Solar Energy Storage Equipment for Grid-Tied Residential Projects
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In this article, we consider some of the use cases and emerging markets for residential grid-...
Technological advancements, constrained electric grids with high penetrations of PV systems and the...
Energy storage systems are an essential enabling technology that allows for the increasing...
New high-density lithium-ion battery technologies, innovative software and power electronics designs, and changes to incentive programs, such as California’s storage-centric Self-Generation Incentive Program (SGIP), are ushering in a new era for grid-connected, customer-sited energy storage projects. This article profiles 15 manufacturers that design and build inventive equipment for residential-scale solar-plus-storage systems. I highlight power electronics, as well as some current lithium-ion battery products that may be less familiar to solar professionals than the more-established lead-acid battery brands and models. In some cases, the equipment detailed is also suitable for small-commercial projects that have an energy storage requirement. While US markets for residential-scale grid-connected PV storage systems are still limited, the continued advancement of product designs and falling storage costs will speed the opening of new markets and opportunities.
Founded in 2013 as JuiceBox Energy and rebranded under its current name in 2016, Adara Power was an early developer of products integrating lithium-ion battery technology with power electronics for residential-scale solar-plus-storage systems. In addition to providing solutions for backup power during grid failures, Adara focuses on energy storage systems layered with monitoring and control software for peak shift, load shave and self-consumption applications. Its flagship product is the 8.6 kWh residential Energy Storage System (ESS), which deploys Samsung lithium nickel manganese cobalt oxide (NMC) cells, configured to operate at 50 Vdc nominal. 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+ inverter-chargers. Designs can dc- or ac-couple solar arrays with the Adara system. Integrators have successfully ac-coupled inverters from vendors including SMA America and SolarEdge with Adara’s first-generation system.
In April 2017, Adara announced its second-generation system, the Adara Pulse. The modular system is driven by Adara's iC3 Controller and expandable to 20 kWh of storage. The Adara Pulse supports ac coupling for off-grid and grid-tied applications. Adara’s peak-shifting, solar-charging and self-consumption, and nonexport algorithms ensure compliance with the federal investment tax credit and adaptability for a wide range of energy storage applications. The monitoring and control system is designed to optimize storage utilization in regions subject to time-of-use rates and supports net-metering programs such as California’s Net Energy Metering 2.0. The Adara iC3 Smart Controls offer cellular connectivity and support out-of-the-box communication between lithium-ion batteries such as LG Chem’s 48 Vdc RESU10, Schneider Electric XW+ inverters and a cloud-based software platform.
Adara Power • San Jose, CA • 888.692.3272 • adarapower.com
When Enphase Energy launched in 2006, it created the modern microinverter product class. Since then, it has continued to refine its microinverter and monitoring systems, as well as their installability. Enphase developed its AC Battery, initially announced in October 2015, to support self-consumption and energy time-of-use optimization across global markets. The company first introduced the battery in Australia, and announced US availability in February 2017. The AC Battery, a scalable, modular energy storage system, is a component of Enphase’s Home Energy System, which includes the company’s microinverters, Envoy networking hub and gateway, and module-level Enlighten monitoring software.
The Enphase AC Battery uses lithium iron phosphate (LiFeYPO4) chemistry from Eliiy Power with cell safety certifications from TÜV Rheinland and UL, including UL 9540. The cells provide 1.2 kWh of capacity at a nominal voltage of 25.6 Vdc. The AC Battery can discharge to 100% of rated capacity and has a round-trip cell efficiency specification of 96%. Weighing only 55 pounds, the AC Battery is designed for single-person installation and interconnection with standard household wiring. Its enclosure is NEMA 2 rated for indoor installation in an unoccupied space. The AC Battery carries a 10-year or 7,300-cycle warranty for greater than 80% of its initial rated capacity.
Enphase Energy • Petaluma, CA • 877.797.4743 • enphase.com
Iron Edison Battery Company
Founded in 2010, Iron Edison Battery Company offers nickel iron and lithium iron batteries for solar energy storage, along with solar energy system design services. Iron Edison developed its lithium iron phosphate (LiFePO4) battery line in standard battery-based solar power electronics voltage configurations of 12 Vdc, 24 Vdc and 48 Vdc nominal. These configurations make it a drop-in replacement for standard lead acid battery banks and compatible with inverters and charge controllers from manufacturers including Magnum Energy, MidNite Solar, OutBack Power, Schneider Electric and SMA America.
