Thermal plant electricity generation Rankin Cycle

The United States derived about 20 percent of its electricity from nuclear energy in 2002 (EIA, Electric Power Monthly, 2003). The 103 power reactors operating today have a total capacity of nearly 100 gigawatts electric (GWe) and constitute about 13 percent of the installed U.S. electric generation capacity. The current U.S. plants use water as the coolant and neutron moderator (hence called light-water reactors, or LWRs) and rely on the steam Rankine cycle as the thermal-to-electrical power conversion cycle. Other countries use other technologies—notably C02-cooled reactors in the United Kingdom and heavy-water-cooled reactors (HWRs) in Canada and India. 

Rankine Cycle. The sleam-Rankine cycle employing steam turbines has been the mainstay of utility thermal electric power generation for many years. The cycle, as developed over the years, is sophisticated and efficient. The equipment is dependable and readily available. A typical cycle (Fig. 21) uses superheat, reheat, and regeneration. Heat exchange between flue gas and inlet air adds several percentage points to boiler efficiency in fossil-fueled plants. Modern steam Rankine systems operate at a cycle top temperature of about 800 K with efficiencies of about 40%. All characteristics of this cycle are well suited to use in solar plants. 

Natural gas is considered as a clean fossil fuel compared to coal and oil, but still, due to the combustion process, emits a lot of carbon dioxide when it used for electrical generation. The most efficient modem thermal power plants with thermal efficiencies within a range of 50—60% (up to 62%) are, so-called combined cycle power plants (combination of Brayton gas turbine and Rankine steam turbine power cycles) (see Figs. Al.l—A1.4, and Tables Al.l and A1.2), which use mainly natural gas as a fuel. 

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