Beacon Power Corp filed for bankruptcy on Sunday just a year after the energy storage company received a $43 million loan guarantee from a controversial U.S. Department of Energy program.

The move comes about two months after solar panel maker Solyndra also filed for bankruptcy, setting off criticism of the government loan program.

The department guaranteed $535 million in loans to Solyndra, and Congress is investigating whether political influence played a role.

Beacon Power used the government-guaranteed-loan to build a 20-megawatt flywheel energy storage plant in Stephentown, New York.

The company said in documents filed with Delaware's bankruptcy court that it had $72 million in assets and $47 million in debts.

The case is Beacon Power Corp, U.S. Bankruptcy Court, District of Delaware, No. 11-13450.

(Reporting by Tom Hals in Wilmington, Delaware; Editing by Dale Hudson)