Smart meter systems company Elster has filed for an IPO, offering 16.2 million initial shares that will be priced between $16 and $18. It is expected to net $152 million from the offering. As Green Tech Media notes, the company’s main business is in gas, and it hasn’t made significant headway into the advanced metering infrastructure business. The IPO would presumably to go pay off some of its debt.

Wholesale power company NRG Energy will buy renewable energy provider Green Mountain Energy in a $350 million cash deal. Green Mountain provides renewable energy to markets such as Texas and Oregon. The acquisition will boost NRG’s green energy holdings, with Green Mountain continuing to act as its own business. The deal should close in November.

Applied Nanotech has received $1.6 million from the Department of Energy to create a pilot production facility for its proprietary inks, which are used to make thin silicon solar cells. The company acknowledges there’s plenty of competition in the metallic inks and metallic conductors business – DuPont and Ferro among them – but says their competition could also become their customers or licensees. Applied Nanotech’s technology allows for non-contact printing, which in turn could allow “the next generation of thin-silicon cells” be mass-produced. The plant is expected to be up and running within three to four months.

Portland General Electric is in talks to buy a 500-megawatt wind project in north Oregon. The company has exclusive rights until year-end to purchase the project, which is planned for development by RES Americas. The wind farm could span 68,000 acres and would begin construction as early as 2013. PG&E, incidentally, contracts with Green Mountain Energy for renewable energy.

The Waltons — heirs to the Wal-Mart fortune — have sold 280,000 shares of First Solar at $140 to $142 per share, reports The Street. The transaction happened last night and follows a move earlier this week in which the family sold 30,000 shares of the solar company. As the article notes, the move could influence solar investors who have grown reluctant to invest further in the solar industry, though the Waltons’ sale could simply be a divestiture, or “normal trading course of action,” due to the family’s large stake in First Solar.