By Kathie Zipp, SPW editor
As the use of energy storage in solar projects grows, so do inverter responsibilities. Traditionally, inverters were only responsible for DC to AC conversion and MPP tracking. But as the solar market matures, inverters increasingly are taking on roles in grid interaction, safety, monito
ring and smart energy management. “Becoming responsible for managing storage is a natural evolution for inverters in PV systems,” said Lior Handelsman, SolarEdge’s vice president of marketing and product strategy.
With rapid changes in utility billing infrastructure, Tim Stocker, product manager of energy storage for SMA America, said battery inverters are almost becoming required to interconnect a PV system and avoid large fees. “Many utilities are enacting changes that require all self-generation customers to utilize time-of-use rates,” he said. “Battery systems allow you to store the energy produced from the PV system to be used at a more cost-effective time when it would otherwise be pushed to the grid at a lower rate earlier in the day.”
Therefore, inverter manufacturers are working to ensure their products have the intelligence to take on this responsibility. Handelsman explained inverters need to know how to read home meters and monitor and control batteries. “This includes having the capability to charge and discharge the battery according to the set profile and monitor its system status,” he said. “In addition, inverters that offer backup need to have the capability to operate without the gird or in islanded mode.”
SolarEdge’s storage solution StorEdge is based on a single SolarEdge DC-optimized inverter that manages and monitors PV production, consumption and storage. According to Handelsman, using only one inverter eliminates additional conversion from AC to DC and back to AC, which reduces unnecessary energy losses in conversion, decreases system cost and provides a simple design and installation for the contractor. The StorEdge is currently compatible with the Tesla home battery Powerwall, and as more HV-DC batteries are made available SolarEdge aims to support them as well.
SMA released its first SMA Sunny Island battery inverter in 2001. Currently, its Sunny Boy Storage high-voltage battery inverter, also compatible with the Powerwall, is only available for the European market. But the company is excited to release the solution in the U.S. in 2017.
Stoker said SMA believes in leaving the battery choice up to the installer. “With the rise in support of high-voltage battery architectures, we are seeing a gravitational shift toward batteries that can offer lower system costs,” he said. “Also, with the rise of lithium-ion battery technology, there are now many more choices to the customer with regards to specific chemistry. Each chemistry has its own trade-offs and this is reflected by the type of application for which it’s being used. With that, it’s best to leave inverters agnostic when it comes to battery types and chemistry and to provide the customer with a list of compatible battery partners.”
Other inverter manufacturers now offer storage options or will soon. Enphase’s AC Battery is a lithium-ion phosphate battery from Eliiy Power that pairs with its microinverters. The Fronius Energy Package, which includes its Symo hybrid inverter and Fronius Battery, is only available overseas, but the company is planning to launch a similar solution based off its Primo hybrid inverter for the U.S. market in December.