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assyntdavid avatar image
assyntdavid asked

Auto connect to grid to export surplus PV

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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 startexport
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2 Answers
Duivert NL avatar image
Duivert NL answered ·

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

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assyntdavid avatar image
assyntdavid answered ·

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 avatar image Duivert NL commented ·
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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