Glossary of power generation

The following is a list of common definitions related to power generation.

Term	Explanation and discussion	References and related terms
Abatement	Effort to avoid emission of carbon dioxide Undertaking abatement activities on a power plant would serve to reduce its carbon intensity.	Carbon intensity
AGC	Automatic generation control Used by the system operators to control the output of generators connected to the electricity network	Governor (device)

Term	Explanation and discussion	References and related terms
Bagasse	Waste plant fibre left after the juices have been removed from sugar cane by crushing. Burning bagasse in boilers at sugar mills is a common form of renewable energy using biomass.	Biomass
Bag filter	A casing containing thousands of long cloth bags used to remove fly ash from flue gas. The bags are back-flushed using compressed air.	Precipitator
Barring	The process of slowly turning the turbine-generator shaft to prevent bowing while it is still hot after shutdown Typically, barring is achieved using turning gear, a small electric motor and gearbox connected to the generator shaft. Early in the history of power plants, barring was done by operators turning the shaft with a bar. This is still done if electric barring is not available, as the consequences of bowing a shaft are enormous.	Turning gear
Biomass	Living or recently dead material such as plant matter, used as either fuel or industrial production as biofuel It is a renewable resource obtained from several different plants, for example wood waste, sugar cane, corn, hemp and others. \|\| Biofuel
Black start	Starting a unit without external power supply from the electricity network In the context of an electricity market, that capability of completing a black start is known as system restart ancillary service (SRAS). Black start capability is typically provided by a local gas turbine, generating sufficient electrical power to drive pumps and fans on only one unit in the power station until it comes online. Once that unit is up, it can provide auxiliary power to the others at the same location, or feed into the grid again. A black start does not require a synchronising step as the network is down, but subsequent generators coming online will need to synchronise.	Ancillary services
Blade	In a reaction turbine, the blade is the main moving part attached to the turbine shaft It extracts the pressure and heat energy from the steam and converts it to rotating mechanical energy by turning the shaft.	Reaction turbine
Bled steam	Steam extracted from the turbine to provide heat to the feedwater heaters Note that the deaerator is also a feedwater heater – it also receives bled steam from the turbine, but the steam is mixed with and heats the water instead of transferring heat through a shell and tube heat exchanger.	LP heater, HP heater, deaerator, auxiliary steam

Term	Explanation and discussion	References and related terms
Mollier chart	Enthalpy–enthalpy diagram, showing the enthalpy on the vertical axis, and the entropy on the horizontal axis This chart is useful for calculating the turbine isentropic efficiency, as a vertical line represents expansion at constant entropy, and the height of the line is the enthalpy drop. Also known as h-s diagram.	T-s chart
Max cap	Maximum capacity One of three modes describing the configuration of the unit around full load Usually achieved by taking the HP heaters out of service, so that the bled steam that normally goes to these heaters now passes through the turbine. This increases the capacity of the turbine due to the increased steam flow, but reduces the efficiency as the boiler must fire much harder due to the colder incoming water. Also known as overload operation.	Valves wide open Maximum continuous rating

Term	Explanation and discussion	References and related terms
Rankine cycle	The thermodynamic cycle used by most boiler–turbine generating units This cycle includes addition of heat in the boiler, extraction of energy through expansion of steam in the turbine, and rejection of heat using the condenser and cooling tower.	Brayton cycle
Reaction turbine	Design of a Turbine where energy is extracted from the steam predominantly by a change in pressure of the steam The vanes (stationary components fixed to the casing) direct the steam toward the blades (rotating components attached to the rotor) which produce a force on the rotor in a way similar to an aeroplane wing. The shape of the blade causes a difference in steam from one side of the blade to the other, causing the rotor to turn.	Impulse turbine

Term	Explanation and discussion	References and related terms
SA	Sealing air The sealing air fan provides air pressure to joints and seals around the moving parts of the pulveriser to prevent pulverised fuel and primary air leaking out.	Pulverizer
Safety valve	A flow control device designed to prevent the pressure in a vessel exceeding its design pressure	Pressure vessel Non-return valve

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References

External links

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Term	Explanation and discussion	References and related terms
Tandem compound	A design of turbine where multiple cylinders are arranged in line on a single shaft	Cross compound
Tap changer	A device in a transformer to change the number of coils used	Since the voltage ratio of a transformer is based on the ratio of the number of turns between the primary and secondary coils, changing the number of turns changes the voltage.	Transformer
TDS	Total dissolved solids A measure of the impurities contained in cooling water Circulating water with high TDS will tend to form a scale on the inside of condenser tubes.	Langelier saturation index

Term	Explanation and discussion	References and related terms
UCG	Underground coal gasification A process to convert coal to gas which occurs underground Coal, and volatiles embedded in the coal (mostly methane) are partially combusted in the presence of steam, oxygen and / or air, to produce hydrogen and carbon monoxide. UCG may be combined with GTL to produce liquid hydrocarbons from low-value coal reserves. This is known as coal to liquid (CTL).	Gasification
Ultimate analysis	The detailed chemical analysis of a fuel that indicates the contents of carbon, hydrogen, sulphur, nitrogen, chlorine, oxygen, and ash – as percentages by mass In some analyses, the ash content may be listed as the specific elements, for example silicon and iron, as these determine the ash fusion temperature and associated slagging behaviour.	Proximate analysis Ash fusion temperature REF slagging