Electric Vehicles as a Mobile Storage Device

International audienceElectricity is a quite recent energy (150 years old) that has developed very much as it allows a flexible use through converters (electrical machines and power electronics). At the beginning, the main use was for lighting and metro. Now, electricity is a major energy for developed countries: 17.7% of the world final energy consumption and 22% for the ECD countries (IEA, 2013a; b, Figure 1), and an economic growth is always linked to an electric consumption growth. Electricity has improved our daily life: washer, dryer, dishwasher, microwaves, internet, TV, air-conditioning, and so on. Humans have become very dependent on electricity consumptions. Nevertheless, electricity is a specific product in the sense that it is a nonmaterial energy, and thus it can only be stored through a costly transformation. Electricity can be classified as a tertiary or secondary energy produced from thermal, potential, hydro (see Volume 5, Chapter XX), wind hces137, or solar energy. For a thermal plant, the primary energy (coal, gas, or uranium) is converted into mechanical energy (secondary energy) by a turbine and is transmitted to the generator to be converted into electricity (tertiary energy). As electricity is difficult to store, it needs an infrastructure to be delivered to consumers: the electrical grid that makes the link between power plants and the consumers through transformers and overhead or cabled lines. At the beginning of the twentieth century, all countries made the choice of the alternating current technology as it allowed—thanks to a key device (the transformer) transmission of high power at high voltages to reduce losses. In the context of emissions reduction (CO2, NOx, etc.), objectives have been given for cleaner energies and the use of more efficient ones. In Europe, there are the “20–20–20” targets: 20% reduction for CO2 emissions, 20% reduction in energy consumption, and 20% increase in efficiency by 2020 (see Volume 6, Chapter XX). To reach these policy goals, electricity is an appropriate vector: it is a flexible energy that can be produced from renewable or CO2-free sources, electrical converters have high efficiency (80–90% for an electric motor) and are bidirectional what makes energy recovery possible for applications such as breaking (trains, vehicles, etc.). Transportation (cars, autobuses, and trucks) is often considered a major contributor to local pollution. Then, constraints for CO2 emissions reduction are more and more severe, especially in Europe. Automakers and their suppliers have optimized their engines with innovations such as start&stop starter/generator, kinetic energy recovery ystems, hybrid systems, and full battery electric vehicles (EVs) and plugin hybrid vehicles. For the two last cases, the energy stored in the batteries will totally or partially come from the electric grid