- 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. This is the most used form for generating electricity and is based on Faraday’s law.
- 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, the direct conversion of temperature differences to electricity, as in thermocouples, thermopiles, and thermionic converters.
- Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals. Researchers at the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a piezoelectric generator sufficient to operate a liquid crystal display using thin films of M13 bacteriophage.
- Nuclear transformation, the creation and acceleration of charged particles (examples: betavoltaics or alpha particle emission)
Electrical generation is the process of generating electrical power from a variety of sources of primary energy. The fundamental principles of electrical 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, electrical transmission, distribution, and electrical power storage and recovery are normally carried out by the electric 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.
PHOTOGRAPH OF STEAM TURBOGENERATOR
Electrical energy can also be generated by other means such as the kinetic energy of flowing water, wind, solar photovoltaics and geothermal power.
SECTION ONE: METHODS OF DIRECT ENERGY CONVERSION:
- 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. Charge carriers are separated and physically transported to a position of increased electric potential.
- Electromagnetic Induction 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.
- Nuclear EnergyThe direct conversion of nuclear potential 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.
SECTION TWO: METHODS OF DIRECT ENERGY CONVERSION:
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) currently generates about 80% of the electric power in the world using a variety of heat sources.
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 of heat:
- Burning Hydrocarbons The burning of fossil fuels (coal, natural gas, or petroleum) is the principal energy source used for the production of electricity to feed the grid. 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%.
Small electrical generators are often powered by reciprocating engines burning diesel, or natural gas. Diesel engines are often used for back up generation, usually at low voltages. However most large power grids also use diesel generators, originally provided as emergency back up for a specific facility such as a hospital, to feed power into the grid during certain circumstances.
- Nuclear Fission: A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation. Heat created from nuclear fission is passed to a working fluid (water or gas), which runs through turbines. The steam created is directed into a steam turbine which in turn drives an electric generator. Nuclear generated steam in principle can be used for industrial process heat or for district heating.
When a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more lighter nuclei, (the fission products), releasing kinetic energy, gamma radiation, and free neutrons. A portion of these neutrons may later be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, and so on. This is known as a nuclear chain reaction.
The reactor core generates heat by converting the kinetic energy of fission products to thermal energy when these nuclei collide with nearby atoms.
A kilogram of uranium-235 (U-235) converted via nuclear processes releases approximately three million times more energy than a kilogram of coal burned conventionally (7.2 × 1013 joules per kilogram of uranium-235 versus 2.4 × 107 joules per kilogram of coal).
1. Solar energy: solar parabolic troughs and solar power towers concentrate sunlight to heat a fluid, which is then used to produce steam.Solar energy is also used directly to produce electricity using the photovoltaic effect.
2. Geothermal power: Either steam under pressure emerges from the ground and drives a turbine or hot water evaporates a low boiling liquid to create vapor to drive a turbine.
3. Ocean thermal energy conversion (OTEC): uses the small difference between cooler deep and warmer surface ocean waters to run a heat engine (usually a turbine).4. Water (hydroelectric): Turbine blades are acted upon by flowing water, produced by hydroelectric dams or tidal forces.
5. Wind : Most wind turbines generate electricity from naturally occurring wind.