TenKsolar, a solar panel manufacturer based in Bloomington, says it will reprogram or replace a failed component on about 100 recently installed solar power arrays mostly at Minnesota homes.
The failure has curtailed solar panels' output in late summer — usually a time of high energy production — and reduces the utility-funded incentive payment to homeowners for buying Minnesota-made panels. The incentive is paid over 10 years based on power production.
As TenKsolar fixes the problem, the state Commerce Department, which administers the Made in Minnesota solar subsidy, is studying whether anything can be done to address homeowners' expected shortfall. Some solar homeowners could lose hundreds of dollars in production payments.
"We noticed a sudden drop in energy production," said Linnea Tani, who with her husband, Doug, had TenKsolar panels installed at their Roseville home in May.
She said that output from their 24 panels was off 40 to 50 percent in August compared with July. After complaining to her installer and others, the couple waited for weeks for answers. On Oct. 18, TenKsolar told solar installers that it would reprogram or replace problem units.
"It's been very disheartening," said Tani, whose system is one slated for reprogramming.
The problem centers on devices called micro-inverters that typically are placed on the back of each panel. One of their main jobs is to convert electricity from direct to alternating current. TenKsolar uses an innovative design that combines multiple micro-inverters so that fewer are needed for each solar project. TenKsolar calls its unit a Redundant Inverter Bus.
APsystems of Seattle custom manufactured the micro-inverters that failed or caused breakers to trip in the TenKsolar bus units. In a statement, APsystems said "the failure resulted from an unforeseen software interaction" between its technology and TenKsolar's. "We have worked closely with TenK to determine the root cause," Jason Higginson, APsystems senior director of marketing, said in an e-mail.