By SETH MASIA November 10, 2012
Around the time you read this, Enphase Energy will ship its 2 millionth microinverter — an astonishing event for a company that sold its first unit just four years ago. It’s the kind of geometric growth one might expect from a Silicon Valley “killer app,” rather than from a mundane transformer/inverter.
Killer app is precisely what the microinverter has proven to be. Just as the electronic spreadsheet put a PC on every desk, the combination of real-time web-based monitoring with MPP tracking and low-voltage AC off the roof made intuitive sense. Everyone who looked at the concept could see it as a way forward toward turning the rooftop module into a simple home appliance.
Easier said than done. Beginning in 1991, half a dozen power-electronics companies tried to build and sell microinverters, all without gaining traction.
Then, in 2005, two telecom engineers realized that programmable logic chips had become affordable just as the solar business turned into a real market.
Raghu Belur grew up in Bangalore and came to the Unit- ed States in 1989, after graduating from Bangalore University, to earn a master’s degree in electrical engineering at Texas A&M. He worked at the Indian Institute of Science, helping to design a biomass gasification heat-and-power system. In 1997 he joined the start-up Fiberlane Communications in Petaluma, Calif., “Telecom Valley.” Within a year, the company was reorganized as Cerent, and then sold to Cisco Systems for $7 billion.
Martin Fornage was born in Morocco and followed his father, a telecom engineer, around Africa until returning to France for university. In 1985 he graduated from the École nationale supérieure d’electronique et ses applications (ENSEA) and, despite majoring in power electronics, went straight to work for Tekelec, the California spin-off of a French avionics firm. There, Fornage worked on wireless broadband devices. In 1992 he was hired as the first engineer at the start-up Advanced Fiber Communications, miniaturizing and mass-producing fiberoptic signal devices in Petaluma.
Belur and Fornage met at Cisco/Cerent. By 2004 both men had begun thinking about new ventures. Belur quit his job to launch a wireless video company. It failed quickly, but he learned how to structure a start-up.
“We knew little about solar but did know that it needed a lot of innovation,” Belur said. “I stayed up until 3 a.m. researching solar, and got very excited. The business was growing rapidly, but the whole thing was driven by modules. There was little or no investment going into power electronics or system engineering.”
“We realized that the real value was in monitoring and adding intelligence to a system,” Fornage said. “Our telecom background would be useful in the solar market. For one thing, we dealt with equipment that had to work with high reliability outdoors, manufactured in high volume and at low cost. More than that, we were both expert in systems. We couldn’t just make a single piece of hardware — we needed communications and software to support the array.”
The timing was critical. “In the 1990s if we had attempted this it wouldn’t have got off the ground,” Fornage explained. “This is the hardest product to design of anything we’ve worked on. The level of complexity means you can’t use government grants — we needed $100 million, and only venture capital has an appetite for technology like this. And venture capital has no appetite for small markets.” The rapid growth of solar made the investment palatable.
A number of hardware breakthroughs made the project feasible. “A major bet we took was the shift to digital control,” Fornage said. “The programmable logic chip became affordable in 2005 — it was expensive but not too much. We had access to silicon carbide switches starting in 2006. Before that we could not have done a good product.”
“The confluence of new hardware and design software meant we could do semiconductor integration,” Belur said. “From our experience in telecom, we established five key goals: high efficiency, high reliability, low cost, high volume and a complete feature set. We knew if we hit those we’d be successful.”
The team incorporated Enphase in 2006 and shipped its first microinverters in 2008. It was a classic Silicon Valley start-up. Enphase, with venture capital backing, did the innovative design, and brought in a manufacturing partner, Flextronics, with high-tech factories on four continents.
From the beginning, Enphase sold microinverters as fast as they could be built. Module manufacturers saw a way to integrate an entire sale. System designers saw architectural flexibility and stable production in changeably shaded conditions. Installers saw the safety of running relatively low-voltage AC off the roof.
Now, with sales rising geometrically, Enphase is unconcerned about outselling supply. The company has forged a distribution partnership in Europe. Flextronic can scale up infinitely, Fornage pointed out. “They can add [production] lines to meet demand. Our manufacturing process is as simple as making cell phones, so it’s very well suited for very large volumes and benefitting from economy of scale.” Fornage and Belur see no physical limit on their ability to keep pace with market growth. If solar installations double each year for the foreseeable future, Enphase can double shipments to keep pace.
Succeeding generations of microinverters will grow smaller, and more efficient, they promise. Eventually, will there be an inverter on a single chip, to be laminated right onto the back of a solar module? “Yes, we can see that coming,” Belur said. “We spend a lot of time figuring out how to make the box smaller and smaller. That leads to efficiency, lower cost and better reliability. And we’ll need maximum efficiency to avoid hotspots when we go to deep integration with the module.
“It’s a revolutionary change in the way systems are designed, installed and maintained,” Belur said. “By creating more energy more reliably and more safely, we’ll help to make solar ubiquitous.”
Seth Masia (email@example.com) is an editor of SOLAR TODAY and director of communications for the American Solar Energy Society.