Plug & Play car: Solutions with sparks

Electrification of vehicles already seems unstoppable. This involves advantages such as the total or partial decrease of tailpipe emissions, the capacity to cover with renewable energy a fraction of transport consumption, more efficient use of energy thanks to improvements suchs as regenerative braking or traffic noise level reduction. However, problems also arise, like increase of long term electric demand, the need to generate that energy and the emissions of that process, full electric vehicles low range of use and a dramatic change for after-sale services technology used during last decade.
These are just some arguments for and against this challenge. But, how should mainstream components such as power electronics, batteries and motors be suddenly implemented?. It’s a difficult task and there’s only one way to face it: step by step. Despite attempts for full electric vehicles have already been made, like the one from CARB in mid-nineties, it still hasn’t become a mainstream technology. However, electric car parts and gas engines have been mixed during last decade and hybrid car technology was created and widely implemented. During last year several fully electric cars have been introduced, fully replacing gas engines. Available setups for these electric vehicles are shown below.

Electric vehicles: Silent power

Electric vehicles use electric motors to move. Depending on their layout, three configurations can be defined [1]:

Those which move always by external energy. Electric motors and power electronics for management are incorporated, but energy is taken from external sources continuously. A complex infrastructure is needed to supply electric energy.

Those which store external energy to use it later. Systems are quite similar to previous category, but energy is stored in batteries.

Those which employ a different energy source to generate all or a part of the electricity used by the car (hybrid electric vehicles). In some cases they can store electricity from external sources, but a generator to create energy for the batteries is always present. This generator can be either a conventional group engine – alternator or a fuel cell using hydrogen.

The last group has many alternatives that are detailed below.

Hybrid vehicles: Mixing volts with octane

Definition for a hybrid vehicle is “that has two or more major sources of propulsion power” [2]. This creates several types of hybrid vehicles, mixing energies such as gas, liquid gas, hydrogen, electricity... Electric-gas hybrids are the most common category. They can include the feature of charging batteries from household power or specific high voltage chargers, but it is not required to be an hybrid vehicle. Moreover, a fuel cell vehicle that uses hydrogen is also included in hybrid definition.
Focusing on electric hybrids, several engine and motors configurations can be carried out:

Serial hybrid: In this layout the electric motor is the only device that moves the vehicle. The thermal engine is used as generator and charges the batteries or creates electric power to the system.

Parallel hybrid: The electric motor and the thermal engine are joined to a conventional transmission. Both are used to move the vehicle, but the electric device is not usually capable of moving the vehicle on its own. Ratio between electric and thermal power is usually lower than in other configurations.

Series-parallel hybrid: It merges the aforementioned options through a transmission that allows both working modes. It’s essentially a parallel hybrid, but allows to uncouple the thermal engine and the power demanded by the driver thanks to a mechanism named “Power Split Device”. Usually two electric motors with different power figures are integrated on this layout. Thus, thermal engine power to move or charge the vehicle can be decreased when battery has charge enough and increased when low battery levels are present.

Depending on electric system capacity to move the vehicle, hybrid electric vehicles can be classified on [4]:

Mild hybrid: Systems with a low electric/gas power ratio where electric motor gives assistance and regenerative braking capability. Usually they’re parallel hybrid systems that don’t allow fully electric traction.
Full hybrid: Electric system power in this configuration is similar to internal combustion engine and usually allow full electric operation.