Wind and solar energy are so-called volatile energy sources, which means that their electricity production is not constant and can fluctuate depending on weather conditions or other factors. However, in order to drive forward the energy transition, a reliable and constant power supply must also be guaranteed for companies. In combination with renewable energies, this works particularly well with large and flexible energy storage systems that are ideally located where the electricity is needed. This is precisely where vehicle-to-grid technology comes in, using the batteries in the company fleet as buffer storage through bidirectional charging. If this becomes established, the grid expansion and grid reinforcement of the entire public electricity grid could also be planned differently.
Electricity storage units on four wheels are ideal for bidirectional charging
The boom in e-mobility makes it possible: current e-car models are equipped with storage units of between 40 and 15o kWh, which can double for larger commercial vehicles. It therefore makes sense to charge the ten or 20 e-vehicles that are usually parked at a business with inexpensive solar power from the company roof or carport and at the same time use them as balancing or buffer storage for the company's own power grid. With vehicle-to-grid (V2G) and bidirectional charging, companies are therefore able to stabilize their power supply and Capping load peaks. However, a few basic conditions must be in place for this.
Requirements for vehicle-to-grid & bidirectional charging
For Vehicle to Grid (V2G) to be possible at all, the e-cars must first be able to feed electricity back into the grid. Although the CHAdeMO standard widely used in Asia is designed for this, the CCS standard widely used in Europe is generally not yet suitable for bidirectional charging. There are currently (as of early 2023) around ten purely electric car models available that can do this.
Cross-system communication infrastructure
In the second step, the charging stations must also enable bidirectional communication between the vehicle and the power grid. Although a vehicle-to-grid solution can already be implemented in a private context by selecting the right wallbox model and vehicle, a truly cross-system communication infrastructure between electric vehicles, charging stations, grid operators, energy suppliers and service providers does not yet exist. Introduced in April 2022 ISO 15118-20 is currently regarded as the basis for communication between charging stations and electric cars and still needs to be developed further. The same applies to IEC 61851-1, which, for example, contains the basic principles for communication to control charging processes for electric vehicles.
"Smart charging" is the goal
In any case, a Intelligent charging infrastructure and an energy management system (EMS) are required to ensure that the batteries of the electric vehicles only feed electricity into the grid when this is permitted, the vehicles are sufficiently charged and their own basic power requirements are secured. The systems must therefore be able to automatically prioritize between the vehicles. This is summarized under the keyword "smart charging".
Additional regulations for Vehicle to Grid
In addition to the technical standards for communication between the individual components, there are - as things stand today - still no further regulations on the grid stability of company-owned and public grids if millions of vehicles are to be connected to the grid and charged bidirectionally. The effects on the respective power grids still need to be examined. However, vehicle manufacturers have already given the all-clear: charging and discharging vehicle batteries should have no negative impact on their service life.
New tariff structures and incentives for bidirectional charging
If energy can be easily transported from A to B in the future, new basic tariff structures will be necessary. For a private individual who only supplies their e-vehicle with electricity and does this at their home wallbox, public charging stations or at their employer, everything is taken care of. But what happens if a company car owner charges his e-vehicle during the day with cheap solar power from the company's own solar carport and uses the electricity in his own home in the evening or feeds it into the public grid? How are electricity mixes or profits calculated, offset or taxed? This is where technical control units need to be integrated, legal guidelines created and new tariffs developed by energy supply companies. Finally, in order to be able to use vehicle-to-grid (V2G) and bidirectional charging in an economically and sustainably climate-friendly way, incentives for private e-car owners to feed their batteries into the grid when electricity demand is high and to charge them when demand is low are still lacking.