ongrid PV system with batteries

[Miguel Santos Silva]

Hi,

I am trying to design a battery system connected to the gridd and I am having some troubles.

The system I wanted to design has three different inverters, each one with 3 batteries connected. But I think I can only connect the batteries to one of the inverters?

Thank you in advance!

Miguel Santos Silva

[developer_mh]

Hi Miguel,

that is correct, at the moment the battery systems can only be connected to one inverter if the battery systems are DC coupled. You can change the amount of (equal) battery systems, however, so if your three inverters are the same, you can have 3 x inverter "xy" connected to 3 x dc battery system "abc".

Hope that helps, kind regards,

Martin

[Miguel Santos Silva]

Thank you Martin,

It does help, but then I have two more questions.

I actually thought I had an AC coupled battery system. Is that possible? How to change from an AC to DC coupled system and vice-versa?

Second, I don't understand how I can have 3x inverter conected to the DC battery system because I difined the battery system and the inverter in different tabs.

Again, thank you, 

Miguel

[developer_mh]

Hi Miguel,

you can change the type of coupling in the battery system itself. Note that you can't change system database entries, you'll have to create your own, e.g. by copying an existing one:

 

What I meant with connecting 3 equal DC coupled battery systems to 3 equal inverters is that. On the inverter page you have 3 times the same inverter:

And then on the battery system page you'll have the battery system amount set to 3:

 

Hope that clarifies the doubts. If you have questions, please let me know!

Kind regards,

Martin

[Miguel Santos Silva]

Thank you Martin,

I would add another question, on the subject of batteries. What happens after the end of the lifetime of the battery,? Does the system stops taking the energy from the batteries into account?

[Vishnu]

Hi Miguel,

To my knowledge I haven't seen any option in PVSol to set the life-time of the battery. May be PVSol considers the degradation of the battery which inturn impacts the efficiency and eventually the energy that can be stored in the battery.

 

-Vishnu

[developer_mh]

Hey Miguel,

the lifetime of the batteres is influenced by two effects: cycle loads and time. So there are the "cyclic lifetime" and the "calendar lifetime", the first of which we can calculate, and the second is more a number that is given by the manufacturer (determined by tests).

The calculation of the cyclic lifetime is described here (at the end of that page, applies also for li ion batteries:

https://help.valentin-software.com/pvsol/2020/calculation/battery-systems/lead-acid-batteries/

According the standards, we consider a battery as "dead" when it has reached 80% of its initial capacity. It is then replaced by a fresh one.

Hope that helps, kind regards,

Martin

[Miguel Santos Silva]

Ok, I undersand. But then PVSol assumes that a new battery will be purchased but not the investment in the new battery, correct?

Thank you for all the help. Best Regards,

 

Miguel

[El_Bay]

Hi Martin,

I have also been trying to build a DC connected system with 2x hybrid inverters and 2x batteries. I think am coming up against the same problem, where I believe the system appears to 'underperform' because both batteries are connected to 1 of the hybrid inverters rather than each battery being connected to it's own hybrid inverter. So, the charging ability is limited. I have two questions:

1. Are there plans to build in this functionality into PVSol in the near future?

2. What is the best work around to be able to model a system like this but without the limitations?

I have been thinking about building as similar a system as possible (but AC connected) to approximate the simulation. However, I am aware I need to match the inverter specs and battery charging specs very well in order for it to be sufficient. Would this be an okay approach?

Thanks for your help in advance, appreciate any guidance you have!

Cheers

Ellie

[developer_mh]

Hi Ellie,

15 hours ago, El_Bay said:

1. Are there plans to build in this functionality into PVSol in the near future?

Yes, we plan to implement this functionality this year, but I can't give an exact date yet.

15 hours ago, El_Bay said:

2. What is the best work around to be able to model a system like this but without the limitations?

As a first approach, the AC connection workaround works quite well, but as you mention, you have to be careful with the parameters. Another option would be to skip the shading calculation of your 3D project. Due to the mechanics of the underlying simulation algorithm, the DC connection problem only occurs when there are shadows in 3D.

Kind regards,

Martin

[El_Bay]

Hi Martin,

Thanks for the quick response. I will try without shading analysis

Kind Regards

Eleanor