One thing is clear: we need to live more sustainably – all of us – if we want to keep global warming as low as possible. Which is why we are moving to 100% e-mobility. By 2030 at the latest, our entire fleet of around 3’000 vehicles will be electric. While increasing e-mobility is a positive trend, it also brings with it higher energy demand and challenges for network stability. Blackouts could become more likely even in the next few years, particularly in the winter months. The recently launched V2X Suisse project is looking to find solutions to this by pooling resources.
The basic idea behind bidirectional charging is that electric cars not only use electricity, but can also return it to the grid when they aren’t being driven. A private car normally sits idle for an average of 23 hours per day. But these stationary vehicles can actually become mobile power banks that can be connected to a large energy storage device, a bit like a reservoir. So essentially, households can draw power from their electric cars during peak hours, and then recharge them to full overnight at a cheaper rate. A single 11 kilowatt car can supply more electricity in one hour than an average Swiss household uses in a day.
Led by Mobility, the V2X Suisse project sees seven companies taking an innovative approach towards stabilising power grids through the medium of electric vehicles. They are: automotive manufacturer Honda, software developer sun2wheel, charging station developer EVTEC, aggregator manufacturer tiko and novatlantis as a scientific adviser. The project is supported by the pilot and demonstration programme of the Swiss Federal Office of Energy (SFOE).
This is the first large-scale test of its kind. From September 2022, some 50 "Honda e” vehicles will be available at 40 Mobility stations across Switzerland for one year. For the first time, mass-produced electric vehicles with bidirectional charging will be available for use across the country for day-to-day journeys.
How the test model compares internationally:
- So far there has never been a comparable test with 50 vehicles – other projects are using a much smaller number
- Widespread distribution at 40 stations across the country – tests have previously been limited to a single station or city
- The test model uses certified mass-produced products in normal operation (CCS charging stations and vehicles) – no specially trained users, laboratory conditions or prototypes
- The flexible power system is being offered to three different consumer types simultaneously (grid regulation, local energy providers and “interconnection for self-consumption” groups) – so far, this has only been tested with a single consumer type
Electric vehicles capable of bidirectional charging can not only store electrical energy for driving purposes, but also feed it back into the home. Vehicle-to-home enables you to supply your own home with the stored electrical energy from an electric car. The entire charging and recovery process takes place behind the house’s electricity meter and is often used to increase the self-supply rate for homes via photovoltaic systems.
As with vehicle-to-home, electric vehicles capable of bidirectional charging can not only store electrical energy for driving purposes, but also feed it back into a building with multiple consumers. Vehicle-to-building can be used to supply an apartment block or commercial/industrial units with the stored electrical energy from an electric car, often as part of an electric car fleet. Peak shaving can also help to mitigate usage peaks within the building. The entire charging and recovery process takes place behind the building's connection to the grid.
Electric vehicles capable of bidirectional charging can not only draw electrical energy from the grid, but also feed it back in as part of an intelligent energy system. This process is managed using signals from the distribution or transmission network operator and can take place both at public charging stations and within buildings via the grid connection. V2G charging and discharging of a larger number of electric vehicles (pooling) count as services in energy trading and for stabilisation within both the distribution and transmission networks. Vehicle-to-grid thereby enables intelligent sector coupling.
V2X is used as an umbrella term for all of the above applications, as well as the combined application of multiple types. For example, electric vehicles capable of bidirectional charging parked in a large property’s car park can be used both for self-consumption optimisation and peak shaving purposes (V2B), as well as to serve the grid (V2G). The autonomous supply of individual consumers and island grids, and the charging of other electric vehicles, completes the spectrum.
How mature is the bidirectional charging technology?
There are a few manufacturers in Switzerland and internationally that have brought technologically mature bidirectional charging stations with CHAdeMO connectors to the market. These have been extensively tested in multi-year trials. Bidirectional charging via CCS connectors has currently only been achieved by one Swiss manufacturer. In Japan, however, bidirectional charging technology has been mandatory for every electric vehicle for a number of years.
Is bidirectional charging allowed in Switzerland?
Essentially, bidirectional charging is equivalent to operating stationary batteries. If the charging infrastructure complies with the Association of Swiss Electricity Companies’ recommendation on grid connection for energy generation devices (NA-EEA) and the technical standards for electrical safety and electromagnetic compatibility, it qualifies for registration with the distribution network operator. Since 1 January 2022, bidirectional charging stations can be registered as standard using the updated technical connection application (TAG).
Are all electric vehicles capable of bidirectional charging?
Unfortunately not yet. All Japanese electric vehicles are essentially capable of bidirectional charging as it is mandated by the state there. Bidirectional charging is mainly possible with cars with CHAdeMO chargers, although it is also possible with a CCS quick charge cable in one case. Generally, bidirectional charging requires approval of the vehicle manufacturer and certification of the charging station for the vehicle type concerned.
Plug-in vehicles capable of bidirectional charging and available in Switzerland (as of August 2021):
|Nissan Leaf, e-NV-200 (delivery van) and EVALIA (people carrier)||CHAdeMO|
|Mitsubishi i-MiEV, Outlander und Eclipse Cross||CHAdeMO|
|Peugeot iOn und Citroën C-Zero||CHAdeMO|
Multiple vehicle manufacturers have announced plans to offer electric vehicle models with bidirectional charging in the near future. There is a general consensus that 2025 will see the introduction of an international standard, which will also include binding rules on bidirectional charging via CCS connectors.
Does bidirectional charging damage my vehicle battery?
Years of practical experience and scientific testing have shown that lithium batteries are very robust. The latest technological developments have also led to further increases in battery lifespan. As the discharging capacity associated with bidirectional charging is far lower compared with actual driving (by a factor of 10 or more), any additional aging of the battery is negligible. Manufacturers’ approvals of vehicle models for bidirectional charging also state that all guarantees remain unaffected.
What do bidirectional charging stations mean for the existing electricity grid infrastructure of the building concerned?
The intermediate storage and targeted recovery of self-generated solar power into the building increases the self-consumption rate for a property or area with photovoltaic systems, and therefore reduces the procurement costs for electrical energy. Bidirectional connection of vehicles also helps to mitigate peaks in electricity consumption as the batteries are discharged based on the load. This recovery process reduces the electricity costs for the user by enabling them to use a cheaper tariff. If there is a large enough number of vehicles returning energy to the grid, the capacity of the charging infrastructure may even come to exceed the delivery rate of the installed connection.
How can V2X improve the stability of electricity supplies?
Pooled charging and discharging of vehicles can mitigate overloads on the grid, for example those caused by irregular sources of power generation such as solar and wind farms. 100’000 connected electric vehicles, each at ±10 kW, for example, represents a ±1 GW decentralised power source. This is the equivalent of Switzerland’s largest pumped storage plant at Limmern. Half of the energy that could be stored across the 100’000 batteries would be enough to supply 200’000 average single family homes with electricity for one day.