definitely a Three-Phase SMETS2 Smart Meter  I can double check it if you would like me to though. All I'll need are a few photos of it and I'll be able to identify it in a jiffy 

I would imagine a Three-Phase inverter would make more sense than a Single-Phase inverter with your setup. I'll dig through some resources in the morning and get back to regarding phase vectoring if possible  

@Blastoise186 Yes, well spotted, my first proper post and I got the model number wrong! 😜

It is the 1433-B, any help is appreciated and the fact you know what they meant by vectoring is also a positive. 

Hi @Mark C - and you’ve definitely arrived at the right place!

The rules for grid-connection of generators, such as PV Solar Panels, are described here.

The starting point is that you may normally export only 16A per phase (3.68kW). So if you have 3-phase, then you can triple that figure!

Moreover, one of the important constraints on grid-export is the losses caused at the substation due to phase-imbalance. If you have a 3-phase inverter, then you won’t be contributing to those losses. So in some circumstances your Distribution Network Operator (DNO) may permit you to operate above the 16A/phase limit.

You’re right on the northern edge of Western Power’s region. So your starting point is to look at their G98 Application Form and then assess your normal Maximum Demand (MD) for the house (excluding the PV Panels at this stage).

Ask here again if you require clarification.

Vector-phase metering is used when you might be exporting on one or two phases whilst importing on the corresponding other one or two. It allows the Energy Supplier to bill you for only the difference between the import and export.

It is more commonly referred to as “Vector sum” in the UK, and was previously discussed here on the Forum at a time when none of us knew what it was!

Further investigation since that topic suggests that a Smart Meter could not gain approval for connection to the National Smart Meter Network unless it supported vector sum metering.

Model SGM1433-B is currently the top-end model of Aclara’s 1430-series. You can download its Aclara Product Description PDF and a more detailed 1430-series specification document running to over 100-pages. The SGM1433-B terminal layout is referred to on page-81, but its features are otherwise little different to the rest of the series.

Vector-sum wouldn’t be an issue if your PV Inverter was 3-phase. But it would be relevant if you decided to store some of that energy in a single-phase Storage Battery.

Thanks for this….

One of the PV solution provider was suggesting “…if you have phase vectoring on the meter that would cancel out the need for a three phase PV system to utilise the solar electricity over all three phases”

We are not sure if this means they really know there stuff, they haven’t got a clue or they only sell single phase solutions!!!

We think our best option is to stick with three phase solar with an AC coupled battery storage

That PV Installer hasn’t understood the way the Grid works, nor how Energy Suppliers create bills for customers with 3-phase.

He is correct if the only consideration is the ability to produce correct billing. But it’s not!

When you think about it, apart from your proposed 3-phase Solar Panel installation, everything else in your house is likely to be running on single-phase electricity. So you are already causing phase-imbalance every time you switch something on.

At present there is no financial penalty for causing phase-imbalance at the substation. But it is highly likely that Ofgem will place it as a high level priority in a year’s time when Western Power is given its targets under the forthcoming RIIO-ED2 contract. The UK simply can’t go on squandering energy when we’re trying to reach net-Zero with increased use of renewables!

In the meantime a DNO can (and will) restrict what a customer can feed back onto the Distribution Grid if that would take the electricity supply outside its statutory limits.

I’m in precisely this position myself.

I was recruited onto the OVO trial of Storage Batteries from PowerVault. An 8kWh unit was installed here in Jan’21 and I proceeded to monitor how it operated in close coordination with Western Power area engineering staff.

OVO/Kaluza have now concluded that their Trial cannot operate at this site due to it already having a high supply voltage. That’s something I already knew, but was not picked up during the pre-installation survey.

Initially the Storage Trial would’ve been ok because the PowerVault battery was DC-connected. But software issues remained unresolved and PowerVault changed the installation to AC-connected by installing a PV Inverter.

The presence of two AC generation devices on the same site meant that a new Application was submitted for G99. That hasn’t been forthcoming and the Trial has been abandoned.

And you’ve just stated that you want AC-connected Battery Storage!

Have a look at the diagrams I’ve posted here on the topic about PV Installation…

and then let’s discuss this further.

@Transparent I will take a look…

it was a different installer that advised I need AC coupled if I ever want to export to the grid and take advantage of variable rate / times tariffs… Maybe this isn’t correct either!

I can feel another reply coming along…

Have a look also at the Solis Inverter here which is being discussed by a customer with billing anomalies.

He and I have both posted diagrams. These show that the inverter sits in the middle of a 3-way junction between the Solar Panels, the Storage Battery and the mains/grid.

There is a 3-phase version of the Solis inverter. I haven’t yet checked whether it is certified for use in the UK, nor how a 3-phase inverter handles battery connections. But I’m happy to do so if this is of interest.

For the moment you can ignore the difficulties being discussed by the customer. They’re nothing to do with the functionality of the inverter. His photos also show a high-quality installation by an electrician who understands the safety requirements and the way to properly attach cabling.

Growatt also offer an inverter which operates in the same fashion. It is not a design strategy unique to just one manufacturer.

You have no need to install everything at the outset. Once you’ve selected an inverter  with adequate capacity, you can add more batteries and PV panels over time.

@Transparent we are looking to ‘fill the roof’, between 15 and 18 panels depending on the provider, and want to take advantage of the scaffolding installation.  Additionally the starting battery can take advantage of the 5% vat rate.

One of the most difficult challenges is sizing the battery requirement, our usage has changed a lot recently along with expansion plans we have for early next year.  Who was it who said Solar is easy 😝