We answer your questions.
The FAQ's and explanations of terms are not exhaustive and will be added to on an ongoing basis.
Term Bidirectional charging
In bidirectional charging, the vehicle battery is used as an intermediate storage of electrical energy (e.g. to store surplus solar power). In contrast to monodirectional charging, which is still common today, a bidirectional charging station can be used to feed electrical power and energy back into the building (V2H/V2B) or the electrical supply network (V2G) as required.
Term V2H (vehicle-to-home)
Bidirectionally chargeable e-cars can not only store electrical energy for driving purposes, but also feed it back into the home. Vehicle-to-home thus makes it possible to supply one’s own household with the stored electrical energy from the e-car. The entire charging and feeding back processes take place behind the house meter and is often used to increase the self-sufficiency rate by means of solar power systems.
Term V2B (vehicle-to-building)
As with vehicle-to-home, bidirectionally chargeable e-cars can not only store electrical energy for driving purposes, but also feed it back into the multi-occupant building. Vehicle-to-building thus enables the building to supply its own multi-family dwelling or commercial/industrial facility with the stored electrical energy from the e-car, often as part of an e-car fleet. In addition, peak shaving can be used to cap in-building load peaks. The entire charging and regenerative processes take place behind the electrical building connection.
Term V2G (vehicle-to-grid)
Bidirectionally chargeable e-cars can not only draw electrical energy from the grid, but also feed it back into the grid as part of a smart energy system. This process is controlled by signals from the distribution or transmission system operator and can take place both at public charging stations and inside buildings via the grid connection. The V2G charging and discharging operations of a larger number of e-cars (pooling) serve as services in both the distribution and transmission grids for energy trading and stabilization purposes. Vehicle-to-grid thus enables smart sector coupling.
Term V2X (Vehicle-to-everything)
V2X is considered a collective term for all of the above applications and also expresses the combined use of multiple modes of operation. For example, bidirectionally chargeable e-cars in a parking garage of a larger property can be used both for self-consumption optimization and peak-shaving purposes (V2B) and for providing grid services (V2G).
The autonomous supply of individual consumers and island grids as well as the charging of other e-cars complete the picture.
How far is the bidirectional charging technology?
There are first manufacturers, including the sun2wheel partner EVTEC, which have brought technically mature bidirectional charging stations with CHAdeMO connectors to the market. These have been extensively tested in advance in trials lasting several years.
Bidirectional charging via the CCS plug, which is the standard in Europe, is currently only possible with our two-way digital and -10 charging stations.
In Japan, on the other hand, bidirectional charging technology has been mandatory for every electric vehicle for years!
Is bidirectional charging allowed in Switzerland?
In principle, bidirectional charging is equivalent to the operation of stationary batteries. If the charging infrastructure complies with the VSE Recommendation Grid Connection for Energy Generation Installations (NA-EEA) and the technical standards for electrical safety and electromagnetic compatibility, it is eligible for approval when registering with the distribution grid operator.
As of 1.01.2022, bidirectional charging stations can be registered regularly by means of an updated technical connection application.
Which vehicles are bidirectional?
The following vehicles are enabled for bidirectional charging as of April 2023:
- Honda e
- Nissan: Leaf & e-NV 200
- Mitsubishi: i-MiEV, Outlander and Eclipse Cross
- Peugeot iOn and Citroën C-Zero
Listed are all vehicles that allow vehicle-to-home via a suitable charging station. Vehicle-to-load, such as the Hyundai Ioniq 5, must be considered separately. Here, you can only draw a limited amount of power via an onboard plug (single-phase, up to 3.6 kW), but you cannot supply a house with electricity.
Further information: In principle, all Japanese electric vehicles can charge bidirectionally because this is mandated by the Japanese government. So far, bidirectional charging is primarily possible for vehicles with CHAdeMO plugs. The Honda e is an exception, it can do bidirectional charging via the CCS plug. Bi-directional charging requires approval from the vehicle manufacturer and certification of the charging station for the specific vehicle type.
Several vehicle manufacturers have announced that their vehicles will be enabled for bidirectional charging in the near future. In general, the introduction of an international standard ISO 15118-2020 is expected by 2025, which will also regulate bidirectional charging with CCS charging plugs in a binding manner.
Will bidirectional charging harm my vehicle battery?
Years of practice and scientific research have shown that lithium batteries are very robust. In addition, the latest technical developments have resulted in an even longer battery life. Since the discharge power during bidirectional charging is much lower compared to driving (factor 10 and more), the additional aging of the battery is extremely low. The approval of vehicle models for bidirectional charging operation by their manufacturers also includes the retention of full warranty services.
What do bidirectional charging stations mean for the existing power grid infrastructure of the building in question?
The intermediate storage and targeted feeding back of self-produced solar power increases the self-consumption rate of a property or an area with a photovoltaic system and thus reduces the purchase costs of electrical energy.
The bidirectional connection of vehicles also makes it possible to reduce power peaks by discharging the batteries in a load-controlled manner. This regenerative power supply results in a reduction of grid costs for the user through savings in the power tariff.
With a larger number of vehicles feeding back, the charging capacity of the charging infrastructure can even be raised above the capacity of the installed connected load.
What can V2X contribute to the stability of the power supply?
By bundled charging and discharging of vehicles, overloads of the grid can be reduced, e.g. by irregularly feeding solar power or wind power plants. For example, 100,000 electric vehicles connected to the grid with ±10 kW each represent a decentralized control power of ±1 GW. This corresponds to the output of the largest Swiss pumped storage plant, Limmern. Half of the energy that can be stored in the 100,000 batteries is sufficient to supply 200,000 average single-family homes with electricity for one day.
Note: there are about 4.6 million cars in Switzerland; the highest total power occurring in the Swiss electricity grid occurs in winter and is about 9.5 GW.
Term ZEV (association for self-consumption)
Owners of apartment buildings, office buildings and commercial buildings can make the self-produced solar power available to tenants for self-consumption. The solution of sun2wheel enables the correct billing in case of aggregation for self-consumption.
Does a bidirectional charging station have to be registered?
Yes, a bidirectional charging station must be registered with the local network operator just like a simple charging station. The technical connection application, which may be completed and submitted by an electrician, for example, is used for this purpose.
How do I notify the grid operator of a bidirectional charging station?
The “technical connection request” form is used for this purpose. This may only be filled out by a certified person such as an electrician. Only the section “Charging facilities for electric vehicles” is filled in. The following data must be entered:
Type of device: “bidirectional charging station”.
Manufacturer of the device: “sun2wheel AG”.
Device type: “two-way-digital” or “two-way-10
Rated current device: 16 A
Rated power device: 10 kVA
Cos Phi: 1
DC charging of the vehicle
Max. Mains draw power: 10 kVA
Max. Mains withdrawal power: 0
Adjustable power by TSO: 0 kVA to 0 kVA
Controllable power by operator: 0 kVA to 10 kVA
Active power controllable: No
Interface between charging pole and distribution grid operator available: No
Comment of the submitting company: “For the regulation of charging as well as discharging, the balance energy is measured. This guarantees that no energy is fed back into the grid.”
Does the bidirectional charging station also run if the power grid fails?
No, the bidirectional charging station is not yet island-capable and cannot operate in the event of a power failure. Likewise, our charging station is not yet compatible with a self-sufficient building. We are working to ensure that our systems can be used in an island system in the near future.