Electric power generation combined cycle plants

Launch a major national effort to use electricity and natural gas more efficiently. We need to slow the growth of co2 emissions, sharply reduce the need for new coal-fired power, and free up inefficiently used natural gas for high-efficiency power generation (either combined cycle plants or chp). Energy ejficiency remains the single most cost-effective strategy for minimizing co2 emissions.8... 

For a modern gas-fired power station in the UK the electrical efficiency is about 45% and for a coal-fired station about 37%. There are combined cycle plants in which the waste heat from the gas turbines is used to produce steam that in turn drives a steam turbine generator. Such combinations, which are... 

From the results presented in Table 7.A, the levelized electricity price for electricity produced by combined-cycle power plants fueled with first generation H2 is too expensive to be considered economically feasible. However, if the 60-year PV module operating life model proves relevant, then the levelized price of electricity generated by combined-cycle power plants using second generation H2 as a fuel source could be as low as 0.15-0.17/kWh. These electricity prices provide some assurance that if other options fail to meet electricity demand in the post-2040 period, dispatchable PV electricity will be a feasible option. Clearly, further progress in PV cost reduction, a near certainty by 2040, will reduce the price of electricity generated by H2 fueled power plants. 

Power Production. Steam cycles for generation of electric power use various types of boilers, steam generators, and nuclear reactors operate at subcritical or supercritical pressures and use makeup and often also condensate water purification systems as well as chemical additives for feedwater and boiler-water treatment. These cycles are designed to maximize cycle efficiency and reliability. The fuel distribution of sources installed in the United States from 1990—1995 are as follow coal, 45% combined cycle, 27% miscellaneous, 14% nuclear, 11% solar, oil, and geothermal, 1% each and natural gas, 0.3%. The 1995 summer peak generation in the United States was 620 GW (26). The combined cycle plants are predominantly fired by natural gas. The miscellaneous sources include bagasse, black liquor from paper mills, landfill gas, and refuse (see Fuels frombiomass Fuels fromwaste). 

The increased efficiency of the combined cycle for electrical power generation results in a 50% decrease in carbon dioxide emissions compared to conventional coal power plants. As the technology is required to develop economical methods of carbon sequestration, the removal of carbon dioxide from combustion by-products to prevent its release to the atmosphere, coal gasification units could be modified to further reduce their climate change impact because a large part of the carbon dioxide generated can be separated from the syngas before combustion. 

A relatively new technology for electric power generation is a combined cycle plant. These use gas turbines driving electric generators for the majority of their power production. However, gas turbines alone have relatively low efficiencies (about 35 percent), because the exhaust gas contains a lot of unused heat energy. In a combined cycle plant, this hot exhaust gas is used to produce steam, and the steam drives a turbine that powers another electric generator. The efficiency of combined cycle plants is very attractive (50 percent or more). 

In apphcation to electric utihty power generation, MHD is combined with steam (qv) power generation, as shown in Figure 2. The MHD generator is used as a topping unit to the steam bottoming plant. From a thermodynamic point of view, the system is a combined cycle. The MHD generator operates in a Brayton cycle, similar to a gas turbine the steam plant operates in a conventional Rankine cycle (11). 

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