Practical Considerations for Low-Emission Thermal Power Plants

Thermal power plants provide the majority of electricity used around the world and will continue to do so for some time. The goal of this paper is to provide an understanding of technology and fuels used in thermal power plants and the byproducts they create. The emphasis is on magnitudes of fuels used, emissions created and the sustainability and practicality of methods of production and control. A basic thermal power plant burns fuel to produce steam, which turns a turbine generator to produce electricity. The basic elements of thermodynamics apply to all thermal power plants: a heat source, a heat engine and a heat sink. Heat sources for thermal power plants include boilers fueled by coal, natural gas and biomass; gas turbines fueled by natural gas; and nuclear reactors fueled by uranium. Topics of discussion include the logistics involved in supplying fuels and handling their byproducts, including carbon compounds; types of heat engines utilized; methods to improve efficiency to reduce the fuel consumed; byproducts generated; and the heat sink required. The focus is on Rankine (vapor) and Brayton (gas) cycles. Although not directly affecting carbon byproducts, the heat sink used affects the heat engine efficiency and the consumption of water, a valuable resource. The types of heat sinks discussed include open-cycle water cooling, closed-cycle water cooling and air cooling. Thermal power plants provide many benefits to the electrical power system. They provide power 24 hours a day and 365 days a year, regardless of the weather. They are relatively compact, making them easier to build, operate and maintain. They also can be located close to electrical load concentrations reducing the need for transmission lines that disrupt the environment. The technologies involved in thermal power plant operation are proven effective and in use today. The challenges are to manage the fuel supply and byproduct disposal in an environmentally acceptable manner.