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Electromobility
“Why does the world need an electric car?”
Climate change is progressing at a visible rate and its expanding effects are becoming apparent. The polar caps are melting, the number of natural catastrophes is increasing and the ecosystems are being destroyed.
A large share of the Earth's warming is due to the emission of carbon dioxide gas. In 2011, the global emission of carbon dioxide was 34,032,700,000 tonnes. Germany was ranked sixth in global carbon dioxide consumption, with a consumption of 802 million tonnes, which represents a share of 2.4 percent of global consumption. The transport sector itself accounts for 23% of global CO2 emissions, making it clear that efficient development in the automotive sector is of high importance.
Forecasts are suggesting that the number of cars will double in the coming years due to the high demand in China, India and Southeast Asia, which may further multiply emissions. This can only be suppressed by improving the efficiency of the current engines or switching to electric cars.
Figure 1: Global CO2 Emissions by industry
Electric cars have many advantages over the nonelectric cars. They are emission-free, make no noise and are more efficient than conventional cars. This would make it easier to regulate the urban air pollution problems caused by the exhaust gases from combustion engines.
A complete switch from the conventional combustion engine to the electric engine will be a reasonable aim considering damages done by combustion engine to large industrialized nations.
State of the art
The hybrid automobile
The hybrid vehicle is, as well, represented in every model portfolio of an automobile manufacturer. More and more sports car manufacturers (e.g. Ferrari) are switching to hybrid technology.
On one hand, the customers are becoming more environmentally conscious. On the other hand, the advantages of hybrid technology are already well known. Hence, many manufacturers look at the hybrid vehicles as an intermediate step to a future-proof alternative drive form. However, this technology is becoming more and more important as a direct transition from the internal combustion engine to the electric motor is not possible.
Figure 2: Efficiency comparison of combustion engine and electric motor
The efficiency of a gasoline engine is at its optimum speed of 37%. Depending on the load condition and speed, the efficiency drops by half, while at the idle it reaches zero. Especially in a partial load operation, gasoline engines have a poor performance. This condition often comes in city traffic, when breaking but this can be avoided with the use of a hybrid drive. By contrast, with an electric motor, the efficiency is 85%, where the stored energy is used much more proficiently.
Table 1: Market Share by Automobile Constructor
Many Manufacturers are adopting a new approach, due to the ever-increasing regulation in cities, through the environmental badge. This is making the electric cars to be the only ones allowed in cities where the emission rate allowed is low. Nevertheless, the internal combustion engine is still widely used.
A way to go is the hybrid system which is a solution that allows combining a different technology with the electric motor without going all the way to EVs.
Table 2: Compare different hybrid models
Many different concepts exist pertaining to hybrid technology.
So far, the best-known concept is the full-hybrid, which is further divided into parallel and serial hybrid.
In the parallel hybrid, the combustion engine and the electric motor are connected in parallel.
The vehicle can disconnect one of the two drives and switch between electric driving and recuperation or recovery, where the battery is recharged. In the case of the serial hybrid ( also known as the extended-range electric vehicles), it is a question of generating batteries. The hydrogen-powered fuel cells in the Mercedes-Benz GLC F-Cell are nothing else but an onboard electrical power station which produces electricity during the journey and thus supplies energy for the serial hybrid.
Figure 3: Hybrid- Concept
The electric car
The electric drive is mostly referred to as "the drive of the future". In recent years, more and more new models have been unveiled into the market which is suitable for daily use.
The cars are powered by AC motors. In comparison to direct current (DC) motors, these anti-reverse systems have the advantage that due to the converter-guided permanent magnet-excited three-phase synchro-machine only a small amount of wear occurs, mostly because no sliding contacts are needed.
In this case, the inverter converts the energy from the transaction battery into alternating current and recharges the battery during recuperation, where the electric motor serves as a generator based on the generated current. Differences are also existing in terms of the drive systems of electric cars. On one hand, there is the front drive, where the power comes directly from the output of the electric motor. On the other hand, the use of two motors is possible, whereby the two motors do not have to be performance identical since all driving scenarios can be represented via an intelligent control unit.
