String Inverters Single-Phase Solutions for the North American Market (2011): Page 9 of 10

When asked about potential permitting or inspection obstacles, Wojciechowski reports that the company has experienced “little to no push-back.” He credits the company’s strong service, support and education programs for the smooth rollout. “SMA America took care to educate integrators, utilities, AHJs and other stakeholders,” he notes. “SMA believes that the imperative to reduce PV system costs and improve energy yields will continue to drive manufacturers to introduce transformerless inverters to the US market.”

SolarEdge Technologies. A group of professional technologists with experience in solar, semiconductor and missioncritical power systems established SolarEdge Technologies as a private company in 2006. Widely recognized for its technological innovation, the company’s global investors include GE Energy Financial Services and several top-tier venture capital firms. With offices in Germany, Israel, Japan and the US, the company has more than 100 employees involved in R&D, marketing, sales, and technical and logistical support. Since early 2009, Flextronics, a global provider of electronics manufacturing services, has mass-manufactured SolarEdge products in Israel; in April 2011, the two companies announced the opening of a new production line for North America, located in Newmarket, Ontario, Canada. The scheduled production capacity in both plants is 250 MW for 2011, but this capacity can be doubled if needed to meet market demands.

The SolarEdge system consists of module-level, dc-to-dc power optimizers and proprietary transformerless inverters. The optimizer is available both as a module-embedded and a module add-on solution. The company’s first products were released in 2009. In 2010, product shipments exceeded 50 MW and went primarily to the European market. Because its product line had to be adapted for North American requirements, SolarEdge did not begin its US and Canadian product rollout until August 2010. The company currently offers four singlephase string inverters in North America—ranging from 3.3 kW to 6 kW in capacity—that interconnect to the grid at either 208 Vac or 240 Vac. The company is currently shipping secondgeneration optimizers and inverters. Third-generation products, offering additional features and improved energy yield, are expected to begin shipping later this year.

The proprietary transformerless inverters from SolarEdge were developed in cooperation with the Franhoffer Institute in Germany. Recognized as a leader in inverter technology, Franhoffer currently holds the world record for PV inverter efficiency, with a 99% efficient 5 kW transformerless 3-phase inverter. The CEC efficiency rating for SolarEdge string inverters is 97.5% at 240 Vac and 97% at 208 Vac. SolarEdge believes that module-level optimization can further increase energy yield by 2% to 3% compared to an ideal unshaded array, with greater gains possible on shaded arrays.

In addition to improving energy yields, the main SolarEdge system differentiators, according to John Berdner, general manager for North America, are design flexibility and improved safety. “The combination of module-level optimizers coupled with our own transformerless inverters frees system designers from nearly all the constraints of traditional string inverters,” he explains. “String lengths of eight to 25 modules are possible, regardless of temperature. Strings can be of dissimilar lengths, modules within the same string can be mounted in different orientations and different types of modules can be used in the same string.”

Module-level optimization also means that the system includes module-level safety and fault monitoring. “During installation and service, the output voltage of individual power optimizers is reduced to a safety voltage of 1 Vdc,” Berdner points out. “The system also automatically reverts to safety mode in response to any grid faults or array ground faults, or if an excessively high temperature is detected, such as during a fire. Fault messages are reported by email, and system performance is verified with web-based module-level monitoring that is included with every inverter.”

Solectria Renewables. Headquartered in Lawrence, Massachusetts, Solectria Renewables is a privately held corporation that manufactures and supports a full range of inverter products for utility, commercial and residential projects. The US company has an interesting history. In 1989, James Worden and Anita Rajan Worden founded Solectria Corporation. At the time, their design and manufacturing focus was on energy management components for automotive, power generation and other industrial applications. From 1989 to 2005, Solectria Corporation manufactured over 4,000 electric vehicles that relied on the proprietary drive system technology it had developed. Solectria Corporation also manufactured power electronics and controls for high-power systems, including inverters, dc-to-dc converters, energy storage and related technologies. In 2005, Solectria Renewables was founded with the sole focus of developing PV inverters, and Solectria Corporation was sold to Azure Dynamics. Solectria Renewables went from EV to PV, carrying the inverter technology utilized in the Solectria Corporation’s electric vehicles to the manufacture of PV inverters.

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