Iron Edison’s lithium-iron battery system includes an onboard integrated battery management system that monitors and regulates each cell in the battery bank to provide balanced charging and discharging while guarding against overcharge, overdischarge and thermal overrun situations. Internal dc disconnects provide battery protection and isolation. An indoor-rated rugged metal enclosure contains the battery system. Iron Edison offers 180 Ah–5,600 Ah battery capacities as well as custom voltages and amp-hour capacities. The company rates its lithium iron batteries at 7,000 cycles at 30% depth of discharge (DOD), 5,000 cycles at 50% DOD and 2,000 cycles at 80% DOD, and backs them with a 7-year warranty.
Iron Edison • Denver, CO • 720-432-6433 • ironedison.com
Established in 2011, JLM Energy designs and manufactures products for energy storage, management, monitoring and control. Its UL-listed Energizr 100 and Energizr 200 grid-tied storage systems are at the center of its product offerings. Both use specific configurations of the JLM Battery Pack. Each lithium iron phosphate (LiFePO4) battery pack has a nominal voltage of 52 Vdc, a nominal capacity of 50 Ah and an operating voltage range of 40 Vdc–57.6 Vdc. JLM specifies a cycle life of 3,000 cycles at 80% depth of discharge (DOD) and discharge under 25°C, and a cycle life of 5,000 cycles at 50% DOD and discharge under 25°C. The Energizr 100 uses four battery packs configured in parallel for a nominal operating voltage of 52 Vdc and a capacity of 10.4 kWh. The higher-capacity Energizr 200 accommodates up to eight battery packs in series for a nominal voltage of 416 Vdc and a storage capacity of 20.8 kWh. JLM Energy backs its batteries with a 20-year warranty.
JLM developed the Energizr 100 primarily as a grid-independent system for backup power applications. Its design allows installers to integrate the battery system with a residence’s grid-direct PV system string inverter, electrical loads, the utility grid and even a backup ac generator. During a utility outage, the product creates a local microgrid that allows the grid-tied inverter to keep generating energy for battery charging. The more feature-rich Energizr 200 offers demand shaving, time-of-use shifting, and solar self-supply, as well as integrated support for smart thermostats, real-time whole-house power measurement and load control. JLM’s Measurz software analyzes user habits and provides efficiency recommendations for homeowners. Its Loadz controller connects appliances to a home's Wi-Fi, allowing users to control and monitor energy use.
JLM Energy • Rocklin, CA • 800.475.3960 • jlmenergyinc.com
Established in 1947, LG Chem is a diversified global chemical company that manufactures a wide range of products, including petrochemical goods, materials for electronics such as LCD displays, and rechargeable batteries. It is one of the largest lithium-ion battery manufacturers globally, with solutions for home electronics, electric vehicles and stationary energy storage systems. Headquartered in Seoul, South Korea, LG Chem has its US headquarters in Troy, Michigan. It manufactures lithium-ion cells and batteries in Korea, China and the US.
In April 2017, LG Chem announced the launch of its UL-listed RESU lithium-ion battery system for residential applications in North America. The RESU product line includes two voltage options and several capacity configurations. Its low-voltage models are available with capacities of 3.3 kWh, 6.5 kWh and 9.8 kWh. The high-voltage RESU models operate at 400 Vdc nominal and offer capacities of 7 kWh and 9.8 kWh. The 400V RESU10H (9.8kWh) product is compatible with SolarEdge’s StorEdge, a dc-coupled storage solution based on a single inverter for both PV and storage. LG Chem will make additional inverter compatibility options available later in 2017 to provide homeowners with a range of pretested solutions.
LG Chem • Troy, MI • lgchem.com
Magnum Energy, founded in 2006, designs and manufactures inverter-chargers for mobile, marine, off-grid and backup power applications, as well as producing PV charge controllers, component integration panels and system monitoring equipment. Magnum was the first manufacturer to offer inverter-charger models with split-phase 120/240 Vac output in the US. Its 24 Vdc and 48 Vdc nominal MS-PAE series inverter-chargers connect to the grid for ac battery charging, but do not export power to the utility grid without the integration of an ac-coupled third-party string or microinverter system. In 2016, Magnum announced its MicroGT 500 microinverter. Designed for integration with the company’s battery-based inverter-charger systems, as well as for use in grid-direct power export applications, the MicroGT 500 communicates with Magnum Energy battery-based inverters in ac-coupled mode to taper the charge based on temperature-compensated battery state-of-charge parameters. Each dual-MPPT microinverter supports two PV modules.
