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AC-coupled BESS in pvDesign

Do you want to add battery storage to your PV plant? Design your hybrid PV + AC-coupled BESS plant in pvDesign.


Now, in pvDesign, you can design an AC-coupled battery energy storage system (BESS). By defining an available area for the storage system in your site, as well as the electrical parameters of the system, you will get the basic engineering of your system and a BESS design report.

Definition of the storage area in the KML

First, it is essential to define a battery polygon (BA) and an MV placemark within that polygon. 

The size of the user-defined area will determine the space available to install the storage system. The MV point will be the interconnection point between the battery area and the substation. 

Some requirements must be considered so that pvDesign can recognize that area as the battery area: 

  • The polygon defining the area of the batteries must be called BA.
  • The MV placemark is mandatory, and is placed inside the BA.
  • The battery polygon cannot be placed inside any AA polygon.
  • The battery polygon has to be located outside the ST polygon. 
  • A restricted area (RA) cannot be placed inside the BA.


How to define the minimum BESS unit?

Once the KML is imported into pvDesign, with the BA defined for the storage system, the "BESS" tab is enabled in the design process. This is where we will design the system.

First, within this tab, the electrical parameters of the unit are defined. The minimum unit or block of the BESS is the set of a PCS and the containers connected to it. 



  • Power Conversion System (PCS): In this first section within the BESS tab, the inverter type and the number of inverters per PCS are selected, thus establishing the power of the PCS or minimum unit of the system.

In this example, the chosen inverter has a power of 1000 kVA, and the number of inverters per PCS is 2, so the power of the PCS is 2000 kW.

  • Battery container: in pvDesign, we assume that the storage solution is modular. As a user, you will set the capacity of a battery container. Alternatively, you can set the capacity of a single battery rack and the number of racks to include per container.

pvDesign will install the necessary number of containers according to the system requirements.

How to achieve your power and capacity requirements?

After having defined the power of the PCS and the capacity of a container, you'll need to define the BESS requirements. This section establishes both the power requirements and the supply hours of the BESS. 

First, choose between maximum capacity or specific capacity.

  • Maximum capacity: selecting this option, the maximum possible power will be installed in the area defined for the BESS. 

  • Specific capacity: In this section, you can configure a specific size for the battery system by defining the number of PCS you want to install. The system power will be the multiple of the PCS power.

You can now define the supply time. The supply cycle duration is calculated as capacity (MWh) divided by rated power (MW). For example, a 2000 kW PCS and a 3000 kWh container, the supply time (time taken for a complete charge or discharge cycle) will be 1.5 hours. If you connect two battery containers (6000 kWh) to the same PCS, you would have a system with 3 hours of supply. 

BESS dimensions

The layout of the BESS will be oriented to maximize the occupancy of the BA area.

In the BESS layout section, you can define the dimensions of both PCS and containers. 

In addition, both the distance between adjacent blocks and the distance between opposing blocks can be defined. According to the NFPA 855 standard, the safety distances between containers or between containers and PCS are fixed: 0.9144 m (3 ft) and 1.524 m (5 ft), respectively.


pvDesign provides the following outputs and documents for the design of the BESS.

The top bar of the results screen will provide the installed capacity, the rated power and the  supply duration of the complete system. 

The BESS layout and a system design report are generated as documentation. The rest of the PV plant documents (SLDs, reports) will include references to the BESS system. 

BESS 1.0 

This is the first tool that has been developed for the design of storage systems in pvDesign. We want to keep adding functionalities in this direction, starting with offering DC-coupled BESS design tools. If this is of interest to you and you feel like collaborating, your suggestions are more than welcome.

For further information or if you would like to give us feedback, please contact us at support@ratedpower.com