Bankrupt flywheel company Beacon Power has found a buyer for its technology and its 20-megawatt energy storage plant in New York -- and that’s going to allow it to pay back at least some of the money it owes the Department of Energy.

Private equity firm Rockland Capital will buy Beacon’s assets for $30.5 million in cash and a promissory note, along with “additional guarantees and funding obligations to DOE of $6.6 million,” according to a Monday press release (PDF).

The sale must still be approved by the bankruptcy court and by federal regulators. But under the deal, the Department of Energy stands to recover 70 percent of the $43 million it loaned to Beacon, a DOE spokesman told reporters on Monday.

That’s a better result than the DOE is expecting from its other big, bankrupt loan recipient, Solyndra. The thin-film solar module maker landed the department’s first clean energy loan guarantee for $535 million in 2009, only to declare bankruptcy last year. Despite attempts to find buyers for its technology and equipment, Energy Secretary Steven Chu has said it’s unlikely the government will recover much of its loan.

Beacon’s situation also differs from Solyndra’s in that its buyer intends to keep its business running -- at least that part of the business that’s already been built. Under Monday’s agreement, Rockland will form a new private company called Beacon Power LLC that will maintain ongoing operations of Beacon’s 20-megawatt grid frequency regulation facility in Stephentown, N.Y., which has been delivering frequency regulation services since early 2011.

Rockland also said it intends to develop a second 20-megawatt flywheel regulation plant in Pennsylvania. Beacon had a $5 million state grant to back the project. The agreement also gives it ownership of Beacon’s Tyngsboro, Mass. headquarters, as well as “many of the contracts associated with operations of the business,” though the companies didn’t specify which contracts were included.

All in all, it sounds as if the Houston-based firm is banking on a recent ruling from the Federal Energy Regulatory Commission (FERC) to substantially increase the value that Beacon’s flywheel plants can earn for their services. That ruling calls for the country’s interstate grid operators to institute market systems that pay more for “fast” responding sources like flywheels and batteries than for slow, fossil-fueled power.

Beacon CEO Bill Capp said last year that the new FERC rule could double the revenues per megawatt-hour that Beacon earned on its services. We’ve seen other startups tackle the market in anticipation of those greater rewards, as well: in November, startups Viridity Energy and Enbala launched smaller-scale projects aimed at responding in seconds to play into frequency regulation markets for Mid-Atlantic grid operator PJM.

It does appear that Rockland has secured a pretty good price for Beacon’s assets. The company’s Stephentown plant cost about $69 million to build but had seen its book value fall from $41.9 million to about $12.6 million in the month before Beacon’s October bankruptcy filing.