In 2015, Magnum launched its PT-100 solar charge controller, which is compatible with 12, 24 and 48 Vdc nominal battery systems and has a maximum output power rating of 6,600 W. Its maximum input voltage is the lower value of either 200 Vdc plus battery voltage or 240 Vdc. The PT-100 controller also provides GFDI and arc-fault circuit interrupter protection. Magnum offers an extensive line of prewired power panels and accessories for component integration.
Magnum Energy • Everett, WA • 425.353.8833 • magnum-dimensions.com
Most people know Mercedes-Benz for its luxury vehicles, but its development efforts in the electric vehicle market have driven its recent entry into the North American market for stationary solar-plus-storage systems. Mercedes-Benz, a global automobile manufacturer and a division of the German company Daimler AG, offers a good example of global automotive manufacturers driving the advancement of battery technology not only for vehicles, but also for stationary applications.
Daimler’s wholly owned ACCUmotive subsidiary manufactures Mercedes-Benz energy storage systems. The Mercedes-Benz Energy Storage Home product line has a modular design based on 2.5 kWh battery modules, with total product storage capacities ranging from 2.5 kWh to 20 kWh. The comp-any backs its energy storage product with a 10-year warranty that guarantees greater than 80% capacity at year 10. Batteries from Mercedes-Benz Energy are currently available in select California markets through national integrator Vivint Solar. Vivint is the first solar provider to offer and install Mercedes-Benz energy storage products in the US.
Mercedes-Benz Energy • Stuttgart, Germany • mercedes-benz.com
Founded in 2001, OutBack Power is a manufacturer of power electronics for stand-alone off-grid and utility-interactive battery-based renewable energy systems. In 2010, the Alpha Group acquired OutBack Power. OutBack’s flagship power conversion equipment includes the FX inverter-charger line and its MX series charge controllers. The FXR/VXFR series hybrid inverter-chargers offer stand-alone, backup and utility-interactive solar export functionality and feature seven operational modes, including GridZero, which prioritizes the use of battery or renewable sources to power loads and uses renewable energy sources such as PV only to recharge a system’s battery pack. An Advanced Battery Charging profile option supports lithium-ion battery technologies. In 2011, OutBack released its Radian series of hybrid, utility-interactive split-phase 120/240 Vac inverter-chargers. Available in 4,000 W and 8,000 W power classes, the Radian features two ac inputs for grid and ac generator connectivity.
Since its launch, OutBack has focused development efforts on system integration packages that allow prewiring and testing at certified facilities to reduce installation time and complexity in the field. OutBack’s SystemEdge prebundled equipment packages build on this early component integration focus. With the introduction of four VRLA storage batteries optimized for specific applications such as float service or regular deep cycling, as well as integration with its power conversion equipment, OutBack now offers an extensive product family for energy storage applications listed to the relevant UL standards from end to end. Additionally, it has a next-generation energy storage system, Skybox, in development.
OutBack Power • Arlington, WA • 360.435.6030 • outbackpower.com
Founded in 2010, Pika Energy manufactures home energy systems that include bidirectional inverters, substring PV array optimizers, and lithium-ion and AGM energy storage systems. The company developed its Pika Energy Island system to provide residences and small businesses with an integrated solution for backup power, self-supply and demand charge reduction. The Energy Island uses three Pika products as building blocks: the Islanding Inverter and Pika PV Link dc optimizer, and either the recently launched Harbor Smart Battery (lithium ion) or the Coral Smart Battery (AGM). Panasonic lithium-ion cells configured to operate at 360 Vdc–420 Vdc power the Harbor Smart battery. Two models are available: 15 kWh/6.7 kW and 10 kWh/4.5 kW. Pika Energy backs the Harbor Smart battery with a 10-year warranty.
Developed for backup power, self-supply and rate arbitrage applications, the Pika Islanding inverter is a bidirectional, storage-ready, transformerless islanding inverter that can operate with or without batteries. With a nominal dc input voltage of 380 volts, Pika Energy’s single-phase 7.6 kWac X7600 Series Inverter connects PV, energy storage, electrical loads and the grid, and supports 120/240 Vac backup loads without requiring an autoformer. Pika also offers its 11.4 kWac X11400 Islanding Inverter for 3-phase applications.
Pika Energy’s PV Link S2501 subarray PV optimizer supports the creation of 380 Vdc nominal arrays compatible with its bidirectional inverters and 380 Vdc system bus. The PV Link can interconnect two to nine modules to create subarrays of up to 2,500 W. The product is rapid shutdown compliant and provides MPP tracking (60 Vmp–360 Vmp range), shade mitigation, ground-fault protection, arc-fault protection and substring monitoring via power line communication.
