Auto connect to grid to export surplus PV

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assyntdavid asked Jun 4, '24

Auto connect to grid to export surplus PV

This is probably a new feature request, rather than a question/discussion point.

I have the illustrated equipment in my house. The inverter is rated 8kW contiuous, battery banks total 20kWh. The inverter can/does supply house needs, and so I run the house 'off grid' when I can. The system is set up up so that it views the grid as a generator, and the 'Periodic Run' function within 'Generator start/stop settings' is used to auto-connect the system to the grid at night to top up the batteries during the darker months as required. This has been working perfectly for 6 months. I have a relatively small PV array, but at this time of year they can be producing up to 1.4kW with the batteries at 100%. The system copes with this situation by shuting down the ac coupled PV inverter.

But it would be so much better to export this surplus power. I can and do reconnect to the grid manually using the Generator options on the VRM dashboad, but it would be simpler and more reliable to do this automatically.

The 'Battery SOC' option within the 'Generator start/stop settings' opperates on SOC, BUT as a generator would normally be turned on when the battery SOC is low, not high, it cannot be used for this purpose. If only the 'Start when battery SOC is lower than' was tweaked to become 'Start when battery SOC is lower/higher than' with a option to reverse the logic.

I suspect I could do this via the 'programmable relay' assistant but if family members are to have any hope of taking over this setup then having the option within the normal menus is much more attractive.

Apart from tweaking the menu options as suggested above, can anyone think of an alternative way of achieving reconnection to export surplus PV power, or have experience of using the programmable relay assistant for such a purpose? I am hoping to increase my PV array to make the house self sufficient for more months at some point, and this would of course exacerbate the situation.

generator auto start export

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Modifications Space

Node Red Space

Answer 1 · 2024-06-04T15:35:15Z

Duivert NL answered · Jun 04 at 03:35 PM

Why dont you just use ESS, it practically does the same thing automatic if set up correctly

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Answer 2 · 2024-06-04T20:40:43Z

assyntdavid answered · Jun 04 at 08:40 PM

I agree @Duivert NL and when I first commissioned the system that is how it operated. But it had two problems for me:

1) In reality the inverter can't prevent import and export of power, and so it is constantly hunting around zero. This means that the system is constantly importingand exporting small amounts of power needlessly. Additionally, this hunting seems to increase the power the Multiplus uses. These two factors totalled over 24 hours were not insignicant for a low energy house like mine

2) Of greater importance, the batteries and inverter are located in the centre of the house. Much as I love Victron gear, the Multiplus is noisy and my 10kW unit especially so, even with the fan mod installed. The noise was intrusive, especially in the evenings. It is significantly quieter when disconnected from the mains. The only thing I use the ESS facility for is the ability to charge to a predetermined SOC at night. That is essential for me.

I think my setup is slightly unusual in terms of the battery storage capacity and inverter size, at least compared to friends I know who have installed battery storage.

Thanks for your comment.

David

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Duivert NL commented · Jun 05 at 04:33 AM

I understand, especially the noise part, i did a few modifications and they are a lot more silent (i have 3 multiplusses)

Changed the fan for a more silent one, and its installed with rubber grommets to the fan frame, and i also isolated the fan frame with rubber grommets from the housing

Last thing i did is put a thick rubber granulate mat on the wall between the multiplusses

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assyntdavid Duivert NL commented · Jun 05 at 04:28 PM

@Duivert NL I decided to bite the bullet and just go ahead and utilise the programmable relay and it has worked perfectly today as far as I can tell. I am still slightly concerned that this is now part of the permanent configuration of the system. Whereas the 'Periodic run' condition within the Generator start/stop menu used to charge the batteries at night can easily be 'Disabled' as it is now during the summer, I cannot do the same with this new feature. That means that in the winter the programmable relay will be switched both via time of day, and by SOC. I don't foresee any logical tension between these two, they should just act as an 'OR' condition, but given the option within the Generator menus I would disable this PV export feature during the winter.

Re multiplus noise I read a lot on the forum about methods to counter the noise problem after I installed it. Regretably I did not foresee it. I had used a 5kW unit off grid for 2 years elsewhere and whilst noisy on supplying significant loads, at night when under low load continues it is virtually silent. Not so the 10kW unit!! The weight of this unit and the confined space it sits in made the notion of removing and reinstalling it a non starter. It was nigh on impossible to get it up on the wall in the first place. Thus I had to look to alternative solutions, and now I seem to be almost alone in runnning an ESS that disconnects from the grid. But if it keeps working then I am happy with that.

Thanks again for your interest and response.

David

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Duivert NL assyntdavid commented · Jun 05 at 04:40 PM

If it works for you then thats great!

You might want to take a look at node red also, i have no experience with that, but it can do some more complex logic

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