Hybrid Car Meaning, Principle, Design, and Energy Sources Explained

A hybrid car is a car which depends on more than one energy source for its operating power [7].

It may also be called a ‘hybrid of a car’, because it combines some of the attributes of multiple car types.

In this article, the concept of a hybrid car is discussed, on the basis of the following outline;


-Hybrid Car Meaning: 5 Ways to Define a Hybrid Vehicle

-Principle of Operation of the Hybrid Car

-Hybrid Car Design: The Configurations of Hybrid Vehicles

-Potential Energy Sources for a Hybrid Car








Hybrid Car Meaning: 5 Ways to Define a Hybrid Vehicle

A hybrid car is a car equipped with two or more power sources, which may include fossil fuel, hydrogen, and solar among others.

In a broader sense, a hybrid vehicle is one which has multiple sources of power, and can be illustrated using a submarine which alternates between battery power and diesel when below and above water respectively.

To add more aspect to the definition, a hybrid car may be described with reference to the purpose for which it is designed;

A hybrid car is a car which uses more than one primary energy source to derive power for its operation, as a means of achieving energy conservation and efficiency [10].

It is believed that hybrid vehicles produce less emissions [3], and are more energy efficient than conventional ones. This perspective is portrayed in the following definition;

A hybrid car is a car which is designed to minimize environmental impact, by combining energy efficient and alternative energy technologies.

Another way to define hybrid cars will include an account of the main technological components that make up the vehicle;

A hybrid car is a car which comprises of a combination of internal combustion engine, electric motor, and power storage in the form of batteries, and which is designed to alternate effectively between these energy sources.

Lastly, the mode of operation of a hybrid car can be used to define it, as follows;

A hybrid car is a car in which an electric motor produces torque, to initiate motion, which is further sustained or supported by an internal combustion engine.


Principle of Operation of the Hybrid Car

Hybrid cars work by power supply, regenerative braking and power storage. These three aspects of the hybrid car operating principle are discussed below;

1). Power Supply

A hybrid car is unique for deriving its power from multiple sources.

In most cases, these sources are fossil fuels and storage units respectively.

In order to derive power from fossil fuels, a hybrid car is equipped with an internal combustion engine, which burns diesel or natural gas to produce energy [6]. In rare cases, a fuel cell may be used in a hybrid vehicle as an alternative energy system, where hydrogen serves as fuel.

The main role of the internal combustion engine in hybrid vehicles is to supply large amounts of power. This role is supported by the electric motor.

Electric motors are commonly installed in a hybrid car [5]. Hybrid cars are generally efficient because of the combined operation of the electric motor and the combustion engine.

In practical scenarios, this combined operation does not imply that both power sources perform exactly the same functions. Electric motors provide efficiency and torque, while combustion engines provide consistent power and operational longevity.

For this reason, it is essential for these alternative power sources to be switched efficiently. Switching is usually an automatic, instantaneous process, and is controlled by the car’s velocity.  It is important to note that the electric motor draws its own power from a battery or group of batteries in the hybrid car system.

One the average, a hybrid car switches from battery power to petrol power at a speed of 17.5 mph (miles per hour). This is based on various speeds that include 15, 20, and 40 mph.

The speed at which switching occurs, differs for different hybrid vehicles. As a rule of thumb; this switch occurs at the maximum power capacity of the electric motor and battery system. Fuel efficiency and energy efficiency are the two main advantages of having alternative energy sources in a hybrid car.

Power Sources in a Hybrid Vehicle include Combustion Engine and Battery (Credit: Inductiveload 2009)
Power Sources in a Hybrid Vehicle include Combustion Engine and Battery (Credit: Inductiveload 2009)


2). Regenerative Braking

The principle behind regenerative braking is similar to that behind cogeneration.

In hybrid cars, regenerative braking is a mechanism by which the batteries are recharged, so as to provide energy to operate the electric motor.

Basically, regenerative braking captures kinetic energy that would otherwise be lost when the vehicle is slowed-down, storing and reusing this energy in the batteries and electric motor respectively [8].

The mechanism involved in regenerative braking is slightly similar to that which is used in generators to generate electricity.

When the brakes are used (by applying pressure to the pedals), the hydraulic force of both the pedals and the frictional resistance to motion (of the vehicle) causes the electric motor to rotate in an opposite direction, thereby producing small amounts of power through electromagnetism, which are instantaneously transmitted to and stored in the batteries.

Based on this mechanism, it can be argued that the hybrid car is a type of energy management system, as it minimizes energy losses and reuses waste energy.

3). Power Storage

Power storage is very important in a hybrid car because the batteries usually supply power to the electric motors which are part of the car’s propulsion system.

Many hybrid cars depend solely on regenerative braking to generate the power which is stored in the batteries. Some hybrid cars are configured like all-electric cars, with components that allow for charging from an external source.

Such vehicles belong to a category that is referred to as the plug-in hybrid cars or plug-in hybrid electric vehicles (PHEVs) [9]. Like all-electric vehicles, plugin-hybrid cars can be charged at any automobile charging station.

A Plug-in Hybrid Car can be Charged by an External Power Source (Credit: Tom Raftery 2010 .CC BY-SA 2.0.)
A Plug-in Hybrid Car can be Charged by an External Power Source (Credit: Tom Raftery 2010 .CC BY-SA 2.0.)


The effectiveness of power storage in a hybrid car partly depends on the type and quality of storage technologies being used. Energy storage options include ultra-capacitors and batteries, among others [4].

Also, the effectiveness of power storage determines the overall performance, sustainability and efficiency of the hybrid vehicle.