Pika Energy • Westbrook, ME • 207.887.9105 • pika-energy.com
Schneider Electric is a global manufacturer of power distribution and automation systems. Headquartered in Rueil-Malmaison, France, Schneider entered the solar industry with its 2008 acquisition of Xantrex Technology (Xantrex acquired Trace Engineering in 2000). Schneider offers two inverter-charger lines suitable for residential energy storage applications. For non-export systems, its Conext SW-NA hybrid inverter-charger offers a nominal dc input voltage of 24 Vdc or 48 Vdc and continuous output power classes of 2,400 W and 3,400 W at 24 Vdc and 3,800 W at 48 Vdc. The inverter-chargers have split-phase 120/240 Vac output and are compatible with flooded and valve-regulated lead-acid (VLRA) battery types. The Conext SW-NA supports ac- and dc-coupled configurations and enables grid backup, self-consumption with solar prioritization, peak shaving and ac engine generator assist.
The more feature-rich utility-interactive Schneider Conext XW+ NA inverter-charger line was one of the first to support integration of lithium-ion battery types. Complete energy storage hardware and software solutions from other vendors commonly integrate this equipment. Like Schneider’s Conext SW-NA inverter-chargers, the Conext XW+ NA supports ac- and dc-coupled configurations and enables grid backup, self-consumption with solar prioritization, peak shaving and ac engine generator assist. It can also export power to the utility grid. Schneider offers system integration panels for its inverter-chargers, as well as two MPPT solar charge controllers, the 150 Vdc MPPT 60 150 and the 600 Vdc MPPT 80 600.
Schneider Electric • Andover, MA • solar.schneider-electric.com
SimpliPhi Power launched in 2009, but its roots date back to 2002, when it first emerged as a company named LibertyPak, which began developing and supplying lithium-ion batteries to the film and television industry. Today, SimpliPhi Power offers deep-cycle lithium ferro phosphate (LFP) battery models as drop-in replacements for lead-acid batteries in 24 Vdc and 48 Vdc nominal power systems. Its UL- and CE-listed Smart-Tech product line does not require ventilation, cooling or thermal regulation. Each battery includes a built-in 80 A dc breaker on-off switch that increases safety during system installation, commissioning and O&M. SimpliPhi Smart-Tech batteries have no memory effect, offer a self-discharge rate of less than 1% per month and an operating efficiency of 98%, and can discharge to 100%. The batteries have a cycle life of 10,000 cycles and a warranty period of 10 years.
The PHI 2.6 model weighs 57.5 pounds and has a rated capacity at C/2 of 2.62 kWh. The higher-capacity PHI 3.4 weighs 75.5 pounds and has a rated capacity at C/2 of 3.44 kWh. Both models have an operating voltage range of 20 Vdc–28.8 Vdc at 25.6 Vdc nominal and 40 Vdc–57.6 Vdc at 51.2 Vdc nominal. SimpliPhi also offers high-output versions of its Smart-Tech batteries, as well as its AccESS energy storage system, which integrates its batteries with Schneider Electric XW+ 6848 NA inverters.
SimpliPhi Power • Ojai, CA • 805.640.6700 • simpliphipower.com
Founded in 1981, SMA Solar Technology was the first manufacturer to offer high-voltage string inverter models in the North American market via its US subsidiary, SMA America. It pioneered the use of ac-coupling grid-direct string inverters with battery-based inverters. SMA America offers single-phase Sunny Boy string inverter models, in power classes from 3,000 W to 11,000 W, that are suitable for ac-coupled residential PV applications. It also offers two models of its Sunny Island battery-based inverters—the 4548-US and 6048-US, with rated power outputs of 4,500 W and 5,750 W, respectively. SMA designed both models for operation with 48 Vdc nominal battery banks. They are compatible with external battery management systems and lead-acid, nickel-cadmium and lithium-ion battery types, and have single-phase 120 Vac output. Split-phase 120/240 Vac output applications require two Sunny Island inverters or an autoformer. In ac-coupled systems, the Sunny Island limits the string inverter’s output power via frequency shift to regulate battery charging.
SMA has significant experience with self-consumption and energy storage systems in Europe and plans to offer additional equipment, such as its Energy Meter, in the US as markets develop. SMA has also been developing a new generation of energy storage power electronics for residential-scale applications in the US. Projected to ship in mid-2017, SMA’s Sunny Boy Storage inverter works with high-voltage lithium-ion battery banks, such as those from LG Chem and Tesla, for energy management tasks including peak load shaving, self-consumption, and zero export.
