A design flaw at the 1,600-MW Raccoon Mountain pumped storage facility in Chattanooga is proving to be a costly issue to repair, HydroWorld.com has learned.
Following reports of a unit fire after a rotor pole broke away from the rim at a similar pumped-storage plant in Austria, the Tennessee Valley Authority inspected Unit 3 in 2010. Nothing was damaged in Unit 3, but a February inspection of Unit 2 showed evidence of rotor cracks. The facility was taken offline immediately, and cracks were found to be present in Units 1 and 2.
“Our engineers felt that this was very serious, and we wanted to inspect the other units immediately. While certainly living without the Raccoon Mountain units has been difficult from an operational perspective, the potential damage that could have been done to our assets and, most importantly the damage that could have been done to our people, certainly warranted us taking the conservative approach,” Kim Greene, TVA executive vice president, said at a recent board meeting.
TVA estimates the repairs will cost $55 million and will delay previously scheduled closings of some coal-fired units at the Johnsonville and Colbert plants until 2014 when repairs are complete.
“Due to unanticipated operating challenges primarily at Raccoon Mountain Pumped-Storage Plant, TVA is re-evaluating the previously announced idling dates of [the coal] units. Depending on capacity needs, TVA may return other idled units into service or extend unit operation beyond previously planned idle dates,” TVA announced in its Form 10-K annual report.
The pumped storage facility cost $310 million to construct in 1978. One of the four units has already been repaired and is online, with the remaining three units expected to be back online within the next two years.