Electricity generation

Electricity generation is the process of creating electricity from other forms of energy.
The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of a loop of wire, or disc of copper between the poles of a magnet.
For electric utilities, it is the first process in the delivery of electricity to consumers. The other processes, electric power transmission, electricity distribution, and electrical power storage and recovery using pumped storage methods are normally carried out by the electrical power industry.
Electricity is most often generated at a power station 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 and geothermal power

History:-Centralised 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.


Methods of generating electricity:-

 There are seven fundamental methods of directly transforming other forms of energy into electrical energy:

• Static electricity, from the physical separation and transport of charge (examples: triboelectric effect and lightning)
• Electromagnetic induction, where an electrical generator, dynamo or alternator transforms kinetic energy (energy of motion) into electricity
• Electrochemistry, the direct transformation of chemical energy into electricity, as in a battery, fuel cell or nerve impulse
• Photoelectric effect, the transformation of light into electrical energy, as in solar cells
• Thermoelectric effect, direct conversion of temperature differences to electricity, as in thermocouples and thermopiles
• Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals
• Nuclear transformation, the creation and acceleration of charged particles (examples: betavoltaics or alpha particle emission)

Static electricity was the first form discovered and investigated, and the electrostatic generator is still used even in modern devices such as the Van de Graaff generator and MHD generators. Electrons are mechanically separated and transported to increase their electric potential.
Almost all commercial electrical generation is done using electromagnetic induction, in which mechanical energy forces an electrical generator to rotate. There are many different methods of developing the mechanical energy, including heat engines, hydro, wind and tidal power.
The direct conversion of nuclear energy to electricity by beta decay is used only on a small scale. In a full-size nuclear power plant, the heat of a nuclear reaction is used to run a heat engine. This drives a generator, which converts mechanical energy into electricity by magnetic induction.
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 and some from renewable sources. The modern steam turbine invented by Sir Charles Parsons in 1884 - today generates about 80 percent of the electric power in the world using a variety of heat sources.



turbines:-

All turbines are driven by a fluid acting as an intermediate energy carrier. Many of the heat engines just mentioned are turbines. Other types of turbines can be driven by wind or falling water.
Sources includes:

• Steam - Water is boiled by: 
• • nuclear fission,
  • the burning of fossil fuels (coal, natural gas, or petroleum). In 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 natural 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%.
  • Renewables. The steam generated by:
    • Biomass
    • 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.
    • 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.
• Other renewable sources:
  • 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 is artificially produced inside the chimney by heating it with sunlight, and are more properly seen as forms of solar thermal energy

Electric potential energy

Electric potential energy (also known as "electrostatic potential energy") is a potential energy associated with the conservative Coulomb forces within a defined system of point charges. The term "electrostatic potential energy" is preferred here because it seems less likely to be misunderstood. The reference zero is usually taken to be a state in which the individual point charges are very well separated ("are at infinite separation") and are at rest. The electrostatic potential energy of the system (U_E), relative to this zero, is equal to the total work W that must be done by a hypothetical external agent in order to bring the charges slowly, one by one, from infinite separation to the desired system configuration:

In this process the external agent is deemed to provide or absorb any relevant work, and the point charge being slowly moved gains no kinetic energy.
Sometimes people refer to the potential energy of a charge in an electrostatic field. This actually refers to the potential energy of the system containing the charge and the other charges that created the electrostatic field.
To calculate the work required to bring a point charge into the vicinity of other (stationary) point charges, it is sufficient to know only (a) the total field generated by the other charges and (b) the charge of the point charge being moved. The field due to the charge being moved and the values of the other charges do not need to be known. Nonetheless, in many circumstances it is mathematically easier to add up all the pairwise potential energies (as below).
It is important to understand that electrostatics is a 18th-19th-century theory of hypothetical entities called "point charges". Electrostatics is categorically not a complete theory of the charged physical particles that make up the physical world, and are subject to the Heisenberg uncertainty principle and other laws of quantum mechanics.

electric current

Electric current can mean, depending on the context, a flow of electric charge  or the rate of flow of electric charge . The electric charge that flows is carried by, for example, mobile electrons in a conductor, ions in an electrolyte or both in a plasma.
The SI unit for rate of flow of electric charge is the ampere. Electric current is measured using an ammeter

electric flux

In electromagnetism, electric flux is the flux of the electric field. Electric flux is proportional to the number of electric field lines going through a virtual surface. The electric flux through a small area is given by

(the electric field, E, multiplied by the component of area perpendicular to the field). The electric flux over a surface S is therefore given by the surface integral:

where E is the electric field and dA is a differential area on the closed surface S with an outward facing surface normal defining its direction.
For a closed Gaussian surface, electric flux is given by:

where Q_S is the charge enclosed by the surface (including both free and bound charge), and ε₀ is the electric constant. This relation is known as Gauss' law for electric field in its integral form and it is one of the four Maxwell's equations.
Electrical flux has SI units of volt metres (V m), or, equivalently, newton metres squared per coulomb (N m² C⁻¹). The SI base units of the electric field are kg•m³•s^-3•A^-1.