14 Types of Electric Generators and their Features Explained
Types of electric generators include AC, DC, diesel, biodiesel, natural gas, solar, gasoline, hydrogen, induction, linear, magnetohydrodynamic, industrial, standby, inverter and portable generators.
Factors used to classify these generators include output current, energy source, mode of operation and application.
This article discusses the types of electric generators and their main attributes as outlined below;
-Types of Electric Generators based on Output Current
-Comparison of Types of Generators: AC and DC
-Types of Electric Generators based on Energy Source
-Types of Electric Generators based on Mode of Operation
-Types of Electric Generators based on Application
-Types of Electric Generators based on Output Current
1). Direct Current Generator as one of the Types of Generators
A direct current (DC) generator is an electric generator which uses electromagnetic induction to generate electricity in the form of unidirectional current and voltage.
DC generators usually comprise of a stator and rotor [1], which work together to create magnetic fields and cause electric current flow through the interaction of these fields. The DC generator is one of the earliest types of electric generators developed [9]. It is also one of the simplest in terms of design and operating principle.
This type of electric generator is self-excited; meaning that it creates its electromagnetic fields without support from any external system.
It is important to note that DC and AC generators are arguably the two most important and common types of electric generators. They represent broad scope of classifications, such that other types of electric generators can mostly be classified either as AC or DC, based on their current output. For example, homopolar generator is a type of DC generator [6].
Based on the type of electrical connection between the rotor and stator, types of electric generators that produce DC electricity include shunt, series, and compound generators [15].
In shunt DC electric generator, the stator is connected in parallel to the rotor. This connection is a series connection in series DC generator, while both series and parallel connections between the stator and rotor coils occur in compound DC generator.
2). Alternating Current Generator
AC electric generator is an device or system that uses electromagnetic principles to convert mechanical energy to alternating current.
In the field of practical electricity generation, AC generators are more common than DC generators. This is because alternating current is a more efficient and applicable form of electricity that can be used for various purposes.
Alternating current occurs as a sinusoidal-trending electric pulse which may occur in one or more phases [8]. It is generated when a moving (usually rotating) conductor, cuts across a magnetic field.
Comparison of Types of Electric Generators: AC and DC
| AC Electric Generator | DC Electric Generator |
| Output electricity is in AC form | Output electricity is unidirectional DC |
| May work without commutators | Commutators are an essential component |
| Electromagnetic induction may influence both stator and rotor | Only the rotor produces current through electromagnetic induction |
| May also be called an alternator or phase generator | May also be called dynamo |
| Output voltage output is relatively high | Output voltage is relatively low |
| Speed of rotation may affect current output | Current output is unaffected by rotational speed |
| Less susceptible to energy loss and efficiency reduction | More prone to energy loss and efficiency reduction, due to design and component-configuration |
| Less maintenance is typically required | Typically requires more maintenance |
| Output can be transmitted, stepped, and used for various purposes | Output has transmission and use limitations |
| Current reversals occur during electricity generation | No current reversals during electricity generation |
-Types of Electric Generators based on Energy Source
3). Diesel Generator
As the name implies, diesel generators depend solely on diesel s their energy source.
In these electric generators, diesel acts as the primary source of energy (chemical) which is used to produce mechanical energy and electricity, through a series of conversions.
Diesel generators may vary in their design, mode of operation, and output current, This means that under diesel generator category, other types of electric generators like DC, AC, standby, portable and inverter generators, can be classified.
However, a significant majority of diesel generators are standby.
In terms of components, we may consider a diesel generators to be equivalent to fuel (diesel)-powered engine and a generator. The parts of diesel generator include control panel, AC alternator, control panel, fuel tank, and engine [4].
4). Gasoline Generator as one of the Types of Electric Generators
Gasoline is one of the most common fuels used for various types of electric generators. All such generators which depend on this source of energy can be classified as gasoline generators.
The wide use of gasoline in electric generators can be attributed to the fact that gasoline is widely available compared to other sources of energy. Diesel generators can be portable and easy to operate.
However, a notable problem associated with this type of electric generator is its tendency to contribute to greenhouse emissions in a significant manner [7]. They may also be less-resilient than other types of generators, and may not function efficiently in cold temperatures.
5). Renewable-Energy Generator as one of the Types of Electric Generators
All types of electric generators that depend on renewable sources of energy can be described s renewable energy generators.
These include generators that are incorporated into solar, nuclear, geothermal, hydro-power, wind and bioenergy systems.
Three relatively common examples of renewable electric generators are hydrogen, bioenergy and solar generators.
Hydrogen generators are a fairly recent development in the field of commercial electricity generation, and operate based on similar principle as that which is used in hydrogen fuel cells.
They derive energy from hydrogen, which is a highly abundant energy resource and can be produced from renewable materials like biomass [10].
There are contentions regarding the renewable nature of hydrogen, especially because its production may also involve non-renewable materials like fossil fuels, which can also cause environmental degradation through pollutant and greenhouse gas emission.
Bioenergy generators depend on biomass derivatives for energy. These derivatives include biogas and biodiesel. It is important to note that these biomass-derivatives are often mixed with fossil fuels like natural gas and diesel when used in an electric generator. In the general scheme of types of electric generators. this type of generator constitutes a minority.
Solar generators convert solar energy to mechanical energy, which is used to generate electricity. This may be done using solar thermal collectors, which capture heat from solar radiation, and use it to drive a turbine, that is part of a generator system.