SMA America • Rocklin, CA • 916.625.0870 • sma-america.com
SolarEdge Technologies was launched in 2006. In 2015 it participated in the public relations wave announcing Tesla’s lithium-ion Powerwall Home Battery. SolarEdge was the first inverter manufacturer to offer fielded Powerwall systems in the US. Since then, SolarEdge has expanded the compatibility of its StorEdge power electronics system to include LG Chem’s RESU lithium-ion battery products.
SolarEdge’s single-inverter StorEdge system has four primary components. The system’s single-phase StorEdge dual-port inverter and Connection Unit functions as an optimized PV inverter that also provides power conversion and management for battery charging. A 120/240 Vac split-phase autoformer performs phase load balancing in StorEdge systems configured for backup power during grid outages. The addition of SolarEdge’s Electricity Meter enables smart energy management functionality that includes export power control, time-of-use shifting, maximized self-consumption, demand response and peak shaving capabilities.
The StorEdge inverter for the US market, model SE7600A-US, has a rated ac power output of 7,600 W and a maximum ac power output of 8,350 W when feeding electrical loads or exporting to the grid. In backup mode, it has a rated power output of 5,000 W and a maximum ac surge rating of 6,600 W. The inverter’s nominal dc bus voltage is 400 Vdc. The SolarEdge’s StorEdge inverter and module-level dc optimizers provide NEC-compliant rapid shutdown functionality for the PV array and battery. The StorEdge system’s Electricity Meter carries a 5-year warranty. Its autoformer and inverter carry a 12-year warranty, with an option to extend that to 25 years on the StorEdge inverter.
SolarEdge Technologies • Fremont, CA • 510.498.3200 • solaredge.com
Founded in Bavaria, Germany, in 2008, energy storage system provider sonnen first offered its storage solutions for European self-consumption applications. In 2015, sonnen established its US headquarters in Los Angeles and announced the availability of its products in North America. In February 2017, sonnen announced its plans for a new product development and manufacturing center in Atlanta, Georgia. The sonnenBatterie eco energy storage solution, designed for residential self-consumption and grid backup applications, integrates OutBack Power’s power electronics, Sony Fortelion lithium iron phosphate (LiFePO4) cells, and proprietary management and monitoring software. The eco comes in seven energy storage capacity options in 2 kWh increments, ranging from 4 kWh (eco 4 model) to 16 kWh (eco 16 model), with a usable capacity based on a 100% cell depth of discharge. The company has configured the LiFeYPO4 cells for a low-voltage dc bus with an operational range of 48 Vdc–56 Vdc, and offers a warranty on the product’s batteries for 10 years or 10,000 cycles.
The sonnenBatterie eco has a split-phase 120/240 Vac output and can be ac-coupled with existing or new PV installations. The eco 4 through eco 8 models have a 100-millisecond maximum power rating of 8,500 W and a 5-second maximum power rating of 6,000 W. The higher-capacity models, the eco 10 through eco 16, have a 100-millisecond maximum power rating of 17,000 W and a 5-second maximum power rating of 12,000 W. Non–revenue grade PV and load metering is standard. The sonnenBatterie eco system’s power electronics are certified to UL 1741 and carry a 10-year warranty.
sonnen • Los Angeles, CA • 310.853.2404 • sonnen-batterie.com
Founded in 2003, Silicon Valley electric vehicle manufacturer Tesla formally entered the US solar energy market with the announcement of its Powerwall Home Battery in 2015. Since then, Tesla has continued to grab media headlines with the launch of its Gigafactory for lithium-ion battery manufacturing, the purchase of national solar integrator SolarCity, and, in October 2016, the announcement of its second-generation stationary energy storage system, Powerwall 2.
With availability announced for 2017, the Powerwall 2 has a usable capacity of 13.5 kWh per unit, offers 100% depth of discharge and can scale up to 10 units for applications that require additional high-storage capacities. The Powerwall 2 integrates an onboard inverter rated for 7 kW peak/5 kW continuous. It is 44 by 29 by 5.5 inches, weighs 264.4 pounds and is approved for floor or wall-mounted installations indoors or out. The Powerwall 2 supports solar self-consumption, time-of-use load shifting, backup power and off-grid applications. Tesla backs the product with a 10-year warranty.
Tesla • Palo Alto, CA • 888.518.3752 • tesla.com
Joe Schwartz / SolarPro / Ashland, OR / solarprofessional.com