Thermal power station
In addition to fossil and nuclear fuel, some stations use geothermal power, solar energy, biofuels, and waste incineration.
Emerging technologies such as supercritical and ultra-supercritical thermal power stations operate at higher temperatures and pressures for increased efficiency and reduced emissions.
Older, less efficient thermal power stations are being decommissioned or adapted to use cleaner and renewable energy sources.
The operation of thermal power stations contributes to the local economy by creating jobs in construction, maintenance, and fuel extraction industries.
Carbon capture and storage (CCS) technology can reduce the greenhouse gas emissions of fossil-fuel-based thermal power stations, however it is expensive and has seldom been implemented.
Government regulations and international agreements are being enforced to reduce harmful emissions and promote cleaner power generation.
Commercial electric utility power stations are usually constructed on a large scale and designed for continuous operation.
Large companies or institutions may have their own power stations to supply heating or electricity to their facilities, especially if steam is created anyway for other purposes.
The reciprocating steam engine has been used to produce mechanical power since the 18th century, with notable improvements being made by James Watt.
The development of the steam turbine in 1884 provided larger and more efficient machine designs for central generating stations.
The air and flue gas path equipment include: forced draft (FD) fan, air preheater (AP), boiler furnace, induced draft (ID) fan, fly ash collectors (electrostatic precipitator or baghouse), and the flue-gas stack.
The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace.
[10][14][15][16] The exhaust steam from the low-pressure turbine enters the shell, where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram.
The large decrease in volume that occurs when water vapor condenses to liquid creates the vacuum that generally increases the efficiency of the turbines.
Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning.
In the United States, about two-thirds of power plants use OTC systems, which often have significant adverse environmental impacts.
The impacts include thermal pollution and killing large numbers of fish and other aquatic species at cooling water intakes.
Nevertheless, they may become internally fouled during operation by bacteria or algae in the cooling water or by mineral scaling, all of which inhibit heat transfer and reduce thermodynamic efficiency.
(The other five being emergency lighting, communication, station alarms, generator hydrogen seal system, and turbogenerator lube oil.)
This system requires special handling during startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen.
Oil lubrication is provided to further reduce the friction between shaft and bearing surface and to limit the heat generated.
A typical flue-gas stack may be 150–180 metres (490–590 ft) tall to disperse the remaining flue gas components in the atmosphere.
The tallest flue-gas stack in the world is 419.7 metres (1,377 ft) tall at the Ekibastuz GRES-2 Power Station in Kazakhstan.
In the United States and a number of other countries, atmospheric dispersion modeling[20] studies are required to determine the flue-gas stack height needed to comply with the local air pollution regulations.
[23] Cost, the absence of measures to address long-term liability for stored CO2, and limited social acceptability have all contributed to project cancellations.
Sometimes, a steam blanketing arrangement or stainless steel doughnut float is provided on top of the water in the tank to avoid contact with air.
DM water make-up is generally added at the steam space of the surface condenser (i.e., the vacuum side).
This small shaft deflection, only detectable by eccentricity meters, would be enough to cause damaging vibrations to the entire steam turbine generator unit when it is restarted.
This system requires special handling during start-up, with air in the generator enclosure first displaced by carbon dioxide before filling with hydrogen.
The generator high-voltage leads are normally large aluminium channels because of their high current as compared to the cables used in smaller machines.
