TenKsolar, an American builder of integrated high-efficiency solar panels, is winding down its operations, according to sources close to the firm.

Few solar hardware startups survive to adulthood in this ruthlessly competitive market. The demise of many PV firms can be blamed on greed, sloth, pride or any of the other deadly startup sins. But in tenKsolar's case, it appears that rampant inverter failures (from other vendors' equipment) are the cause of this company's imminent end.

The firm was founded in 2008 as a builder of integrated PV panels with intra-module power conditioning in tandem with a reflector. The company started shipping in 2010 with a focus on commercial roofs. It designed a system which mated an "illumination-agnostic solar panel and a novel wiring scheme." Innovations in PV-cell-to-PV-cell interconnections ensured there was no single point of failure, according to Dallas Meyer, the CTO and founder of tenKsolar, in a previous interview. "We're talking 30 percent to 40 percent advantage in power harvesting and a far better LCOE," he said. Meyer no longer works at the company.

In October 2015, tenKsolar had to reprogram or replace APsystems microinverters at about 100 installation sites in Minnesota, most of them residential.

[updated] "We provided tenKsolar with an inverter which met specifications they outlined, however we found that they were operating the product far outside the parameters of those specifications," said Chris Barrett, APsystems' Director of Engineering and Technical Services. "No other APsystems inverters have experienced similar issues."

And just a year and a half ago, tenKsolar raised $25 million from Goldman Sachs, Kresge Foundation, Oaktree Capital Management and Greencoat Capital. Investors from earlier financing rounds included PrairieGold Venture Partners, ESB Novusmodus and Korea's Hanwha. Since 2010, the firm has raised more than $60 million.

TenKsolar claimed it has produced panels for more than 500 installations, with many in the 1-megawatt range. It partially constructs panels in China and completes them in Minnesota.

At one point, tenKsolar employed more than 90 workers in its Bloomington factory. The CEO at the time, Joel Cannon, said the firm expected sales of $40 million in 2015 and $100 million in 2016. Last year, the company named Jeffrey Hohn, former GM of 3M's renewable energy division, as CEO.

Hohn and other executive staff have not responded to inquiries from GTM.

We've heard from several sources close to the firm suggesting that microinverters, this time from a different vendor (Lead Solar), are the cause of a series of disastrous field failures.

There were "catastrophic potting failures on their Lead Solar 700 and 1400 inverters, and they're failing everywhere," said a source.

Layoffs have impacted "two-thirds" of the staff, with the rest slated to be let go by the end of June. The company is selling off its inventory and looking for a buyer for its technology.

EPC customers of tenKsolar are "using Dow 832 sealant to seal existing Lead Solar 700 W and 1,400 W inverters that are failing from water intrusion owing to failed potting installation during manufacturing in China," a source said.

TenK had a number of good design ideas but "should have focused on one or two of those ideas," according to sources, who acknowledged the difficulty of popularizing a unique solar panel. GTM Research solar analysts and tenKsolar partners appeared to genuinely like the company's technology. Price point was a big issue, but in the end, inverter choices hastened tenKsolar's downfall.


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