String Inverters Single-Phase Solutions for the North American Market (2011): Page 3 of 10

According to Andreas Schmitt, head of marketing for Delta Energy Systems, Delta began investing in the research and development of solar inverter products at its Teningen, Germany, location in 1999. Delta’s first solar inverter product was a microinverter that was developed for a Belgian OEM customer and released in 1999. Over 30,000 microinverter units were sold up to 2003. In 2002, development and production of string inverters for OEM customers began. In 2005, Delta launched OEM string inverters for the US market. Three years later, it introduced Delta solar inverters for the European market at the annual Intersolar conference in Munich, Germany. In 2010, Delta Energy Systems launched the SOLIVIA brand solar inverters and shipped the first SOLIVIA EU models. Also in 2010, Delta released a 100 kW central inverter, as well as 15 kW and 20 kW transformerless string inverters for European projects.

In 2010 Delta strategically decided to enter the US market with its own SOLIVIA TR String Inverter brand and began building US sales and support. This year, Delta Energy Systems is launching four models of SOLIVIA string inverters for the US and Asian-Pacific markets and a PV monitoring system that is compatible with all the singlephase SOLIVIA string inverters available worldwide. Delta Energy Systems’ design R&D headquarters is located in Teningen, Germany. The SOLIVIA line of inverters is manufactured in Dubnica nad Váhom, Slovakia, and Bangkok, Thailand. The Slovakia factory was opened in May 2007, and has a current production capacity of 600 MW, which the company projects will grow to 2 GW by 2015. Inverters destined for the US and Asia-Pacific markets are manufactured in the Thailand factory that was opened in 2010 with a production capacity of 600 MW. Currently, central inverter solutions represent 10% of Delta Energy Systems’ total inverter revenue, with string inverters accounting for 90% of the company’s inverter revenue.

“There is stability offered in the $6.6 B company behind our products,” says Schmitt. “The PV business, while appearing to be quite mature to many, is just in its early stages. We believe local installers are the most influential group determining what solutions end-users choose, so we continue to focus on working with installers and trying to make their job easier.”

Delta Energy Systems’ current SOLIVIA TR string inverter line for the US market includes four units with rated power specifications ranging from 2.5 kW to 5 kW. The 4.4 kW and 5 kW units were pending CSI eligibility at the time of publication. The inverters are field configurable for 208/240 Vac output and feature NEMA 4X enclosures, a fused string combiner and array dc disconnect standard.

Exeltech. Exeltech is a privately held company headquartered in Fort Worth, Texas. While grid-connected inverters have only recently been added to the company’s product portfolio, Exeltech has been manufacturing inverters for stand-alone, battery-based applications for the telecomm and renewable energy industries since the company was founded in 1990. Veteran installers who were working in the off-grid marketplace in the early 1990s likely remember integrating Exeltech’s SI Series inverters, the first high-frequency pulse width modulation sine wave inverter available on the market, into systems outfitted with (now largely defunct) modified square wave inverters. At the time, it was a technical revelation to have the option of specifying a true sine wave inverter to run sensitive electronic loads in off grid applications. Exeltech also pioneered the redundant, hot-swappable stage inverter concept with its MX Series battery-based inverter product line.

Exeltech recently entered the grid-tied string inverter market with the introduction of its transformerless XLGT18A60 inverter, which received ETL listing to UL 1741 in February 2011. At 14 pounds, the 1.8 kW 120 Vac unit is the lightest inverter listed in the accompanying specifications table. All of Exeltech’s inverters, including all circuit boards, transformers and enclosures, are manufactured at its Fort Worth facilities.

While the XLGT’s transformerless topology is new to Exeltech, senior engineer Dan Lepinski points to Exeltech’s track record of reliability building battery-based inverters for the telecomm industry. He says, “Exeltech has been manufacturing power inverters for over 20 years and markets its products to applications where high-reliability is paramount. This same philosophy went into the design and manufacture of our grid-tied inverters. While it has become accepted in the solar energy industry that inverters may have to be replaced every 8–10 years, Exeltech took the approach that you buy it and install it once. That’s it.”

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