Solar retrofitting consists of upgrading a solar installation where there is no energy accumulation in photovoltaic batteries, to a system with such storage. Self-consumption of energy is becoming more and more widespread at residential, industrial and commercial levels. Although nowadays it is very common to make installations with  solar batteries to accompany the solar panels and thus provide electricity even when the  photovoltaic modules are not generating energy, there are a large number of installations where there are only solar panels. A number of factors must be taken into account for retrofitting: system design, installation and choice of inverter.

System design

Photovoltaic systems with storage are divided into two categories: alternating current (AC) and direct current (DC).

In DC systems, direct current flows from the solar modules to the  hybrid inverter  or charge controller and then to the batteries to be charged. When the energy stored in the batteries is needed, the hybrid inverter converts the direct current into alternating current so that it can be used. For customers with existing PV systems, DC systems are often not the best option. The power conversion may require significant rewiring of the entire system and may require replacement of the existing inverter.

On the other hand, the AC system is the most suitable. In these installations the  solar inverter remains inside the system to send the AC power from the  PV panels to the batteries. By retaining the wiring from the PV inverter, only the wiring to the batteries needs to be added.

Installation

Most existing PV systems are connected to the main building service panel. In some cases, the interconnection point is located in a subpanel or in a connection on the load side of the service conductors. Whatever the case, to retrofit an AC storage system, the inverter must be installed so that it is isolated from the grid during a power outage. For this purpose, a critical loads panel is added to the installation where the inverter will be interconnected. This  solar module will also contain the loads to be backed up in the event of a grid outage.

Other configurations using the main service panel as a common panel are also possible with the use of an automatic transfer switch.

Inverter selection

If the storage system is coupled to AC it will operate in grid backup mode. In this case it is important to ensure that the inverter and the inverter for the batteries communicate effectively. If they do not, the PV system could overcharge the batteries during a grid outage when local loads are minimal. To ensure optimal operation, make sure that the inverter is capable of changing frequency or meeting the corresponding specifications.

Design the retroffiting with a professional

If you are thinking of upgrading your installation to include solar batteries, we recommend that you contact a professional to ensure that everything is done correctly based on the existing installation and consumption needs.

f you want more information you can contact us, Techno Sun technicians will help you to solve your doubts and choose the best possible materials.