Hybrid Car Design: The Configurations of Hybrid Vehicles

Based on design and configuration, the types of hybrid cars include parallel, series, and series-parallel types. These are each discussed briefly below;


1). Parallel Hybrid Car

A parallel hybrid car features a parallel connection among the alternate power systems.

In most cases, these are the internal combustion engine (ICE) and electric motor. Parallel hybrid car designs have the combustion engine terminals and the electric motor(s) connected in parallel to the mechanical transmission system [11].

What this implies is that there is minimal isolation between the combustion engine and electric motor in a parallel hybrid design. Because they both share connection with the transmission system, it is difficult to isolate these components (motor and engine) during operation. Therefore, they function purely as supportive power supply units to each other.

2). Series Hybrid Car

In a series hybrid car, the electric motor(s) and batteries are connected in series to the transmission system.

The most unique attribute of this type of hybrid configuration is the connection between the internal combustion engine and a power-generation unit.

In parallel hybrid cars, there is usually no power-generation unit because the combustion engine is directly connected to the transmission system which propels the vehicle. In series configuration, the combustion engine rather supplies energy to a power-generation unit which converts this to electricity.

The electricity generated is used to recharge the batteries and operate the electric motor. This mechanism of operation makes the hybrid car efficient, and simplifies the power supply process. All-electric vehicles also use a similar mode of operation, since the vehicle depends solely on the batteries and electric motors, which are recharged with power from a source.

3). Series-Parallel Hybrid Car

As the name implies, series-parallel hybrid cars combine characteristics of both series and parallel designs.

This means that the combustion engine can either operate independently by supplying power directly to the transmission system, or may supply energy to a separate power-generation unit which recharges the battery and operates the electric motor. In practice, series-parallel hybrid vehicles can function like a typical gasoline vehicle, or an all-electric vehicle.


Potential Energy Sources for a Hybrid Car

1). Biofuel

Being a derivative of biomass, biofuels are being incorporated into the hybrid car sector as a renewable energy source.

Examples of these biofuels include biodiesel, biogas and ethanol [1]. In order for biofuel to be used as an energy source in hybrid cars, slight modifications to the internal combustion engine are necessary.

Biofuels are considered a potential alternative energy resource to address environmental degradation and greenhouse emissions, although the cleanliness of these fuels is in question.

2). Liquid Hydrogen

In a hybrid car that uses liquid hydrogen, the internal combustion engine (ICE) is usually replaced with a fuel cell.

Power is commonly derived from liquid hydrogen through an electrolytic process [2], and this differs from combustion which is used to extract heat energy from fossil fuels.

As a fuel, hydrogen has a fairly-high energy density, and is also used in other systems like space shuttles. The main challenge with the use of this energy source is the need to store it under cryogenic (low-temperature) conditions.

3). Petroleum Derivatives

Hybrid cars that use petroleum derivatives like gasoline, diesel and natural gas are most common.

In order to use these fuels, a combustion engine is usually installed in the hybrid car system. While diesel and gasoline are more conventional, natural gas can also be used, although in its compressed form (known as ‘compressed natural gas’; CNG).

The combustion of fossil fuels makes hybrid vehicles similar to traditional gasoline vehicles, in terms of the reliance on petroleum, and the potential environmental problems.



A hybrid car is a car which combines various power supply technologies like combustion engine and electric motor-battery systems, to improve energy efficiency, conservation and performance.

The types of hybrid cars based on design are;

  1. Parallel Hybrid Car
  2. Series Hybrid Car
  3. Series-Parallel Hybrid Car


A hybrid car works by;

  1. Power Supply
  2. Regenerative Braking
  3. Power Storage


The sources of energy used by a hybrid car are;

  1. Biofuel
  2. Liquid Hydrogen
  3. Petroleum Derivatives



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6). Ott, T.; Onder, C.; Guzzella, L. (2013). “Hybrid-Electric Vehicle with Natural Gas-Diesel Engine.” Energies 6(7):3571-3592. Available at: https://doi.org/10.3390/en6073571. (Accessed 19 June 2022).

7). Pereirinha, P. G. , & Trovão, J. P. (2012). “Multiple Energy Sources Hybridization: The Future of Electric Vehicles?” In (Ed.), New Generation of Electric Vehicles. IntechOpen. Available at: https://doi.org/10.5772/53359. (Accessed 19 June 2022).

8). Sai, A.; Rama, K.; Raju, C.; Sri, B.; Raju, S. V.; Vemuri, V. P. B. (2019). “Regenerative Braking System Ch.Dharanesh.” Available at: https://www.researchgate.net/publication/336685493_Regenerative_Braking_System_ChDharanesh. (Accessed 19 June 2022).

9). Yang, Y.; Jiang, W.; Suntharalingam, P. (2014). “Plug-In Hybrid Electric Vehicles.” Advanced Electric Drive Vehicles (pp.465-490). Available at: https://doi.org/10.1201/b17506-15. (Accessed 19 June 2022).

10). Zhou, B.; Zhang, S.; Wu, Y.; Ke, W.; He, X.; Hao, J. (2018). “Energy saving benefits from plug-in hybrid electric vehicles: Perspectives based on real-world measurements.” Mitigation and Adaptation Strategies for Global Change 23(14). Available at: https://doi.org/10.1007/s11027-017-9757-9. (Accessed 19 June 2022).

11). Zulkifli, S.; Saad, N.; Mohd, S.; Aziz, A. A. R. (2012). “Split-parallel in-wheel-motor retrofit hybrid electric vehicle.” Power Engineering and Optimization Conference (PEDCO) Melaka, Malaysia, 2012 Ieee International. Available at: https://doi.org/10.1109/PEOCO.2012.6230915. (Accessed 19 June 2022).

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