As the energy storage market grows rapidly, technology diversifies. Battery chemistry, PV integration and hardware layout are all critical factors to consider when managing customers expectations and ensuring their needs are met.
For example, there are two ways solar is integrated with the energy storage system (ESS)—either AC- or DC-coupled. Each has strengths and weaknesses.
AC-coupled systems, such as the sonnenBatterie, require a separate PV inverter that must be installed to charge the batteries. Meanwhile, DC-coupled systems allow a direct connection between the PV array and a charge controller or other DC-DC converter. AC-coupled systems can easily be used to retrofit any existing PV inverter topology (string, microinverter or AC panel). DC-coupled storage systems do not offer this type of flexibility.
The general rule of thumb is that if most of the loads are consumed at night, DC-coupled systems offer a more efficient way of using the solar. However, AC-coupled systems offer a more efficient way to feed the daytime loads since the PV inverter power is directly consumed and the excess is sent to the batteries.
Batteries can also vary significantly in chemistry, safety ratings, longevity and performance. Many energy storage manufacturers are switching to lithium-ion batteries. These batteries do not have the same restrictions as their lead-acid cousins because they are safer and can provide greater efficiency and longevity. However, it’s important to note that even within different lithium-ion based technologies (nickel cobalt and iron phosphate) environmental impact and lifetime performance vary—from a few years to more than 20 years, as seen in sonnenBatterie lithium iron phosphate batteries.
Energy storage systems are still considered a new form of technology, so manufacturer training is essential to ensure a smooth installation process. Beyond covering the actual installation, these trainings usually delve into design and sizing. Accurate storage system sizing is necessary to ensure that your customers have reasonable expectations and their needs can be met, bringing them greater overall satisfaction with the system long-term. Understanding household loads and the average household energy use (in kWh) is the key to properly sizing a system. Storage manufacturers like sonnen have developed tools to help you determine your customer’s needs—in terms of both PV and storage—to ensure they engage in solar self-consumption, manage time-of-use and have access to backup power when the grid goes down.
In addition to manufacturer training, a thorough site survey is also a critical part of the design and pre-installation process. It is crucial to identify the optimal ESS placement in relation to the homeowner’s AC panels, distances for NEC-required clearances and communication placement (Ethernet, Wi-Fi, etc.). Gathering this knowledge prior to the installation can eliminate trips to the local electrical supply store and maximize efficiency once the installation is underway. If you have any doubts or concerns about the electrical integration of the ESS into the house, it is important to confirm that the single line diagram is approved by the manufacturer.
During an installation, it is always important to follow the safety precautions recommended by the manufacturer, National Electrical Code, OSHA and other applicable safety codes.
This installation tip was provided by Greg Smith, senior technical trainer, sonnen