Designing and justifying the cost of a solar array with battery storage can be challenging. Here are three steps to consider when designing a solar+storage system to ensure the most ROI.
Step 1: Choose a programmable inverter of appropriate capacity
Depending on its capabilities, a programmable inverter can connect to the power grid and control the flow of power to and from the grid. With a broad choice of storage options, custom programing will optimize the system’s performance for varying seasonal light conditions and other factors. A programmable inverter’s settings can be re-configured to maximize the storage solution’s performance in every season or weather condition.
Custom inverter settings, such as support amps to loads and charging settings for batteries, can help determine how to optimize a solar storage system. The more options an inverter has, the better it will perform at peak efficiency, increasing a customer’s ROI.
Step 2: Calculate system losses
Industry professionals know that a 250-kW solar array does not mean 250 kW of power output. There may be as much as 25% loss in the PV modules alone. Total system losses can be much higher when battery efficiency, loss from the charge controller and the length and gauge of conductor in the PV arrays are factored in.
Step 3: Scale batteries for maximum ROI
If the installation is designed for self-consumption, a battery system is key to the installation’s ability to provide a high ROI. In addition to emergency backup power, batteries can deliver solar-sourced power when peak-use periods don’t match peak sun.
Battery cycle life is a critical factor in a battery’s value, and a battery’s life can be significantly extended by managing the depth of discharge. A higher depth of discharge lowers battery life, which effectively increases the cost per delivered kilowatt hour.
While some experts recommend that batteries discharge to a maximum of about half their capacity in each cycle, our data shows that 25 to 30% depth of discharge is the “sweet spot.” That amount of discharge provides reliable power while extending battery life, which dramatically drops the cost per kilowatt hour. Our research shows that doubling the battery capacity can triple the life of the battery bank. This is a case where a larger initial investment actually delivers a superior ROI.
This tip was contributed by John Webber, global training manager at Schneider Electric.