Navigant Research reports that annual installations of global module-level power electronic (MLPE) capacity will grow from 1,185 MW in 2013 to 12,844 MW by 2020.
By Kathie Zipp
Brad Dore, director of marketing for SMA America, says that module-level electronics, a category that includes microinverters and power optimizers, have proven popular for a number of reasons.
“They’ve addressed common system-design challenges and have provided professionals with an easy-to-understand solution,” Dore says. “Despite higher costs, they give installers greater flexibility, which is a valuable trait.”
Raghu Belur, co-founder of Enphase Energy, says MLPE technology has been so disruptive because it creates more profitable businesses for solar professionals and a better return on investment for system owners.
“Installers find value in the microinverter’s design flexibility and ease of installation, while also having an integrated software platform to manage operations and maintenance remotely,” Belur says. “System owners receive a naturally more reliable and higher performing system because of the microinverter’s module-level power conversion benefits.”
Likewise, Michael Rogerson, marketing manager of SolarEdge North America, notes module-level power electronics’ rapid movement beyond “niche” product status and into the mainstream. They appeared on more than half of U.S. residential solar installations in 2013. Installers are also seeing opportunities to slash costs with MLPE at the commercial level, too.
“DC optimizers are gaining traction for their ability to remove the electrical roadblocks of traditional system design and enable more modules per project,” Rogerson says. “This corresponds to increased revenues for developers and installers, increased output and faster payback for system owners.”
As panel manufacturers look for new ways to differentiate their products, more are partnering with MLPE providers to offer an integrated product commonly referred to as a “smart module.” Smart modules also allow installers to reduce the part count at a project rather than add MLPEs to the panels on-site themselves.
James Bickford of Tigo Energy says that enabling the inverter to talk to the module offers benefits such as enhanced safety functionality, lower DC-boost multiples and lower balance of system costs.
“We see the need for a communication-based solution that enables solar to tap into a rich ecosystem of features currently unavailable to a non-communicating PV module,” Bickford says. “Think of how connecting the phone to the internet created applications that, 10 years ago, no one would have conceived. Once the phone could communicate with the cloud and software developers had an agreed-on set of standards, the features and functions the ‘phone’could provide became nearly unlimited. The same thing is true for a smart module.”
Bickford sees establishing a standard application programming interface API to allow multiple devices from multiple vendors to transparently interoperate as a major challenge in the solar industry.
Another challenge with smart modules, according to Craig Lawrence of SolarBridge Technologies, is different levels of integration.
“Consumers need to be wary of companies creating smart modules that really aren’t that smart,” Lawrence says. “Integration isn’t just a matter of combining two products. The best product integrations are the result of hard work, jointly testing the product in the lab and in the field, and qualifying the combined product under UL standards. Only then will you get an integrated product that is safe, reliable and, of course, smart.”
Still, Lawrence believes that reliability is going to be the most critical challenge of the solar industry for the next several years. “Now that the solar industry has finally come into its own and become a viable alternative to fossil-fuel electricity, we absolutely have to ensure that our products are every bit as reliable as we say they are,” he says.
SMA America’s Dore agrees: “When you look at the number of electrical components in a module-level power electronic system and consider that most of these devices are installed on a roof where temperatures can routinely exceed 140°F, you quickly realize that reliability is paramount to long-term success.”
With so many residential installations now built with module-level electronics, many think the industry is overdue to evaluate how to test them.
Michael Ludgate, VP of business development at APS America says reliability standards are common in other industries, but are still making their way into solar.
“It’s common practice in telecommunication and military power equipment to meet certain predictions on product life and reliability, better known as mean time between failures (MTBF) estimates,” he says. “This is a textbook-type evaluation to predict reliability. Having some form of MTBF in solar could separate the good from the bad, and force manufactures to address failures with analysis and constant product improvement.”
“Inverter reliability is as important as module reliability, mainly because the inverter is the operating system for the entire array that performs 100% of all conversion work,” says Enphase’s Belur. “While module issues do affect performance, high microinverter quality will keep entire systems producing even with module reliability issues.”
SolarBridge’s Lawrence believes that the entire PV market needs a dedicated focus on reliability.
“Inverters are the single leading cause of failure in PV systems,” SolarBridge’s Lawrence says. “They’re also typically the most expensive failures. This is a risk to lease and PPA companies that are providing performance guarantees for energy production. The industry may begin to see significant unplanned O&M expenses related to inverters that will erode returns from financed systems, unless tough new reliability standards are adopted.”
SolarEdge’s Rogerson thinks components that go near or on the modules should be tested with similarly to modules, such as with thermal cycle, damp heat and humidity freeze. He says they also need electrical component testing that solar modules don’t require such as burn-in tests.
Still, Enphase’s Belur believes that quality cannot be tested into a product, but must be considered at every stage –— from design through manufacturing and field analysis.
Inverter manufacturers are increasingly stepping up to redefine inverter testing standards with organizations such as Sandia National Labs and with IEC working groups.