Main types of electric vehicles

Electric Vehicles (EVs) are a promising technology for drastically reducing the environmental burden of road transport such as air pollutants, especially carbon dioxide emission and noise.

The main electrical resources for EVs are batteries and supercapacitors. There are other resources which could be used, such as fuel cells and flywheels. The battery type, capacity, performance, and cost represent the greatest challenges for commercially deploying the different type of EVs, whereas supercapacitors have a longer lifetime and are less costly compared to batteries. Generally, the other major challenge of large EV usage is recycling resources. Each battery generation is likely to be in production for four to five years, as claimed by battery manufacturers. Both the battery and supercapacitor are modelled with a capacitive characteristic which has a positive impact when connecting to the microgrid in terms of reducing the inductive characteristic of the microgrid elements and therefore enhancing the power factor. Therefore, focusing on the type of EVs that could be connected to the grid is much better from the point of view of adding an extra capacitive characteristic to the microgrid. In practice, EVs can be the dynamic capacitive compensation to the grid because of the capacitive characteristic of the electrical elements of the EVs, such as the battery and supercapacitor.

EVs are classified according to their battery capacity, which correlates directly with the battery mass and performance, and the travelling ranges into hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs). HEVs could be either regular hybrid (RHEVs) or plug-in hybrid (PHEVs), depending on their connectivity to the microgrid.

RHEVs combine a battery-powered electric motor and a gasoline/diesel engine and does not have to be connected to the microgrid . The majority of battery charging comes from the internal compostion engine (ICE) whereas a smaller portion comes from regenerative braking by capturing the kinetic energy of the vehicle. The battery can increase the fuel efficiency of the HEV by 25% when compared with an ICE car [58], [59]. The PHEVs are similar to the RHEVs except for having the ability to plug the vehicle into the power grid for charging batteries to increase the electric driving range of HEVs. The battery of this system has a high capacity that could make it a primary source, whereas petroleum is considered as a secondary energy source for driving a car [58], [59]. The battery charging is obtained from a grid, non- grid sources such as photovoltaic panels, and braking energy. The driving range for such cars depends directly on the battery size and capacity [58], [59]. The BEVs are more efficient than ICE vehicles in terms of noise, local pollutant emission, carbon dioxide emissions, and their interaction with the microgrid; they are also able to reach zero local greenhouse gas and pollutants emissions.

On the other hand, a large number of BEVs will increase the electricity demand of the microgrid substantially. Therefore, the generating grid capacity should be able to meet the additional demand of the BEVs. The power flow in BEVs is bidirectional. Therefore, the microgrid could utilise EVs to allow them to enter the market in short term periods at higher growth rates, when compared to the electricity generation, to keep the system stable without adding extra generation units, whereas the grid capacity needs to grow. Furthermore, the behaviour of the distribution network and the microgrid as part of the distribution network will be modified from a single direction power flow to bidirectional power flow. Such a system is very difficult to control, and congestion could occur affecting elements of the microgrid, which can then result in local power-outages. Uncontrolled charging of BEVs can significantly increase the peak load of the distribution network and thus result in a high cost. Therefore, a hierarchical modular structure is required to manage and control each element of the system,

including EVs similar to those proposed in this thesis, which will then allow a much greater number of EVs in the network. Managing and controlling the EVs may also allow integrating the intermittency of the renewable energy by using EV resources’ capacity for mobile storage devices.

The cost of EVs is one of the main barriers to their uptake. In particular, calculation of the total cost of ownership involves a large number of variables such as:

 Cost of batteries.  Lifetime of batteries.  Cost of EV use.

 Distance range of EV based on the battery size and cost.  Electricity use cost per distance units.

 EV taxes.

 Manufacturing age of the EV.

There are many manufacturers competing in the EV market; the EV culture provides a variety of EVs to satisfy each user group which are different in vehicle size and associated battery capacity and lifetime. EVs can be classified into sub compact models, medium sized models, and luxury models. The battery capacity is 12–21 kWh, 22–32 kWh, and 60–90 kWh respectively. The most common EVs are listed in Table 1-1.

In general, the EVs are classified according to their fuel use into partly electrically fueled such as RHEVs and PHEVs or wholly electrically fueled, such as BEVs. The PHEVs and BEVs are the two main technologies which are suitable for grid connection. Depending on the level of sophistication of the vehicle charging process, the EVs may be considered, from the view of the microgrid, as:

 A simple load that draws a continuous current independently from discrete network nodes.

 A flexible load of an aggregation of EVs with coordinated charging.

 Generation units where EVs are using their storage devices to inject power into the grid according to available resources [60]–[62].

Table 1-1: Battery capacity of different types of Electric Vehicle

Model Battery Capacity 1. _{Toyota Prius 4.4kWh} 2. _{Chevy Volt 16kWh} 3. _{Mitsubishi iMiEV 16kWh} 4. _{Smart Fortwo ED 16.5kWh}

5. _{Honda Fit 20kWh} 6. _{GM Spark 21kWh} 7. _{BMW i3 22kWh} 8. _{Ford Focus 23kWh} 9. _{Fiat 500e 24kWh} 10. _{Nissan Leaf 25kWh} 11. _{Mercedes B 28kWh} 12. _{Nissan Leaf 30kWh} 13. _{Tesla S 60 60kWh} 14. _{Tesla S 70 kWh} 15. _{Tesla S 85 90kWh}