Maintaining the competitive thermal efficiencies over a wide load range, while achieving flexible operation in response to demand fluctuation

By adding 6 units of H-25 gas turbines and a HRSG connecting the plant’s existing steam turbines, it is possible to convert an existing 132MW plant into a 225MW combined cycle plant at 50% better efficiency.   One advantage to using multiple small gas turbines is that “it allows the plant to maintain competitive thermal efficiencies in incremental blocks of power over a wide load range starting at around 20MW on up through 225MW.”   Once-through stream generators are applied as HRSG because they simplify plant design and installation, are easy to operate, and can run dry to serve as a gas turbine exhaust stack without having to generate steam.   A single operator can start as many as five units at one time and switch to simple cycle operation without having to bypass the gas turbine exhaust. In addition, the once-through design enables fast response to changing load demand and facilitates shutdowns even at minus 40℃ ambient air temperatures.   The repowering option proved to be the most feasible in terms of cost, efficiency, operating flexibility, scheduling, and meeting environmental regulations. *In some part, the article utilizes the past issued article in Gas Turbine World magazine.