UPDATE 2-US green energy projects get $59 mln in guarantees

* Beacon Power storage project to get $43 mln guarantee

* Nordic Windpower gets $16 mln guarantee to expand plant

* Part of $6 bln stimulus funds to boost renewable energy (Recasts, updates throughout)

By Ayesha Rascoe

WASHINGTON, July 2 (Reuters) - The U.S. Energy Department on Thursday offered loan guarantees worth $59 million to two renewable energy companies as the agency tries to quickly boost green energy production with a windfall of funding from the economic stimulus package.

Energy storage company Beacon Power Corp (BCON.O) was awarded a $43 million loan guarantee for building a 20-megawatt flywheel energy storage plant in Stephentown, New York.

The department also offered Nordic Windpower a $16 million loan guarantee to help expand the company's assembly plant in Pocatello, Idaho.

"These projects represent the innovative technologies that will help America reduce its dependence on fossil fuels and fight climate change," Energy Secretary Steven Chu said in a statement.

U.S. President Barack Obama has touted clean energy development as a way to boost the economy, pledging to double renewable energy production in three years.

The loan guarantees will be funded by the U.S. economic stimulus package passed earlier this year, which allocated about $6 billion in loan guarantees for renewable energy and electricity transmission projects.

Beacon Power's project will introduce a new technology, not yet commercially available, that will help ensure reliable delivery of renewable energy to the electricity grid, the department said.

The expanded Nordic Windpower plant will produce a one megawatt wind turbine for the company that is at least 10 percent less costly to manufacture, install, operate and maintain than competing systems, the department said.

Nordic is a privately held company owned by Goldman Sachs (GS.N), Impax Asset Management, Pulsar Energy Capital and other investors.

The loan guarantee program was created in 2005, but only got off the ground earlier this year when the department offered its first loan guarantee to California solar company Solyndra.

Under the program, the department agrees to repay commercial loans the companies receive for the projects if they happen to default.

Facing a backlog of applications and deluge of additional funding from the stimulus package, Chu has made streamlining loan guarantee process a top priority for the department. (Reporting by Ayesha Rascoe; Editing by John Picinich)