In the future, electric vehicles could make a considerable contribution to smart and flexible electricity use, as well as grid stability. Pilot projects for bidirectional charging are being carried out all around the world. The challenges are significant, but so are the potential rewards.
Europe, the second-largest market region, set a record with little more than one million new BEV registrations. Private vehicles, whether driven by electricity or internal combustion, have one thing in common: they are parked for an average of 23 hours every day. However, because of its driving mechanism, e-vehicles could also be used in other ways, such as additional electricity storage for the domestic power grid. The vehicle stores the electricity produced by the solar power system but is not used immediately during the day. This stored energy might subsequently be fed back into the family power grid in the evening or at night, supplying electricity to all household appliances. This is made feasible via bidirectional charging, which requires the electric automobile to be able to replenish itself as well as discharge the stored energy. And the potential of these mobile energy storage devices is constantly expanding.
Swarm intelligence
The concept of incorporating e-cars as electricity storage devices into the home or public grid is not novel. What appears to be a straightforward task is not that simple, both technically and practically. This technique has been the subject of years of research. There are various options. The "vehicle-to-home" (V2H) technology connects e-cars to the home network. The "vehicle-to-grid" (V2G) technique expands in scope. In this case, as many electric vehicles as feasible are intended to be incorporated into the public electricity grid. The advantage is that energy generated during peak periods can be temporarily stored and called up during evening consumption peaks. This "swarm battery" concept could absorb excess renewable energy production and help reduce reliance on fossil fuels. At the same time, this method of utilising electric vehicle batteries generates revenue for its owners. When demand for electricity exceeds supply, e-vehicle batteries act as a backup. Their owners obtain remuneration without basically reducing their range and consequently mobility by returning a small percentage of the stored energy to the grid.
Bidirectional charging
Vehicle integration into the broader power grid may also provide flexible storage alternatives to compensate for the unpredictability of energy provided by solar or wind power facilities. E-mobility's potential not only provides a sustainable choice for mobility via V2G, but it may also contribute to grid stability and security. However, several obstacles must be overcome in order to technically implement this tremendous promise. Bidirectional charging requires BEVs to be outfitted with unique chargers and control software. The power grid must also be designed to handle energy from a variety of sources without becoming unstable.
The charging software must go from charging to discharging (or vice versa) in milliseconds or less so that the grid frequency remains constant at roughly 50 hertz and the power grid functions smoothly. Another technical consideration is the vehicle itself; an electric car, in fact, only works on direct current because the battery is designed in this manner. It necessitates the use of a converter to convert direct current to alternating current. The converter can be mounted directly in the car or integrated into a DC wall box, making it ideal for PV installations. There are also some regulatory standards that must be completed. Electric vehicles, for example, must be approved as "rolling electricity storage units" by grid operators. Despite these obstacles, several research programs in the United States, Japan, and a few European countries are striving to develop bidirectional charging. Vehicle manufacturers, grid operators, and research organizations are all looking into how bidirectional charging affects vehicle batteries, among other things. One major criticism leveled towards V2G is the stress placed on batteries while charging and discharging, as well as the consequent aging. However, real experience reveals that battery stress during grid-serving activities is substantially lower than during traffic light starts or fast charging.
Current know-how
Dekra is one of the leading businesses active in this technology, with e-mobility laboratories in Arnhem, the Netherlands, and Concord, California, to assist manufacturers and regulators in removing technical and regulatory barriers. Both labs include the necessary equipment to simulate the influence on the electrical grid as well as communication between the car and the charging station using the recently issued worldwide V2G standard ISO 15118-20.
The California Energy Commission (CEC) is supporting the DEKRA Vehicle Grid Innovation Lab in Concord - ViGIL for short - to reduce regulatory hurdles in California and create a uniform standard for bidirectional charging so that in the near future, every vehicle can participate at every charging station as a dynamic storage device. Even though some technical and regulatory challenges remain, a few measured instances demonstrate how significant the positive effects of intelligent swarm power storage are: if all of Germany's approximately one million electric vehicles were simultaneously linked to a wall box with 11 kilowatts of charging power, their batteries could deliver or absorb up to 11 gigatonnes of power. This equates to the short-term flexibility of at least 2,500 current wind turbines, 30 gas-fired power plants, or the total capacity of all German pumped storage power facilities.
