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HarmLessSolutions

974 posts

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#2939151 7-Jul-2022 12:44

CrazyM:

HarmLessSolutions:

One question that was asked on another forum was from someone who had "3 phase power and a 3 phase 10kW inverter, but the car only charges off 1 phase. So what's the economy there? I admit to being a bit confused." Is this going to be the same as my situation of feeding into just one phase and if so how will this affect metering? We're billed for just one import quantity despite having 3 phase supply so if the demand on each phase is different are these just totalled to calculate usage?

You are correct in that NZ does not have net metering, so you can be selling power on 2 phases at 8c/Kwh while simultaneously buying on the other phase at 30c/kwh (for example). Makes it harder to self-consume your solar generation and it makes adding batteries even less cost-effective.

Almost no 3 phase inverters will output an unbalanced load (i.e supply power to the phases with the most load). The only examples I know of are the Goodwe ET and the Solax X3 Hybrid. Everything else just evenly distributes your solar generation down all 3 phases. And even with those models the most they can 'unbalance' is 1/3rd of their maximum output (e.g. on the 10kW Goodwe the maximum it can send down one phase is 3.3kW; for example it can split 6kW of generation 3kW/1kW/2kW but it could not split 10kW of generation 6kW/3kW/1kW)

Thanks for your reply. A bit to unpack there as I now realise the two examples I asked about weren't comparable.

Your answer relates to the 3 phase inverter feeding a single phase EV charger which I can relate to but in our situation we have a single phase 5kW inverter feeding into one of the 3 (incoming?) phases we have here.

The PV generation therefore all goes down one phase and we have transferred as much daytime use circuits as we can, without risking demand above the 63 amp pole fuse. In doing so we are also essentially helping balance our otherwise uneven load between phases as long as we are generating and thereby reducing load on that phase due to our self consumption. Also worth baring in mind that our HWC will virtually never need to draw from grid supply due to the Paladin's efforts.

This seems to be what is happening as by monitoring our grid import/export data as displayed on the Paladin (which monitors the house flow by way of a CT clamp) we can see, for example, export decrease by ~3.3kW when the (7kW) EV charger is turned on to charge our Leaf which has a 3.3kW max. AC charge input.

Am I assuming correctly in regard to how we are benefitting from our PV generation? If not how could we better configure our set-up?

https://www.harmlesssolutions.co.nz/

CrazyM

110 posts

Master Geek
Inactive user

#2939182 7-Jul-2022 13:51

Yep, you've got it. If you have a single phase inverter the best thing to do to maximise your self consumption is to put all the daytime loads you can onto the same phase as your inverter. And anything on your non-inverter phases gets no advantage from your solar at all.

I went for a 3phase inverter that splits power evenly down all phases, so I want to try and have my daytime loads evenly distributed over the phases.

This means that when I look at a system overview like the image below everything looks great. Green is solar generation, red is consumption, and blue is where our consumption is taken from PV rather than the grid. So it appears that from 0800-1630 that I dont use the grid at all and I have a healthy export. This is how things work in most countries as they have net metering over phases.

....but in NZ this is not the case. We have to look deeper at what is happening on each of the phases. Here is a graph of the same day but showing the active power on each phase. Basically when each line is above 0 I am exporting to the grid and when it is below 0 I am buying from the grid.

So in this example there are almost no users on my b phase (green) all day so it only really exports power.

Phase a (blue) wriggles up and down but no major consumers so thats probably my fridges/freezers/computer etc.... The big spikes downward are probably my water pump.

Phase c (yellow) is my big consumer, you can see the 3kW hot water cylinder turn on at 1000 and then off at 1230 (with some on and off spikes at 1300 and 1400). At these times the graph has gone negative so I am importing power on this phase while selling on the others. And at 1630-1700 it looks like the oven and the hob are on preparing dinner so I'm really sucking the power and there is very little solar to offset it.

Since this graph I have shifted my loads around and phase b is more utilised, but you get the general idea...

HarmLessSolutions

974 posts

Ultimate Geek

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#2939200 7-Jul-2022 14:21

@CrazyM,

Thanks for your reply and very cool data presentations.

My initial impression is that the biggest load that isn't compensated from solar seems to be your HWC. This occurs simultaneously with export happening on the other phases so you obviously have the capacity to offset this with PV generation. Have you considered adding a diverter such as a Paladin to your system? This would put a portion of the exported generation into your HWC which as well as storing the energy would also prevent the big import events seen at 10:00 - 12:30 and possibly also reduce the 6:30 one if that is morning shower use, and possibly 00:30 - 1:00 if that is a scheduled dishwasher event.

