Download Power plants that can be dispatched (scheduled

What is Power Plant?
A power plant or a power generating station, is basically an industrial location that is utilized for the
generation and distribution of electric power in mass scale, usually in the order of several 1000 Watts. These
are generally located at the sub-urban regions or several kilometers away from the cities or the load centers,
because of its requisites like huge land and water demand, along with several operating constraints like the
waste disposal etc. For this reason, a power generating station has to not only take care of efficient
generation but also the fact that the power is transmitted efficiently over the entire distance. And that’s why,
the transformer switch yard to regulate transmission voltage also becomes an integral part of the power
plant.
Classification:
By heat source
Fossil-fuel power stations may also use a steam turbine generator or in the case of natural gasfired plants may use a combustion turbine. A coal-fired power station produces heat by burning coal in a
steam boiler. The steam drives a steam turbine and generator that then produces electricity. The waste
products of combustion include ash, sulphur dioxide, nitrogen oxides and carbon dioxide. Some of the
gases can be removed from the waste stream to reduce pollution.
Nuclear power plants use a nuclear reactor's heat that is transferred to steam which then
operates a steam turbine and generator. About 20 percent of electric generation in the USA is produced
by nuclear power plants.
Geothermal power plants use steam extracted from hot underground rocks. These rocks are heated by
the decay of radioactive material in the Earth's crust.
Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid waste, landfill
methane, or other forms of biomass.
In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.
Waste heat from industrial processes is occasionally concentrated enough to use for power generation,
usually in a steam boiler and turbine.
Solar thermal electric plants use sunlight to boil water and produce steam which turns the generator.
By prime mover
Steam turbine plants use the dynamic pressure generated by expanding steam to turn the
blades of a turbine. Almost all large non-hydro plants use this system. About 90 percent of all electric
power produced in the world is through use of steam turbines.
Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products)
to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start
rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost
than base-loaded plants. These may be comparatively small units, and sometimes completely
unmanned, being remotely operated. This type was pioneered by the UK, Princetown[7] being the
world's first, commissioned in 1959.
Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and
steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly
increases the overall efficiency of the plant, and many new baseload power plants are combined cycle
plants fired by natural gas.
Internal combustion reciprocating engines are used to provide power for isolated communities and are
frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other
critical facilities also use them to provide backup power in case of a power outage. These are usually
fuelled by diesel oil, heavy oil, natural gas, and landfill gas.
Microturbines, Stirling engine and internal combustion reciprocating engines are low-cost solutions for
using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas
from oil production.
By duty
Power plants that can be dispatched (scheduled) to provide energy to a system include:
Base load power plants run nearly continually to provide that component of system load that
doesn't vary during a day or week. Baseload plants can be highly optimized for low fuel cost, but may
not start or stop quickly during changes in system load. Examples of base-load plants would include
large modern coal-fired and nuclear generating stations, or hydro plants with a predictable supply of
water.
Peaking power plants meet the daily peak load, which may only be for one or two hours each
day. While their incremental operating cost is always higher than base load plants, they are required to
ensure security of the system during load peaks. Peaking plants include simple cycle gas turbines and
sometimes reciprocating internal combustion engines, which can be started up rapidly when system
peaks are predicted. Hydroelectric plants may also be designed for peaking use.
Load following power plants can economically follow the variations in the daily and weekly load,
at lower cost than peaking plants and with more flexibility than baseload plants.
Non-dispatchable plants include such sources as wind and solar energy; while their long-term
contribution to system energy supply is predictable, on a short-term (daily or hourly) base their energy
must be used as available since generation cannot be deferred. Contractual arrangements ("take or
pay") with independent power producers or system interconnections to other networks may be
effectively non-dispatchable.