PV System With Batteries

[Deac99]

Hello,

Not really a Loxone specific question but looking for input from people who have PV and batteries.

I have a PV array, Fronius inverter, Fronius Smartmeter, and Fronius (BYD) battery system.  It is all working well except I am putting about 2 - 3% of my energy into the grid even though the battery is not at 100%. 

I can understand some small fraction of energy going to the grid, but this seems excessive to me - I fully admit, I have no experience in the subject.  Anyone have any opinions as to what normal is?

Thanks

[JohnR]

hi

Is the grid export persistent or occasional? What is the peak output of the inverter? What are the house loads and do you have large loads that are switched on/off regularly? 

I can offer some comparison with my own system. I have a Victron ESS system with Pylontech batteries. The system is setup to manage grid export at a set point of zero (no feed in). This puts house loads first, then battery and finally grid export any remaining - at which point the Loxone energy manager switches on a variable output immersion heater to consume the 'excess' energy. 

 

I see from time to time the system will overshoot the grid set point if PV output suddenly changes or a large load is stopped or started in the house. It takes the software some time to react to the input/output changes and this has the effect of causing a very short export or import spike on the grid. Overall, though (just looked at the past week stats) it's close to zero (<1%). 

[Techdoctor]

What is the size of your system in kW. Amount of energy going back into the grid will vary depending on your daily usage.The system may decide that it can easily put 2-3% back into the grid and still maintain enough power to supply your house.  And  often batteries will charge at night, from the grid, when people are asleep and most countries have cheaper night time tarrifs.  You need to give us more information about your system. Like how often is the house empty during the day, in which case the system in all likelyhood will feed in to the grid since power consumption will be a lot less than when occupied.  Have you had the system from day one or was it something you had installed at a later date. If so do you know your average power consumption per month or week or day before the solar system was put in.

[Deac99]

Hi,

Thanks for the feedback / followup questions.

I have 2 solar arrays:

Array 1:  7.1KW going into a standard inverter capable of 12.5KW

Array 2:  8KW going into a hybrid inverter capable of 10KW.

The 2 arrays are in different locations / angles so our peak production is typically 10ish KW for a longer part of the day.  I just looked at the raw data from Fronius which gives a better illustration of what is going on and I noticed that the battery charge rate seems to be a max of 8ish KW.  (see below) So that may well be the issue.  At 13:30 it's putting 1.7KW into the grid and 7.8KW into the battery and showing the consumption to be 0.00 (which is not true as there are always a few hundred watts being consumed from the computer equipment etc.

And yes, the peak consumption is correct.  This is a building with 2 heat pumps on a mountain in Austria where it is still -10 and snowing. 

I can verify max battery charge rate from the installer.  I suspect the mystery is solved

[Van Fanel]

Hi:

No being an expert, I know that for the last 5% - 10% of the battery charge, the current needed is very low. What is happening most probably is that you have an excess of production at that moment, so the Inverter injects it to mains instead of damaging your battery array.

Hope it helps.

Regards,

Libre de virus.www.avast.com

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