Additional Considerations for Storage

Sustainability and Green Building
Contact: Sustainability and Green Building

DC versus AC Coupling

If the battery is installed at the same time as the solar PV system, it might be DC coupled, which refers to an installation that shares an inverter with the solar electric system. With this configuration, the battery is charged not by electricity from the grid, but directly from the energy produced by the solar PV system. Because the inverter is being shared, this configuration can help save the homeowner initial upfront costs.

In an AC coupled configuration, the battery and solar PV system operate independently from one another and have two separate inverters. In this case, the battery can be charged by electricity from either the utility grid or the solar PV system. An AC coupled system might be more common if the battery is installed as a retrofit, or at a later time from when the solar PV was originally installed. With two separate inverters, the solar PV system maintains its existing wiring and components. This allows for the energy produced by the solar panels to enter the electric panel where it fulfills the home’s load, and excess energy that is not used immediately by the homeowner is then stored in the battery.

Battery Sizing

Understanding your customer’s main goals for why they want a battery backup system will be essential for determining the battery’s size, type, and configuration. Do they want it mainly for power outages, just to charge a few essential devices such as lights, the refrigerator, and freezer? Or are they looking to be entirely off-grid, and not connect to the local utility at all (this would require a much larger battery bank with a different configuration)?

Many battery manufacturers have designated, licensed installers. Early communication with the solar installer in the design phase of the home building process is important if the customer is considering solar PV plus storage, as this will help set expectations for the battery’s capacity to do desired tasks. Doing a projected load analysis to understand what the home’s average daily load is will help inform the battery’s size and capacity.

Battery Maintenance

Maintaining the battery’s operation will be critical for ensuring that your customer is receiving their desired benefits. Below are a few suggestions for how you can work with your client to make sure the battery is functioning properly:

  • Exposed electrical terminals within batteries necessitate safety precautions — a locked battery box will help prevent any unwanted changes from happening.
  • Adequate ventilation around the battery box is also essential, since it can generate heat.
  • Additionally, it is important that only trained professionals troubleshoot, commission, and maintain the batteries.
  • Periodic checks from the solar company or certified battery specialist to make sure the solar PV system and battery are communicating correctly (either in-person or verifying battery performance online). This is typically done through an app supported by the battery manufacturer.