With its model S P100 D, Tesla offers an all-wheel-drive variant with the dual motor installed on both axles of the vehicle. This variant achieves Ludicrous acceleration, from zero to 100 km/h in 2.7 seconds, without the usual jerks from shifting operations, which is a remarkable value with a weight of 2.5 tons.
A further possible solution is the use of wheel hub motors that achieves maximum efficiency with lower transmission losses. It is, thus, possible to design new vehicle concepts based on wheel hub motors, which was previously impos-sible due to space issues.
Table 3: compare of electric cars
One of the problems that many people are missing out on, from buying an electric vehicle, is the lack of infrastructure to charge the vehicles, as well as the longer recharge time. Lately, the German car manufacturers have solved this problem by investing together in the charging network.
The major problem faced by the electric vehicle buyers is the lack of infrastructure to recharge vehicles as well as the charging time. Again, the German automotive manufacturers are solving this problem by investing in the retail network and hence, the new charging stations are created, and many interesting plans are under consideration e.g. street lanterns to be used as a charging station.
What types of batteries are available and how are they constructed?
In the production of electric cars, it is from high importance that certain safety, performance, capacity, volume and service life requirements can be guaranteed.
It is, therefore, relevant in terms of safety that no overcharge, as well as, no electrical short circuit takes place, which can lead to the injury of the car or its occupants.
Figure 4: Losses in the power transmission
In the case of performance optimization, the losses during the transmission from component to the component are to be minimized. At the current state, the drive shaft receives only 60-68% of the energy from the energy source via the charger, the engine control unit and the engine.
Another important point to highlight is the capacity of the batteries, which is crucial for a long range and a small number of charges. The service life of the battery is mainly influenced by the number of charges. Frequent charging, for example, is often associated with short battery life.
The batteries that, currently, best meet these requirements are lithium-ion batteries. These batteries exist in the form of a cylinder, a prism and a bag (see Fig.5).
With the cylindrical shape, the dimensional ratio of the length and diameter of the cell is usually unfavorable, as it can lead to high-temperature differences within the cell. The distance from the inner edge of the cell to the outer edge is usually too high to make uniform cooling within the cell impossible. Furthermore, the packing density is relatively low. The advantages are that the production costs are low and the cell is robust.
Figure 5: Battery cell geometries
Another type of the cell structure is prismatic. In the opposite, to the cylindrical cell, the shape allows low-temperature differences and the packing density is high. However, one disadvantage is that the production costs are very high.
The third type is built like a bag and it has the advantage that the packing density is very high and the surface causes small differences in temperature. Yet, in this case, another advantage is the low production costs. As a disadvantage could be counted the high vulnerability of the outer shell.
Depending on the chemical composition, e.g. Fig. 6 there are also different types of batteries. Zebra (sodium nickel chloride), zinc-air and NiMH batteries are the most powerful, as they are lithium-ion batteries. Although the performance values of some batteries seem promising at first glance, they are still unsuitable for electric cars. Zebra battery, for example, only works at a high operating temperature of 270 - 350 °C.
The most commonly used battery is the lithium-ion battery. Reason for this is that these batteries are reaching the highest Energy on volume with 250-730 [Wh/l], energy per kg 100-250 [Wh/kg]. It’s the highest benefit is that lithium is very light and has a small ion radius, which makes it possible to build particularly small high-performance batteries.
Figure 6: Energy density by technology
This type of accumulator, which is constantly being developed, enables ranges up to 600 km, partly with the newly introduced technology of the "21700 " from Samsung, which can also be charged up to 80% in 20 minutes.
However, many developers and researchers see solid lithium-ion batteries as the highest energy store of the future. Hence, they have the capability to solve many of the negative sides of today's batteries. They feature a higher energy density and allow a more compact cell design. Furthermore, solid accumulators are safer and more durable because their inorganic solid electrolytes are non-combustible and more resistant.
How are batteries cooled in the electric car?
Batteries life span and power capabilities degrade at both blistering hot summer temperatures and at sub-zero winter temperatures. So, batteries should be optimized to function over a wide range of temperatures without incurring performance degradation and service life. This optimum temperature range varies depending on the type of battery, but usually between 30 and 50 ° C. However, due to hot/cold climates, the temperature of the battery may deviate from the optimum temperature range. For this reason, a thermal management system is needed to keep the battery temperature range optimally at about 45 ° C.
