Steam power generation

The steam turbine fossil fuelled plants have been the principal systems used to generate electricity in the 20th century. Starting from the first decades of the century, the configurations and the thermodynamic parameters of these plants were progressively modified and improved: so, the overall efficiency gradually increased and the environmental impact per energy unit, which was really huge at the beginning, decreased to quite low values in the recent years. The evolution of these plants was closely connected with the improvement of i) the thermodynamic cycles, ii) the design, manufacture and maintenance of the single components, iii) the use of materials having suitable mechanical performance, iv) the treatment of water, fuels and flue gases, v) the operation modes and strategies. Coal, under pulverized form, has been and still is the main fuel used in these plants; but, because of the environmental concern about greenhouse gas emissions, in the last years there have been increasing acceptance problems of coal fired plants by the public opinion in the industrial countries. So, since large coal resources are still available, it is very important to further improve these plants in order to meet more and more severe environmental standards. In fact, the coal-fired plants technology has shown very important and progressive improvements; for example, the overall efficiency, which was about 15% in the first decades of the 20th century, is expected to reach 55% by 2020. This paper will retrace the history and the evolution of the coal fired plants over the last century, outline the present state of the art and show the perspectives for the next years.