Coal-fired power plant development started with the introduction of the first dynamo built for power generation in 1866 by Werner von Siemens, illustrated in Figure 1-1. In 1882, Thomas Edison built the first central power station in New York. The first coal-fired steam generators provided low-pressure saturated or slightly superheated steam for steam engines driving the DC dynamos. The historical development of coal-fired power plants is listed in Figure 1-2.
In 1884, Sir Charles Parsons built the first steam turbine-generator with a thermal efficiency of only 1.6%. Two years later he improved the steam turbine performance by introducing the first condensing turbine, which drove an AC generator. His effort to build larger and more efficient turbines led at the turn of the century to a 5-MW condensing steam turbine with a thermal efficiency of 21%, which relates to a net power plant efficiency of about 15%. Introduction of the AC generator technology developed by Nicola Tesla opened the way to larger central power stations that could be remotely located since AC power could be transformed and transmitted efficiently using high-voltage transmission lines.
In the early 1900s, the power plants were rated in the range of 1- to 10-MW unit output. As depicted in Figure 1-3, they featured a coal-fired steam generator with an economizer, evaporator, and a superheater section to generate slightly superheated steam for a condensing turbine. The exhaust steam of the steam turbine entered the condenser to be condensed and fed from the condenser hotwell as feedwater by the feedwater pump back to the steam generator to close the steam/water cycle loop. The listed power plant component efficiencies result into a 15% coal-fired power plant net efficiency. Figure 1-4 shows a typical steam generator and steam turbine of such early power plants. The steam generator with 4 drums was designed for saturated main steam with a pressure of up to 420 psig (30 bar). At that early stage, boilers were equipped with travelling grates for coal combustion, which put a limit on the size of this boiler type. The condensing steam turbine was a single casing design, which also limited the maximum output of a unit, especially when applying a low backpressure with a consequentially large volumetric exhaust flow.