Electric vehicles have long been more than just a means of transportation. They also function as flexible, environmentally friendly electricity storage systems.
Thanks to modern battery technology and innovative charging solutions, electric vehicles can be flexibly integrated into private and public energy systems. With so-called bidirectional charging capability, the electric vehicle is no longer just charged, but can also feed electricity into the grid or into your own home. This makes electric vehicles valuable components of a decentralized and sustainable energy supply.
What does bidirectional charging mean?
Bidirectional charging is the ability of an electric vehicle and the charging infrastructure (e.g. home charger) not only to absorb electricity, but also to release it again. While conventional charging (unidirectional) only allows electricity to flow in one direction, from the power grid to the electric vehicle, bidirectional charging allows electricity to flow in both directions. This means that a charged electric vehicle can use its stored electricity for other purposes instead of just storing it for the journey.
The ISO 15118-20 standard is the central basis for communication between the electric vehicle and the charging infrastructure in bidirectional charging.
Bidirectional charging is a generic term for various applications that are summarized under the collective term Vehicle-to-X (V2X). In detail, a distinction is made between two types: vehicle-to-grid and vehicle-to-home.
What is vehicle-to-home (V2H)?
Vehicle-to-home refers to the use that typically takes place at the end user’s home. If the home charger is connected to the home grid, the electric vehicle can not only be charged, but can also be used to store energy. If there is also a PV system on the roof of the house, the home charger establishes a connection between the generator and the storage unit at times of surplus electricity and the battery of the electric vehicle is charged. If the electric vehicle is not being used at night and is therefore parked, the home charger detects whether there is an additional demand for energy in the household, for example because appliances are running or electricity is being consumed. If this is the case, the home charger can feed energy from the electric vehicle’s battery into the household grid to cover this demand.
This allows you to increase your own consumption without having to install an expensive stationary battery in your home. In times of rising electricity prices and declining feed-in tariffs, this is an increasingly attractive model. In addition, a vehicle battery is usually larger than a classic residential storage unit, which provides additional capacity for self-consumption.
What is vehicle-to-grid (V2G)?
With V2G technology, the electric vehicle can not only be charged from the supply network, but can also feed energy back into the grid. This process follows the standard ISO 15118-20 and is carried out to stabilize the grid, balance peak loads or sell surplus electricity when electricity prices are high. Vehicle-to-grid supports the entire public grid.
Conversely, the e-vehicle can also be charged when electricity prices are particularly low. In sunny regions such as California, for example, where photovoltaic systems produce more electricity than is needed, electricity prices may even fall into negative territory. In these cases, charging is rewarded with a tariff.
Advantages of V2G for energy suppliers
For energy suppliers, bidirectional charging, known here as vehicle-to-grid (V2G), is also attractive for a completely different reason: strong fluctuations and loads on the electricity grid can be absorbed. The batteries of the electric vehicles form a buffer storage and absorb renewable electricity at times of high availability in order to make it available again to a certain extent later at times of lower availability. V2G can increase the share of renewable energies in the energy mix.
It is crucial that these capacities are used in a consolidated manner. A single vehicle only has a limited influence on the power grid. Only by networking and bundling many electric vehicles can a scalable energy storage system be created that can actually contribute to grid stabilization, for example through the targeted control of charging and discharging processes via intelligent systems.
Technical requirements for vehicle-to-grid (V2G) and vehicle-to-home (V2H)
Various technical requirements and components are necessary to pave the way for bidirectional charging and the integration of electric vehicles into the energy system. These include, among others:
The right charging infrastructure:
DC home chargers are able to carry out vehicle-to-grid and vehicle-to-home energy feeds thanks to bidirectional converter technology . The electricity can flow in a controlled manner from the vehicle battery via the home charger into the power grid or your own home.
In principle, bidirectional charging is also possible via AC (alternating current), but this requires an additional external converter, as most vehicles do not support bidirectional conversion internally.
The integrated charging controller:
With the right measurement and charging technology , electric vehicle batteries can be charged intelligently. However, they can also return electricity to the grid whenever necessary. This turns fleets into profitable energy storage systems by using electric vehicles as electricity buffers. The technical requirements and framework conditions for this are described in of ISO 15118-20 .
Compatible electric vehicles:
Universal vehicle charging inlets for electric vehicles enable AC and DC charging from low power temperatures to High Power Charging. The charging technology in the home charger generates the PWM signal in accordance with the ISO 15118-2 and ISO 15118-20 standards. This signal is transmitted via the signal contacts and lines of the CCS charging inlet and is essential for functions such as plug & charge and vehicle-to-grid (V2G).
Suitable charging cables:
For these vehicle-to-grid (V2G) and vehicle-to-home (V2H) applications, compact CCS charging cables are the optimal solution, which are available on the market specifically for DC charging in the home with low charging powers of up to 80 kW.
Looking to the future: Charging infrastructure until 2030
Technologies such as High Power Charging (HPC) and vehicle-to-grid (V2G) are considered key to the widespread integration of electric vehicles into existing energy systems. They not only enable ultra-fast charging, but also the active participation of vehicles in grid stabilization. Read more in the article “Charging infrastructure for electric vehicles: High Power Charging and vehicle-to-grid as key technologies by 2030”.
Conclusion
Bidirectional charging turns electric vehicles into active components of the energy system by feeding electricity into the grid (V2G) or to the household (V2H). This supports grid stability and turns electric vehicles into flexible electricity storage systems.
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