6). Natural Gas Generator
Natural gas generators depend on natural gas as a primary energy source.
As a non-renewable resource, natural gas can be extracted from petroleum reservoirs and shale deposits [16], and is fairly abundant.
Some advantages of natural gas as a fuel source include its ability to be used under a broad range of temperature conditions. Also, natural gas does not produce as much harmful emissions from combustion, as other petroleum derivatives [5].
However, natural gas generators are not as widely used as gasoline and diesel generators because of the complexities involved in the storage, handling, and transport of natural gas, as well as the installation of these generators.
-Types of Electric Generators based on Mode of Operation
7). Magnetohydrodynamic Generator as one of the Types of Electric Generators
Magnetohydrodynamic generator encompasses all types of electric generators which generate electricity through the electromagnetic interactions of a charged, moving fluid.
Typically, this type of electric generator does not comprise of all the physical components found in conventional generators. The rotor is replaced by a moving, conductive fluid [13], which is influenced by a magnetic field, to produce consistent current flow and electricity.
Magnetohydrodynamic generators also depend on Faraday’s electromagnetic principle. In this case the fluid, which is usually ionized gas, acts as a moving conductor.
Some studies suggest that an increase in the pressure and density of the moving fluid can increase efficiency and output of the generator [12]. Other factors affecting performance and efficiency include temperature, rotary velocity and fluid conductivity.
8). Homopolar Generator as one of the Types of Electric Generators
The homopolar generator is a type of electric generator which produces direct current from the interaction of magnetic fields and electric charges, without any AC current losses [6].
Homopolar generators are an adaptation from the early model of the DC generator; the Faraday Disk, which was developed by Michael Faraday. They may alternatively be referred to as disk dynamo, acyclic generator, or unipolar generator.
Due to low internal resistance, these generators can produce large voltage output. They are however not very practical and used mainly for experimental and analytical purposes.
9). Induction Generator as one of the Types of Electric Generators
The induction generator generates electricity in form of alternating current, through electromagnetic induction of motion in a rotor or armature, by a magnetic field.
It may also be described as an asynchronous generator, because the rotary speed of the rotor is not usually in synchrony with the magnetic field which induces it.
There is much similarity between the operating mechanism of an induction electric generator and an induction electric motor.
Induction generators may depend on an internal or external source to produce the inducing magnetic field. Based on this dependency, they may be classified as externally-excited or self-excited.
10). Linear Generator as one of the Types of Electric Generators
The linear generator uses linear (rather than rotary) motion in a magnetic field, to generate electricity.
In place of a rotor and stator, this type of generator makes use of a sliding permanent magnet which moves in a linear (backward-forward) direction through copper winding or solenoid that acts as a source of magnetic field potential [3].
The magnet itself is usually attached to a shaft or piston, which transmits mechanical energy from the energy source. Through electromagnetic induction, an electric current begins to flow through the solenoid.
-Types of Electric Generators based on Application
An electric generator can power a house, office, commercial or industrial outlet. Generators can be differentiated based on specific uses to which they are most suited. Examples of such generators are discussed as follows.
11). Standby Generator as one of the Types of Electric Generators
Standby generator is one of the most commonly-used types of electric generators within domestic settings.
They are also called “backup” generators, because they are usually configured to serve as a support or backup power-supply system. When the primary power source fails, standby generators supply power [2]. This substitution is often an automatic process.
Standby generators are usable in any facility or building where consistent power supply is needed, including residential and commercial buildings. The need for this type of generator is highest in places where the utility grid is unreliable.
Primary energy sources for standby generators may include diesel and gasoline, among others.
12). Industrial Generator
An industrial generator is a large, high-output electric generator that is used to supply power for large-scale commercial purposes.
In order to meet its purpose, an industrial generator is designed to be more resilient, reliable and sturdy than conventional generators. They may have power-output capacity variations across a wide range, based on the existing needs.
The primary energy source may vary for industrial generators, to include natural gas, diesel, propane, and gasoline.
Industrial generators are used by industrial outlets and companies to power systems used in manufacturing and other commercial processes.
13). Inverter Generator
Inverter generator carries out two separate conversions in the process of generating electricity.
First, they produce alternating current (AC) from the energy source, through electromagnetic induction. This AC is then converted to direct current (DC), and back to AC [14].
The two-step conversion results in AC which is more stable than the alternating current produced by other types of electric generators [11]. Inverter generators are used where such stable current is needed, such as with appliances like refrigerators and air-conditioners.
Aside the stable output, inverter generators are generally efficient in terms of their design and operation. However, they are more expensive than most other types of generators, and may not have high power capacity.
14). Portable Generator
Portable generator is a type of electric generator that is relatively easy to transport.
It is generally smaller than other types of generators and are used where there is need for mobility. Although portable generators can be used as a standby power supply system, they are not equivalent to standby generators, as both differ in their main characteristics.
The energy source for portable generator may be diesel, gasoline or any other usable resource. Due to their relatively-low capacity, portable generators are suited for low-energy-demand applications, such as providing power to small residential and commercial buildings.
Conclusion
Types of electric generators include;
- Direct Current Generator
- Alternating Current Generator
- Diesel Generator
- Gasoline Generator
- Renewable-Energy Generator
- Natural Gas Generator
- Magnetohydrodynamic Generator
- Homopolar Generator
- Induction Generator
- Linear Generator
- Standby Generator
- Industrial Generator
- Inverter Generator
- Portable Generator
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