Advantages of electric vehicles compared to internal combustion engine vehicles
Pure electric vehicles, also called battery electric vehicles (BEV), are the long term solution for mobility. Compared with internal combustion engine (ICE) powered vehicles, battery electric vehicles have a series of advantages which are summarised in the table below.
|Advantage||Electric vehicle||Internal combustion engine vehicle|
|Powertrain efficiency||Electric vehicles are powered by electric motors and single speed gearboxes which, depending on the operating point (speed and torque), have an overall efficiency between 75 … 95 %. This means that, for the same amount of power at the wheel, less energy is used from the high voltage battery compared with an internal combustion engine vehicle||The typical efficiency of an internal combustion engine is between 18 … 24 %. Diesel engine have slightly higher efficiency than gasoline engine but overall, internal combustion engines are 4 times less efficient than electric motors. Compared with an electric motor, for the same amount of wheel power, an internal combustion engine has to consume 4 times more energy|
|Vehicle acceleration||An permanent magnet synchronous electric motor has an ideal traction characteristic. Also, at zero speed, the electric motor can deliver the maximum available torque which translates in very good launch capabilities of the vehicle||An internal combustion engine can not deliver maximum torque from minimum speed (idle). They also need more time to reach maximum torque because of engine dynamics (air and mechanical inertia, turbo-lag, etc.)|
|Reliability||Having less moving parts, compared with an internal combustion engine, an electric motor has fewer sources of possible failures. Also, due to the high torque and high speed characteristic of the electric motor, there is no need for a multi-stage gearbox, a single-step mechanical gearbox is enough for propulsion||The internal combustion engine has many moving parts and also additional systems (fuel system, air induction system, exhaust gas after-treatment system, etc.) which can lead to possible failures. Due to the torque characteristic of the ICE, the vehicle requires a multi-step gearbox, which can also be a source of possible failures|
|Torque vectoring||For an all-wheel drive (AWD) electric vehicle, stability during cornering can be improved by controlling the torque at the wheels. Compared to the internal combustion engine, an electric motor has faster torque response and can also provide negative torque, which could prove essential in the stability of the vehicle||The internal combustion engine has limited contribution to the vehicle stability, most of the times, the electronic stability control system (ESC) it’s only reducing the amount of torque delivered by the engine|
|Total cost of ownership||Having less moving parts and components an electric vehicle is easier and cheaper to maintain. Also, the price of electric energy, in most of the countries, is less than fuel (petrol/gasoline or diesel). Moreover, since electric vehicles can perform regenerative braking, the main braking system of the vehicle has a lower usage factor which translates in longer service life||In order to preserve a good operating condition, internal combustion engines need regular maintenance (service) intervals for air filters, fuel filters replacement, spark plugs, oil change, etc.). For this reason a vehicle with internal combustion vehicle is more expensive to maintain compared with an electric vehicle|
|CO2 and exhaust gas emissions||Since there is no internal combustion engine present, electric vehicles have zero exhaust gas emission. Also, depending on the source of the electric energy (e.g. renewable) the overall CO2 impact of an electric vehicle is smaller compared with a internal combustion engine vehicle||Internal combustion engine vehicles are subject to legislative exhaust gas emission limits. Also, in some urban areas, they are forbidden to be driven. The general trend is to ban even further internal combustion engine vehicles in the highly dense populated urban areas|
Disadvantages of electric vehicles compared to internal combustion engine vehicles
A battery electric vehicle has lots of advantages compared with conventional vehicle, mainly because there is no internal combustion engine. On the other hand, the main drawback of an electric vehicle is the energy storage system, the high voltage battery.
Compared to gasoline (petrol) and diesel fuels, for the same volume, the energy stored in a battery is around 10 times less. In the figure below we can see that batteries have bigger volume, mass and store less energy compared with gasoline and diesel fuel.
The poor energy density of the battery has a direct impact on the vehicle range. For a battery electric vehicle, with the current performance of battery cells, in order to have a decent range (above 200 – 300 km), the high voltage battery pack will turn out to be quite heavy and bulky. Also, in cold environments, the range of an electric vehicle is further decreased due to the degradation of battery performance (due to low temperatures) and significant usage of the electrical energy for heating (cabin, battery).
The recharge time of the battery is another major drawback of a battery electric vehicle. If for an internal combustion engine powered vehicle fuel refilling takes on average around 5 minutes, in case of a battery powered vehicle the recharge can take between 30 minutes (“fast charging”) and 8 – 10 hours (“normal charging”).
Another concern of the battery powered vehicles is the charge/recharge cycle. If the battery is often charged with a high current (“fast charging” method) the energy storage capacity decreases in time.
Charging infrastructure is currently an issue for the battery electric vehicles. There is a clear need for more charging points which should accommodate the increasing number of electric vehicles. Also, the distribution of the charging point must be carefully planned, taking into account traffic management data. For a certain country there should be electric vehicle charging point (EVCP) hubs in and around major cities. The charging hubs should allow an electric vehicle to travel across the country, whereas the maximum distance between two charging shouldn’t be bigger than 80 km (which is below the range of current electric vehicle on the market).
Current improvements on electric vehicle infrastructure and technology
It is clear that a battery electric vehicle has major obstacles to overcome in terms of energy storage, battery lifetime and charging infrastructure. Nevertheless progress is being done in all areas. For example, according to zap-map.com, there is a net increase (year-on-year) of charging points and locations across the UK. This is a significant infrastructure improvement for battery charging, which demonstrates that local and central authorities are supporting BEV and PHEV development.
Also, in the United Stated of America, the number of electric vehicle charging points has increased dramatically between 2012 and 2017. More effort is still necessary, taking into account that USA is a very large country with significant distance between the major cities.
High voltage battery technology is also developing at a sustained pace. The volumetric energy density for Lithium-ion battery cells improved from 190 Wh/l, in 1991, to 580 Wh/l, in 2005. Current
production lithium-ion cells have 676 Wh/l. On average, every 10 years, the energy density of high voltage batteries used in electric vehicles doubles.
Currently marketed battery electric vehicles have a high purchasing price, mainly due to the high voltage battery price (which is around 30 … 40 % of the total price of the vehicle). However, according to the International Energy Agency (IEA), the price of the high voltage batteries is estimated to decrease year-on-year and will go below 200 USD per kWh by 2020.
Looking at the facts, it’s obvious that the internal combustion engine vehicles will lose the battle against electric vehicles. The switch point towards mass adoption of the electric vehicles will come when the purchasing price and range of the electric vehicles will be similar with the engine powered vehicles. Also, governmental plans to ban diesel engines and to further reduce CO2 emission will accelerate the adoption of electric vehicles as main mean of transport.