Maybe a bit more complex to include a diverter in a 3 phase set-up like yours but I imagine it's doable.

The Paladin we have on our current installation is definitely the biggest single improvement we have over the set-up we had at our previous place.

https://www.harmlesssolutions.co.nz/

CrazyM

110 posts

Master Geek
Inactive user

#2939234 7-Jul-2022 15:33

I did look into a Paladin but didnt get a reply from the seller/distributor. After multiple attempts I gave up on it.

Later on I ran the numbers and with my 180L hot water cylinder I figure it would be unlikely to pay back the install cost over its lifetime. And also it is another smart piece of equipment to conflict and manage around future batteries/EV's/time-of-use power rates etc....

When my hot water cylinder dies I will probably replace it with a 300L model with a 1-2kW element in the bottom set to a high temp and on a solar timer, and a 3kW boost element at the top at a lower temperature, maybe on a different phase. And maybe a Paladin will fit better then.

Heck, by then I might have an EV with V2G and then Id rather have my excess energy in a battery rather than my hot water cylinder...

HarmLessSolutions

974 posts

Ultimate Geek

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#2939569 8-Jul-2022 10:09

CrazyM:

I did look into a Paladin but didnt get a reply from the seller/distributor. After multiple attempts I gave up on it.

Later on I ran the numbers and with my 180L hot water cylinder I figure it would be unlikely to pay back the install cost over its lifetime. And also it is another smart piece of equipment to conflict and manage around future batteries/EV's/time-of-use power rates etc....

When my hot water cylinder dies I will probably replace it with a 300L model with a 1-2kW element in the bottom set to a high temp and on a solar timer, and a 3kW boost element at the top at a lower temperature, maybe on a different phase. And maybe a Paladin will fit better then.

Heck, by then I might have an EV with V2G and then Id rather have my excess energy in a battery rather than my hot water cylinder...

Unfortunate you weren't able to contact Paladin. We were in direct contact right through to the installation process when we had a couple of queries, which Paladin addressed expertly.

We installed a 250L HWC when we took possession of our current property in 2016 due to a HWC that had failed on the eve of settlement. Our intention was to replicate dual input as PV was on the drawing board back then and we had a dual element HWC in our previous property which worked together with the evacuated tube solar we had there.

Paladin's advice was that a dual element HWC wasn't helpful in a diverter powered HWC and seeing how the Paladin works I can now understand why. Perhaps the reduction in cost between a dual element vs. single element will help the viability of adding a Paladin in your situation. The functionality of the Paladin isn't that complex so wouldn't be hard to integrate into the future plans you mention.

I agree that V2G will change the distributed generation landscape completely including its cumulative value as a buffer for grid demand peaks. Hopefully this technology isn't too far away, including its adoption in New Zealand.

https://www.harmlesssolutions.co.nz/

CrazyM

110 posts

Master Geek
Inactive user

#2939681 8-Jul-2022 10:51

HarmLessSolutions:

CrazyM:

I did look into a Paladin but didnt get a reply from the seller/distributor. After multiple attempts I gave up on it.

Later on I ran the numbers and with my 180L hot water cylinder I figure it would be unlikely to pay back the install cost over its lifetime. And also it is another smart piece of equipment to conflict and manage around future batteries/EV's/time-of-use power rates etc....

When my hot water cylinder dies I will probably replace it with a 300L model with a 1-2kW element in the bottom set to a high temp and on a solar timer, and a 3kW boost element at the top at a lower temperature, maybe on a different phase. And maybe a Paladin will fit better then.

Heck, by then I might have an EV with V2G and then Id rather have my excess energy in a battery rather than my hot water cylinder...

Unfortunate you weren't able to contact Paladin. We were in direct contact right through to the installation process when we had a couple of queries, which Paladin addressed expertly.

We installed a 250L HWC when we took possession of our current property in 2016 due to a HWC that had failed on the eve of settlement. Our intention was to replicate dual input as PV was on the drawing board back then and we had a dual element HWC in our previous property which worked together with the evacuated tube solar we had there.

