**1. Introduction**

The massive dissemination of electric vehicles (EVs) is believed to be able to improve the total energy efficiency of the vehicles as well as reduce the emission of greenhouse gases and oil

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consumption [1]. In Japan, considering that the gasoline price, total annual driving distance, electricity price during night time, and fuel consumption of both gasoline-fueled vehicle and EV are 110 JPY l−1, 10,000 km, 12 JPY kWh−1, and 15 km l−1 and 6 km kWh−1, respectively, the total operational cost of EV may be less than 30% of gasoline-fueled vehicle. Furthermore, the accelerationinthedevelopmentofEValsohasbeeninfluencedstronglybysomevarious factors including fluctuating oil and gas prices, successful advancements in battery technology, and broadersupportinginfrastructure[2,3].Unfortunately,therearestillsomechallengingproblems to expand in a broader scope of the community including high capital cost, long charging time, and relatively short travelable distance [4]. In addition, although the operational cost of EVs is cheaper than the conventional gasoline-fueled vehicles (internal combustion engine–based vehicles), the initial cost of EV is still higher due to high production cost.

To further reduce the initial and operational costs of EV (increase its economic performance), innovative value-added utilization of EV is requested. Furthermore, massive deployment of EVs can disturb significantly the grid electricity, especially when individual charging of EVs in large capacity and number occurred. According to [5], in case that a half of vehicles in Kanto (Tokyo and its surroundings) area are transformed to EVs and half of them are demanding a quick charging simultaneously, about 7.31 GW of additional electricity supply is required. Recently, to give an answer to the above problems, the idea of vehicle-to-grid (V2G) has been proposed and investigated [6–8].

The adoption of EVs to support the electricity of grid or any electricity-related system becomes possible because of controllable charging and discharging behaviors resulting in the possibility of scheduled and coordinated charging and discharging. Therefore, the parked and connected EVs can be assumed as a largely bundled battery which is able to consume (absorb) the electricity from the grid, store it, and release back to the grid. In addition, V2G can be achieved when minimally three fundamental preconditions are totally satisfied: (1) an electricity line connecting both EV and power grid, such as charging station, (2) a communication system transferring the information and control command between EV and grid operator, and (3) an accurate and trusted metering system facilitating fair service measurement [9]. Furthermore, in case that there is any demand for electricity, the grid operators and/or energy management system (EMS) are able to dispatch a control command instructing the connected EVs to discharge their stored electricity to the grid. On the other hand, they can instruct the connected EVs to absorb the electricity due to surplus of electricity or decrease of electricity demand. Therefore, the balance between supply and demand, as well as quality of grid electricity can be maintained.

V2G provides various possible ancillary services to the electricity grid or any electricity-related system such as load leveling and spinning reserve. In addition, the distributed EVs also can be assumed as a large-scale energy storage (battery) which is potential to be bundled and utilized to minimize the effect of fluctuating supply. As EVs are moving from and to different times and places, they also could be employed as an energy carrier transporting the electricity in different places and times due to some factors such as electricity price difference and emergency condition. From the economic analysis, the massive adoption of EVs to give ancillary service to the grid (V2G) is considered beneficial because the projected profit is still significantly higher than the initial cost of EVs, especially the battery including the consider‐ ation of battery wear and life cycle [4]. This feasibility study has been performed based on the actual data of EVs, especially the life cycle of battery.

Until now, battery cost stands as the highest share in total EV production cost. In addition, as the number of produced EVs increases, the number and total capacity of the used batteries increase accordingly. According to [10], the EV batteries are generally replaced after their storage capacity drops to about 70–80% of its initial capacity. The decrease in battery capacity leads to shorter possible driving range. Therefore, although these used EV batteries are not appropriate anymore for EVs, they can be reutilized as a stationary energy storage (stationary battery). This kind of battery utilization is believed to be able to further improve the overall economic performance of EV as well as reduces their impacts to the environment because it can lengthen the battery end-of-life. The study on the utilization of EV batteries acting as stationary battery to take part in ancillary service to certain EMS or grid can be found in several literature [11, 12].

Several studies focusing on theoretical analyses of the application of both EVs and used EV batteries have been conducted well. However, those studies are generally lack of experimental investigation including demonstration tests and real application. This chapter deals mainly with the employment of EVs and used EV batteries in supporting the electricity in any typical small-scale EMS including both theoretical and experimental studies. In addition, the results from the demonstration test are also studied and analyzed.