Figure 7: Battery heatmap sample
The goal of the Thermal management system is to maintain temperature balance between cells of the battery. A thermal management system or BMS (battery management system) should have four necessary functions that will ensure the correct operating conditions of the battery pack, including cooling, heating, insulation, and ventilation. It is important that the system is compact and lightweight on one side and not too expensive and reliable on the other.
There are two thermal management systems: the active thermal management system and the passive thermal management system. Active thermal management systems have a built-in source that provides active heating and cooling. However, in the passive thermal management systems, the ambient air is used to keep the temperature of the batteries in the optimum window. In most regions, active thermal management systems are mainly in use, as the ambient temperatures rarely correspond to the optimum desired temperatures for the battery cells.
Such systems are usually more expensive and time-consuming to implement, since all components, such as the refrigeration circuits, heating, drive, electronics, onboard computer, and control system (BMS) must be harmonized (integration). Here, the focus is on the amount of heat that must be removed from a battery pack and what are the permissible temperature limits in order for the battery to function optimally. With too much cooling, the battery will deliver less energy to the electric motor, making it difficult to accelerate the electric car and with too less cooling, the life of the battery will eventually run out. One of BMS' tasks is to prevent these two scenarios through the so-called SOC and SOH (State of Charge and Health) calculations.
Efficient air conditioning of an electric car
The air conditioning of an electric car in winter plays an important role in the further development of electromobility. In conventional cars, the inefficiency of the internal combustion engine has the advantage that the resulting energy can be used as waste heat to heat the interior in winter. In the electric cars, however, it is not possible to use this waste heat due to the lack of internal combustion engine. For this reason, many manufacturers are increasingly relying on the concept of the heat pump. This is a closed circuit, which contains a special liquid or gaseous medium (coolant). This principle removes heat from the environment and directs it to the interior of the car without the need for high temperatures. The high benefit of this is that the power consumption for operation is low.
Another way to make the air conditioning of the electric car more efficient involves a close-to-body climate control according to Peltier. This takes into account the fact that a small room with less energy can be easily air-conditioned than a larger one.
Furthermore, the human perceives only the air temperature in the immediate vicinity, making little sense to air-condition the entire vehicle compartment. The advantage is that due to the more efficient air conditioning, the battery is no longer heavily loaded.
Figure 8: Passenger focused Air Conditioning
Battery charging: What types of chargers are there?
Many electric car manufacturers differ not only in terms of their specific designs and types of accumulators but also in the way they are charged. In different countries, there are different standards for loading. The components of an Electric Vehicle Supply Equipment (EVSE) usually consist of cables, plugs, sockets, and connectors.
The European standard (Table 4) for charging is divided into three modules. The first part contains the "normal power" charging method, which is a 1-phase alternating current connection, which is operated with 3.7[kW], 10 - 16[A] and 230[V]. The second charging method describes a 1 - 3-phase alternating current connection and is operated with
11-22[kW], 16-32[A] and 400[V]. The last type is a DC connection charged with 350[kW], 800[V] and has a current of over 430[A].
Table 4: Loading methods - EU
The American standard showed a distinction between Level-1 and Level-2 charging modules, where each module uses a built-in charger.
Both modules are charged with AC from a residential source, where Level-1 EVSE is charged by a 120V power source, while Level-2 is charged by a 240V power source. Another alternative is DC fast charging, charged by a 480V power source.
Table 5: Charging method– USA
China and Japan are using mechanical structure, so-called “Medium Power” (Table 4) system, in contrast to the European system. However, “Plug” and “coupling” are reversed. Still, a DC charging standard has not yet been implemented.
Figure 9: Tesla Supercharger
Fast charging stations
Prevailing DC fast charging stations for electric cars operate with a voltage of approximately 400 volts, whereby the charging power moves in the range of 50 kilowatts which means 400km range can be deployed in just 80 minutes. By increasing the charging power to 100 kilowatts, it is possible to reduce this time to half, but this requires the charging pins in the charging circuit to be extremely efficient. On the basis of new cooling concepts, it is currently possible to increase the charging speed to approximately 30 minutes, which can not yet be compared in time with a refueling process of a conventional car.
