The most important facts in brief:
- Definition: Bidirectional charging enables electric cars not only to refuel, but also to serve as a mobile energy source.
- Possible applications: There are various utilisation options. For example, utilising the electricity stored in the electric car battery for the domestic grid or feeding energy back into the general electricity grid to reduce peak loads.
- Challenges: Compatibility between direct current (e-cars) and alternating current (power grid). The need for specialised charging stations and suitable electric vehicles.
- Current status: The legal framework in Switzerland is still unclear, but there are positive developments thanks to new legal adjustments and promising results from pilot projects.
The term sounds a bit unwieldy, but the idea behind it is ingenious: "bidirectional charging" describes the ability of an electric vehicle not only to refuel with electricity, but also to store the surplus/unused energy and feed it back into the power grid. The technology might already be advanced in other countries, but in Switzerland, bidirectional charging is still in its infancy. In the following five points, you will find out what bidirectional charging is all about - and what hurdles still exist in Switzerland in this regard.
1. What is bidirectional charging?
With bidirectional charging, the electric car battery temporarily becomes an energy store. The stored electricity can be used later, for example in the household, or fed into the power grid.
An electric car can therefore not only be charged with electricity, but also emit electricity. One of the greatest challenges facing renewable energies is the issue of storage. When the sun shines on a rooftop photovoltaic array, the electricity produced isn’t always needed immediately.
To stop the energy being wasted, it needs to be stored somewhere until it is. This can be achieved with dedicated batteries, but they aren’t cheap. However, there’s often an effective alternative right there on the doorstep: the electric car. Given the right technology, the electric car can be used as a mobile powerbank.
While the technology is already well advanced in other countries, it is still in its infancy in Switzerland. Our article "Is Switzerland ready for bidirectional charging?" gives you an overview of the situation in Switzerland.
2. Where is bidirectional charging used?
There are several ways in which bidirectionally chargeable electric cars can be used in practice:
- Vehicle-to-Home (V2H): bidirectional charging enables the electricity stored in the car to supply the house where you live. Here, having previously been supplied with electricity by the home’s PV system when the sun was shining, it’s the electric car’s turn to power the home. All part of a virtuous cycle.
- Vehicle-to-Grid (V2G): it’s also possible to feed the energy in the car back into the grid. In this way, current peaks could be smoothed out. If the electric car is charged at off-peak times, the stored energy can be fed into the grid at peak times to relieve the load on it.
- Vehicle-to-Building (V2B): The electricity stored in the car can also be used to power a building. The electric car can supply office buildings, schools or other commercial buildings with energy and thus help to reduce energy costs and maximise the use of renewable energies.
- Vehicle-to-Everything (V2X): This technology makes it possible to share the electricity stored in the electric car with various end devices and infrastructures. This includes not only households and the electricity grid, but also other vehicles, appliances and public facilities. V2X stands for comprehensive networking and utilisation of energy sources to improve the efficiency and stability of the entire energy system.
- Vehicle-to-Load (V2L): Bidirectional charging makes it possible to use the electricity stored in the car for the direct operation of electrical devices and machines. The electric car acts as a mobile power source for tools, household appliances or camping equipment.
Another argument in favour of bidirectional charging is the fact that private cars stand around unused for up to 23 hours a day on average. It is precisely during this time that they could feed electricity back into the grid. To do this, the bidirectional charging station only needs to be registered with the local grid operator as a "simple" charging station.ation angemeldet werden.
3. Why is bidirectional charging not yet available across the board?
Although the technology behind the "power banks on wheels" is promising, there are still a few hurdles to overcome:
- Conversion: Electric vehicles generally run on direct current, while our electricity grid operates on alternating current. Most electric car models are equipped with an on-board charger that converts the alternating current into direct current - but only in one direction.
- Suitable wallbox: To allow the electricity to flow in the opposite direction as well, specially designed charge points and plugs are required. These are beginning to be available in Switzerland, but overall there’s a lot of catching up to do.
- Vehicle compatibility: Not all electric vehicles on the market are yet suitable for bidirectional charging. However, this will change quickly. Japan, for instance, has long made it mandatory for electric vehicle to be equipped with bidirectional charging technology.
- Standards and protocols: There are still different standards and protocols for bidirectional charging. This can lead to incompatibilities between the electric vehicle and the charging station. Different manufacturers sometimes use their own systems, which makes interoperability difficult and limits the choice of suitable charging stations.
- Costs for bidirectional wallboxes: The costs for a charging station are considerably higher if it can also charge bidirectionally. The additional functions and technical requirements for bidirectional charging significantly increase the acquisition costs, which is a hurdle for many users.
- Intelligent load management: Bidirectional charging requires intelligent load management in order to optimise charging and discharging. This means that energy flows must be monitored and controlled in real time to ensure efficient utilisation of resources. Such systems are complex and require additional investment in hardware and software to ensure smooth and efficient operation.
4. What is the legal and political framework?
The legal framework is also not clear. There is no law in Switzerland that prohibits bidirectional charging. Rather, it is equated with the stationary battery operation mentioned at the beginning.
Incorporating e-cars into the national power grid is a more complex issue. To ensure that this is not only technically but also economically feasible, the Electricity Act needs to be amended at national level. The result of the vote on 9 June 2024 on the Federal Act on a Safety Electricity Supply from Renewable Energy Sources is an important step in this direction. Thanks to the positive decision of the Swiss electorate, local associations beyond the individual house are now possible, known in technical jargon as the association for self-consumption of solar power (ZEV). Although the primary legislation put to the vote does not explicitly mention e-mobility, it definitely opens the way for the technology.
5. What is Mobility doing to promote the new charging technology?
The potential of bidirectional charging is obvious – especially so far as Mobility is concerned. By 2030, all of our 3,000 vehicles will be electrically powered. However, electromobility increases the demand for electricity and poses challenges in terms of grid stability. This is where bidirectional charging could turn out to be a trump card. Together, such a fleet of vehicles can form a virtual power plant that can help to stabilise the electricity grid if necessary.
Mobility has therefore recently successfully completed its two-year pilot project for bidirectional charging. Between September 2022 and March 2024, 50 Honda e all-electric cars were available at 40 Mobility stations dotted around Switzerland. Among other things, the electricity from the vehicles was offered to three different customers. The results of the trial are currently being analysed. One thing is already clear, though: the technology works – but there’s still a lot of work to be done in Switzerland before it can be used on a widespread basis.
FAQ
Is bidirectional charging allowed in Switzerland?
Yes, it is equivalent to the operation of stationary batteries and can be registered regularly.
How far along is bidirectional charging technology?
The first manufacturers are offering sophisticated bidirectional charging stations. The technology is already mandatory in Japan.
Does bidirectional charging damage the vehicle battery?
Studies show that the additional ageing of the battery is minimal.
What are the advantages of bidirectional charging?
It increases the self-consumption rate and reduces grid costs. This is because the bidirectional connection of vehicles makes it possible to reduce power peaks.
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