Energy Storage Power Electronics
Inside this Article
For decades, off-grid battery-based energy storage systems powered by PV or other renewable energy sources such as wind and small-scale hydroelectric turbines have been cost-effective for many rural and remote residences across the US. The financial case for deploying energy storage in residential grid-connected applications has been a more difficult one to make. However, technological advancements, constrained electric grids with high penetrations of PV systems and the gradual erosion of net energy metering programs across the US may usher in a new era for distributed, grid-connected energy storage systems.
Numerous manufacturers are banking on the expected proliferation of highly integrated, customer-sited energy storage systems. This article provides manufacturer and product line overviews for 14 power electronics and battery system vendors that are positioning themselves for the new energy storage market. Some of the companies, or current incarnations of them, were foundational to the US solar industry a decade before grid-tied systems began to gain popularity. Others are recent entrants to energy storage and solar energy. And a third group of established solar power electronics manufacturers are reimagining their products for modern energy storage applications.
Founded in 2013, Adara Power (formerly JuiceBox Energy) develops lithium-ion energy storage systems layered with monitoring and control software for peak shift, load shave and backup power applications. As of early June 2016, it has units deployed in seven US states. Adara aims to ramp up the adoption of its energy storage technology in key markets, including Hawaii, Nevada and California, via its Adara Energy Storage System Certified Installer program.
At the core of Adara’s 8.6 kWh residential Energy Storage System (ESS) are Samsung lithium nickel manganese cobalt oxide (NMC) cells, configured to operate at 50 Vdc nominal. Adara specifies a rated energy capacity of 8.6 kWh, 5.5 kW continuous power output and a round-trip battery charge and discharge cycle efficiency of 98%. Rated power at a C/2 discharge rate per the California Self-Generation Incentive Program (CA SGIP) is 4 kW. The Adara energy storage system uses a web-enabled interface that allows homeowners to monitor real-time and historical system performance. Integrators have access to 140 battery, inverter and charge controller parameters for remote system diagnostics. Safety protection includes over-voltage and over-temperature shutdown, three-level redundancy on over-voltage control, eight independent temperature measurements and autonomous operation of the product’s safety systems if web connectivity is lost. The system’s battery is certified to UL 1642, and has a specified minimum life of 10 years.
The Adara ESS is compatible with the Schneider Electric XW+ 5548 inverter/charger. Designs can dc- or ac-couple solar arrays to the Adara system. While system designers should verify available support and warranties for ac-coupling products from different manufacturers, integrators have deployed ac-coupled Adara systems with various string inverters, including products from SMA America and SolarEdge.
Adara Power • Milpitas, California • 844.223.2969 • adarapower.com
concept by US
Based in Pompano Beach, Florida, and founded in 2012, concept by US has developed a scalable utility-interactive energy storage system, the Powerstation 247, for residential and small business backup power and self-consumption applications. The product line is ETL listed to UL 1741. Concept by US reports that it designs and manufactures all the product’s main components in house, with the exception of the system’s lithium iron phosphate (LiFeYPO4) batteries. This is a high degree of vertical integration for a relatively young company.
The Powerstation 247 integrates up to three 5 kW Powermodule hybrid inverters, MPP trackers, charge control, batteries and all required field wiring terminals, disconnects and overcurrent protection in a NEMA 1 enclosure intended for indoor environments. Regardless of the number of Powermodules it includes, the Powerstation 247 employs 17.28 kWh of battery storage configured for a nominal dc bus voltage of 96 Vdc (93–105 Vdc operating voltage range). The battery is ETL certified to UL 1642.
Each Powermodule includes two MPP trackers along with PV wiring terminals and disconnects integrated with the unit’s enclosure. Electrical specifications for each PV input are 500 Vdc maximum, 180–500 Vdc operational voltage range, 240–400 Vdc MPPT range and 3,000 W maximum power per PV input channel. The Powerstation 247 is available with one, two or three Powermodules for ac power outputs of 5 kW, 10 kW and 15 kW, respectively. AC output in both grid-tie and stand-alone modes is 120/240 Vac. The Powerstation 247 has a 5-year warranty.
concept by US • Pompano Beach, Florida • powerstation247.com