Porsche solved this problem by developing a new fast-charging system which is based on the formula of the electrical energy (E = U * I * t, U = voltage, I = current). By changing this formula to t = E / (U * I), it can be inferred that the charge duration (t) decreases with an increase in the voltage and constant influencing factors. Hence, Porsche’s new system is operated at 800 volts, which further reduces the charging time to 15 minutes.
Various connector systems
The construction methods of the connector systems differ in three areas (America, Europe, and China & Japan). In America and Europe, three different connector systems are used. By contrast, only two in Japan and China (Figure 10).
The American standard is further divided into 3 different levels. Level 1 is the single-phase socket with 120V/15A which can be found in the households.
Figure 10: EV Plug Type
The Type 2 device is a DC plug system, which is usually provided by the state or the public. This requires special equipment, such as the Supercharger from Tesla. Type 3 is a CCS charging system (Combined Charging System) capable of implementing both DC and AC charging processes with its standardized plug system. The performance data of the European Type 2 connector systems are similar to those of the American Type 2 device, although the design differs slightly. The design of the Chinese and Japanese connector systems is very similar to the European Type 1, although Type 2 is very unique. However, Type 3 is an equivalent product to the European and American markets in terms of performance.
The future aim is to develop a universally standardized plug-in system which can simultaneously be operated with AC and DC.
Energy and Environmental considerations
Electric cars are often criticized for the fact that the promised properties of these cars are not actually realized. In this section, the energy balance of the car and the environmental considerations are discussed.
The energy balance of an Electric car
In a study conducted by the Wuppertal Institute for Climate, Environment and Energy GmbH, different vehicles were compared with each other in terms of energy balance. In addition to conventional passenger diesel cars, gasoline, and natural gas propulsion, the compact diesel vehicles were also considered to be cost-effective. The study showed that in the case of compact cars, the electric vehicle generates far less greenhouse gas emissions than conventional gasoline, diesel, and natural gas vehicles, but the difference from a low-consumption diesel vehicle is only minimal. It is important to consider the energy mix which can, for example, affect the results of electric cars. If carbon capture is required, the result for the electric vehicles is much poorer than in conventional vehicles.
Lambrecht (2011) estimates that in the case of electric vehicles, depending on the service life and the storage requirements, approx. 17 g CO2 per km is required for the battery production. In addition, the aspect of resource availability must also be considered. Important metals such as nickel and lithium are not available in the EU, which would lead to a full dependency on the imports.
New results from a study from PIGS indicate that the production of a kilowatt hour produces 150-200 kg of carbon dioxide emissions. According to this calculation, Tesla would consume approximately 17.5 tons of CO2 for battery production on a 100-kilowatt battery. For this reason, an optimization of the manufacturing process, or a smaller storage capacity in the accumulators is required. Tesla tries to solve this problem with a new factory. Based on the current data, the Tesla model S pays off for the environment after the time of 8 years has passed.
Environmental consideration
This section uses graphics to illustrate why it is important that alternative projects such as the electric car continue to be promoted. Due to the continuing climate change, it is becoming increasingly important to establish concepts such as the electric car to protect the environment. The efficient use of renewable resources has a major impact on the conservation of the environment for future generations. The following graphs illustrate the harm that global warming will pose by the year 2060 (Figure 11), expressed in US dollars. Furthermore, carbon dioxide emissions from different countries are compared (Figures 12 and 13).
Figure 11: Damage in Billion US Dollar
Chart 11 describes the costs that could arise from global warming up to the year 2060. The figures amount to an increase of 1.5 degrees Celsius to 20 trillion US dollars and increase per degree Celsius.
Figure 12: Per Capita CO2 emissions in tones
Figure 13: CO2-Emissions per capita in tons
Graphs 12 and 13, however, show once the emissions of carbon dioxide emitted per country and emissions per inhabitant. It is striking that countries such as China and India have a relatively high value of emissions emitted per country but have low values per inhabitant. This is due to the fact that the number of populations in these countries is particularly high.
