Module-level rapid shutdown requirements that originated in the 2017 National Electrical Code gave microinverter manufacturers a boost as a simple way for rooftop systems to comply. But as the code and consumer needs have changed, string inverters are having a resurgence. Over the past year, some microinverter makers have decided to go bigger and add string solutions to their offerings.
Hoymiles Power Electronics USA is one microinverter company that has moved into the hybrid string inverter market. Rocky Gao, Hoymiles USA CEO and president, said his company wanted to offer a relatively low-cost string-hybrid and AC-coupled inverter to “enrich customers’ choices.”
The Hoymiles hybrid string inverter.
He called the company’s new single-phase inverter “the best solution for customers’ home green energy systems,” citing features such as a 1.5 DC:AC ratio, up to 11.5 kW of power and a safer low-voltage system. Gao also noted its multiple working modes that adapt to various installation scenarios and the more convenient app-based operation with remote monitoring.
Ultimately, Gao said, the string-hybrid and AC-coupled inverter is preferable over microinverters because it is easier to maintain, with a larger capacity and simpler scalability in the residential market.
“With the increase in single-unit power, string hybrid inverters will also become one of the C&I energy storage solutions and have huge market potential,” Gao said.
For Northern Electric Power (NEP), creating a three-phase string inverter solution that worked correctly and safely was a way of taking responsibility.
“Installers and developers/owners need less finger-pointing across suppliers and higher-level ownership of the inverter and RSD and data solution,” said Ed Heacox, CEO of NEP. “While the RSD system and inverters can be installed to operate independently, there can be interactions that are important to manage.”
NEP sought to broaden its scope beyond just RSD devices to include inverters and data monitoring so that installers could use one brand for all needed functions. Heacox said that its Neptune inverter + Galaxy data monitoring solution ensures full support of site design and installation from one company.
With a consolidated data portal and smart app with RSD and inverter data in one tool, the product is easily integrated and cost-effective.
“The transmitters are in the inverters, the data gateway can be in the inverters, the portal and smart app include both RSD data and inverter interactivity,” Heacox said.
This kind of offering can help project logistics. All the RSD and inverter solutions can ship to a project in one batch from NEP fulfillment partners like Rexel, Sonepar and Greentech Renewables. The result is lower cost and less risk of logistics delays.
But not all microinverter manufacturers are expanding to string options. Although APsystems recently added a residential storage solution and associated AC-coupled inverter to its offerings, the company has no plans to introduce string solutions.
“What we’re seeing is a lot of inverter and PV module companies adding microinverters to their portfolio,” said Jason Higginson, head of marketing for APsystems. “They’re migrating away from producing and selling string inverters because of the NEC mandate requiring additional rapid shutdown equipment.”
Higginson highlighted some of the well-known issues that come with string inverters: their shorter lifespan, the riskier high-voltage DC format, the cost and hassle of pairing them with rapid shutdown devices and the fact that, in applications where optimizers or RSDs are not required or used, one panel can significantly impact the energy production of the other panels it’s wired to.
Higginson also noted the high saturation of the string inverter market as a deterrent. He said the biggest names in the residential solar market, like SolarEdge and Ginlong Solis, are offering string inverters with optimizers or RSD devices that enable rapid shutdown for each panel.
Given the relative newness of their choice, only time will tell if Hoymiles and NEP’s efforts to move into the string inverter market will be fruitful. But it may very well end up becoming a trend to watch in the inverter manufacturing space.
This story is part of SPW’s 2024 Trends in Solar. Read all of this year’s trends here.
