Karl Taft, a co-founder of Hoku Corp. who led the local technology company’s expansion into the solar energy field, has resigned as chief technology officer after nearly 10 years with the firm.

Taft, who spent much of the past three years in Idaho overseeing Hoku’s construction of a polysilicon plant, said he was looking forward to spending more time with his family in Hawaii and pursuing "new career challenges and opportunities." His resignation is effective Nov. 30, the company announced yesterday.

Taft had been reducing his equity stake in the company in recent months, according to filings with the Securities and Exchange Commission. Taft sold 60,000 shares of Hoku during a three-month period, ranging in price from $3.20 a share on July 13 to $2.57 a share on Oct. 6. Taft held 974,643 shares after the latest sale.

Taft, along with former Hoku CEO Dustin Shindo, founded Hoku in 2001 as a fuel cell technology company. Taft was a key member of the board of directors and management team that led Hoku’s 2005 initial public offering on the Nasdaq Global Market.

In 2006 Hoku identified solar energy as having growth potential, and put Taft in charge of moving the company in that direction. He led the diversification into the solar integration and polysilicon businesses and managed the engineering, procurement and construction of Hoku’s polysilicon production plant in Pocatello.

In April, Taft led the team that conducted a pilot run at the plant that successfully produced the first chunks of polysilicon, a basic component used in semiconductors and solar panels.

Completion of the plant has been delayed by financing difficulties. In its latest earnings report, Hoku revised its projected launch to between April and June.

Hoku also said its previous $390-$410 million estimate of the cost to complete the plant at full production capacity will be low. However, the company didn’t provide a revised estimate because it is still assessing technology and negotiating with vendors.

Karl Stahlkopf, the longest serving director on Hoku’s board, praised Taft’s contributions to Hoku.

"Without his vision, his innovative problem-solving abilities, and his peerless technical expertise, there would be no Hoku today," he said.

Hoku said it has no immediate plans to replace Taft.

Shares of the company fell 12 cents, or 4.3 percent, yesterday to close at $2.65.