Shares of Evergreen Solar (NASDAQ: ESLR) are up 14 percent in after hours trading on news the company signed two sales contracts worth approximately $600 million.

The contracts bring the Marlboro, Mass.-based company’s backlog to $1.7 billion worth of orders.

The two new contracts are for the company’s popular String Ribbon wafer technology, and have been signed with Vermont-based groSolar and Germany-based Wagner & Co Solartechnik GmbH, it said today.

According to the solar panel manufacturer, both contracts extend through 2012.

In May, the company announced $1 billion worth of contracts for the same String Ribbon technology (see Evergreen Solar signs $1B in sales contracts).

Evergreen said the panels for today’s order and the one in May are to be manufactured at the Devens, Massachusetts facility, which is to begin production in July.

The four contracts represent approximately 65 percent of the expected 160MW of annual production capacity at Devens through 2013, according to the company.

Evergreen said it has six other customer contracts with a current backlog of approximately $850 million, which is to primarily be supplied by EverQ, the company’s Germany-based joint venture.

Richard Feldt, Evergreen’s CEO, said he hopes to commit up to 75 percent of the Massachusetts facility’s capacity to long-term contracts.

After hour shares are up to 11.69 from this afternoon’s close of 10.24.