The problem in the future will be that the standard of living in these countries will continue to improve because of advanced industrialization. As a result, emissions per inhabitant will converge to countries such as Germany, which may lead to a very large increase in exhaust emissions.
The aim should be to establish concepts in all countries, such as the electric vehicle, to regulate the emission rate in the future, but also not to raise the temperature. After all, the additional costs incurred by the increase, such as repair work in the event of natural disasters, are constantly increasing in parallel with the average temperature.
For these reasons, the Chinese government will introduce a quota for electric cars from 2019. This commits carmakers, who import more than 30,000 vehicles annually, to meet certain shares via a so-called points system. In 2019, the proportion of electric cars supplied per manufacturer is expected to be 10%, and from 2020 to 12%, which puts high pressure on the auto industry. The reasons for this are, as explained earlier, the high emissions emanating from conventional vehicles, with air pollution being the main focus.
In Germany, as well, this problem is becoming ever more present, so, according to a complaint from the EU, solutions are sought to counteract this. One of the key solutions here is to leverage the strength of e-mobility to relieve air pollution in the heavily polluted areas, through emission-free vehicles.
State of the market
How does the market develop?
In recent years, when it comes to Electromobile technology Top Spot "competition", Germany has lost it's leading position from France. Even tho, it is estimated that it will be actually China dominating the market in the foreseeable future.
In China, there are many startups that focus on building EVs. They are approaching close to the Premium segment by having the possibility of owning sufficient capital for their further development. For example, 3.5 million electric vehicles are forecasted to be produced by the year 2019 and in comparison, by that time the USA will only be possible to produce one-third of this amount. In addition, 90% of the lithium-ion cells are to come from companies’ own production.
Figure 14: EV registration per country
In Germany, by comparison, there was no cell production in 2016 because German car manufacturers source their cells from Asian countries such as Korea (e.g. LG Chem and Samsung), Japan (Panasonic). Daimler, a famous German Autoproducing company, is investing 500 million this year in a new factory to produce lithium-ion batteries. The focus will be on the assembly of batteries from the cells previously supplied externally. It is assumed that by 2025 every fourth car will be powered by an electric motor. Currently, Panasonic, LG Chem, and Samsung SDI are the largest battery manufacturers. Last year Panasonic's market share in the field of batteries for electric cars was 39%. Large electric car manufacturers such as Tesla are supplied by Panasonic. Other companies such as GM, VW, Daimler, and Ford are equipped by LG Chem. BMW is currently working with Samsung SDI.
The aim of these companies is to reduce the cost per kilowatt hour to the extent that the cost of the electric car and the combustion car are equal. In 2010, for example, when €900 per kilowatt hour was paid, it was assumed that the car would not reach €300 per kilowatt hour until 2020. However, this cost reduction already occurred in 2014.
From this, it can be concluded that the development is progressing much faster than what was initially assumed, which indicates that the costs are approaching more and more towards 130 € per kilowatt hour. According to the equation, this is the goal which should be reached.
In 2016 most electric cars were sold in China with 351,000, followed by the USA with 158,000, France with 34000 and Germany ranks fourth with 28,000, ahead of Japan and South Korea. In Germany alone, 2,642 cars were sold in March 2017 with Tesla, Renault, and Post had a market share of 25.4%, 24.2%, and 15.4% respectively.
Figure 15: Market Share by country
Tesla Model S and the upcoming Model 3 are very popular, however, Renault’s model Zoe has a larger market share.
Furthermore, Opel in collaboration with the German manufacturers has developed Ampera E, which is very promising in terms of the performance.
Since the main goal is to redesign the market, the market leaders namely, Tesla, Renault, and Nissan are relentlessly focusing on the production of electric cars to avoid possible issues pertaining to the supply side. As an example, one can compare the Tesla Model S with a conventional car. In addition, these companies are increasingly investing in a structured store network that is fundamental for electric car drivers. Switching from a conventional combustion engine to an electric car is only possible if the charging stations not only offer different charging systems but also if there are enough charging stations. It must be possible to travel longer distances without worrying that there are still 100 kilometers to go to the nearest electricity filling station.
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