Paladin's advice was that a dual element HWC wasn't helpful in a diverter powered HWC and seeing how the Paladin works I can now understand why. Perhaps the reduction in cost between a dual element vs. single element will help the viability of adding a Paladin in your situation. The functionality of the Paladin isn't that complex so wouldn't be hard to integrate into the future plans you mention.

I agree that V2G will change the distributed generation landscape completely including its cumulative value as a buffer for grid demand peaks. Hopefully this technology isn't too far away, including its adoption in New Zealand.

I agree the Paladin would currently fit, but it still can only optimise the PV consumption of a single phase and I'd still have 2 others doing their own thing. There are definitely solutions out there, it just depends how far down the rabbit hole you want to go for diminishing returns.

A lot of these problems would go away if NZ metered their 3phase like the rest of the world but I dont expect power/lines companies will revert without a fight. Until then I'll just try and balance my consumption over the phases and get 3 phase appliances where available (3ph heatpump, 3ph EV charger, 3ph HWC???....)

HarmLessSolutions

974 posts

Ultimate Geek

Subscriber

#2985912 21-Oct-2022 16:59

Our PV situation has changed so I've successfully requested an unlocking of this thread as from previous discussions here it seems to have a lot of collective quality PV knowledge among the posters here.

We have recently added to our EV ownership with a Polestar2 now sharing our 7kW wall charger with our Leaf. This means that the charger is being used to its full 7kW output capacity when charging the Polestar which means that our 5kW of PV generation must always be supplemented from the grid. So in order to better enable our charger to be fully solar supplied we are planning on adding an extra 3.5kW of solar panels.

When I proposed this to our installer he pointed us at PowerCo's distributed generation standards which disallows export to be unbalanced by more than 5kW between phases (page 5). The fact that we already have close to 15kW of consumption potential on the phase that our PV exports into was disregarded by PowerCo, though they did see the logic in us doing so to best be able to self-consume our own generation. I realise that we're approaching the pole fuse rating but as most consumption is correlated with PV generation I'm satisfied that limit is very unlikely to ever be met.

Although our property has three phase supply the PV is located on an outbuilding which is 25m+, a sealed driveway and two sub boards away from the incoming line and meter board at the house. The logistics and cost involved in running three phases out to the shed where the PV is located makes this impractical.

We are considering a set-up where the additional PV feeds into a second inverter that can be essentially disabled when export to the grid exceeds the 5kW threshold. This needs to be monitored wirelessly by use of a CT clamp on the grid side of our meter board. Presently we have wifi communication with our existing inverter (an SMA Sunnyboy 5kW) and a similar connection with the second (3.6kW SMA) inverter is planned.

The missing link in the chain would seem to be a wifi compatible monitoring device (CT clamp) that could be used as the activation data to disable the smaller inverter. As we have significant usage relegated to the PV export phase this threshold would only rarely be breeched but without a system like this installed Powerco will disallow the installation of the additional PV capacity.

What 'device' am I looking for in order to make such a system work as required?

I realise that some inverters have inbuilt technology that could throttle back output with the result we require but this would involve having to sell our 5kW existing inverter and would still require remote export measuring connectivity in order to do so.

Suggestions??

https://www.harmlesssolutions.co.nz/

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billgates

4705 posts

Uber Geek

Trusted

#2985929 21-Oct-2022 18:13

SMA Data Manager M (or Lite) or SMA Home Manager 2.0 should be able to manage this for you. Submit a technical ticket to SMA support and they should be able to confirm for you.

Do whatever you want to do man.

eonsim

398 posts

Ultimate Geek

Trusted

#2985964 21-Oct-2022 20:58

A fair number of inverters have support for controlling/synchronising output of multiple inverters to stay under specific export limits. Usually, the inverters just need to be wired together (ethernet) and one of them is set to be the master inverter which then controls the secondary one and makes sure the combination of both of them don't export more power than they're allowed. I assume what billgates has mentioned is probably SMA's version of this.

HarmLessSolutions

974 posts

Ultimate Geek

Subscriber

#2988266 26-Oct-2022 13:14

billgates:

SMA Data Manager M (or Lite) or SMA Home Manager 2.0 should be able to manage this for you. Submit a technical ticket to SMA support and they should be able to confirm for you.

Thanks for your suggestion. Do either of these units have wifi connectivity? My primary issue is an inability to monitor our property's import/export with a wired connection.

The installer of our existing set-up is familiar with SMA's range of products but has limited technical problem solving ability.

https://www.harmlesssolutions.co.nz/

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