The Tennessee Valley Authority recovered less than half of its $36 million investment in a failed power storage process in Mississippi, according to a financial report released Tuesday. In its latest quarterly report, TVA said a venture organized by the German conglomerate RWE paid TVA $15 million on April 30 for losses from the canceled project.

TVA had invested $36 million in the venture, known as Regenesys, before the project was canceled because RWE didn’t want to proceed with the joint venture through its Innogy Ventures Ltd subsidiary. Regenesys was designed to act like a giant battery to store energy and improve the reliability of TVA’s electric service in Columbus, Miss