Solar farm integrated with BESS

[Afshin]

What steps can we take to ensure that our system prioritizes charging the Battery Energy Storage System (BESS) before supplying excess power to the grid? I'm particularly interested in achieving a scenario where the power supplied to the Electrical Grid (E_Grid) approaches zero, while the majority of the kilowatt-hours (kWh) are stored in the Battery (E-Bat) in the following result table. 

 

[Linda Thoren]

Dear Afshin,

For a Grid-connected system with energy storage, any excess power will be stored in the battery before supplying energy to the grid. If the battery storage is fully charged, you have the choice to inject power to the grid or not by ticking the box “Allow solar injection into the grid” in the Operating conditions box.

Regards

[Afshin]

Thank you! Actually, I wanted a scenario that the PV system charges the batteries first and then if we have extra power, we can feed the grid. For example, I have 2-MW solar system and 10-MW BESS. I need to first charge the BESS completely. 

[Linda Thoren]

In PVsyst we have 3 strategies for Grid-storage. In the Self consumption strategy, the produced electricity from your PV system will firstly supply the user’s need (consumption), secondly charge the BESS and lastly supply energy to the grid. With the Peak shaving strategy doesn’t involve an internal use of the energy and you can define the operating conditions such as Grid power limit and discharging. In the Weak grid islanding strategy, you define the Grid unavailability and your storage pack is meant to fill up for the times when you have no production from your solar panel, nor power from the grid.

You can read more about this in the PVsyst help in the following link:
https://www.pvsyst.com/help/grid_storage.htm

Or watch some of the youtube-videos we have on the topic:
https://www.youtube.com/watch?v=-PGRnnF1VuA&list=PLxdyykgAqoynTXUHWrdCxPSYLkhJ9mW7c

https://www.youtube.com/watch?v=49d5pAV907Y&list=PLxdyykgAqoynTXUHWrdCxPSYLkhJ9mW7c&index=3

https://www.youtube.com/watch?v=jZKdz248WJQ&list=PLxdyykgAqoynTXUHWrdCxPSYLkhJ9mW7c&index=4

Regards

[Rhett]

Hi, 

I am just following the thread, I have the same question.

Peak shaving in my mind is about generating revenue as an IPP by manipulating the time of use tariffs. This means that charging the battery should always be a priority to ensure it can be discharged in the peak time of use period. I understand the strategies PVsyst uses but this does not coincide with the industry per se. 

I am trying to design an 8.2MW plant with 2.5MWh of storage to be able to discharge in peak, particularly in winter where the peak tariff costs 3 x more than the summer peak tariff in South Africa. In winter I get zero values for the battery discharge when I run the simulation. I know why this is but it does not make sense as it is not a true reflection of how the plant would be operated. I would always prioritize charging the battery first with any excess power being evacuated to the grid. 

 

Is this something PVsyst is taking into consideration for near future versions, because at present it is a limiting factor?

[Linda Thoren]

Hi!

Thank you for your input and concrete example. In PVsyst, peak shaving has primarily been developed as a strategy to manage scenarios with grid limitations by shifting the production peak, rather than as an economic strategy for discharging at peak prices or peak electricity consumption. Further development of storage strategies is planned for next year.

Kind regards

[Rhett]

Hi Linda, 

Thanks for your prompt reply. I look forward to the updated version of PVsyst that can take this into account as this is where the industry is moving towards.

Regards

[Sulith]

Hello, 

I'm using pvsyst to model a 100mw solar power plant (nameplate capacity) and i'm using battery energy storage system. I have chosen the grid limit as 50MW. In the peak shaving option when i use the battery dispatch mode as when energy is needed, i found out that when the solar generation peak is declining, the batteries are charging as well as discharging. Can you tell me a reason for that 

Thank you 

[André Mermoud]

In this tool, you have probably defined discharging hours which are already active during the end of the day.

 

 

[Sulith]

On 1/10/2025 at 7:46 PM, André Mermoud said:

In this tool, you have probably defined discharging hours which are already active during the end of the day.

 

 

1. Can you explain that in more i didn't get your point. I have attached the output graph here (Simulation : peak shaving with li-ion batteries using dispatch mode as soon as energy is needed)

2. I have another problem. In pvsyst the batteries start to charge when about 80% of the set cutoff limit is achieved and i continue to charge below the cut off also. To you know why that happens and if there is a relevant documentation can you mention it? I tried to find it by myself but couldn't 

[André Mermoud]

For the first question: as I said previously, please check what you have specified for your discharging hours.  This probablx includes 14:00. Note that the values of the hour are shown at the middle of the hour (situation between 14:00 and 15:00 os shown at 14:30.  Between 13:00 and 14:00, the graph shows  that you have a solar production inferior to 50 MW, so that the battery will discharge itself for complementing it to 50 MW. 

The situation between 12:00 and 13:00 is a little bit more complex, as during this hour, the solar production passed from overload (charging) to not sufficient (battery discharge) state. Therefore the battery begins the hour by charging, and then discharging. 

For the second question, I really don't understand what you mean. The max. charging and min. discharging thresholds are specified by the user in the Grid storage dialog, page "peak shaving":

If these values are exceeded in your hourly values, please send us  (at support@pvsyst.com) the project, using "FIles => Export projects" in the main menu.

 

 

 

[Sulith]

I think you solved my problem. I didn't know that the situation between specific 2 hours are shown at the middle point of the graph. Thank you. Earlier i had a problem why the charging curve starts even before when the solar generation reaches 50MW which is my cutoff point. So when thinking about the middle point representation it can be solved.

 

Thank you .

[Sulith]

hey, 

As previously mentioned, i created a pvsyst model with peak shaving storage strategy such that generation above 50MW is sent is batteries. i selected the battery dispatch mode as between a specified time period and set the time as 6pm to 10 pm. But i my output graph the battery is not discharging. Do you know why? 

Does pvsyst assume a load curve in these type of simulations? (in peak shaving, you don't need to define the load curve) 

[André Mermoud]

Yes sorry, in the Peak shaving option, the consumption of the stored energy is not supposed to arise  the next day after Sunrise.

This could indeed be improved, but delivering 50 MW to the grid just in the morning when the sun is shining doesn't make much sense, and is not a usual requirement.