The figure below illustrates a combined-cycle power system using a gas turbine generator with waste heat recovery and steam turbine generator. Figure 1: Combined cycle power system using a gas turbine generator with waste heat recovery and steam turbine generator. For a more detailed description of this technology in typical onshore applications, please refer to:.
The following are technologies that provide similar benefits high efficiency power generation and may be considered as alternatives to a combined-cycle system:. Figure 2 illustrates high-level applicability of technologies based on the demand for power and heat.
Figure 2: The applicability of technologies based on the demand for power and heat. Issues and risks are few and known. Combined-cycle technology has been used for many years for onshore applications.
The technology has also been used for more than 10 years for offshore applications, including both floating Snorre B and fixed Oseberg D installations. Home Resources Combined cycle gas turbines. Commercially available? Thus, continuous energy supply is guaranteed in places where production is mostly fueled by renewables.
Undoubtedly, this type of technology allows to raise generation capacity at a lower cost, thereby increasing available energy. This means that a higher production of electric energy is achieved with a lower primary energy natural gas consumption. Obviously, this has both environmental and economic benefits for the places where these plants are installed, at better prices for end consumers.
Lower emissions of pollutants that are highly harmful to the environment and human beings, such as carbon dioxide CO2 , nitrogen oxide NOx , and sulfur dioxide SO2 , because natural gas is a cleaner fuel than coal, fuel oil, diesel and other petroleum derivatives used to produce electricity in many cases.
Furthermore, transportation and supply of the main fuel natural gas to these plants is made through a buried pipeline, so the traffic impact from coal or fuel oil supply trucks or trains is avoided.
Lower water use. Because combined-cycle power plants require water only for steam condensation, they only use one third of the water required for conventional thermal power plants.
Sewage, treated, salt or sea water is used, i. If it is not available, air is used through air conditioning condensers. Installation and operation. Combined-cycle power plants require a minor infrastructure compared to conventional plants. The steam turbine can be run with only 25 percent of the engines at full load, or 50 percent of the engines at half load. For a engine power plant of around megawatts MW , this means only three of the engines need to be operating to produce enough steam to run the steam turbine.
The result is a very efficient power plant that retains the operational agility of a power plant based on simple-cycle engines. The process for converting the energy in a fuel into electric power involves the creation of mechanical work, which is then transformed into electric power by a generator in a "simple cycle", causing efficiency losses in the process.
This means that a significant amount of the latent energy of the fuel ends up wasted. Much of this wasted energy ends up as thermal energy in the hot exhaust gases from the combustion process. To increase the overall efficiency of electric power plants, multiple processes can be combined to recover and utilize the residual heat energy in hot exhaust gases.
What is the difference between simple cycle and combined cycle? Combined cycle operation employs a heat recovery steam generator HRSG that captures heat from high temperature exhaust gases to produce steam, which is then supplied to a steam turbine to generate additional electric power. In combined cycle mode, power plants can achieve electrical efficiencies of up to 60 percent.
The process for creating steam to produce work using a steam turbine is based on the Rankine cycle. The HRSG is basically a heat exchanger, or rather a series of heat exchangers.
It is also called a boiler, as it creates steam for the steam turbine by passing the hot exhaust gas flow from a gas turbine or combustion engine through banks of heat exchanger tubes. The HRSG can rely on natural circulation or utilize forced circulation using pumps.
As the hot exhaust gases flow past the heat exchanger tubes in which hot water circulates, heat is absorbed causing the creation of steam in the tubes. The tubes are arranged in sections, or modules, each serving a different function in the production of dry superheated steam.
Designs and configurations for HRSGs and steam turbines depend on the exhaust gas characteristics, steam requirements, and expected power plant operations.
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