Impact of incremental changes in meteorology on thermal compliance and power system operations

The sensitivity of the TVA reservoir and power supply systems to extreme meteorology was evaluated using a series of mathematical models to simulate the relationship between incremental changes in meteorology, associated changes in water temperature, and power plant generation. Single variable analysis techniques were applied at selected TVA facilities for representative average and extreme weather conditions. In the analysis, base case simulations were first conducted for each representative year using observed meteorology (i.e., the no change condition). The impacts of changes in meteorology were subsequently analyzed by uniformly constant at their respective base case values. Project results are generally presented in terms of deviations from base case conditions for each representative year. Based on an analysis of natural flow and air temperature patterns at Chickamauga Dam, 1974 was selected to represent extreme cold-wet conditions; 1965 as reflecting average conditions; and 1986 as an example of an extremely hot-dry year. The extreme years (i.e., 1974 and 1986) were used to illustrate sensitivities beyond historical conditions; while the average year provided a basis for comparison. Observed reservoir conditions, such as inflows, dam releases, and reservoir elevations for each representative year, were used in the analysis and were assumed to remain constant in all simulations. Therefore, the Lake Improvement Plan (which was implemented in 1991) and its consequent effects on reservoir operations were not incorporated in the assessment. In the model simulations, computed water temperatures were based on vertically well-mixed conditions in the reservoirs