PV-Battery question

Mykhailo
Topic Author

24 Apr 2024 17:39 - 24 Apr 2024 21:23 #13123 by Mykhailo

PV-Battery question was created by Mykhailo

Hi there!
Please help me to understand the following:
I have a question regarding Energy storage - Detailed PV-Battery - Distributed - Residential Owner - Battery - Battery Cell and System.

I have a 4 kW SES installed in my company, which is installed for the company's own needs (lighting and sockets for low-power consumers). The system has an lead-acid traction battery (such as those used in electric forklifts) for storing electrical energy. The battery has a total capacity of 400Ah, 24kW of power and a voltage of 48V. The battery consists of 24pcs ‘cans/cells’, voltage 1 = 2.2≈2V, so 24pcs*2V=48V.

I am trying to model my own station with SAM, but I am getting something wrong in Computed Properties or I am doing something wrong.
What is unclear to me is the final numbers in the Total number of cells parameters, which gets a value of 29,400 and Strings in parralel, which is 1,225.

I will add a .sam file to make it more clear what I mean. I hope that you will be able to help me. Thanks!

PV_Battery 2.sam

Last edit: 24 Apr 2024 21:23 by Paul Gilman.

Please Log in or Create an account to join the conversation.

Paul Gilman

25 Apr 2024 15:35 #13124 by Paul Gilman

Replied by Paul Gilman on topic PV-Battery question

Hi Mykhailo,

The system you describe has a bank capacity of 400 Ah * 48 V = 19,200 Wh, or 19.2 kWh, and a bank power of 24 kW. If the system has 24 batteries, then each battery has a capacity of 400 Ah / 4 batteries = 16.67 Ah/battery.

If you assume a nominal cell voltage of 2 Vdc, you should set the following inputs:

Desired bank power = 24 kW
Desired bank capacity = 19.2 kWh
Desired bank voltage = 48 Vdc
Cell nominal voltage = 2 Vdc
Cell capacity = 16.67 Ah

That results in a battery bank with 24 cells in series (for a 48 Vdc bank voltage), and 24 strings in parallel (for 19.2 kWh bank capacity).

This configuration defines a "cell" as the smallest unit in the battery: Each "string" is a forklift battery consisting of 24 cells. You could also define a "cell" as a 48 V battery by changing the cell nominal voltage to 48 Vdc.

Best regards,
Paul.

Please Log in or Create an account to join the conversation.

Mykhailo
Topic Author

25 Apr 2024 16:32 - 26 Apr 2024 16:23 #13128 by Mykhailo

Replied by Mykhailo on topic PV-Battery question

Hello Paul,
Thank you for your reply.

Indeed, if Cell nominal voltage = 2 Vdc, the simulation works and runs without errors during the download.

I decided that it is still more suitable for me when Cell nominal voltage = 48 Vdc, that is, as you said, the battery can be defined as a ‘cell’. In this case I get exactly the numbers I wanted to see, but in simulation I get an error which I can only clear by changing the parameter from 48 Vdc back to 2 Vdc

Error:

Last edit: 26 Apr 2024 16:23 by Paul Gilman. Reason: Please attach images as files and then insert them into your message

Please Log in or Create an account to join the conversation.

Paul Gilman

26 Apr 2024 16:30 #13132 by Paul Gilman

Replied by Paul Gilman on topic PV-Battery question

Hi Mykhailo,

The voltage table (under "Battery Voltage" on the Battery Cell and System page) for the default lead acid battery type is based on a 2 Vdc cell voltage, so it would probably be best to set the cell nominal voltage to 2 Vdc and recognize that a "string" represent a single battery. Otherwise you would have to modify the voltage table.

I apologize for suggesting that changing the cell nominal voltage to 48 V would work.

Best regards,
Paul.

Please Log in or Create an account to join the conversation.

Mykhailo
Topic Author

26 Apr 2024 19:21 #13133 by Mykhailo

Replied by Mykhailo on topic PV-Battery question

Hi Paul,
Thank you so much for your reply and help!

Please Log in or Create an account to join the conversation.

Ricardo Riveros

02 May 2024 00:07 #13137 by Ricardo Riveros

Replied by Ricardo Riveros on topic PV-Battery question

Hello Paul,I wanted to make an inquiry regarding an analysis of a commercial "Merchant Plant", in which I set up a photovoltaic system with batteries, loading hourly data for the next 25 years and expecting a generation result, a correct dispatch ("automatic"), and also cash flow. However, I don't understand why it stops detecting the capacity and by year 14 it stops accounting for the revenues as shown in the image.

Thanks in advance!