James Montgomery, Associate Editor, RenewableEnergyWorld.com
December 23, 2013 | 7 Comments
New Hampshire, USA -- Back in mid-August, Vine Fresh Produce in Ontario unveiled a 2.3-MW solar rooftop array on its greenhouse, the largest commercial rooftop project under the province's feed-in tariff (FIT). This system notably incorporates a technology that's been more familiar in the U.S. residential solar market: microinverters. (The devices, made in Enphase's Ontario plant, helped the project qualify for that FIT.) Weeks ago Enphase followed that up with another large-sized project using microinverters, 3.1-MW of distributed solar across 125 buildings for the San Diego Unified School District.
Vine Fresh Produce’s 2.3-MW (2-MW AC) solar project in Ontario, Canada. Credit: Enphase.
Those announcements were meant as stakes in the ground. "We've proven [microinverter technology] in residential, we're proving ourselves in small commercial... but our ambitions are much bigger than that," said Raghu Belur, Enphase co-founder and VP of products and strategic initiatives. "We're seeing people deploy [microinverters] in significantly larger systems."
The technology is rapidly gaining traction, according to Cormac Gilligan, IHS senior PV market analyst. Microinverter shipments will reach 580 MW this year, with sales topping $283 million, and average global prices sinking 16 percent to $0.49/Watt, he projects. By 2017 he sees shipments soaring to 2.1 GW with revenues of about $700 million, and expansion beyond the U.S. into several regional markets, especially those in early stages of development that might be more open to newer technologies: Australia, France, the U.K., Switzerland, and even Hawaii. Japan's big residential solar market is especially attractive, but poses certification challenges and strong domestic competition.
But as those two Enphase projects illustrate, there's another growth area for microinverters that's emerging alongside regional expansion — up into commercial-sized rooftop solar installations. The same reasons residential customers like microinverters apply to small-scale commercial projects as well: offset partial shading, more precise monitoring at the individual module level, provide a more holistic readout of what the system is producing, and improve safety because they typically use a lot lower voltage. Just nine percent of microinverter shipments in 2012 were to commercial-scale use, noted Gilligan — but he sees those surging to nearly a third of shipments by 2017.
Who’s Making Microinverters
The microinverter space is getting crowded (see table below), if not yet a model of parity. Enphase continues to dominate with more than half of the sector's revenues in 2012, four million units cumulatively shipped and four product generations. "We are a high-tech company that happens to be in the solar sector," Belur explained. Compared with what he called the "big iron, big copper guys" who are now broadening their inverter portfolios with microinverters, "we're all about semiconductors, communications, and software." The company designs its own chips for its microinverters, and outsources manufacturing to Flextronics.
SMA got its entry into the game with the 2009 acquisition of Dutch firm OKE. "In the residential market it became clear to us that customers were interested in the microinverter architecture," said Bates Marshall, VP of SMA America's medium-power solutions group. SMA also sells the string inverters that have gained favor over big centralized inverters, so SMA's simply broadening its portfolio. With the emergence of the U.S. solar end-market, SMA is more willing to push some R&D and product development over here; "we get to drive the bus to a greater extent," he said. SMA recently started shipping microinverters to the U.S. from its German inventories, but a production line is now being qualified at the company's Denver facility.
Similarly to SMA, Power-One (recently bought by ABB) aims to supply whatever type of power conversion capability customers need, noted Chavonne Yee, Power-One's director of product management for North America. So far demand for microinverters has come in the U.S. residential market, offering high granularity and maximum power point tracking (MPPT), but she sees most of the commercial-scale demand switching from traditional central inverters to three-phase string inverters, not microinverters.
Module supplier ReneSola sells a standalone microinverter, touting the typical features with some higher (208-240) voltage options for small light commercial, but at a 15-20 percent lower price point, explained Brian Armentrout, marketing director for ReneSola America. "We are seeing some demand" in small light commercial applications ranging from 50-kW up to 500-kW at which points there's "the breaking point where string inverters make more sense." Down the road the company wants to take the end-around route of integrating microinverters directly onto panels; its gen-2 microinverter should be available in the spring of 2014. Armentrout projects ReneSola will be "in the top three" next year for microinverter sales, while simultaneously aiming high for the top spot in module shipments.
Others are looking to integrate microinverters directly into the modules. SolarBridge has worked closely with SunPower and BenQ to design its microinverters to eliminate several components that typically fail, notably the electrolytic capacitors and opto-isolators, explained Craig Lawrence, VP of marketing. They also minimize other typical costs such as cabling, grounding wires and even tailoring the microinverter for a specific module type to optimize the microinverter's firmware, he explained. He sees the trend to bring microinverters into the commercial-scale environment, particularly with SolarBridge's more recent second-generation microinverters in the past year or so.
Microinverters vs. String Inverters
In general, installers are making a choice between microinverters and string inverters, comparing functionalities and costs. Both sides make a case for reliability: microinverters use fewer components and represent lower cost when something does fail; string inverter vendors point out microinverters have only been on the market for a few years and can't make substantial claims about reliability. IHS's Gilligan noted the sheer number of microinverter devices in the field potentially requiring repair/replacement could be daunting.
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