Everything about Electricity Generation totally explained
Electricity generation is the process of converting non-electrical
energy to
electricity. For
electric utilities, it's the first process in the delivery of electricity to consumers. The other processes,
electric power transmission and
electricity distribution, are normally carried out by the
electrical power industry. Electricity is most often generated by electromechanical
generators, primarily driven by
heat engines fueled by chemical combustion or
nuclear fission
but also by other means such as the kinetic energy of flowing water and wind. There are many other technologies that can be and are used to generate electricity such as solar
photovoltaics.
History
Centralized power generation became possible when it was recognized that
alternating current power lines can transport
electricity at very low costs across great distances by taking advantage of the ability to raise and lower the
voltage using power
transformers.
Electricity has been generated at central stations since 1881. The first power plants were run on
water power or coal, and today we rely mainly on
coal,
nuclear,
natural gas,
hydroelectric, and
petroleum with a small amount from
solar energy,
tidal harnesses,
wind generators, and
geothermal sources.
Electricity demand
The demand for electricity is met in several ways. Large centralized generators have been the primary method thus far.
Distributed generation uses a larger number of smaller generators throughout the electricity network. Some use waste heat from industrial processes, others use fuels that would otherwise be wasted, such as landfill gas.
Wind and
solar generation tend to be distributed because of the low density of the natural energy they collect.
Methods of generating electricity
Most electric generation is driven by
heat engines. The combustion of fossil fuels
supplies most of the heat to these engines, with a significant fraction from nuclear fission.
Turbines
Virtually all of the heat engines just mentioned are turbines. Other types of turbines can be driven by wind or falling water. All turbines are driven by a fluid acting as an intermediate energy carrier. These fluids can be:
- Steam - Water is boiled by nuclear fission, the burning of fossil fuels (coal, natural gas, or petroleum) or biomass. Some power plants use the sun as the heat source: solar parabolic troughs and solar power towers concentrate sunlight to heat a heat transfer fluid, which is then used to produce steam. Another renewable source of heat used to drive a turbine is Geothermal power. Either steam under pressure emerges from the ground and drives a turbine or hot water evaporates a low boiling liquid to create vapour to drive a turbine.
- Water (hydroelectric) - Turbine blades are acted upon by flowing water, produced by hydroelectric dams or tidal forces.
- Wind - Most wind turbines generate electricity from naturally occurring wind. Solar updraft towers use wind that's artificially produced inside the chimney by heating it with sunlight, and are more properly seen as forms of solar thermal energy.
- Hot gas (gas turbine) - Turbines are driven directly by gases produced by the combustion of natural gas or oil.
Combined cycle gas turbine plants are driven by both steam and gas. They generate power by burning natural gas in a
gas turbine and use residual heat to generate additional electricity from steam. These plants offer efficiencies of up to 60%.
Reciprocating engines
Small electricity generators are often powered by
reciprocating engines burning
diesel,
biogas or natural gas.
Diesel engines are often used for back up generation, usually at low voltages. Biogas is often combusted where it's produced, such as a landfill or wastewater treatment plant, with a reciprocating engine or a microturbine, which is a small gas turbine.
Photovoltaic panels
Unlike the solar heat concentrators mentioned above,
photovoltaic panels convert sunlight directly to electricity. Although sunlight is free and abundant, solar electricity is still usually more expensive to produce than large-scale mechanically generated power due to the cost of the panels. Low-efficiency silicon solar cells have been decreasing in cost though, and multijunction cells with close to 30% conversion efficiency are now commercially available. Over 40% efficiency has been demonstrated in experimental systems. Until recently, photovoltaics were most commonly used in remote sites where there's no access to a commercial power grid, or as a supplemental electricity source for individual homes and businesses. Recent advances in manufacturing efficiency and photovoltaic technology, combined with subsidies driven by environmental concerns, have dramatically accelerated the deployment of solar panels. Installed capacity is growing by 40% per year led by increases in Germany, Japan, California and New Jersey.
Other generation methods
Various other technologies have been studied and developed for power generation. Solid-state generation (without moving parts) is of particular interest in portable applications. This area is largely dominated by
thermoelectric (TE) devices, though
thermionic (TI) and
thermophotovoltaic (TPV) systems have been developed as well. Typically, TE devices are used at lower temperatures than TI and TPV systems.
Piezoelectric devices are used for power generation from mechanical strain, particularly in
power harvesting.
Betavoltaics are another type of solid-state power generator which produces electricity from radioactive decay.
Fluid-based
magnetohydrodynamic (MHD) power generation has been studied as a method for extracting electrical power from
nuclear reactors and also from more conventional fuel combustion systems.
Electrochemical electricity generation is also important in portable and mobile applications. Currently, most electrochemical power comes from closed electrochemical cells ("
batteries"), which are arguably utilized more as storage systems than generation systems, but open electrochemical systems, known as
fuel cells, have been undergoing a great deal of research and development in the last few years. Fuel cells can be used to extract power either from natural fuels or from synthesized fuels (mainly electrolytic
hydrogen) and so can be viewed as either generation systems or storage systems depending on their use.
Producers
In 2005, USA continued to remain as the top producer of electricity with a global share of at least 25% followed by China, Japan and Russia.
Further Information
Get more info on 'Electricity Generation'.
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