Glossary of power generation

Undertaking abatement activities on a power plant would serve to reduce its carbon intensity.

Used by the system operators to control the output of generators connected to the electricity network

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.

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.

It extracts the pressure and heat energy from the steam and converts it to rotating mechanical energy by turning the shaft.

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.

An analysis of coal based on removal of water and ash from the coal sample

• Coal
• Bottom ash
• Fly ash
• Ash (analytical chemistry)
• Proximate analysis

Calculation of availability based on unit outages and load reductions

Where the gasification is carried out immediately prior to combustion in a combined cycle gas turbine, this configuration is known as IGCC. Gasification of coal may also be carried out underground, as in UCG. Finally, some gasification plants target synthetic oils as the end products, in gas to liquid.

• IGCC
• GTL

Heat rate is the inverse of efficiency, incorporating a factor of 3600 due to the differing units of fuel energy (kJ) and electrical energy (kWh) – there are 3600 kJ in 1 kWh.

Transition between the liquid and gas phases is called evaporation and condensation.

• Plasma (physics)
• Condensation
• Evaporation

If this pressure drop occurs as the gas passes through a valve or other restriction, this would be called a throttling process. The effect is applied in air conditioning and refrigeration equipment, which incorporates a thermal expansion (TX) valve.

The Kyoto Protocol is an addendum to the United Nations Framework Convention on Climate Change. The protocol includes the Clean Development Mechanism (CDM), designed to encourage energy-efficiency initiatives in developing countries. The Certified Emission Reduction (CER) process validates the effect of the initiatives.

• CDM
• CER

Used in sealing of steam on turbine shafts, and sealing of oil and hydrogen on generator shafts.

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.

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

Typically, natural draft cooling towers are constructed as hyperboloid lattice steel and concrete. The shape is for structure not airflow.

A simple configuration of gas turbine including a compressor, combustion chambers and turbine

The open-cycle gas turbine uses the Brayton cycle.

• CCGT
• Brayton cycle

This term typically applies to fans, that is, primary air fans supply air to the pulverisers to carry pulverised fuel from the pulveriser to the burners. The term also applies to ductwork relating to the primary air system, for example hot and cold primary air ducts and dampers lead to the pulverisers.

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.

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.

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.

• Pressure vessel
• Non-return valve

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.

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).

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

As the name implies, in this mode the governor valves are positioned at 100%. The boiler is at rated pressure. Often abbreviated as VWO.

Supplying the electricity network with electricity stored in the batteries of battery electric vehicles or plug-in hybrid electric vehicles

• Battery electric vehicle
• Plug-in electric vehicle
• Hybrid electric vehicle
• Grid energy storage

The type of warm start, or whether it is in fact a cold start, depends on the degree of cooling experienced by the boiler and turbine during the shutdown. For example, the boiler may have been subjected to a forced cool to enable rapid progress on repair of a tube leak.

• Forced cool
• Hot start
• Cold start

Typically, protection of electrical power systems is duplicated to ensure that the plant remains properly secure in the event of a failure of one of the protection systems. To ensure that the protection systems are completely independent of each other, they are installed by different vendors.