Electromobility is a central research area of the FFE and is part of numerous research projects. In the following series of articles, different topics are presented. One focus is on scenarios for electric vehicles and charging stations in Germany. Furthermore, the different charging plugs are explained and different possibilities of grid integration by controlled and bidirectional charging are described. Finally, the climate footprint of electric vehicles is discussed.
This article is the fifth of a series of 7 articles which will now be published successively on our website.
|Overview of the topics of the article series on electromobility|
|1.||Development of electromobility
|4.||Private and public charging|
|6.||Use Cases for bidirectional charging|
On average, cars are parked 90 % of their lifetime. Accessing their storage capacity during this time, electric vehicles (EV) could be an attractive flexibility solution to support the electricity system. If vehicles become grid-connected storage units, a broad range of services can be provided to the system that could not only mitigate EV-caused demand peaks, but also could adjust the load curve to better integrate variable renewable energy (VRE). 
One of the main challenges of electric mobility are load peaks due to simultaneity in consumption. Without controlled charging, the electricity grids would have to be expanded to meet the maximum peak load. This costs of expansion and adaptation of the distribution grid in Germany have been estimated at 2.4 billion euros per year (2015-2030) for an integration of 6 million cars. With controlled charging, this investment is reduced by 40 % to 1.4 billion euros per year. 
While traditional charging is based on charging the battery until it reaches its full capacity, smart charging refers to any kind of EV charging (uni- or bidirectional) in which the charging time and rate can be controlled by a “smart” device. Smart charging, sometimes called V1G, refers to the ability to dynamically modify the charge rate or the charge time. Thus, individual EV owners or energy companies can decide when it is most efficient to charge energy in terms of demand and cost. V2G can be used for all applications of V1G but also for bidirectional energy flow between an electric vehicle's battery and the charging station, also called electric vehicle supply equipment (EVSE).
Figure 1: Normal and smart charging representation
To this end, network operators provide electricity suppliers and charging point operators (CPOs) with forecasts of the expected load on their networks in advance. They would then be able to control the charging stations based on signals (e.g. local electricity consumption) as to prevent network overloads.
Among the smart charging possibilities, four levels are differentiated. These levels, represented in Figure 2, are built on each other and have an increasing integration with the network.