Go electric or (com)bust
Back to the future - literally.
Get in, buckle up and close your eyes. Welcome to 1839. You are in Aberdeen, Scotland. The first electric vehicle is driving down the street. It’s rather bumpy on the cobblestone streets of the city. You rub your eyes. Was it your imagination? Not at all! Electric car technology, which still has a strange and unexpected effect on most people today, was actually born in the 19th century.
The rise and fall of the first electric vehicles
Admittedly, from today's point of view, the performance of the vehicles from that time was rather modest. Low speeds limited driving pleasure and you couldn’t make it as far as the next city. Accumulator technology was still in its infancy and for a time, there were more electric cars on the streets than gas-driven models, but they fell into a Sleeping Beauty sleep at the beginning of the 20th century. Cheap oil, higher reliability and an electrical starter for the combustion engine got in the way of the electric cars from then on.
Electric makes a comeback
But times changed: oil prices went up, more people became environmentally aware and with increasing political pressure, automobile manufacturers had to go back to the drawing board at the beginning of the 1990s. Despite new developments in battery technology, however, no model could be produced in a larger series. It wasn’t until 2008 when the Tesla Roadster did the impossible: with a range of 350 kilometres, even at higher speeds, this car was suitable for long-distance driving – all with a purely electric motor. Since then, more and more car manufacturers have been supplementing their range of models with electric cars. In 2013, with the launch of the BMW i3, Germany also got in on the act. It was the first mass produced and purely electrically driven vehicle from a German car maker. This was a comparatively late reaction from the land of the "Energiewende" (energy transition), which is also primarily an automobile nation.
Can electric cars be a wide-scale alternative to the internal combustion engine? The answer depends on three factors. First is storage capacity, which limits the range of the vehicles. Second is charging cycles. While you can fill a conventional vehicle within a few minutes, you need much more time at the “pump” to charge an electric vehicle. Third is the cost-benefit ratio. Electric vehicle buyers currently pay a high additional charge for emission-free driving - despite government subsidies.
The heart of the electric vehicle:
Responsible for these extra costs is the so-called traction battery, which is additional to the starter battery. It’s the most expensive component of an electric vehicle and almost always consists of lithium-ion cells. The starter battery, on the other hand, is a lead accumulator. It’s responsible for the constant power supply of the vehicle’s electrical systems and for starting the engine. Due to the low internal resistance, the voltage drop during load is minimal. However, the traction battery has to be more robust against deep discharge processes, since it’s solely responsible for the engine. Currently the lithium-ion cells reach about 900 watt hours per litre of volume. However, one litre of diesel contains 10,000 watt hours, so the energy density is much higher. But, this advantage is shrinking. The focus of the manufacturers is therefore on the optimization of the energy density of batteries. Thus, the costs can be reduced and the range can be increased.
In electric vehicles, it’s not a single, large battery pack that’s installed. Rather, it’s a combination of many individual cells, or so-called stacks. Their efficiency, and thus the range, is also dependent on the outside temperature. In many traction batteries, there are cooling and heating systems that keep the cells at an optimum operating temperature. In addition, the energy management of the vehicle ensures that a given percentage of charge (between a 20% low and 90% high, depending on the battery) is maintained. In order to increase the service life, the battery is normally never fully charged or discharged. Furthermore, the charging technology also influences the durability of the energy storage device. The dilemma: a high charging current charges the battery quickly, but is bad for durability. However, according to the current state, running capacities of up to 200,000 kilometres with a remaining capacity of 80% are possible before the energy storage tank is worn out.
Apart from the battery technology, vehicles with electric motors are less complex than vehicles with combustion engines. The advantage: expensive parts that wear easily, such as the gearbox, the clutch and the complex engine cooling system, are no longer necessary. Also the brakes need less maintenance, as you can decelerate quickly by stepping off the pedal. Since many mechanical components are not needed, more space is left in the interior for the occupants – and in the trunk there's more space for luggage. Often, electric vehicles have two trunks, one in the rear and one in the engine compartment, where there’s no more need for a big engine. Instead, it’s mounted either on the axle or directly on the wheel hub.
Almost all electric cars use three-phase motors with two types of magnets: static magnets are located in the outer ring, and a rotating magnet is mounted in the centre. When electricity flows through the coils, a magnetic field is created through which the rotating magnet is permanently attracted by the static magnets. This rotation sets the wheels in motion. A converter moves the energy from the traction battery into alternating current during acceleration. When the car brakes, energy can be recovered and discharged to the battery as a charging current.
Fossil fuels and hybrid vehicles remain the options of choice for long-distance transport. For short and medium-haul routes in metropolitan areas, on the other hand, electric vehicles will increasingly set the pace. A prerequisite for this is the expansion of the charging infrastructure, as well as the creation of economies of scale in battery production, which reduce the new price of an electric vehicle. The plans and technical possibilities are promising. Even today, vehicles can be charged four times faster by wall-mounted charging stations via an ordinary socket. The network of rapid-charging columns at highway rest stops and in inner cities, which recharge the battery to 80 percent within 30 minutes, is also growing. In the future, this should be possible in five to ten minutes.
Particularly interesting is the non-contact charging via induction plates, which are built into the ground. As soon as you park the car over this plate, the charging process starts. This means that no more plugs are required and you save time. The vehicle could be charged at many different locations when the infrastructure is expanded accordingly. No matter if you are parked at the doctor, at the shopping mall, or at home, the plates will be charging your car. This technology has another advantage: short charging cycles, so-called “snack charging”, which increases the service life of the traction battery.
In the long term, electric cars can be integrated into the local and transregional electricity network and even recharged when driving. But it’s not only the charging of electricity that’s possible. The vehicle-to-grid concept also allows you to feed energy from electric cars back into the power grid - for example, with a high grid load. They then function as local energy storage devices which are available on demand for our common electricity network, which is an important step towards a decentralized energy supply. The networking of vehicles also plays an increasingly important role, as you can adjust your speed according to the current traffic volume. In addition, energy-optimized route planning is possible, which leads you to your destination in a battery-safe manner. Sit back, buckle up and enjoy the ride. Welcome to the future.
At a glance: advantages and disadvantages of electric vehicles
- No exhaust emissions when driving
- High torques make driving fun because of more traction
- Low maintenance costs due to fewer movable parts
- Low operating costs. A full charge costs only a few euros
- Vehicles can be integrated into the infrastructure (vehicle-to-grid)
- High driving comfort due the quiet motor and no need to shift gears
- Depending on the storage technology, ranges of 400 kilometres or more can be achieved
- Efficiency: 95% of the energy is put into motion. The internal combustion engine is only 30% efficient
- High purchase price in the short to mid term
- Charging infrastructure still needs to be expanded
- Heavy weight reduces the range of the vehicle
- Comparatively low energy density of the traction battery
- Usage of rare metals for permanent magnets of the engine
- Time-intensive charging cycles when no fast-charging stations are used