TenK Solar is getting a sizable investment from Goldman Sachs. 2012 file photo of solar arrays on the roof of the company's headquarters in Bloomington. (The Minnesota Star Tribune)

TenKsolar, a Bloomington-based manufacturer of solar panels, said Wednesday that it has raised $25 million in equity for expansion — its largest single investment — from Goldman Sachs & Co., Kresge Foundation and others.

The solar company said the investment will help it broaden sales, which have seen three consecutive years of growth.

"We have really sold in limited parts of the U.S. and the world," said TenKsolar Chief Executive Joel Cannon in an interview. "We need to improve our operational footprint for growth."

He said the company expects $100 million in sales in 2016, a threefold increase over 2015.

TenKsolar mostly sells solar panels for commercial and institutional projects, offering an integrated rack and reflector system designed for flat rooftops or ground mounting. Its technology has several novel features, such as operating at a lower voltage, that the company wants to promote in the market.

In one of its biggest sales ever, TenKsolar is supplying most of the solar panels for Washington, D.C.'s plan to deploy solar panels on the roofs and parking lots of 34 District of Columbia-owned facilities. TenKsolar supplied half the panels for Minnesota's largest solar array atop parking ramps at the Minneapolis-St. Paul International Airport.

"The TenK module is the most reliable way to deploy at scale," Cannon said. "It is a fundamentally different design that eliminates a lot of the cost of ownership and a lot of the safety risks associated with high-voltage solar."

The $25 million investment is TenKsolar's largest capital injection in eight equity or convertible debt transactions since 2010 that have raised a total of $61 million. In the latest deal, Goldman Sachs & Co's Alternative Energy Investing Group invested $20 million, Detroit-based Kresge Foundation invested $3 million and private-equity firms Oaktree Capital Management and Greencoat Capital made up the rest, according to Chris Shen, investment associate with Kresge Foundation.

Kresge Foundation, created by the founder of retailer S.S. Kresge Co. and Kmart, makes socially motivated investments to private companies in addition to grants to nonprofits. Shen said one of the foundation's missions is to promote climate resilience, and the investment in TenKsolar is part of that effort.

"Their vision is to help make solar a more viable alternative to traditional sources of electricity. … We thought it was a nice fit," Shen said in an interview.

Cannon, asked whether TenKsolar intends to stay private, said it is getting ready for an initial public stock offering. "It is good practice to get a company IPO ready — there is a certain discipline that comes with that," he said. "That doesn't necessarily mean we will choose to do one, but it is good management practice."

Oaktree and Greencoat, which previously had invested in TenKsolar, now have seats on the board, as does Goldman Sachs, Cannon said. Other institutional investors from earlier financing rounds are PrairieGold Venture Partners of Sioux Falls, S.D., the National Rural Telecommunications Cooperative of Herndon, Va., and Hanwha, a Korean maker of solar technology. Minneapolis-based Piper Jaffray & Co. served as TenKsolar's financial adviser on the latest transaction.

TenKsolar said it has produced panels for more than 500 installations in 19 countries. It partly assembles panels in Shanghai, China, where it employs 110 people, and finishes them in Bloomington with 92 workers, Cannon said.

David Shaffer • 612-673-7090 @ShafferStrib