The Tennessee Valley Authority (TVA) has 109 conventional hydroelectric generating units with a capacity of 3,783 megawatts (MW). The hydro fleet supports TVA’s mission of providing clean, reliable, and affordable electricity to people and businesses of the Tennessee Valley. As of 2021, 53 of TVA’s 109 hydro units had low asset health scores indicating the need for repair. To extend the life of the hydro fleet, the Hydro Life Extension (HLE) program was formed in 2021. Due to the importance of TVA’s hydro fleet in providing low cost, clean, and reliable energy, we performed an evaluation of TVA’s HLE program to determine if the program was achieving intended results.
We determined the HLE program achieved the intended results on completed projects for availability, efficiency, and flexibility, but did not meet the efficient project execution goal for some projects. Specifically:
- All hydro units that have completed an HLE project have availability greater than 85 percent.
- All 4 hydro units that have completed a turbine replacement as part of an HLE project met contractual vendor efficiency guarantees and increased efficiency.
- All hydro units that have completed an HLE project achieved their intended result to increase generation output capability. In total, the HLE projects added an additional 29 MWs of capacity.
- All HLE projects met budget targets, but only two met In Service Date (ISD) targets. Variances between target and actual ISDs ranged from 59 to 261 days.
While HLE projects have increased the maximum output capability, these additional MWs cannot be transmitted to the system due to transmission limits for the hydro sites. The transmission limits (1) were not evaluated during HLE project planning and (2) have not been increased due to a lack of funding. In addition, we found one lesson learned related to cost and schedule had not been incorporated into future projects as required.
