Authors: C. Robinson, A. R. Griffith
Abstract
Tacoma Power owns and operates two hydroelectric projects on the Cowlitz River in Western Washington: Mossyrock and Mayfield. The Mossyrock Project, which was commissioned in 1968, contains of two units, each rated at 150 MW, and contains a currently unused space for a third unit. Tacoma Power engaged Acres International Corporation (Acres) to perform a study evaluating the various upgrade opportunities for the project. In order to capture the effect of the interaction of these two projects on the Cowlitz River, Acres used its AUTO Vista operations model to compare the revenue potential of the project under various upgrade scenarios over a 20-year hydrologic period. The economic model used for this study indicated a positive Net Present Value for several of the alternative configurations studied with a slight economic advantage to a scenario that included rebuilding both units with differing performance characteristics for purposes of achieving better efficiency over a wider range of output levels and heads.
